ALBERT

Beschreibung: Apple snails are freshwater gastropods with highly diverse feeding mechanisms (shredding, scraping and collecting) to exploit diverse food sources. Pomacea canaliculata is listed among the world's 100 worst invaders, mainly due to its effects on aquatic crops and submersed macrophytes through shredding, its main feeding mechanism. In one of the alternative mechanisms, the snails obtain material from the water surface through a funnel formed by the anterior part of the foot, here termed pedal surface collecting (PSC). Our aims were to study the potential trophic spectrum of PSC and the effects of snail size and sex, density of food particles and particle size on efficiency of this feeding mechanism under laboratory conditions. We also explored occurrence and daily fluctuations in the field. Pomacea canaliculata snails were able to capture different food types irrespective of their physical nature (liquid, organic particles and biofilms) and size, although not all of them could be ingested. PSC was performed only when food was available on the surface by snails from the whole size range tested (3–52.8 mm shell length), although it was less frequent in snails 〈10 mm. The amount of food captured by unit mass decreased with animal size, but is partially compensated by a corresponding increase in frequency and duration of PSC. The specific capture rate increased, and the time spent forming pedal funnels decreased, with food density, but no effects of particle size were observed. In the field, PSC was observed only occasionally during the day, but showed a marked increase after sunset, and was observed even when submerged macrophytes and associated periphyton were abundant. The wide trophic spectrum, the high and adaptable capture rates and the wide size tolerance likely allow P. canaliculata to take advantage of highly variable and unpredictable food resources present on the water surface, thereby contributing to the invasion success of the species.

Beschreibung: The epizoic bonnet limpet Hipponix conicus adheres to various species of sublittoral and littoral gastropods throughout the Indo-West Pacific province. In the northern Sea of Japan, we studied the cause-and-effect relationships of different host species for H. conicus . We investigated five species of host: two muricids ( Thais clavigera and T. bronni ) and three turbinids ( Chlorostoma turbinatum , Omphalius rusticus and O. pfeifferi carpenteri ). Our field observations suggest that differences in prevalence among five host species are unrelated to differences in their food habit, shell shape or phylogenetic affinity. The pattern of the prevalence of H. conicus on the two species of muricid hosts differs from that of the primarily littoral barnacle Chthamalus challengeri on the same host species, probably reflecting the amount of time the host species spend emersed in the littoral zone. Our laboratory experiments show that the juveniles of H. conicus died if they spend several hours out of water, and that new hatchlings indiscriminately chose five host species on which to reside when they were continuously submerged. Thus, the differences in the prevalence and intensity of infection of H. conicus in the northern Sea of Japan appear to be more strongly driven by the differential rates of migration and/or survival of the limpets caused by differential duration and frequency of their exposure to the air, rather than preferential adhesion to different hosts.

Beschreibung: The validity of the muricid subfamily Ergalataxinae has recently been confirmed with molecular data, but its composition and the relationships among its constituent genera remain unclear. In order to investigate this, we use four genes (28S rRNA, 12S rRNA, 16S rRNA and cytochrome c oxidase subunit I) to construct a Bayesian phylogeny of 52 ergalataxine species in 18 genera, representing c. 40% of the currently accepted species and 86% of the genera. This is the most complete phylogeny of this taxonomically confusing subfamily yet produced. Our results indicate the polyphyly of many traditional genera, including Morula , Pascula and Orania . In order to improve the correspondence between classification and phylogeny, we restrict the definition of Morula , resurrect Tenguella and elevate Oppomorus to full genus, but describe no new genera. Several species in this analysis could not be identified and may be new, but we do not describe them. Further molecular and morphological analyses, in the context of this framework, should help to resolve the remaining ambiguities in the classification of this subfamily. The oldest fossil member of the Ergalataxinae known to us is of Early Oligocene age.

Beschreibung: For the first time, bacterial symbiosis is recognized in the bivalve family Montacutidae of the superfamily Galeommatoidea. The ctenidial filaments of Syssitomya pourtalesiana Oliver, 2012 are extended abfrontally and a dense layer of bacteriocyte cells cover the entire surface behind a narrow ciliated frontal zone. The bacteria are extracellular and held within a matrix of epithelial extensions and microvilli. There is no cuticular layer (glycocalyx) covering the bacteria as in many thyasirid symbioses. The bacteriocytes hold more than one morphotype of bacteria, but bacilli, 1–3 μm in length, dominate. Scanning electron microscopy observations show a surface mat of filamentous bacteria over the extreme abfrontal surfaces. Filter feeding was confirmed by the presence of food particles in the stomach and the bivalve is presumed to be mixotrophic. Syssitomya is commensal and lives attached to the anal spines of the deep-sea echinoid Pourtalesia . In this position, echinoid feeding currents and echinoid faecal material may supply the bacteria with a variety of nutrient materials including dissolved organic matter.

Beschreibung: The antipredatory responses/attachment behaviour of the green-lipped mussel Perna viridi s were studied under combined stresses of hypoxia and low salinity in the presence/absence of its predator, the swimming crab Thalamita danae . There were two oxygen concentrations (1.5 mg l –1 O 2 = hypoxic and 6.0 mg l –1 O 2 = normoxic) and two salinity levels (15 = low, 30 = normal). Byssus production performances (including byssal-thread number, byssal-thread diameter, byssal-thread length, cumulative byssal-thread length and volume and frequency of stalk-shedding) were evaluated after 48 h. All variables were significantly affected by dissolved oxygen (DO), salinity and predator presence. Interactive effects of these three factors on byssus production were also observed. Byssus production and frequency of stalk-shedding were lowest in hypoxia x low salinity, followed by normoxia x low salinity, hypoxia x normal salinity, while normoxia x normal salinity exhibited the highest values in both predator-presence and non-predator-presence groups. At each treatment of DO and salinity, all parameters in predator-presence groups were significantly higher than in non-predator-presence groups. Our results indicate that the environmental hypoxia and low salinity impair anti-predatory/attachment behaviour and show some synergistic effects. Since reduced byssus production makes the mussels more vulnerable to crab predators, the co-occurrence of hypoxia and low salinity may increase the rates of crab predation on P. viridi s in the field.

Beschreibung: The large slug known as Arion lusitanicus (or A. vulgaris ) is an important pest that is spreading through much of Europe. Arion rufus disappears at sites where A. lusitanicus has established strong populations. The finding of morphological intermediates suggests that A. lusitanicus hybridizes with A. rufus , but interspecific mating had not been proved. Considering the marked differences in their genitalia, it has been hard to envisage how mixed couples might transfer sperm. Arion lusitanicus and A. rufus were collected from pure populations near Görlitz, Germany, and used for laboratory mating trials involving either two individuals of A. rufus (henceforth RR), two of A. lusitanicus (LL) or one of each species (mixed). Matings were video recorded and some couples were killed during or after copulation to study spermatophore transfer and genital anatomy during mating. Three mixed pairs copulated. However, mixed pairs were significantly less likely to copulate than either RR or LL pairs (7% vs 52 and 36%). At each stage of mating, the probability of proceeding further was lower in mixed pairs than predicted from rates in RR and LL pairs, but this effect was strongest for yin-yang formation and initiating copulation. One problem was that A. lusitanicus tried to circle after yin-yang formation, whereas A. rufus remained stationary. In this respect, and in the repositioning of its everted oviduct, it was A. lusitanicus that compromised. LL copulations lasted over twice as long as RR copulations, but spermatophore formation took similar times, permitting reciprocal spermatophore exchange in mixed couples even though their copulations ended much earlier than in LL pairs. Our observations of mating behaviour of intraspecific pairs largely agree with previous descriptions of A. rufus , but we discuss some discrepancies between our findings and the fuller descriptions available for A. lusitanicus .

Beschreibung: Cryptobranch dorids are typically thought to have specialized diets limited by prey skeletal architecture and chemistry, but recorded diets for some species are broader than expected. Few studies have directly compared prey use with prey availability over multiple sites to test the dietary range of separate populations. Diets of dorids at sites in British Columbia, Canada were not simply related to the richness and diversity of the local sponge assemblage, partly because all dorids avoided the most common sponges and instead consumed rare, inconspicuous species. At each site, three dorid species ( Cadlina luteomarginata , Diaulula sandiegensis and Peltodoris nobilis ) consumed multiple species, while two others ( Doris montereyensis and D. odhneri ) each consumed one species almost exclusively, so total dietary ranges may sometimes reflect true oligophages and sometimes mosaics of stenophage populations. Diets in all cases shifted greatly among sites and geographic regions and included sponges with different skeletal types, indicating that all species are nonstereotyped specialists. The diets of these dorids may be determined primarily by haphazard encounters among scarce or patchy palatable prey, with other prey attributes playing a lesser role.

Beschreibung: The population dynamics of the mediterranean snail, Cernuella virgata (Hygromiidae), which is a pest of grain crops and pastures in southern Australia, was studied in three adjacent fields used for continuous cropping on Yorke Peninsula, South Australia, for 20 years. The cropping sequence was commonly a rotation of faba beans, wheat and barley. Population densities were measured every month for the first 4 years and thereafter only in autumn and spring each year. Autumn and spring were the respective breeding season for adults and the resultant juvenile population that infested grain harvests. Populations varied greatly in abundance between years and fields. Spring abundance was correlated, albeit weakly, with prevailing spring and previous autumn rainfall. The latter can thus be used as an early warning of harvests suffering from snail contamination. Snails grew largest in faba bean crops and were more abundant in the wheat crops that followed faba beans than they were in the subsequent barley crop. No evidence was found of increased snail abundance near field edges, which would suggest biased seasonal movements of snails between adjacent fields, as has been reported for other studies of C. virgata in different agricultural systems (interfaces between crops and pastures, pastures and woody/weedy roadside vegetation). It seems probable, in this case, that the similarities in vegetative form of adjacent crops provided limited stimulation for differential dispersal between fields. The frequencies of banded (darkly coloured) shells also did not vary with distance from field edges, suggesting that the fence posts and tall weeds that occurred at the interfaces between fields were insufficient to provide (cooler, above-ground) shelter in summer and enhance local survival of banded C. virgata relative to locations further into fields.

