ALBERT

Description: The squid Gonatus fabricii (Lichtenstein, 1818) is the most abundant pelagic cephalopod in the Arctic and the only squid to spend all of its life cycle in this region. Despite being highly abundant, its reproductive biology remains poorly known, and data on large maturing and mature specimens are especially rare. This study, based on extensive material (51 large specimens and 〉35,000 specimens in all), fills major gaps in the knowledge of the reproductive biology and ecology of G. fabricii. The fecundity of females ranged from 8,862 to 16,200 oocytes, with mature and late maturing specimens having between 8,862 to c. 10,000 and 11,402 oocytes, respectively. Oogenesis was synchronous, and oocyte resorption was observed; resorbed oocytes constituted up to 23.5% of fecundity. Between two to five ripe oocytes were observed, and these were 4.0–5.5 mm in diameter (maximum dimension). Males possessed between 77 and 257 spermatophores (length = 5.8–10.8 mm). Spermatophores were characterized by a cement body with well-developed collar and discs at the oral end, an ejaculatory apparatus longer than the cement body and the lack of a tapered, sharp tip to the cement body. Spermatophore size showed a uniform increase in relation to increasing male size. In newer spermatophores, the length, width and volume of the seminal reservoir also increased. Females possessed between 62 and 84 spermatangia (length = 1.8–2.6 mm); the spermatangia were present on the buccal membranes and lacked special attachment structures. Seminal receptacles were not found on the buccal membranes of females. Our findings are consistent with the hypothesis of geographically restricted spawning in G. fabricii. The study found evidence for one new breeding area in south-eastern Greenland. No differences in sizes at maturity were found between the breeding areas. Such geographically localized reproduction is relatively common in non‐deep-water squids, but is much less common in deep-water squids. Localized reproduction may be especially important for G. fabricii because increased food availability in the epipelagic layers would likely increase the survival of epipelagic juveniles, with surface currents potentially aiding in their dispersal.

Description: Molecular phylogenetic research on the octocoral-associated gastropod family Ovulidae is still in its infancy and, as a consequence, the relationships between subfamilies and genera are not well defined. Previous research on various ovulid genera has shown that their conchological characters are often too fluid when dealing with species delimitations. For this study, Ovulidae were collected in Indonesia and Malaysia, with some additional specimens obtained from Thailand and the Red Sea. Relationships between the Aclyvolvinae and other ovulid subfamilies were assessed using sequence data from two mitochondrial genes (cytochrome c oxidase subunit I (COI) and 16S rRNA); the dataset contained ovulid species (including type species) from the subfamilies Eocypraeinae, Ovulinae, Pediculariinae and Simniinae. The type species of the subfamilies Eocypraeinae and Sulcocypraeinae are fossils, and hence could not be included in the analyses. The phylogeny and systematics of the subfamily Aclyvolvinae were assessed based on four DNA gene regions (mitochondrial COI and 16S rRNA, and nuclear 28S rRNA and histone H3) and morphometric analyses. Shell morphological characters were analysed to help clarify species delimitations within the Aclyvolvinae. The results from the molecular analyses showed that the subfamilies Aclyvolvinae, Eocypraeinae and Simniinae are polyphyletic, whereas the Ovulinae and Pediculariinae appear to be monophyletic. Within the subfamily Aclyvolvinae, the type species of Hiatavolva, H. depressa, did not form a clade with the other species of Hiatavolva. Instead, H. rugosa and H. coarctata formed a clade that is sister to the clade comprising Aclyvolva lamyi, A. lanceolata and A. nicolamassierae, and are therefore now considered as belonging to the genus Aclyvolva. Aclyvolva lamyi and A. nicolamassierae were shown to be synonyms of A. lanceolata, and A. rugosa (n. comb.) is a synonym of A. coarctata (n. comb.). The genus Kuroshiovolva could not be retrieved in a fixed phylogenetic position within the Aclyvolvinae, nor did it cluster with H. depressa or Aclyvolva spp. Our morphometric analyses are in agreement with the results of the molecular analyses, and furthermore show that juvenile shells are morphologically significantly different from their adult conspecifics. Photographs of the type material of Ovulum lanceolatum, O. coarctatum, Neosimnia lamyi, Hiata rugosa and A. nicolamassierae are provided, and new information is given on the geographical distribution and host species of Aclyvolvinae. The subfamily Aclyvolvinae is redefined and now includes only A. lanceolata and A. coarctata. The genus Hiatavolva is now monotypic, containing only H. depressa, but the subfamily to which this genus belongs remains unclear. Kuroshiovolva is not part of the Aclyvolvinae, but its subfamily level placement is unclear.