Beschreibung: The genus Agaronia includes dominant predators in the eulittoral zone of dissipative sandy beaches of the tropical Eastern Pacific, which show specific adaptations to this environment such as swash-surfing locomotion. We studied A. propatula in its natural habitat in El Salvador and Costa Rica, and performed field experiments to obtain insights into its ecology, behaviour and sensory physiology. Agaronia propatula is not attracted by carrion and preys mostly on the ubiquitous beach snail Olivella semistriata . This, however, reflects community composition rather than prey specialization; A. propatula is an investigative hunter and will, quite literally, attack everything that moves (with the notable exception of echinoids). Prey is identified at short range by tactile and, to a lesser degree, by chemosensation located in the propodium. We found no evidence for long-distance sensory capabilities; A. propatula rather seems to rely on the regular physical structure of its wave-dominated environment when it moves between its shallow subtidal resting zone and its upper intertidal hunting grounds where potential prey predictably congregates. On the other hand, behavioural patterns such as the rapid yet haphazard cruising of foraging individuals, or the complex prey capture sequence in which the prey is transferred to a metapodial pouch, are similar in A. propatula and Oliva . Thus, our results lead us to speculate that the development of behavioural features that proved adaptive in the intertidal environment was essential in the evolution of Agaronia from Oliva -like ancestors.

Beschreibung: Sampling of land snails in 19 small sites on Santa Maria (Azores) in 2008 and 2011 yielded a total of 52 species; 26 were Macaronesian endemics, of which 23 are restricted to the Azores. These represent nearly all the described endemic fauna. Forest faunas were the richest and contained the highest proportion of endemic species. Widespread European species were the major components of assemblages in open habitats, subject to greater human disturbance, while secondary or heavily disturbed forests were intermediate. A small suite of endemic species showed no habitat preference and may represent a fauna living in relatively open conditions prior to human occupation. Within forests, congeneric species frequently occur in the same site. All seven endemic Oxychilus species recorded occurred in a single site; there is no evidence of allopatric replacement or restricted distribution other than that imposed by habitat. This may reflect the age of the island, the oldest in the archipelago. Nearly all forest endemics are found near the summit of the highest peak, a small area vulnerable to habitat destruction or climate change; even without these, there may be an extinction debt to be paid in the absence of conservation measures.

Beschreibung: Animals should naturally select diets that provide the most benefit for the least cost. Many factors, however, can alter diet selection and may impact the ability to choose optimal diets. For example, dietary history may play a large role in how quickly an animal will switch to a novel and perhaps more optimal diet. The current study first aimed to evaluate diet quality using growth rate as a proxy in Planorbella trivolvis (Planorbidae) fed a range of common laboratory lettuce diets. Next, we sought to determine the extent to which diet acclimation influenced subsequent diet selection using the same laboratory lettuce diets. Snails fed cooked green romaine grew significantly more than snails fed cooked yellow romaine, uncooked green romaine or cooked kale. In a series of acclimation/selection experiments, snails naïve to all diets showed no selection, suggesting that prior experience with a diet item is necessary for rapid selection. When reared on a particular diet, however, snails showed a significant preference for that diet after a 5-d starvation period. Unexpectedly, we found that even snails reared on diets that yielded lower growth rates (e.g. uncooked lettuce) selected that same diet when also provided access to diets that were previously shown to yield higher growth rates. Diet acclimation clearly influenced subsequent dietary selection. The implications of acclimation and preference for different dietary items by wild snails are unknown, but are likely ecologically important.

Beschreibung: We have established an in vitro glochidial culture of the freshwater mussel, Hyriopsis (Hyriopsis) bialatus , with the potential of restoring natural populations. However, to develop a successful in vitro culture process the synchronous release of glochidia needs to be achieved. In this study we investigated the distribution of serotonin and its effect on inducing synchronous parturition. Using confocal microscopy on whole-mounted tissues, we show that serotonin is highly expressed in the peripheral neuron somata and their axonal processes in the central neuropils of the visceral ganglion. Serotonergic nerve fibres were also detected along the branchial nerve innervating the demibranchs. A hierarchical ramification from the branchial cord into nerve rootlets and subsequently into the small nerve fibres within the demibranch epithelium was evident throughout this organ. In both visceral ganglia and demibranchs, immunoreactivity of serotonin was relatively higher in female than male tissues, suggesting a role of serotonin in female reproductive functions. Administration of serotonin to the demibranchs, the sites of larval settlement, stimulated synchronous parturition in a dose-dependent manner. A single-dose injection of serotonin yielded a large number of released larvae within 1–2 h, with no adverse effect on the quality of cultured larvae.

Beschreibung: Reproduction is influenced by many external factors. For egg laying of pond snails, one important trigger is the transfer from dirty, oxygen-poor water to clean, oxygen-rich water. This response is due to the combined effects of elevated oxygen level, chemical water composition and clean substrate. Whether this clean-water stimulus (CWS) resembles the natural egg-laying process has remained untested. Given that the response relies heavily on a pretreatment that suppresses egg laying, the animal's internal state is clearly important. Egg laying is known to be influenced by day length, hence external factors signifying time of day or season may be involved. We here study the effect of light on the CWS in the freshwater pulmonate Lymnaea stagnalis . Clean water was more effective in inducing oviposition in the light than during darkness, irrespective of the presence of eyes. Thus, light has a profound influence on egg laying, which is most likely mediated by nonocular photoreceptors. We show that more eggs are laid during the day than during the night in wild-caught animals kept outside, which indicates that the effect of light on CWS-induced egg laying is relevant for the induction of egg laying under natural conditions.

Beschreibung: The hyperdiverse group of venomous Conoidea has eluded attempts to construct a robust and stable classification owing to the absence of a robust and stable phylogenetic framework. New molecular data have greatly enhanced our understanding of conoidean evolution, allowing the construction of a new family-level classification. This expanding framework has also allowed the discovery of several independent lineages that merit recognition at familial rank. One of these, based on seven specimens collected over more than 20 years from deep waters off New Caledonia, represents a unique, monotypic lineage closely related to Mitromorphidae, which we here name as the new family Bouchetispiridae. This new lineage bears a unique combination of teleoconch, protoconch and anatomical characters previously unknown within the Conoidea, including a translucent, fusiform shell with sculpture of strong axial ribs crossed by spiral cords, a multispiral protoconch of only 2.5 whorls with punctate sculpture, hypodermic marginal teeth and a multilayered venom bulb with two layers of muscle separated by connective tissue. This lineage may represent the sole survivor of a previously more diverse clade, or is simply one of many unique taxa that have arisen among the isolated sea mounts off New Caledonia.

Beschreibung: This paper provides the first records of freshwater rissooidean gastropods from the Palaeogene (uppermost Eocene to Lower Oligocene) of northern Vietnam (Cao Bang Basin). The most abundant element of the assemblage is the new genus Bacbotricula (Pomatiopsidae: Triculinae?), comprising numerous well-preserved specimens belonging to two new species, B. nhamaygachensis and B. dongbangensis . The assemblage also contains poorly preserved specimens of two other species, one of which is tentatively assigned to the Bithyniidae. The Cao Bang assemblage is among the earliest Cenozoic freshwater gastropod faunas described from Southeast Asia and Bacbotricula is the only pomatiopsid that has been recorded for the Palaeogene. The occurrence of Bacbotricula in northern Vietnam during this period of time suggests that the palaeo-Red River may have served as an early dispersal corridor for the Triculinae. The gastropods likely lived on deltaic plains in Lake Cao Bang and were preyed upon by cyprinid fishes.

Beschreibung: Males of Neptunea arthritica have been shown to mate preferentially with copulated females (CFs) over noncopulated females, which is unexpected due to the increased risk of sperm competition. To investigate how this preference for CFs affects the reproductive success of males, paternity was examined in the offspring of 13 females that had each copulated with three different males following male mate-choice trials. The paternity of each offspring was assigned to its most likely sire using polymorphic microsatellite markers. Males consistently chose CFs. During intromission in the females' second and third matings, live sperm cells were detected in the mucus exiting the female shell whereas no sperm were detected during the first matings. In the 13 analysed clutches, single paternity was found in seven clutches, dual paternity was found in three and triple paternity was found in three. These results suggest that males can achieve considerable reproductive success with a mated female through sperm removal.

Beschreibung: The Evolution Megalab database on the shell polymorphism of Cepaea nemoralis contains data on the majority of populations sampled over the last 100 years. Here, we use the database to examine geographical variation in the strength of the known relationship between morph frequencies and habitat. Unique pairs of samples from woodland and the nearest open habitat (hedges and grassland) are used to analyse the direction and magnitude of differences in morph frequencies. Shell colour shows stronger and more consistent variation with habitat than do banding patterns, yellow shells being at higher frequencies in open habitats than in woods. There is, however, marked geographical variation in this relationship, which is stronger in southern England and northern France than elsewhere. In some regions there is no evidence of any effect. Only in southern England are there significant associations between habitat and banding, with unbanded shells being at higher frequencies in woods than in open habitats. Within Great Britain a more refined analysis shows that the effects of habitat are evident mainly in areas of ancient countryside, in which many woods suitable for the species have existed for centuries. Less stable areas frequently exhibit ‘area effects’ in which variation does not relate to habitat. In a smaller set of pairs, such regional variation is not apparent in Germany. Earlier disputes about the role of drift and natural selection in determining patterns are in part a reflection of the region in which studies were carried out. The Megalab database does not cover all aspects of the polymorphism. In particular, band fusions are not recorded. The lack of evident effect in many regions does not demonstrate that there is none; more data and some knowledge of historical changes in habitats might reveal trends not apparent in this limited and conservative study.

Beschreibung: Although Planorbidae are one the most common and diverse families of pulmonates, their mating behaviour is known only for a few species. This paper describes mating behaviour and copulatory mechanics in four species of the Planorbidae: Anisus vortex (Linnaeus, 1758), Bathyomphalus contortus (Linnaeus, 1758), Choanomphalus riparius (Westerlund, 1865) and Planorbis planorbis (Linnaeus, 1758), and supplements previously published observations on two other species: Segmentina oelandica (Westerlund, 1885) and Planorbella (Seminolina) duryi (Wetherby, 1879). Patterns of musculature of the penial complex [in all species except P. (S.) duryi ] were studied using fluorescent phalloidin dye specific for actin filaments. Choanomphalus riparius , P. planorbis and S. oelandica were shown to mate by shell mounting and display an elaborate courtship behaviour accompanied by shell-circling. Planorbella (S.) duryi mates in a face-to-face position; in this species, courtship is accompanied by mechanical stimulation of the partner's plicae. Anisus vortex and B. contortus do not exhibit any distinct precopulatory behaviour and mate face-to-face. It is argued that Planorbidae show a relationship between gender expression (functional protandry vs simultaneous hermaphroditism) and mating behaviour (unilateral vs reciprocal mating). The taxonomic utility of the copulatory behaviour and penial musculature is discussed.

Beschreibung: Land snails usually exhibit cycles of activity and dormancy (aestivation or hibernation). The transition between these two states is accompanied by a range of behavioural and physiological responses to ensure their survival under adverse environmental conditions. Furthermore, aestivation plays an important role in shaping species' distribution patterns. We examined the seasonal patterns in biochemical tissue composition in relation to aspects of behavioural ecology in three land snail populations: one mainland and one insular population of the widespread Helix aspersa and a population (sympatric with the latter) of Helix figulina , a congeneric species with a narrow and declining distribution. Helix figulina aestivates in underground borrows, while H. aspersa spends the summer under stones and may interrupt aestivation when conditions become favourable. Prior to aestivation H. figulina accumulates metabolic fuels, which it consumes later during summer, and at the same time loses substantial body water and increases lactate dehydrogenase (LDH) activity. The insular H. aspersa population follows a similar pattern (regarding metabolites and LDH activity), with the difference that water loss is limited. However, the mainland population of H. aspersa deviates from this model with energy metabolites and water levels showing little variation throughout the year, while LDH activity is reduced. These differences probably reflect the particular behavioural and physiological patterns adopted by each species. The specialist and range-restricted H. figulina shows a constant and more predictable seasonal pattern, which may be effective for surviving in its historical biogeographic range, but it seems to be more vulnerable to possibly changing environmental conditions. On the other hand the generalist and cosmopolitan H. aspersa adopts a more flexible pattern that compensates for the effects of adverse conditions during aestivation and permits a more effective exploitation of energy resources.

Beschreibung: We explored the prey-size preference and drillhole-site selectivity in Euspira fortunei preying on Ruditapes philippinarum by means of laboratory experiments. Euspira fortunei was a size-selective predator and there was a positive correlation between predator and prey sizes. Our experiments and observations showed that prey-size limits in E. fortunei were determined by the size of its foot, which is the organ used for capturing and handling prey, as in other naticid species. Within the manipulation limits, attacks on relatively small or large prey were detected after prey of the preferred size classes became scarce. Our experiments also suggested that there was no size refuge for R. philippinarum (shell length range 0–35 mm) from attack by E. fortunei and that R. philippinarum of shell length range 10–25 mm were especially vulnerable to predation. These results imply that introduction of E. fortunei probably causes significant loss in R. philippinarum stocks. The sizes of E. fortunei individuals were significantly correlated with the diameters of the drillholes left on the shells of prey. Drillhole location was generally stereotypical in size-matched prey but anomalous drillhole placements commonly occurred in size-mismatched prey. Because E. fortunei captured prey using its foot and manipulated prey in a stereotypical manner, handling of size-mismatched prey was difficult and thus attacks on such prey tended to result in anomalous drillhole placements. Euspira fortunei did not make drillholes on the edges of bivalve prey when it competed for prey.

Beschreibung: In the marine gastropod Littorina saxatilis differences in relative shell apertural form between two ecotypes from NW Spain have been associated with an environmental cline related to the degree of wave exposure. Such differences have been claimed to have a strong genetic basis, with little influence of phenotypic plasticity. However, dietary changes are expected to affect the growth rate and, potentially, the shell shape, and could thus challenge the adaptive interpretation of the polymorphism. To address this issue we performed a laboratory experiment to grow one of these ecotypes under different food treatments with the aim of testing differences in shell growth. We then investigated the correlation of shell size and shape to quantify the impact of growth on shell aperture. Our results reveal significant dietary effects, an increase in growth rate leading to larger relative apertural size. However, this change occurs in the opposite direction to that expected from the differences between the two ecotypes in nature. This is in line with the low contribution of phenotypic plasticity to the polymorphism observed in previous studies.

Beschreibung: Knowledge of the regulation of molluscan reproductive systems is limited. Many studies have described how the development and maturation of molluscan gonads are regulated by oestrogen. Vertebrate-type oestrogen, 17β-oestradiol, has been detected in molluscs and its concentration in the gonads has been suggested to change in conjunction with reproductive cycles. However, it is unclear if molluscan gonadal tissues are relatively high in aromatase activities. Thais clavigera has been shown to possess a preferential expression of the oestrogen receptor gene in the ovary and ganglia, suggesting an association with gonadal maturation and expression of the oestrogen receptor gene. Therefore, it is interesting to explore the existence of vertebrate-type sex steroid hormones and aromatase activity in T. clavigera . We applied gas chromatography–mass spectrometry techniques to detect steroids in the gonadal tissues of T. clavigera and identified testosterone, androstenedione, 17β-oestradiol and oestrone. The aromatase activities converting androstenedione and testosterone into oestrone and 17β-oestradiol were much higher in gonads than in digestive glands. These data provide insights into the endocrinological system of neogastropods, prompting molecular evidence for the aromatase gene.

Beschreibung: Cephalaspid gastropod molluscs are increasingly being utilized in studies of tradeoffs associated with conflicts in simultaneous hermaphroditic reproduction. Chelidonura sandrana exhibits a wide range of colour forms, from black to yellow-spotted or marked with white. One of these colour morphs was described as Chelidonura tsurugensis Baba & Abe, 1959, while others have been accepted as natural variation within C. sandrana Rudman, 1973. Previous work has mostly assumed (1) that colour forms represent the same species and (2) that reproductive behaviour does not differ among colour forms. Mating behaviour between three co-occurring colour forms (simplified to ‘black’, ‘yellow’ and ‘white’) of the Chelidonura tsurugensis–sandrana species complex was investigated to test the above assumptions. Individuals of each colour form were crossed with individuals of the same form, and then with each of the two other colour forms, and with additional species as controls. Mating frequency, duration and an individual's role of sperm donor or receiver were recorded. The results show that there was no evidence for positive assortative mating with respect to colour form. Instead, at least one colour form was shown to mate significantly more often, and for longer, with individuals of colour forms other than its own. There was no evidence for trading of intromissions or intromission duration among colour forms. Although all three colour forms readily mate and behave like a single biological species, the questionable identity of C. tsurugensis prevents synonymization of C. sandrana with this species. Conservatively, we suggest that until a systematic revision of Chelidonura is carried out, the application of the name C. tsurugensis should be restricted to Japan, and elsewhere the yellow-spotted colour form should be referred to as C. sandrana .

Beschreibung: Some marine gastropod species are characterized by having marked polymorphism in the shape, colour and thickness of their shells. This variation can be induced by physical or biological factors such as wave exposure and predation. We examined shell variation in the direct-developing Acanthina monodon . In a field survey, we collected and analysed two snail ecotypes: a thick-shelled ecotype from environments with intense predation by the crab Homalaspis plana , and a thin-shelled ecotype from environments where predation was negligible. When we controlled for shell length, the thick-shelled ecotype had a heavier and thicker shell, but lower body weight, than the thin-shelled ecotype. However, only shell thickness and body weight showed a significant difference between habitat types. In order to determine the nature of shell variation in A. monodon , we conducted a laboratory experiment with juvenile snails from sites where the predation was low or absent. Seawater aquaria containing crabs were connected to aquaria containing snails via a cylinder with flows that enabled the transport of seawater from crabs to the snails' aquaria. The snails treated with seawater-borne stimuli (predation treatment) developed thicker shells than the snails raised in the absence of the stimulus (control treatment). We suggest that adaptive phenotypic plasticity may account for part of the shell variation surveyed in the field. We discuss the metabolic and reproductive costs of maintaining anti-predator defence strategies that involve adaptive morphological changes to a particular environment.

Beschreibung: The fauna of the volcanic island Malpelo located west of Colombia's Pacific coast includes only two species of land snails. One is a new endemic species of the subulinid genus Ischnocion , with which Rectobelus , Microbeliscus and Nannobeliscus are provisionally synonymized. Ischnocion conica new species differs from other species of the genus in the conical shell with radial palatal folds in juvenile stages. The other land snail species from Malpelo Island represents a new endemic thysanophorid genus. This genus, Malpelina (type species: Malpelina labiata new species), differs from other taxa of the Thysanophoridae in the yellowish-brown, depressed-globular shell with a distinctly thickened peristome, a broad glandular genital atrium, the lack of a vagina, a long penis, a long and exposed talon and the lack of entocones from all radular teeth. Malpelina is more closely related to Central American taxa than to thysanophorids from the Colombian mainland. Thus, it is more likely that Malpelo Island has been colonized by Malpelina from the north in accordance with palaeotectonic reconstructions. It is less clear whether Ischnocion reached Malpelo Island from Central or from South America, because the genus is distributed in both regions. Both species are patchily distributed on Malpelo and live under rocks in high densities. Their abundances increase towards higher altitudes. There is some segregation concerning the resting sites. Ischnocion conica rests on the soil or partially buried, while M. labiata almost always hangs from the underside of rocks.

Beschreibung: Ensis macha has a wide distribution along the Pacific and Atlantic southern coasts of South America. The pattern of morphological shell variation of this razor clam was analysed in 12 populations sampled along its whole Atlantic distribution, covering a latitudinal range of 3,700 km. The southernmost extant population of E. macha was recorded in the Beagle Channel. Variation in shell outline was assessed using elliptic Fourier analysis of adult individuals followed by different multivariate analyses. Significant shell-shape variation was found along the latitudinal range. Elliptical Fourier analysis revealed that trends in shell slenderness and curvature were associated mainly with salinity and water depth of the localities. Each locality presented a distinct shell shape, different from all other localities. Nevertheless, the populations could be grouped into four large assemblages between which a latitudinal gradient of shell shape was observed. Phenotypic divergence in shell shape is suggestive of population differentiation, but assessing the underlying processes is not straightforward because of the complex interaction between genetic and environmental factors. The possible evolutionary processes that mediate the effects of environmental variables and geographical distances on the shell-shape variation are discussed.

Beschreibung: Seasonal variations in oestradiol-17β and testosterone levels of the razor clam Sinonovacula constricta from the Yellow River delta in China were investigated in relation to the reproductive cycle from April 2007 to March 2008. Histological analysis indicated that gametogenesis began in June–July when water temperature was 22.0–27.0°C and ended during September–October when food was abundant. Oestradiol-17β and testosterone concentrations were determined by enzyme-linked immunosorbent assay in the gonad of S. constricta . Oestradiol-17β concentration in the female gonads was higher than that in the male gonads, while testosterone concentration in the male gonads was higher than that in the female gonads during sexual maturation. A positive correlation between oestradiol-17β and mean oocyte diameter was observed during the study period ( r = 0.664, P 〈 0.05), indicating that oestradiol-17β may play an important role in regulating vitellogenesis. Oestradiol-17β and testosterone increased during sexual maturation in females and males, respectively, and then decreased markedly after spawning. These findings indicated that the fluctuations in the levels of both steroids were closely related to the reproductive cycle, thus oestradiol-17β and testosterone could have a role as endogenous modulators in sex determination, development and maturation of S. constricta .