Description: Alcohol oxidases and dehydrogenases are poorly studied in the Mollusca, the second largest phylum of metazoans. In order to obtain an overview of the distribution of aromatic alcohols and ethanol-oxidizing enzymes in the gastropod phylogenetic tree, we investigated the activity of these enzymes in the digestive gland of 26 gastropod species in the clades Patellogastropoda, Neritimorpha, Vetigastropoda, Caenogastropoda and Heterobranchia. Marine, freshwater and terrestrial species, as well as herbivores and carnivores, were sampled so that gastropods varying widely in habitat and diet were included in the study. An aromatic alcohol oxidase, which was previously reported in herbivorous terrestrial gastropods, was detected in 25 of the studied species. The activity of a cinnamyl alcohol dehydrogenase was detected for the first time in gastropods and this enzyme was found to be present in all the species that were studied. Our study, thus, demonstrates that alcohol oxidases and dehydrogenases are ubiquitous enzymes among gastropods; these enzymes are found across the gastropod phylogenetic tree and across species varying widely in habitat and diet. The enzymes that catalyze the oxidation or dehydrogenation of cinnamyl alcohol must be involved in the metabolism of aromatic alcohols of very different dietary origins and conceivably have a detoxification function. Oxidase or dehydrogenase activities involving ethanol as a substrate were detected only in a few species, mostly those belonging to the Panpulmonata. This suggests that for many gastropods ethanol may not be metabolically relevant.

Description: Female-biased sex ratios are adaptive in populations founded by a small number of individuals and are mainly due to local mate competition (the haystack model). However, little empirical support for this theory exists and, with the exception of terrestrial vertebrates and arthropods, very little is known about the possible mechanisms for biased sex ratios under this model in animals. The highly invasive freshwater snail Pomacea canaliculata usually reproduces in small temporary water bodies and is characterized by genetically based variable brood sex ratios. We conducted a mating experiment to test the prediction that sex ratio is biased towards females in inbred populations. Inbred lines (pairing of a male and a female from the same brood) and outcrossed lines (pairing of a male and a female from different broods) were reared in the lab, and sex ratios were compared between these two breeding types for three generations (the F1 generation was produced by outcrossing only). As predicted, the sex ratios of the inbred lines showed greater bias towards females (average proportion of males per generation was 0.38–0.40) than the outcrossed lines (0.45–0.55). The female-biased sex ratios of P. canaliculata may facilitate rapid population growth and may thus enhance the invasive capacity of this snail. Female-biased sex ratios under metapopulation structures, as predicted by the haystack models, may be more common than previously considered.

Description: The polymorphic land snail Cepaea hortensis was introduced to the city of Sibiu, central Romania, in the first decade of the 20th century and has spread widely across the city. A total of 97 locations were examined in 2017 across the city to determine the habitat preferences and variation in shell size, shape, colour and banding polymorphism of C. hortensis, and to relate these to the same features in the likely source population from Mannheim, Germany, and the first established population in Sibiu. We found that C. hortensis was largely restricted to sites with some woody vegetation cover and showed a marked preference for abandoned and overgrown private gardens. Mean adult shell size in present-day populations was almost always smaller than in both the presumed population of origin from Germany and the first recorded population from Sibiu. Populations showed a wide range of variation in frequencies of shell colours and banding morphs. This variation was not related to habitat or cover, and there was no evident geographical structure in the patterns. Comparisons with a smaller-scale sampling in 2004/5 showed that some populations had gone extinct, some remained stable and in some morph frequencies had changed drastically, but in no consistent direction. These results are similar to those obtained for the related species C. nemoralis in comparable circumstances, but differ from those obtained from regions where C. hortensis is long established and where habitats have been stable. The patterns we observed most likely reflect the effect of passive dispersal by humans, genetic drift and founder effects.

Description: The Chinese pond mussel, Sinanodonta woodiana, an invasive species indigenous to Asia, naturally colonizes new locations as a glochidium that parasitizes fish. Human activity has facilitated a continental-scale spread of S. woodiana in Europe, where it is found in artificial reservoirs and has begun to invade natural habitats. This study aimed to investigate the reproductive activity of males in a female-biased population of S. woodiana that lives in a riverine channel linked to a power plant with a cooling water system in NW Poland. Cells formed during spermatogenesis and morphological changes in reproductive follicles (acini) were analysed over a 2-year period using light microscopy. Typical and atypical spermatogenic pathways were identified. The atypical spermatozoa were released from multinucleated cysts and had significantly shorter heads than typical spermatozoa. Spermatozoa formed in the typical way occurred consistently in all months over the study period, while the atypical spermatozoa were recorded occasionally in the first year of the study and more frequently in the second study. The highest proportion of males with spent gonads was found in late summer and early autumn. Our data show that mussels produce spermatozoa year-round, but that the levels of typical and atypical spermatogenesis varied. The two pathways of spermatogenesis in S. woodiana provide an important insight into potential mechanisms underlying the evolution of doubly uniparental inheritance of mitochondrial DNA, a phenomenon observed in S. woodiana. Additionally, a detailed understanding of the reproductive cycle of this non-native species can help to understand its reproductive potential and predict the likely direction of population change in a newly colonized area. The breeding population of S. woodiana studied by us inhabits a tributary of the Odra River, one of Poland’s largest rivers, and thus poses a threat to the natural environment. Riverine habitats like our study site are local heat islands and the mussels reproducing in them over time may colonize natural waters and expand the range of their distribution.