Beschreibung: Quaternary climatic fluctuations had major impacts on species’ distributions over the last 2.5 Myr. Expansions and contractions of the polar ice caps throughout glacial cycles strongly affected terrestrial fauna and flora whereas eustatic sea level variations had major consequences on rocky-shore communities. The effect of these glacial episodes on marine organisms inhabiting oceanic islands is still poorly understood. We analysed the genetic structure of the marine mussel Brachidontes puniceus from the Cape Verde Islands using mitochondrial sequence data. The apparent absence of physical oceanographic barriers or ecological filters in the geographical range of B. puniceus is reflected in the lack of genetic structure found among populations from the entire archipelago. Larval dispersal in B. puniceus likely played a critical role in the demographic connectivity of populations across the Cape Verde archipelago. Results from demographic analysis were consistent with a population expansion promoted by an increase in the habitat available for larval settlement resulting from a low sea-level stand during the last glacial maximum.

Beschreibung: Linkage between cold hardiness and desiccation tolerance was examined in an invasive freshwater apple snail, Pomacea canaliculata , collected from locations in three different climatic zones. Snails collected from temperate Kyushu, Japan, showed enhanced cold hardiness after cold acclimation, and cold-tolerant snails survived longer after exposure to desiccation than cold-intolerant snails without cold acclimation. Progenies of tropical snails collected from Luzon and Mindanao, the Philippines, which had never experienced cold weather revealed the same response as Japanese snails to cold stress: enhancement of cold hardiness after cold acclimation. Cold-tolerant snails from tropical populations also attained better survivorship under desiccation conditions. Thus, linkage of tolerance between cold weather and desiccation appears to be a general feature of P. canaliculata . Cold hardiness of snails before and after cold acclimation, respectively, did not differ among the three populations from temperate and tropical regions. A trend was found for snails from Mindanao, in the tropical rainforest climatic zone (having a milder dry season), to be less desiccation-tolerant than snails from Kyushu and Luzon, having a colder or more severe dry season.

Beschreibung: This study investigated the growth rate of Limnoperna fortunei postlarvae on experimental frames over the course of a year, to evaluate the effects of physicochemical environmental factors on their growth in a reservoir, Lake Ohshio, Gunma, Japan. The median shell size of L. fortunei slightly increased in the autumn after recruitment, exhibited little growth in winter and then greatly increased in summer. Water temperature was positively correlated with growth rate of L. fortunei . However, we found no correlation between the growth rate and dissolved oxygen, chlorophyll a or turbidity. The settlement pattern of L. fortunei was also investigated during the course of a year. Second-year recruit density was much higher than for first-year recruits.

Beschreibung: Understanding factors that determine the fitness of invasive species may help us predict their spread and impact. Previous studies of the survival, growth and reproduction of Pomacea canaliculata , a freshwater apple snail native to South America now widely spread in Asia, North America and Hawaii, have emphasized the use of fresh leaves as food. We compared the consumption and growth of P. canaliculata reared on fresh and decaying leaves of three species of macrophytes with contrasting content of phenolics (general plant defence chemicals) and nutrients. We conducted 1-day consumption assays using adult snails and a 1-month survival and growth experiment using snails of various sizes. Our results showed that the consumption, survival and growth of P. canaliculata were determined by plant nutrients and phenolics, rather than plant freshness. For Murdannia nudiflora , a species with low phenolic content, fresh leaves with high nitrogen content were more palatable and valuable for growth than decaying leaves with low nitrogen content. Survival was high and not different between the fresh and decaying leaf treatments. For Myriophyllum aquaticum , decaying leaves with moderate nitrogen and low phenolic contents were more palatable and valuable for snail survival and growth than fresh leaves with high nitrogen and high phenolic contents. For Polygonum barbatum , a species with low nitrogen and medium phenolic contents, both fresh and decaying leaves were unpalatable, resulted in low snail survivorship, and did not support snail growth. The results thus indicate that P. canaliculata can utilize both fresh and decaying leaves of adequate levels of nutrients and low levels of phenolics. This dietary flexibility may have contributed to its successful colonization of many types of freshwater wetlands in regions where high-quality fresh leaves are not available throughout the year.

Beschreibung: A histochemical and ultrastructural study of the crop and oesophagus was carried out for the first time in Aglajidae. In Philinopsis depicta , the hind region of the crop contains two large folds creating a channel between them, lined by a ciliated epithelium. This ciliated groove continues through the posterior oesophagus. In addition to these larger folds, both crop and posterior oesophagus present many smaller longitudinal ridges lined by a nonciliated epithelium formed by cells bearing microvilli embedded in a layer of extracellular material. Lysosomes and mitochondria are common in the supranuclear region of these cells, and in the basal region hemidesmosomes are frequent. Epithelial secretory cells contain many large vesicles with a low electron-density content rich in acid polysaccharides, but without detectable amounts of protein. The basal region of the secretory cells comprises the nucleus and several Golgi stacks formed by many flat cisternae with low electron-density content. Secretory cells were not observed in the ciliated epithelium of the channel between the two large folds. The connective tissue of the crop and posterior oesophagus contains many large vacuolar cells with a thin layer of cytoplasm around the single vacuole that occupies about 90% or more of the cell volume. Tubular invaginations of the cell membrane are frequent in these cells and some also contain large vesicles that can open to the central vacuole, suggesting an intense transport activity across the cytoplasm. These vacuolar cells could be related to the calcium cells reported in the connective tissue of other gastropods. Ultrastructural and histochemical studies of the organs of the digestive system in carnivorous and herbivorous cephalaspideans can lead to the discovery of important unknown features, like the vacuolar cells, which might be useful to establish correlations with molecular phylogenetic data or food sources.

Beschreibung: Forming a small group of mainly marine meiofaunal slugs, the Acochlidia have recently been separated from the traditional opisthobranch gastropods and placed within a mixed clade of pulmonates, Sacoglossa and Pyramidelloidea on the basis of molecular data. In the light of this new phylogenetic framework, we examined several populations of a comparatively giant Strubellia (Acochlidiidae s. l. ) found in rivers of the Solomon Islands and Vanuatu, combining microanatomical and molecular methods (interactive three-dimensional models are given in the online version). Novel features include an extended set of nerves, a ‘cephalic gland’ of unknown function and an osphradium, all detected here for the first time in Acochlidia. The protandric genital system is characterized by three receptacles in the male phase, a possibly secondary open seminal groove and a complete reduction of the elaborate cephalic copulatory apparatus during ontogeny. Combined evidence from copulatory features and DNA sequences indicate a specific separation between the type species S. paradoxa (Strubell, 1892) from Ambon and the eastern Melanesian Strubellia wawrai n. sp. Live observations show the species to feed on the highly mineralized egg capsules of limnic Neritidae using a special piercing radula. Limnic Pacific acochlidians are suggested to be amphidromic, as are their prey organisms. A unique type of adhesive larva, observed in an Acochlidium species, indicates a possible dispersive stage in Acochlidiidae. Molecular phylogeny confirms the morphology-based placement of Strubellia as sister taxon to other Acochlidiidae.

Beschreibung: Despite the long history of meiofaunal research in Europe our knowledge of its Acochlidia—the most diverse, abundant and widespread group of interstitial slugs—is still fragmentary. Distribution ranges and modes of dispersal are unknown and taxonomic hypotheses based on traditional light-microscopical examination have never been tested against a modern integrative approach combining microanatomical techniques with molecular analyses. This study redescribes Microhedyle glandulifera (Kowalevsky, 1901), a key species for microhedylid taxonomy and focus of taxonomic disorder. Three-dimensional reconstructions from histological semithin serial sections reveal several previously unknown characters, in particular concerning the nervous system (e.g. presence of gastro-oesophageal ganglia). There are no jaws, but a ‘cuticular element’ is attached anteriorly to the radula cushion. Scanning electron microscopic examination shows a radula with the formula 34–38 x 1.1.1. Microhedyle glandulifera can be distinguished from other Microhedylidae by a combination of external and radular features, and the unique presence of triaxonic spicules. Population genetic analyses based on mitochondrial markers support M. glandulifera as a widespread European species known to range from the North Sea to the Sea of Marmara (eastern Mediterranean). Accordingly, northern Atlantic ‘ M. lactea ’ and Mediterranean ‘ M. glomerans ’ are confirmed as junior synonyms of M. glandulifera . Molecular data indicate a recent radiation of M. glandulifera in European waters and potential means of dispersal in meiofaunal slugs with low reproductive output and no pelagic larval stages are discussed. Based on our molecular phylogeny and revision of distinguishing morphological characters, four valid Microhedylidae species occur in European waters: Pontohedyle milaschewitchii , Parhedyle tyrtowii , Parhedyle cryptophthalma and Microhedyle glandulifera . Morphological and molecular evidence indicate that Microhedyle odhneri is a member of the genus Parhedyle , and possibly a junior synonym of Parhedyle tyrtowii .

Beschreibung: The amphibious ‘bug-eating slug’ Aiteng ater Swennen & Buatip, 2009 shows a worm-like, compact body shape lacking any cephalic tentacles or body processes. Anatomically it has been described as showing an unusual mix of sacoglossan and acochlidian characters, thus the systematic affinities are uncertain. The species is redescribed here with an integrative microanatomical and molecular approach. All major organ systems were three-dimensionally reconstructed from serial histological sections using AMIRA software. Aiteng ater has a prepharyngeal nerve ring with separate cerebral and pleural ganglia rather than cerebro-pleural ganglia, and no sacoglossan-like ascus is detectable histologically. The radula is triseriate rather than uniseriate, showing one lateral tooth on each side of the rhachidian tooth. A well-developed two-chambered heart is present. The vas deferens in A. ater splits off distal to the female glands. The intestine is short and opens into a small mantle cavity. Long cavities in the connective tissue are remains of dissolved calcareous spicules. Only a few characters thus remain to support a closer relationship of A. ater to Sacoglossa, i.e. the Gascoignella -like body shape lacking cephalic tentacles, the presence of an elysiid-like system of dorsal vessels, and an albumen gland consisting of follicles. Additionally we describe in microanatomical detail an equally small and vermiform new aitengid species from Japan. Aiteng mysticus n. sp. differs from A. ater in habitat, body size and colour, central nervous system and presence of a kidney. Both aitengid species resemble acochlidians in the retractibility of the head, by possessing calcareous spicules, a prepharyngeal nerve ring with separated cerebral and pleural ganglia, a triseriate radula with an ascending and descending limb, but without sacoglossan-like ascus, and a special diaulic reproductive system. The prominent rhachidian tooth of Aitengidae, which is used to pierce insects and pupae in A. ater , and the large, laterally situated eyes closely resemble the anatomy of members of the limnic Acochlidiidae. The acochlidian nature of Aiteng is strongly indicated by our molecular analysis, in which it forms a basal hedylopsacean offshoot or the sister clade to limnic Acochlidiidae and brackish or marine Pseudunelidae within Hedylopsacea. Such a topology would, however, imply that Aitengidae have lost the most characteristic acochlidian apomorphy, the subdivision of the body into a headfoot complex and a free, elongated visceral hump. Also, the absence of cephalic tentacles gives the Aitengidae an appearance that is very different to other, strictly aquatic Acochlidia. Differences of the external morphology and the internal anatomy are discussed in the light of a habitat shift of Aitengidae within the Acochlidia.