Description: Although the pond snail Lymnaea stagnalis is an emerging model organism for molecular studies in a wide variety of fields, there are a limited number of verified endogenous control genes for use in quantitative real-time PCR. As part of a larger study on snail chirality, or left–right asymmetry, we assayed gene expression in pond snail embryos. We evaluated six candidate control genes, by comparing their expression in three tissues (ovotestis, foot and embryo) and used three software programmes (geNorm, Normfinder and Bestkeeper) to do so. The specific utility of these control genes was then tested by investigating the relative expression of six experimental transcripts, including formin Ldia2, a gene that has been associated with chiral variation in L. stagnalis. All six control genes were found to be suitable for use in the three tissues tested. Of the six experimental genes, it was found that all were relatively depleted in the early embryo compared with other tissues, except the formin Ldia2 gene. Instead, transcripts of the wild-type Ldia2dex were enriched in the embryo, whereas a nonfunctional frameshifted version, Ldia2sin, was severely depleted. These differences in Ldia2sin expression were less evident in the ovotestis and were not evident in the foot tissue, possibly because nonsense-mediated decay is obscured in actively transcribing tissues. Our work provides a set of control genes that may be useful to the wider community and illustrates how these genes may be used to assay differences in expression in a variety of tissues.

Description: Genetic connectivity plays a crucial role in shaping the geographic structure of species. Our aim in this study was to explore the pattern of genetic connectivity in Bursa scrobilator, an iconic marine caenogastropod with long-lived pelagic larvae. Our study was based on the analysis of DNA sequence data for the 658-bp barcoding fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene. This is the largest DNA sequence dataset assembled to date for B. scrobilator. These data confirm that the two recently described subspecies B. scrobilator scrobilator (Linnaeus, 1758), from the Mediterranean and Macaronesia, and B. s. coriacea (Reeve, 1844), from West Africa, constitute two evolutionarily significant units (ESUs). We found that for the nominal subspecies, the variation in morphology (shell, radula and gross anatomy) and DNA sequences was not geographically structured, and this agrees with what we would expect in a species with high connectivity at the larval stage. The divergence between the two subspecies cannot be easily explained by isolation by distance, and we would argue that one or more extrinsic factors may have played a role in isolating the two ESUs and maintaining that isolation.

Description: We conducted a taphonomic field experiment to evaluate the effects of (1) depth below the sediment–water interface (SWI) and (2) time of exposure on the accrual of damage (particularly through dissolution) to empty mollusc shells in freshwater environments. The experiment, which lasted 30 months, was carried out in the littoral area of Lake Nahuel Rucá, a shallow freshwater lake in the Pampa plain of Argentina. Bags (0.5-cm mesh) containing empty, cleaned shells of the freshwater gastropods Heleobia parchappii, Biomphalaria peregrina and Pomacea canaliculata were buried at three different depths (5, 20 and 35 cm) below the SWI. Damage was assessed every 3 months. All experimental shells exhibited fine-scale surface alteration, but the extent of this damage was relatively low, even in shells recovered after 30 months of exposure. Most of the damage consisted of minor pitting. For H. parchappii and B. peregrina, shell surface alteration varied significantly with depth, but not with time; in both species, alteration occurred mainly at the beginning of the experiment. For P. canaliculata, shell surface alteration varied significantly only with respect to time and this was the case for all three burial depths. All shells of this species exhibited a lower level of damage than what was observed for H. parchappii and B. peregrina. These differences may be related to the fact that P. canaliculata is characterized by a larger and thicker shell than the other two species. The shell attributes of larger size and greater thickness are known to confer a greater resistance to shell dissolution. In addition, the reactive surface area available for dissolution varies with shell size. Larger-sized shells have a lower potential for dissolution than smaller shells due to their lower surface-area-to-volume ratio. In contrast, species such as H. parchappii and B. peregrina, which have smaller and thinner shells, are likely to be more rapidly destroyed because they are more vulnerable to dissolution and have less preservation potential. Our results demonstrate that dissolution is a significant taphonomic process affecting shells even during burial and that the influence of dissolution on shell alteration might be significant in cases of long persistence within the taphonomically active zone. Consequently, we suggest that when working on taphofacies in the context of aquatic environments, assessments of taphonomic alteration should include changes at and below the SWI.