Beschreibung: The turbellarian-like, radula-lacking Rhodope has been a mystery to taxonomists for over 160 years and was considered a specialized off-shoot of either opisthobranch or pulmonate Euthyneura. Occasionally reported from intertidal waters and sand habitats from all continents, most species of these minute slugs are poorly known and characterized mainly by differences in pigmentation. To understand the evolution of heterobranch microslugs, we established a morphological dataset for Rhodope by describing a new species found in the temperate waters of southern Australia. To set a standard for rhodopids, all major organ systems of R. rousei n. sp. are reconstructed three-dimensionally from series of semithin sections using the software Amira. Microanatomy confirms the loss of many general gastropod features such as foot, cephalic tentacles, shell, radula, mantle cavity, gill and heart. Excretory and digestive systems are heavily modified, with free rhogocytes in the presumed position of the heart, and a secondary buccal bulb replacing the function of the vestigial pharynx. Structural details of the monaulic but hermaphroditic genital system suggest cutaneous fertilization via spermatophores formed in specialized glands. The highly concentrated central nervous system is compared to those of other species of the genus and targets of all detectable nerves are summarized. These characters are compared with adaptations shown by other interstitial gastropods.

Beschreibung: The endangered patellid limpet Patella ferruginea is a protandrous species endemic to the Mediterranean. Previous studies have shown that sex change occurs in the species when individuals reach a range of 4–6 cm shell length. In our study individuals were sexed and population structure, mean density, mean shell length and sex ratio determined for seven populations in Ceuta (North Africa, Strait of Gibraltar). Our results indicate that sex change appears to occur at smaller sizes when large individuals (presumably females) are rare. All of the populations had a male-biased sex ratio. The greatest differences between the number of males and females were recorded in those populations that had the largest females and the greatest densities of large individuals, suggesting that a shortage of this fraction of the population would affect the proportion of sex-changing individuals. The fact that P. ferruginea may exhibit environmentally mediated sex change could influence population management decisions.

Beschreibung: Terrestrial gastropods are both herbivores and detritivores, but the ratio between these two modes of feeding can be highly variable over time. While previous studies have examined long-term seasonal patterns in the consumption of fresh material, mechanisms explaining short-term variation in dietary preferences have not been explored. We used faecal analysis to determine how short-term variation in weather affects the ratio of herbivory to detritivory in the land snail Cepaea nemoralis . Averaged across sampling dates, c. 9% of the faeces were composed of fresh plant material, with the remainder consisting of plant litter and soil. Temperature, relative humidity and soil moisture did not affect the proportional consumption of fresh material; however, snails consumed more soil with increasing temperature. If there had not been a recent precipitation event, the mean proportion of fresh material in the faeces more than doubled on average; however, this increase only occurred in areas of low herbaceous cover. Our results suggest that an increased proportion of snails consume fresh material during dry periods to compensate for water losses. Moreover, our study highlights that studies of dietary composition in the field need to account for short-term variation in feeding preferences caused by weather.

Beschreibung: Large-scale patterns of encapsulated embryo development and causal factors determining developmental success in the marine environment have been relevant issues of research for decades. We studied the embryonic development and intracapsular oxygen availability of Trophon geversianus in egg capsules from northern Patagonia (Golfo Nuevo, Argentina). The intracapsular embryonic development had a mean duration of 112 days (at 12–14°C). The initial number of eggs per capsule was 197 (mean diameter 270 µm), but on average only four embryos per capsule reached the juvenile stage. Embryos fed on nurse eggs (which disintegrated spontaneously 48 h after oviposition). The sequence of intracapsular developmental stages was recorded from egg to hatching occurred at the crawling stage (mean shell length 2.8 mm). Maximum growth rate was observed at the ‘veliger’ stage, while nurse eggs were consumed. A decrease in embryo number was observed between prehatching and hatching. Cannibalism was recorded in an egg capsule containing a prehatching embryo, which showed signs of shell drilling by the accessory boring organ. Intracapsular oxygen availability decreased from 90% during the cleavage stage to 45% of air saturation in the final stages of development (at 13°C). Abnormal embryos were recognized in egg capsules, probably associated with food competition or oxygen limitation.

Beschreibung: The superfamily Conoidea constitutes one of the most diverse and taxonomically challenging groups among marine molluscs. Classifications based on shell or radular characters are highly contradictory and disputed. Whereas the monophyly of the Conidae and Terebridae has not been challenged, the other constituents of the superfamily are placed in a ‘trash’ group, the turrids, the non-monophyly of which has been demonstrated by anatomical and molecular evidence. We present here a new molecular phylogeny based on a total of 102 conoidean genera (87 ‘turrids’, 5 cones and 10 terebrids) and three mitochondrial genes [cytochrome oxidase I (COI), 12S rRNA and 16S rRNA]. The resulting tree recognizes 14 clades. When the Conidae ( Conus s.l .) and Terebridae are ranked as families for consistency of usage, the ‘turrids’ must be split into 12 families of comparable rank. A new genus-level classification of the Conoidea is published in an accompanying paper.

Beschreibung: Using an approach based on molecular, reproductive and morphological characters, four independent evolutionary lineages represented by the following species were identified in Tunisia: Unio ravoisieri Deshayes, U. gibbus Spengler, U. durieui Deshayes and Potomida littoralis (Cuvier). The species U. ravoisieri and U. durieui are redescribed, including details of their distribution, biology and glochidium morphology. The puzzling distribution of the former (Algeria, Tunisia and two localities in Northeast Spain) could reflect introduction or natural dispersal. In Tunisia, the release of the glochidia of U. ravoisieri starts in March, but in Spain this is delayed until August or September. The entire interlamellar space of the outer demibranchs acts as a marsupium (ectobranchy). Glochidia are rounded-triangular, globose, and either hooked or hookless. Unio durieui is distributed across Algeria and Tunisia, where it releases glochidia in December and in March. Glochidia are always hooked, but the elaboration of the hook is variable. The molecular phylogenetic analysis supports two clusters within Unio , each including both European and North African species. Strong bootstrap support was obtained for the two clades within U. ravoisieri , of which one includes specimens from the Iberian Peninsula as well as Tunisia. Unio durieui appeared as the sister species of U. gibbus . The Tunisian populations of P. littoralis were not segregated from those in Europe, and U. fellmanni should be considered a synonym.

Beschreibung: Larval developmental strategy is a key life-history trait governing many aspects of the ecology and evolution of marine invertebrates. We compared developmental strategies of two geminate, or sister, species of mud snails (Potamididae) on either side of the Isthmus of Panama, Cerithideopsis californica on the Pacific and C. pliculosa on the Atlantic coast. We found that these snails, separated by the rise of the Isthmus about 3 Ma, had different reproductive strategies. Larvae of C. californica hatched as small swimming veligers, whereas larvae of C. pliculosa hatched as large swimming–crawling veligers. Additionally, the larval duration of C. pliculosa was about 1 week shorter than that of C. californica under controlled laboratory conditions. This pattern of larval development is consistent with models of life-history evolution in which larger propagules are selected in low-productivity environments (in this case, the Atlantic) and smaller ones are favoured in highly productive environments (the Pacific).

Beschreibung: The dark falsemussel Mytilopsis leucophaeata (Conrad, 1831) (Dreissenidae) is an uncommon epifaunal bivalve of oligohaline–mesohaline habitats in Chesapeake Bay. It is small and weakly attached to different substrates by its byssi, but is presumably somewhat protected from predators by its habit of living within byssate clumps of hooked mussels Ischadium recurvum (Rafinesque, 1820) attached to eastern oysters Crassostrea virginica (Gmelin, 1791). It is less active than I. recurvum in terms of crawling from under encumbrances or moving and reattaching when detached from a substrate. Its extensible inhalant siphon should enable it to obtain food and oxygen from the water column even when confined within I. recurvum clumps or its own single-species clumps. In terms of egg size and the timing of larval development, it shares a number of characteristics with the freshwater dreissenids Dreissena polymorpha and D. rostriformis bugensis and with I. recurvum . Given the limited numbers of M. leucophaeata that seem to be the rule in its native habitat, there are questions, so far unanswered, as to how the population persists, how its spawning is coordinated and how successful is fertilization when widely separated individuals do spawn.

Beschreibung: Mediterranean land snails such as Xeropicta derbentina (Hygromiidae) and Theba pisana (Helicidae) are known for their remarkable tolerance to elevated temperatures and desiccation, yet the biochemical and cellular mechanisms underlying this tolerance are relatively unknown. We investigated the effects of increased temperatures and the ability of these snail species to recover from heat stress, examining the condition and amount of different types of hepatopancreatic cells (histopathology) and heat-shock protein 70 (stress protein) levels. Snails were exposed to defined control and increased temperatures and allowed a postheat phase for possible recovery. Results indicate the ability of X. derbentina to recover from natural and experimental temperature stress to some extent within the set time, whereas no such ability was found in T. pisana. Xeropicta derbentina is more heat-tolerant in general and less affected by heat stress than T. pisana . This is probably due to its greater ability to increase size and number of hepatopancreatic calcium cells that are essential for osmoregulation. The hypertrophy and hyperplasia of calcium cells can be regarded as a general response of molluscs to osmotic stressors, e.g. heat, as long as the organism is not overwhelmed by the stressor. Additionally, it can be assumed that the robust stress-protein system of X. derbentina plays a crucial role in this species’ high thermotolerance.

Beschreibung: Cryptochiton stelleri is the largest herbivore in the intertidal and subtidal zone throughout its North Pacific range, but its larval development and metamorphosis have not been well documented. A description of larval development for specimens in Hokkaido, Japan, has been used in multiple textbooks yet shows many features atypical of chiton development. In the present study in Oregon, C. stelleri larvae were raised in culture and displayed developmental stages similar to other chitons, very different from the previous description. Plate development began 3 days after hatching. Larvae were competent beginning 3 days posthatching and metamorphosed in response to extract from encrusting coralline algae. Larvae survived for over a month without metamorphosing and did not metamorphose in response to increased temperature, presence of adults or the addition of algal foods of adults or juveniles. Juvenile C. stelleri were discovered in the field and grew c. 4 mm per month in captivity. Juveniles had exposed shell plates and fed on the red alga Cryptopleura .

Beschreibung: Nudibranch molluscs of the genus Corambe differ from most other Doridoidea by having ventral rather than dorsal anus and gills. Because of these and other features, such as separate cerebral and pleural ganglia, corambids have been considered as an archaic or enigmatic group. The first tropical eastern Pacific Corambe species is described in morphological and some histological detail. Selected organs such as circulatory and central nervous features are reconstructed from serial semithin histological slides and visualized in three dimensions using Amira software. Anatomical findings include two separate ganglia on the visceral loop and an additional ganglion on the right side of the body that is connected to the pedal ganglion. Corambe mancorensis n. sp. is dorsoventrally depressed, has an oval, fleshy notum covered with a cuticle, and has a wide posterior medial notch that can be closed completely by unique lobules. Gills are arranged in an unusual horseshoe-like manner including both phanerobranch anal (=medial) gills and corambid lateroventral gill rows, and are connected to the atrium by a complex vessel system. The three medial gills arise from a posterodorsal gill cavity within the notal notch, similar to the case in Corambe evelinae Marcus, 1958. By scanning electron microscopy a vestigial gill cavity is also detectable in C. pacifica MacFarland & O'Donoghue, 1929, but here it is situated ventrally. Our new information on adult corambids is compared with new and published ontogenetic data on phanerobranch and cryptobranch dorids, to contribute to a novel interpretation of the ontogeny of dorid mantle and gill complexes. The progenetic evolution of corambids ‘recapitulates’ early juvenile dorid stages – turning Haeckel's Law upside down.

Beschreibung: Nearly 13% of opisthobranch gastropods in the Atlantic Ocean are regarded as amphi-Atlantic (i.e. species occurring on both eastern and western coastlines of the Atlantic realm). This assumption has been broadly based on morpho-anatomical similarities and has rarely been tested within a molecular phylogenetic framework. Among opisthobranchs, the order Sacoglossa is renowned for its difficult and confusing species taxonomy, particularly in some genera like Elysia , where several cases of cryptic speciation have been documented. Moreover, the width of the Atlantic realm poses a serious challenge to the idea of trans-Atlantic dispersal, particularly in nonplanktotrophic species. The species Bosellia mimetica , Elysia timida and Thuridilla picta are three sacoglossan opisthobranchs with amphi-Atlantic status, but doubts have been raised about the conspecificity of eastern and western populations. Here we used methods to test molecular phylogenetic whether the Atlantic Ocean constitutes a barrier for dispersal and hence whether eastern and western populations belong to the same species. We used the criteria of divergence and reciprocal monophyly, supported by concordant genealogically independent genetic markers, to define species. Maximum-likelihood and Bayesian analyses of partial DNA sequences of the mitochondrial cytochrome c oxidase subunit I and 16S rRNA genes and nuclear gene Histone-3 (H3) were used to produce phylogenetic trees. We conclude that the eastern Atlantic species B. mimetica is not amphi-Atlantic, although the H3 gene did not recover reciprocal monophyly between western and eastern populations, perhaps in a result of incomplete lineage-sorting. Elysia timida is the only species showing an amphi-Atlantic distribution, but possibly due to recent introduction in the tropical western Atlantic. Thuridilla picta is restricted to the western Atlantic and therefore not amphi-Atlantic. Populations of ‘ T. picta ’ inhabiting the Macaronesian archipelagos of Azores and Madeira are a colour form of the eastern Atlantic T. hopei . Our results highlight the difficulty surrounding systematics of Sacoglossa sea slugs and provide further evidence that cryptic speciation is common in the group.

Beschreibung: Most aquatic snails derive their energy by grazing periphyton. However, certain species, including the invasive island apple snail, Pomacea insularum , readily consume aquatic macrophytes. These snails often overlap in their distribution with other exotic, invasive plants. We sought to discover if juvenile P. insularum could survive and grow when fed only three reportedly less palatable food sources: Eurasian watermilfoil ( Myriophyllum spicatum ), wild taro ( Colocasia esculenta ) and water hyacinth ( Eichhornia crassipes ). Snails received nonrooted macrophytes simultaneously in a multiple-resource experiment. Using enclosures with compartments that separated plants but allowed snails full access, we housed individual early (10.7 ± 0.9 mm operculum width; 0.56–1.11 g blotted wet weight; mean ± 1 SD) or late (23 ± 2 mm; 4.60–14.82 g) juvenile P. insularum. We monitored snail survival and growth for 6 weeks. As controls, we placed standardized nonrooted macrophytes in enclosures without snails for 1 week. Replacing plants weekly, we calculated average daily consumption rates. Both size classes of snails grew substantially in terms of operculum width, shell height and blotted wet weight, with early juveniles exhibiting relatively larger gains in size over the 6-week period. No mortality occurred. Both size classes consumed significantly more watermilfoil than taro and more taro than water hyacinth. Collectively, these results translate into the potential for one single 10-g P. insularum (i.e. representative of the larger snails used in our experiment) to consume a combined 0.35 g of dried plant matter (or c. 3.5 g) of live macrophytes per day. Our study suggests that available resources offered by a community of exotic invasive plants may sustain snail survival.

Beschreibung: With the advent of molecular phylogenetics, the systematics and taxonomy of Patellogastropoda have been greatly improved. Eight families and 36 genera are currently recognized in the order. We review recent published papers that have used molecular data, discuss the resulting advances in systematics and evolution of Patellogastropoda and suggest directions of future research.

Beschreibung: The minute snail Pupilla alpicola (Stylommatophora: Pupillidae) is known as a threatened glacial relict restricted to treeless calcareous fens with Holocene continuity, mainly in the Alpine and Carpathian regions. We summarize all available data on the distribution of P. alpicola and analyse its ecological requirements in the Western Carpathians both at a larger, regional scale (162 sites) and at a smaller, within-site scale (10 sites). Viable populations of Pupilla alpicola occurred in 31 sites out of the 162 fens studied. Water conductivity, Ellenberg's indicator values for soil reaction, light and nutrients were the main ecological variables that explained these occurrences. The species preferred sites with extremely high calcium carbonate precipitation, low nutrients and sparse herb vegetation cover. Its present distribution in the Western Carpathians is strongly related to a spatial–temporal continuum of calcareous fens throughout the Holocene; none of the modern populations was located further than 40 km from the known palaeorefugium. Direct fossil evidence shows that these palaeorefugial fens have persisted since the Pleistocene/Holocene transition. A conservation strategy for this rare species needs to take account of both historical continuity and the maintenance of appropriate ecological conditions.

Beschreibung: The freshwater gastropod genus Cincinnatia (Hydrobiidae: Nymphophilinae) contains a single species, C. integra (Say, 1821), which is distributed across much of eastern North America from the Great Lakes region to the Texas Gulf Coastal Plain. Here we use morphological and molecular evidence to evaluate the taxonomic status of a Cincinnatia population that was recently discovered in an upper reach of the Rio Panuco basin (northeastern Mexico) c. 700 km distant from its most closely proximal congeners. The Panuco basin population cannot be consistently differentiated from C. integra by its shells, although it differs from previously reported material of this species in several details of reproductive anatomy. The Panuco basin population differs from specimens from the type locality area and five other populations of C. integra by 1.5–2.6% mtCOI sequence divergence, but was no more differentiated than most of the other populations and was not consistently resolved as a monophyletic subunit of Cincinnatia using these molecular data. Based on this evidence we treat this population as belonging to C. integra pending a more comprehensive study of morphological and genetic variation across the broad geographic range of this species. This new record represents a large range extension not only for Cincinnatia , but also for the entire North American nymphophiline radiation, whose previously recorded southern limit was the Cuatro Ciénegas basin in Coahuila.

Beschreibung: The effects of climate on abundance depend on local environments. A predicted interaction was tested in the land snail Theba pisana , in contrasting habitats of dense Acacia thickets and adjacent areas of low open vegetation, in introduced populations in Western Australia. The snails aestivate on vegetation over summer and mortality is higher in the Open habitat than in the Acacia. Growth experiments in winter showed that this advantage of the Acacia habitat in summer is countered by more rapid growth and higher survival of juvenile snails in the Open habitat. Thirty-four successive annual censuses of adult and subadult T. pisana were analysed, to test (1) the prediction that harsher summers would reduce abundance in the Open habitat, with less impact in the sheltered Acacia, and (2) the relative importance of summer (survival during aestivation) and winter (reproduction and growth) for abundance. As predicted, abundance in the Open habitat was lower following hotter, drier and sunnier summers. More surprising, abundance in the Acacia habitat showed the reverse association. Correlations with individual weather variables indicate that, while summer temperature and sunshine are important in the Open habitat, low summer rainfall, rather than high temperatures, is associated with higher abundance in the Acacia habitat. Winter conditions do not predict subsequent abundance of adults in either habitat, indicating the greater importance of summer mortality in determining abundance, but in different ways in the two habitats. This contrast is an example of the importance of considering specific habitats in the search for effects of changing climate on abundance.

Beschreibung: A new genus-level classification of the Conoidea is presented, based on the molecular phylogeny of Puillandre et al. in the accompanying paper. Fifteen lineages are recognized and ranked as families to facilitate continuity in the treatment of the names Conidae (for ‘cones’) and Terebridae in their traditional usage. The hitherto polyphyletic ‘Turridae’ is now resolved as 13 monophyletic families, in which the 358 currently recognized genera and subgenera are placed, or tentatively allocated: Conorbidae (2 (sub)genera), Borsoniidae (34), Clathurellidae (21), Mitromorphidae (8), Mangeliidae (60), Raphitomidae (71), Cochlespiridae (9), Drilliidae (34), Pseudomelatomidae (=Crassispiridae) (59), Clavatulidae (14), Horaiclavidae new family (28), Turridae s. s. (16) and Strictispiridae (2). A diagnosis with description of the shell and radulae is provided for each of these families.

Beschreibung: Saxitoxin (STX) is one of the main phycotoxins that contribute to paralytic shellfish poisoning (PSP). This toxin is mainly produced by marine microalgae of the genus Alexandrium . There is evidence of changes at the physiological level in bivalves exposed to STX, although transcriptional responses to STX in bivalves have not yet been studied. The present work evaluates the expression of 13 candidate genes associated with cellular stress and immune response in Mytilus chilensis exposed to STX. Analysis by qPCR showed higher gene transcription levels in M. chilensis injected with STX than in control mussels. High levels of differential gene expression were observed for superoxide dismutase, catalase, ferritin and heat-shock protein genes. To a lesser extent, ependymin, fibrinogen-like, galectin and mytilin B genes were also significantly more expressed in haemocytes of mussels injected with STX that in control mussels. Our results provide insights into how marine toxins could modulate the innate immune system of marine invertebrates.