Description: Antarctic animals share many traits that are attributed to evolution in a stable, extremely cold climate. Among invertebrates, development is exceptionally slow, making observational studies of development logistically challenging, particularly when conducted under natural conditions in the field. Using multiple deployments to McMurdo Station, Antarctica, we characterized the development, in the field, of an unidentified buccinoidean gastropod species with encapsulated development. Thirteen egg capsules collected at Granite Harbor, McMurdo Sound, Ross Sea, were attached to natural rock and outplanted at a depth of ~25 m at the base of the McMurdo Intake Jetty on 2 December 2007, photographed on 5 October 2011 and 6 September 2012 and then returned to the laboratory on 27 November 2015. In 2015, four capsules were open and empty, five were open and contained a single large hatchling and the remaining four capsules were intact but not open, each containing a single large juvenile snail. To identify the developing embryos, we sequenced mitochondrial cytochrome c oxidase subunit I (COI) from two hatchlings and compared those sequences with those from adults collected near the egg mass, as well as with sequences of other buccinoideans from GenBank. Based on the close match between hatchling and adult COI sequences (hatchling sequences differed from those of an adult at only 2 of 658 nucleotide positions), we identified the embryos as Antarctodomus thielei (Powell, 1958)). The egg mass morphology and development of this species have not been previously described. Our study shows that A. thielei has a development time of more than 8 years, which is the longest measured for any gastropod.

Description: We investigated the land snail fauna of the Panguana conservation area on the western rim of the Amazonas basin in Peru. A total of 2,322 individuals assigned to 65 land snail species were collected in 32 plots. Ten additional species were found in collections made on previous expeditions to Panguana. On the basis of available data, Panguana is the most species rich locality for land snails in South America. The species density of 75 land snail species in c. 2 km2 of rather homogeneous rainforest is also high on a global scale. The land snail fauna of Panguana is characterized by a very high proportion of species belonging to the carnivorous family Scolodontidae, many of which are likely to be new to science. The fauna includes seven species that are new records for Peru, and the species Hirtudiscus sp., Xenodiscula venezuelensis, Geostilbia aperta, Guppya gundlachii and Thysanophora plagioptycha represent genera not previously recorded from the country. The synanthropic species Allopeas gracile, Opeas hannense, Subulina octona, Geostilbia aperta and Gastrocopta servilis form an ecologically distinct group that occurs mainly in sites strongly modified by humans. The presence of these species on the margin of the Amazon rainforest is evidence of the ongoing homogenization of the global fauna.

Description: Marginelliform gastropods are a heterogeneous and diverse group of molluscs encompassing over 1,600 living species, among which are the smallest known neogastropods. The relationships of marginelliform gastropods within the order Neogastropoda are controversial, and the monophyly of the two marginelliform families the Marginellidae J. Fleming, 1828 and the Cystiscidae Stimpson, 1865, remains unconfirmed. DNA sequence data have never been used to assess the relationships of the marginelliform gastropods, making this group the only major branch missing in our current understanding of the neogastropod tree of life. Here we report results of the first multilocus phylogenetic analysis of marginelliform gastropods, which is based on a dataset comprising 63 species (20 genera) of Marginellidae and Cystiscidae, and a wide range of neogastropod lineages. The Marginellidae and Cystiscidae form a moderately supported clade that is sister to the family Volutidae. Marginellona gigas appears to be sister to all other marginelliforms. The subfamily Marginellinae was recovered as a well-supported clade, and good resolution of this part of the tree makes it possible to propose amendments to the family-level classification of the group. The relationship between Granulina and other marginelliforms could not be resolved and requires further study. Due to poor resolution of basal relationships within the Marginellidae–Cystiscidae clade, the monophyly of the Cystiscidae was neither confirmed nor convincingly rejected. The shell morphology of most marginellid and cystiscid genera is taxonomically not very informative but, nevertheless, of the traditionally recognized genera only Gibberula and Dentimargo were shown to be polyphyletic. Although a comprehensive systematic revision of the group requires more extensive taxonomic sampling (e.g. with better representation of the type species of nominal genus-group names), our results support the superfamily Volutoidea, comprising four families (Volutidae, Cystiscidae, Marginellidae and Marginellonidae), with the placement of the Granulinidae uncertain for the time being.

Description: The recent discovery and exploration of deep-sea hydrothermal vent fields in the Mid-Cayman Spreading Centre, Caribbean Sea (Beebe Vent Field, 4956–4972 m depth) and the East Scotia Ridge, Southern Ocean (E2 and E9 vent fields, 2394–2641 m depth) have yielded extensive collections of two new provannid species, Provanna beebei n. sp. and P. cooki n. sp. Morphological and molecular taxonomy (530 bp of the mitochondrial cytochrome c oxidase subunit I gene) confirm P. beebei n. sp. and P. cooki n. sp. as distinct species; these species are formally described, and details are provided of their distribution, habitat and species associations. Bayesian and maximum likelihood analyses support the placement of P. beebei n. sp. and P. cooki n. sp within the genus Provanna and show that these two new deep-sea species form a well-supported clade with the abyssal West Pacific P. cingulata. Provanna beebei n. sp. and P. cooki n. sp. represent the first records of Provanna from hydrothermal vents in the Caribbean Sea and Southern Ocean, respectively, and extend the known geographic range of the genus. For the first time, intraspecific phenotypic variation in size and sculpture has been reported for Provanna. At the East Scotia Ridge, shell-size frequency distributions and median shell size of P. cooki n. sp. varied significantly between the E2 and E9 vent fields, as well as between diffuse flow and high-temperature venting habitats within each field. The variation in shell sculpture in relation to habitat was also observed in P. cooki n. sp.

Description: The conoidean family Terebridae is an intriguing lineage of marine gastropods, which are of considerable interest due to their varied anatomy and complex venoms. Terebrids are abundant, easily recognizable and widely distributed in tropical and subtropical waters, but our findings have demonstrated that their systematics requires revision. Here we elaborate the classification of Terebridae based on a recently published molecular phylogeny of 154 species, plus characters of the shell and anterior alimentary system. The 407 living species of the family, including seven species described herein, are assigned to three subfamilies: Pellifroniinae new subfamily, Pervicaciinae and Terebrinae. The Pellifroniinae comprises five deep-water species in two genera, Pellifronia and Bathyterebra n. gen. Pellifroniinae possess a radula of duplex marginal teeth, well-developed proboscis and venom gland, and a very small rhynchodeal introvert. The Pervicaciinae includes c. 50 species in the predominantly Indo-Pacific genera Duplicaria and Partecosta. Pervicaciinae possess salivary glands, a radula of solid recurved marginal teeth and a weakly developed rhynchodeal introvert, but lack proboscis and venom gland. The remaining Terebridae species are classified into 15 genera in the subfamily Terebrinae (including four genera described herein); nine genera are defined on the basis of phylogenetic data and six solely on shell morphology. The Indo-Pacific genera Profunditerebra n. gen., Maculauger n. gen. and Myurellopsis n. gen. each include about a dozen species. The first is restricted to the deep waters of the Indo-West Pacific, while the latter two range widely in both geographic and bathymetric distribution. Neoterebra n. gen. encompasses about 65 species from a range of localities in the eastern Pacific, Caribbean, and Atlantic, and from varying depths. To characterize the highly diversified genera Terebra, Punctoterebra, Myurella and Duplicaria, each of which comprise several morphological clusters, we propose the use of DNA-based diagnoses. These diagnoses are combined with more informative descriptions to define most of the supraspecific taxa of Terebridae, to provide a comprehensive revision of the group.

Description: The systematics of several Eastern Atlantic conoidean species, traditionally ascribed to the genus RaphitomaBellardi, 1847, are revised on the basis of DNA sequence data from three gene regions (cytochrome c oxidase subunit I, 16S rRNA and 12S rRNA). We assign genus ranking to three major lineages (Raphitoma, CyrilliaKobelt, 1905 and LeufroyiaMonterosato, 1884) and suggest that two West African species belong in the subgenus Daphnella (Paradaphne) Laseron, 1954. A new classification, based on molecular systematics and critical study of morphology, is provided for all Eastern Atlantic and Mediterranean species that are currently ascribed to Raphitoma s.l. The genus ClathromangeliaMonterosato, 1884 is confirmed as belonging to Raphitomidae. Phylogenetic relationships and genetic distances suggest that Raphitoma maculosaHøisæter, 2016 and R. obesaHøisæter, 2016 may be divergent morphotypes of R. bicolor (Risso, 1826) and Cyrillia aequalis (Jeffreys, 1867), respectively.