Beschreibung: Gravireception in gastropods occurs by the displacement of statoparticles (multiple statoconia or a single statolith) inside statocysts, resulting from changes in the animal's position. An easy method for extraction and processing of statoliths is given and their morphology and microstructure described in 12 species of caenogastropods collected on the NW Portuguese coast, belonging to eight different families. In addition, statolith growth was studied in two species, Nucella lapillus and Nassarius reticulatus . The relation between statolith diameter (StD) and shell height (SH) follows logistic curves [in N. lapillus SH = 34.98/(1 + 190.817 –49.082 StD ), P 〈 0.001; and in N. reticulatus SH = 31.03/(1 + 116.709 –36.577 StD ), P 〈 0.001]. All statoliths observed are hard and translucent, with several concentric layers delimited by well-marked growth rings. Recently, some studies have shown that these rings are annual and can be used to determine the age of some gastropods and we show that this applies in a wider range of caenogastropods. Statolith rings were clearer in species collected offshore ( Aporrhais pespelecani , Ranella olearium , Charonia lampas and N. reticulatus ), because additional disturbance rings were more often present in statoliths from inshore species ( Crepidula fornicata , Littorina littorea , Peringia ulvae , Trivia monacha , N. reticulatus , Nassarius incrassatus , N. lapillus , Ocenebra erinaceus and Ocinebrina aciculata ). Statoliths thus have potential for sclerochronology and may provide an important record of the physical and chemical characteristics of the marine environment throughout ontogeny.

Beschreibung: Light reflecting structures (iridophores) were examined in live Doryteuthis gahi with mantle lengths (ML) between 50 and 420 mm, both during trawl surveys onboard ship and in shallow-water spawning grounds (10–15 m depth) by SCUBA divers around the Falkland Islands. Several types of iridophores were distinguished based on their shape, colour reflection and position on the body. Ventrally, silvery iridophores cover pigmented organs such as the eyeballs and ink sac and might be used for countershading the squid body. Pink iridophores (splotches) cover the whole mantle, head, fins and arm bases. Green-red iridophores on the dorsal side of the eyeballs, as well as pink splotches on the dorsal and lateral mantle, head and arm bases can be either uncovered or masked by overlaying chromatophores. Two specific bright green stripes of iridophores develop under the fins only in females with ML 〉80 mm; these may be involved with distant sex recognition, both in forming unisex schools and in ‘preliminary mating’ in the twilight feeding grounds located at the shelf edge. During solitary egg laying in shallow waters, females mask these green stripes almost completely using the overlying chromatophores.

Beschreibung: From 2003 to 2008, research on spatial and temporal dynamics of Corbicula fluminea was conducted at 10 sites along the Mondego Estuary (Portugal). A clear spatial and temporal variation in terms of density and biomass was observed, the highest values being found in the upstream oligohaline site, especially in warmer seasons. Seasonal density ranged from 4 to 11 500 individuals m –2 . Biomass ranged from 0.01 to 323 g ash-free dry weight m –2 . Comparing the results collected in the Mondego Estuary with other European and American invaded ecosystems, the density values are extremely high, but the biomass is lower than some of the reported values. This can be explained by the dominance of very small animals in the Mondego Estuary. Furthermore, the stepwise multiple regression model combining environmental variables and biomass of C. fluminea predicted that the areas with higher values of temperature and phosphate, together with lower values of salinity, water flow and silt and clay, support higher biomass. In 2005, a large reduction in density was recorded and was related to the massive mortality of small individuals as a consequence of the severe drought that occurred in the Mondego Estuary.

Beschreibung: Diets of most snail species are unstudied, but the diets of non-native snails are of special interest because these species may be pests or compete with native species. We tested whether the apparent leaf-litter diet of a colony of the non-native land snail Patera appressa from a plant nursery was adequate to support growth, and whether growth rate could be altered by changing diet. Growth was tested in two laboratory experiments using combinations of leaf litter and live plant matter (romaine lettuce). In the first experiment, snails were given a diet of litter, lettuce or both. In the second experiment, the snails from the first experiment were all given both litter and lettuce, and additional colony snails were given only litter (i.e. loss of lettuce). Snails showed rapid growth with live plant material and stunted growth on a diet of only leaf litter, indicating that leaf litter alone is not a good diet and that the snails are likely consuming live plants at the nursery. Changing the diet revealed growth plasticity. The addition of live plant material reversed the previously stunted growth on a litter-only diet, and the stunted snails caught up in size with non-stunted snails. Under conditions of changing food resources, growth plasticity enables large size at maturity, which likely has fitness consequences.

Beschreibung: The ribbed mussel ( Geukensia demissa ) is a keystone species in the salt marshes of the North American Atlantic coast. We investigated the clearance rates (CRs) and pathology of ribbed mussels exposed to cultures of two toxic algae, Aureococcus anophagefferens and Heterosigma akashiwo , for 5 d and contrasted the results with mussels fed the nontoxic alga Tetraselmis chui . We also conducted a separate, in vitro experiment in which we exposed extracted mussel haemocytes to the three different algae, their respective media and sea water, as a toxicity bioassay. Results show that mussels exposed to either of the toxic algae had significantly decreased CRs during the entire exposure period. Histopathology revealed thinner digestive tubules, gonad reabsorption and a decrease in gill ciliates in response to both toxic algal species. There was a significant increase in mortality of haemocytes exposed in vitro to both toxic algae compared with seawater controls. Results suggest that ribbed mussel feeding behaviour and physiology can be impacted in several ways by harmful algae, which could undermine their contribution to pelagic-benthic coupling processes.

Beschreibung: By amalgamating all seagrass-associated grazing invertebrates into an epiphyte-feeding guild, the currently accepted model of seagrass trophic dynamics ignores the diverse range of invertebrates that feed directly on, and do considerable damage to, seagrasses. Of the wide range of invertebrates documented to damage seagrass directly, the gastropod genus Smaragdia has adaptations and ecology that suggests it could be a specialized seagrass-feeding group, of which at least two species are known preferentially to consume seagrass. This paper investigated the dietary associations of Smaragdia souverbiana , one of the most widely distributed but least studied species of the genus, in the subtropical eastern Australian part of its range. Using field-based assessments of grazing damage and targeted laboratory feeding trials, we assessed the dietary associations, digestive ability and feeding preferences of S. souverbiana with local seagrasses ( Halophila ovalis , Zostera capricorni and Cymodocea serrulata ). We found that this species consumed and damaged all available species, but showed a strong preference for the most abundant and moderately digestible Z. capricorni . Although it avoided seagrass bearing a high epiphyte load in a laboratory context, considerable amounts of epiphytic material were found in the faeces of field-caught individuals. Grazing and digestibility of seagrass cells was higher in Z. capricorni and H. ovalis , and the former was preferred when both were available. This study adds to the growing body of literature demonstrating that S. souverbiana —and potentially many other grazing invertebrates—cause considerable damage to seagrasses directly, rather than targeting epiphytes.

Beschreibung: This is the first study of species composition of holoplanktonic molluscs of the Pacific coast of southern Mexico, focusing mainly on the Gulf of Tehuantepec. From two oceanographic surveys during summer 2007 and 2010, 40 zooplankton samples were obtained. A total of 40 species contained within 17 genera and 8 families was found. The results show 15 range extensions, including Atlanta californiensis and Carinaria japonica which were previously considered as endemic to the Transition Zone waters of the California Current, and Limacina helicina which was thought to only inhabit polar and subpolar waters. Atlanta gibbosa and Creseis chierchiae f. constricta are two new records for the American Pacific. The use of holoplanktonic molluscs as indicators of water masses is a common practice; however, these reported range extensions limit the validity of their use as indicators, at least within the environmental parameters established in previous studies. Although the 40 species found represent only 43% of the species recorded for the Pacific Ocean, it is noted that this species richness only represents summer conditions and an increase could be expected if sampling was extended to winter.

Beschreibung: The high rates of substitution in mitochondrial genes and assumed neutrality of their polymorphisms encourage the use of mtDNA in phylogenetic and evolutionary studies. However, the true nature of the mitochondrial genome and its influence upon processes of adaptation and speciation are not fully understood, particularly where associations appear to exist between ‘neutral’ mitochondrial haplotypes and characteristics that are under direct selection. In snails, one such characteristic is shell shape. In this study a mitochondrial haplogroup is found to be confined towards one end of the spectrum of shell variation in an ecotype of the rough periwinkle Littorina saxatilis on a shore in the British Isles. We speculate that this may signal hitherto unexpected selection, and perhaps even some reproductive isolation between this group and the rest of the population, and we propose intergenomic coadaptation as a possible mechanism through which this occurs.

Beschreibung: Direct observations using digital videography in an aquarium showed that hairs on the valve surfaces of Modiolus traillii are not periostracal in origin, as often assumed for similar features in other mussels, but are secreted and planted individually by the foot, so they are correctly termed ‘byssal hairs’. Deposition of byssal hair occurred most frequently just after dark, and the time taken to form a strand of serrated hair varied between slightly more than 1 min to almost 10 min, with a mean time of 4.4 min. We observed one individual deposit a total of 11 hairs in 3.5 h. The formation of some 25 hairs were successfully observed on video for six individuals, and about 3,000 individual hairs from 12 mussels were measured in relation to their position, size and density. While hairs varied considerably in length and width, they are consistently flattened, with one edge bearing serrations and the other edge being smooth. Long hair required more time to form compared with shorter hair, and longer hair was deposited farther away from the byssal gape towards the posterior end of the valves. However, a higher density of short hair was laid around the byssal gape. Smaller mussels tended to have an overall higher density of hair compared with larger individuals. There was no discernible pattern in the order in which long and short hairs were secreted on the periostracal surfaces of either valve. Byssal hair microstructure was generally consistent with the distal region of byssal threads, having a tough but thin outer cortex surrounding a ‘spongy’ honeycomb matrix.

Beschreibung: Many animals show alarm responses (ARs) to chemical cues released from predators or injured conspecifics. However, the prey often makes a trade-off between predation avoidance and reproduction, resulting in pronounced sex differences in AR and in sex-biased predation. This phenomenon has rarely been investigated in snails. The freshwater snail Pomacea canaliculata is reported to exhibit an AR to chemical cues released from predators or injured conspecifics. Here, we investigate the sex differences in AR in the snail to chemical cues released from its predator turtle Chinemys reevesii and injured conspecifics. By exposing adult females and males of equivalent size to turtles, we also evaluate the sex-biased predation in the snail. We find that females respond to chemical cues significantly more strongly than males. The predation experiment shows that more females survived than males after a week of predation. These results suggest that males may reduce their antipredator behaviour in order to increase the chance of mating, suggesting a trade-off between predation avoidance and reproduction.