Description: Abralia veranyi and Abraliopsis morisii were the most abundant cephalopods caught during epipelagic and mesopelagic surveys off the Canary Islands and accounted for 26% and 35% of the cephalopod catch, respectively. Diel vertical migration patterns were observed in both species. At night, A. veranyi was recorded at depths as shallow as 38–90 m, whereas Abraliopsis morisii occurred at depths of 98–219 m. As individuals grow in mantle length, their diet changes substantially. Abraliopsis morisii showed ontogenetic shifts at 22.9 mm and 35.3 mm dorsal mantle length (DML), while A. veranyi showed ontogenetic shifts at 20.5 mm and 30.9 mm DML. Prior to the first ontogenic shift, both species fed mainly on copepods and mysids. After this shift they fed on larger prey, such as decapods and fish; the diets of larger individuals also contained cephalopods.

Description: Despite its widespread geographic distribution and applications, the herbivorous land snail Cornu aspersum represents an understudied animal host. In this study, we used a culture-based approach, in combination with a population analysis based on 16S rRNA amplicon sequencing, to describe changes in the faecal microbiota of wild-caught snails that were fed a nonsterile plant diet over a period of 21 days. At the beginning of the experiment, wild-caught snails harboured diverse populations of Gammaproteobacteria. The two most abundant genera of Gammaproteobacteria were soil-associated Pseudomonas and Buttiauxella; the latter is an understudied genus often reported in snails and slugs. During penicillin treatment, the diversity of Gammaproteobacteria in experimental snails bottlenecked, resulting in Pseudomonas takeover. Following penicillin treatment, experimental snails began to recover, with faecal samples containing pre-treatment Gammaproteobacteria groups by day 21. There was a significant difference in the colony-forming units/g across days and across treatments. Additionally, there was a significant interaction between day and treatment. The food source was not sterile and supported its own population of Gammaproteobacteria, primarily Pseudomonas, which would have been taken up by the snails daily. Given that Buttiauxella was not observed on the food source, we hypothesize that it was present and maintained within the digestive tract of C. aspersum, and this is consistent with the idea that C. aspersum maintains an endogenous gut microbiome.

Description: Empty mollusc shells provide evidence of the species’ presence over various temporal and spatial scales. However, the persistence of the shell can differ depending on the levels of soil pH and soil humidity. Although this is generally known, there are virtually no experimental data on shell decomposition rate and its relation to shell size and site conditions. Here we study disappearance and degradation rates of shells of nine common species covering the variation in shell size and ecological requirements of temperate European land snails. These shells were exposed to decomposition during a 3-year field experiment in six forest types, representing a gradient of soil pH and humidity. Rates of disappearance and (in larger species) of degradation were estimated by removing the exposed shells and measuring their condition after 6, 12, 24 and 36 months. The disappearance rate was modelled by generalized linear models in relation to species and forest type. The data showed an increase in shell disappearance rate from dry alkaline through to wet acidic forests, but the effect of species size outweighed that of habitat. While shells of large species only started to disappear after 3 years in wet acidic sites, most shells of small species had already disappeared by that time. In contrast, in dry habitats the loss of small shells only started after 3 years. The results clearly support the benefits of using empty shells in mollusc research, especially less damaged shells, which represent the individuals that were alive less than 2 years ago, regardless of shell size and habitat type. However, the marked differences in decomposition rate related to shell size and habitat also highlight the need to take these into account if a studied parameter is confounded with variation in shell size and/or site alkalinity or humidity.

Description: Spermcasting is an unusual reproductive strategy in some aquatic species in which functional males release gametes to fertilize eggs inside the body cavity of functional females. As some spermcasting bivalves have high ecological and economical importance, the understanding of their reproductive strategy is crucial for aquaculture, fisheries and conservation. This study investigates gametogenesis, sex ratio and energy metabolism in Ostrea angasi to elucidate the reproductive strategy of spermcasting bivalves. Gonad histology indicated asynchronous development of spermatozeugmata, but synchronous development of oocytes within an individual. The hermaphroditic individuals released spermatozeugmata before egg ovulation. The population of 2–3 year old oysters comprised 46.7% hermaphrodites and showed a highly skewed male to female ratio of 7:1. This species primarily metabolized glycogen as the energy source for gametogenesis, with an overlapping period of energy storage and utilization. This pattern of gametogenesis suggests multiple production of spermatozeugmata in a reproductive season in male and hermaphroditic oysters, but a single episode of egg ovulation in female and hermaphroditic oysters. The dynamics of energy metabolism indicate that O. angasi follows a strategy for energy metabolism that is intermediate between those of conservative and opportunistic species. This study suggests that unsynchronized gamete development, skewed sex ratio and intermediate energy metabolism are adaptive strategies in the reproduction of spermcasting bivalve species.

Description: Despite Lissachatina fulica being a pest of agricultural and ornamental plants in the worldwide tropics for more than 100 years, information on its biology is limited. In this study, 360 snails were reared in the laboratory from a colony collected from the wild (non-native) population in Miami-Dade County, Florida, and were monitored for growth (height and mass) and egg production for up to 930 d. Snails averaged 195 d old and 97 mm in height when egg laying was initiated. Though the average snail peristome thickness was lower (0.1 mm) before eggs were first laid than after (0.4 mm), peristome thickness was inconsistent in predicting full reproductive maturity. Egg production averaged 4,698 eggs per snail and egg viability averaged 49% in the first 540 d after hatching. Oviposition without mating was shown to be possible, but occurred rarely (3% of snails) and with lower viability rates and smaller clutch sizes. The ability to oviposit without mating and the high reproductive rates found in this study indicate that eradication efforts addressing new infestations must be complete, because even one snail may start another population.

Description: Grazing influences the structure and function of seagrass meadows. Like terrestrial plants, seagrasses have evolved nutritional, structural and chemical mechanisms to either tolerate or resist grazing. Phenols are common secondary metabolites that have multiple roles, including grazing deterrence, and their content in seagrass tissues can vary both among species and within a single species in response to biotic and abiotic processes. Such variability influences the grazing behaviour of species that consume seagrass, but few studies have addressed mesograzers that consume or damage seagrass, such as the nerite Smaragdia souverbiana . We assessed the effect of environmentally-mediated differences in phenol concentration on these seagrass mesograzers by testing: (1) if phenol content is different between sites and seagrass species ( Zostera muelleri vs Halophila ovalis ) and (2) if S. souverbiana inflicts different amounts of damage on different seagrasses from different sites, according to their phenol content. Phenol content was consistently lower in Z. muelleri than H. ovalis , and concentrations were about 60% lower in both species at one of two sites in eastern Moreton Bay, Queensland. These differences corresponded to different foraging patterns of S. souverbiana , with the snails generally choosing the seagrass species with the lowest phenol content. These results suggest that S. souverbiana chooses among locally available seagrasses based on a trade-off between phenol content and digestibility (related to cell size). This work demonstrates how subtle local processes can create complex changes in seagrass–grazer interactions with potential ecological consequences at local and regional scales.

Description: Mitochondrial COI sequence variation was examined in members of the Pyrgulopsis kolobensis complex to clarify further the confused taxonomy of these springsnails, which were treated as a single species prior to a recent study that recognized five morphologically and genetically distinct species for the populations in the Virgin River drainage of southern Utah. Phylogenetic analyses of 44 currently undescribed populations in this complex from the eastern Great Basin and Snake River basin congruently resolved five divergent lineages. One of the lineages contained most of the newly sequenced specimens as well as the haplotypes of three currently recognized regional species. The mean genetic distance within this lineage was slight (0.7%) and consequently we treat it as a single, morphologically variable species for which the name P. pilsbryana has precedence and should be used. Two of the other lineages (both having small geographic ranges) are sometimes sympatric both with each other and with P. pilsbryana (as envisaged herein), but could not be distinguished morphologically and may be divergent haplogroups of P. pilsbryana or undescribed cryptic species. The remaining two lineages are single populations in eastern Nevada and southern Utah that, together with other, previously detected lineages from these areas, will require additional morphological study to determine their taxonomic status. Further molecular sampling, especially of the many populations in Nevada that have not been analysed so far, is also needed to help complete the taxonomic revision of the P. kolobensis complex.

Description: The bivalve family Vesicomyidae comprises two subfamilies: Pliocardiinae and Vesicomyinae. The Pliocardiinae include conspicuous mostly large- and medium-sized clams, which live in symbiosis with chemoautotrophic bacteria and often dominate chemosynthetic communities in the deep sea. The Vesicomyinae comprise poorly-studied tiny bivalves, which at first sight differ considerably from their better known, large-sized relatives. Vesicomyines have a worldwide distribution from mid-slope to hadal depths and reach abundances of thousands of specimens in one trawl catch in deep-sea trenches. The genus Vesicomya is morphologically very similar to the genus Kelliella , the type genus of family Kelliellidae. This fact has long caused taxonomic ambiguities and it has been suggested that Vesicomya and Kelliella , as well as their respective nominate families, should be synonymized. In this paper we study the relationship between Vesicomya and Kelliella , for the first time using not only morphological characters but also genetic divergence based on the mitochondrial cytochrome c oxidase subunit I (COI) gene. Our molecular data indicate that the genera Vesicomya and Kelliella are clearly distinct and that Kelliella is distantly related to the Vesicomyidae. Results of morphological analysis support the molecular inferences. We provide further evidence for the relationship of vesicomyines and pliocardiines and propose an evolutionary scenario according to which Vesicomyinae is the less derived group and Pliocardiinae the more derived. We provide the first information on stable carbon and nitrogen isotopic composition of soft tissues of Vesicomya and Kelliella . These data do not suggest involvement of chemosynthetically fixed carbon in the nutrition of either Vesicomya or Kelliella . We revise current usage of these two genera and provide lists of the species of each, with details of their distribution. A new species, Vesicomya alleni , is described on the basis of morphological and molecular characters.