Beschreibung: We investigated the land-snail fauna of rain forests on the eastern slopes of Pico Biao on Bioko Island in the Gulf of Guinea. Thirty-seven plots were studied along an altitudinal transect reaching from sea level (lowland rain forest) to an altitude of 1,830 m (mossy forest). A total of 1,755 specimens were collected and were assigned to 68 land-snail species. Eleven species were new records for Bioko. At least 15 of the recorded species are endemic to Bioko. The degree of endemism was high in mossy forest (23%) and in lowland rain forest (20%), but lower in montane forest (8%). Species richness showed a hump-shaped distribution along the altitudinal gradient with a maximum at 500 m a.s.l. Species richness peaked in forests in which there had been selective logging more than 50 years ago, indicating that some disturbance may have beneficial effects on biodiversity. Species richness was correlated with the thickness of leaf litter. The availability and quality of suitable microhabitats is more important for the occurrence of snail species than gradients of otherwise often decisive environmental parameters like temperature, which are strongly correlated with altitude. A lack of clustering of the occurrences of different snail species along the altitudinal gradient indicated a Gleasonian meta-community structure with individualistic responses of the various species to environmental parameters. No negative co-occurrence patterns that might provide evidence for interspecific competition could be detected. The frequent coexistence of morphologically similar, and presumably ecologically equivalent, congeneric species may indicate that such equivalents do not exclude each other as predicted by the neutral theory of biodiversity. However, current knowledge about individual snail species is too scanty to exclude the possibility that niches of congeneric species differ in some details.

Beschreibung: Myostatin is a negative regulatory protein of growth and muscular development in several vertebrate species. However, for molluscs there is currently little information about the structure and function of the myostatin gene ( MSTN ), and its implications at the physiological and ecological levels. The aims of this study were to molecularly characterize the MSTN gene in Argopecten purpuratus ( ApMSTN ) and analyse gene expression patterns between wild and hatchery-bred populations. A complete ApMSTN sequence of 1,062 base pairs (bp) was obtained, which encodes a 354 amino acid. The amino acid sequence indicated a characteristic proteolytic processing site of MSTN (RXXR), nine conserved cysteine residues, and 344 and 919 bp corresponding to 5'UTR and 3'UTR, respectively. Furthermore, ApMSTN sequences revealed a total of four single-nucleotide polymorphisms (SNPs). Of these, SNP –186G/A was only found in the wild population, while SNP –305A/T was found in both populations. SNP +779A/G, located in the coding region, was identified in wild scallops. In contrast, mutations identified in the 3'UTR were only found in hatchery-bred individuals. An upregulated expression pattern of ApMSTN was mainly associated with the adductor muscle of hatchery-bred scallops. The molecular differences found for the ApMSTN gene in A. purpuratus provide relevant information for future evaluations on the ecological implications of this gene.

Beschreibung: Many members of the bivalve superfamily Galeommatoidea have symbiotic associations with other marine benthic invertebrates. Among them, Koreamya arcuata (A. Adams, 1856) is distinctive because it is the only known bivalve symbiotic with brachiopods. Here we describe Koreamya setouchiensis n. sp. as the second example in this genus, based on specimens collected in and around the Seto Inland Sea, Japan. Similar to K. arcuata , this bivalve species attaches to the anterior end of the shell valve of living Lingula anatina Lamarck, 1801 by means of byssal threads . However, shell morphologies of the two bivalve species are clearly different; K. setouchiensis has an ovate shell, while K. arcuata has an elongated-triangular shell. These morphological differences are probably due to the difference in posture on the hosts. To understand how symbiotic association with Lingula evolved in Galeommatoidea, we performed molecular phylogenetic analyses using three nuclear (18S, 28S and H3) and one mitochondrial (COI) genes. The two Koreamya species with remarkably differently shaped shells were monophyletic, suggesting that their symbiotic associations with Lingula have the same evolutionary origin. Furthermore, the Koreamya clade formed a monophyletic group with anemone-associated galeommatoideans ( Nipponomontacuta actinariophila and Montacutona sp.). This result and their morphological similarities suggest the possibility of host switching between sea anemones and Lingula .

Beschreibung: The Japanese Archipelago harbours high diversity of endemic bradybaenid land snails. However, there have been few systematic studies of these snails. The resolution of the taxonomy and phylogenetic relationships of these bradybaenid land snail taxa is important both for describing species diversity and for promoting the conservation of these land snails. We investigated the molecular phylogeny of Bradybaena and Phaeohelix using the CO1 and internal transcribed spacer genes, to clarify whether morphological traits and the current species taxonomy of these genera reflect their phylogenetic relationships. Our results show that the Japanese species in these genera are genetically divided into three clades, and the geographical distribution pattern of the lineages tends to reflect phylogenetic relationships. Although the nominal species taxonomy of these genera was not consistent with their molecular phylogenetic relationships, their shell and genital morphology reflected phylogenetic relationships to some extent. Inferred phylogeny and observed genital morphology showed that Phaeohelix submandarina , P. miyakejimana and Bradybaena circulus oceanica from Hachijo-kojima Island belong to P. phaeogramma . In addition, the distinction between Bradybaena and Phaeohelix was not supported by molecular phylogeny, showing instead that Phaeohelix should be synonymized with Bradybaena . This study suggests that a further taxonomic revision of Japanese Bradybaenidae is needed and, to address this issue, genital anatomy is useful in addition to molecular phylogenetic analyses.

Beschreibung: Inter-population variation in the life histories of stream animals has been demonstrated to be induced by environmental differences between sites, which could be a direct consequence of differential food availability. The caenogastropod Sulcospira hainanensis (Bröt, 1872) is an abundant consumer in tropical Hong Kong streams. This gonochoristic, ovoviviparous pachychilid tends to maintain higher standing stocks and productivity in less shaded sites. We hypothesized that differences in algal food availability induce diversification of life-history and demographic traits between snail populations. To test this, we compared S. hainanensis populations in four Hong Kong streams with differing conditions of shading (two shaded, two unshaded) and algal availability. Life-table analyses were also conducted for two of these snail populations in a shaded and an unshaded stream. Snails tended to grow faster and reach sexual maturity more quickly in the unshaded streams we studied, which may reflect higher assimilation of more nutritious algal food. Except for shorter life spans of snails in these unshaded streams, other reproductive and demographic attributes were mostly similar among populations; in particular, brood size and reproductive output did not appear to be strongly affected by the availability of algae. Seasonal disturbances due to wet-season spates in monsoonal Hong Kong, which appear to cause significant stochastic variability in snail abundance, may override the deterministic role of resource availability and/or other environmental variables, in inducing the observed pattern of phenotypic plasticity of S. hainanensis . The present study is the first to incorporate both life-table and secondary-production analyses for a tropical stream snail. Such combined studies have rarely been undertaken on stream animals, which mainly comprise amphibiotic insects, because of the difficulty of constructing life tables for insects with biphasic life cycles and high mobility. Snails are more readily studied and we advocate the wider use of field-based life tables and production estimates in combination so as to provide greater understanding of the role of snails in energy flow and trophic dynamics.

Beschreibung: This study describes euspermatogenesis and paraspermatogenesis in Adelomelon ancilla (Volutidae) and compares them with the same processes in other caenogastropods. Spermatogenesis in A. ancilla followed the general developmental pattern of caenogastropods. The pattern of nuclear condensation involves granular, fibrillar, lamellar and homogenous electron-dense phases. Acrosome development begins with the posteriorly located proacrosomal vesicle arising from the Golgi complex in euspermatids. The proacrosomal vesicle develops into a preattachment acrosome which, together with the Golgi body, later moves towards the apex of the nucleus. In the early stage of paraspermatogenesis, the pattern of chromatin distribution in dense patches, together with the cytoplasmatic characteristics of paraspermatogonia, allows the recognition of the apyrene line from the euspermatogonia. Later features, including the peripheral condensation of nuclear chromatin followed by nuclear invagination, the posterior breakdown into nuclear vesicles (‘caryomerites’), centriole multiplication and the synthesis of secretory products, are the most conspicuous changes in the process of paraspermatogenesis.

Beschreibung: When attacked by predators or subjected to mechanical disturbance, trimusculid limpets, like many other marine pulmonates, produce white sticky mucus from glands located in the lateral regions of the headfoot. Histology and electron microscopy were used to describe the structure of the glands of Trimusculus costatus . Based on the histochemistry and appearance of their secretory products, three types of unicellular gland cell were identified. Type 1, which was the most prevalent and largest (up to 200 µ x 30 µm), stained positively for neutral mucins only and had a secretory product that was electron-lucent. Types 2 and 3 were smaller (up to 50 µm) and stained positively for acidic, neutral and sulphated mucins as well as protein. The secretory product of Type 2 glands was homogenously electron-dense, whereas that of Type 3 was vesicular and granular in appearance. Each gland releases its contents by holocrine secretion through an opening between the epithelial cells. Unlike other marine pulmonates (Siphonariidae and Onchidellidae), T. costatus does not have large multicellular glands encapsulated in a well-developed muscle layer. Its glands are more similar in structure to those of some terrestrial pulmonates.

Beschreibung: We report here on the abundance and distribution of a metapopulation of smooth-shelled blue mussels (genus Mytilus ) from northeastern New Zealand (NZ), in the latitudinal range 37–35°S. Site surveys revealed the presence of blue mussels at 12 of 20 locations on the east coast of the Northland Peninsula, in the Hauraki Gulf and into the Bay of Islands region. Additional material was collected subsequently from three sites, including an estuary location in Auckland, which is the southern-most record of blue mussels in this northern region. This new record of an extensive, but patchily distributed metapopulation in northeastern NZ identifies the existence of a pronounced geographic discontinuity between 37°S and 41°S in the distribution of Mytilus throughout NZ. Based on its geographic isolation, we suggest that the northeastern metapopulation is genetically isolated from other more southerly distributed blue mussels in NZ. Molecular identification of the mussels was carried out by both nuclear and mitochondrial DNA RFLP assays. While the majority of mussels were identified as native Southern hemisphere M. galloprovincialis , a substantial number of individuals with a nonnative (Northern hemisphere) M. galloprovincialis mitotype were also identified. The identification of this new metapopulation composed of both northern and southern lineage M. galloprovincialis has challenging biosecurity and conservation implications. Because of the pronounced geographic break in the distribution of blue mussels in NZ it may be possible to minimize further spread of the northern lineage mitotype to the rest of the country using an internal borders containment approach. However, based on introductions of (Northern hemisphere) M. galloprovincialis elsewhere in the world, we believe that the most likely outcome in NZ of this bioincursion is extensive interbreeding and introgression between the northern and southern lineages of M. galloprovincialis .