Description: The Ampullariidae (apple snails) are freshwater snails of tropical and subtropical regions. Recent research has concentrated on a few species that are invasive or potential biocontrol agents, but the basic life history traits of most species remain unknown. One such poorly known species is Pomacea americanista , endemic to the Alto Paraná and Iguazú Rivers in southern South America, which may be vulnerable to environmental degradation. We studied the growth, survivorship, maturation and reproductive activity of P . americanista to help evaluate its resilience under different scenarios of environmental change. Fifty snails that hatched in the laboratory from two egg masses collected in San Francisco Stream (Misiones Province, Argentina) were reared under controlled conditions until their natural death. Shell growth was almost linear up to the 20th week of life, subsequently decreasing smoothly. Growth rate, asymptotic sizes, time to reach asymptotic size and age at maturity were greater for females than males. Mortality patterns were similar for both sexes, with no deaths up to 38 weeks and steady mortality thereafter, the maximum longevity being 143 weeks. The fecundity of P . americanista is lower than that of other apple snails under similar conditions. Under laboratory conditions males and females underwent a single extended reproductive period, but under the seasonal climate in their natural habitats their life cycle would probably extend for more than 3 years, with two or more reproductive periods. The low fecundity and the late maturity of P . americanista indicate slow population growth and low resilience relative to invasive apple snails. These traits, combined with a restricted geographical range and an association with hard substrates in swiftly flowing waters, suggest that P . americanista could be vulnerable.

Description: There are 108 species of nematode that are known to have co-evolved with gastropods and use them as definitive, intermediate or paratenic hosts. One nematode ( Phasmarhabditis hermaphrodita ) is lethal to eight species of snail, but nine species are resistant for unknown reasons. This study investigated whether a previously untested snail species, Arianta arbustorum , was susceptible to P. hermaphrodita . Snails were exposed to 0, 30 and 90 P. hermaphrodita per cm 2 applied to the soil surface for 40 days. Survival, feeding inhibition and differences in weight were monitored. It was found that A. arbustorum was resistant to P. hermaphrodita. The nematode did not cause mortality, induce feeding inhibition or affect weight. At the end of the experiment, surviving A. arbustorum had encapsulated and killed the invading nematodes in their shells. Inspection of shells of A. arbustorum collected on sand dunes in the north of Scotland, and in those collected by others in 1966 and 1908, revealed the presence of encapsulated nematodes. Arianta arbustorum can encapsulate and kill invading nematodes under laboratory conditions and in the wild, and the evidence of encapsulation remains for a long time.

Description: The genetic diversity of one of the most abundant species in the Arctic and subarctic oceans, the pelagic snail Limacina helicina , has not yet been characterized in the north Pacific. This species has different ‘forma’ ( L. helicina forma helicina, acuta, pacifica and ochotensis ), but whether or not the morphological differences between these forma are caused by phenotypic plasticity or genetic differentiation remains unclear. Here, we analysed partial nucleotide sequences of the mitochondrial cytochrome c oxidase subunit I gene in L. helicina from the subarctic western North Pacific Ocean (SWNP; L. helicina f. acuta ) and compared them with those from Svalbard ( L. helicina f. helicina ) and other localities (Beaufort Sea, eastern Pacific, northern Sea of Japan and western Atlantic). The results show clear genetic differentiation between populations in the SWNP and Svalbard (Φ CT = 0.59282, P 〈 0.001). These genetic differences are consistent with the previous description of the two forma L. h. f. acuta (SWNP) and L. h. f. helicina (Svalbard) based on shell morphology.

Description: We used a molecular phylogenetic approach to investigate species delimitation and diversification in the northeastern Atlantic and Mediterranean musseldrills of the Ocinebrina aciculata complex, based on molecular data from topotypical material of many of the nominal taxa. The complex is shown to consist of at least five species: Ocinebrina aciculata (Lamarck, 1822) from the Atlantic and western Mediterranean; O . cf. corallina (Scacchi, 1836) from the central Mediterranean Sea; O. reinai Bonomolo & Crocetta, 2012 from the Tyrrhenian Sea; O. corallinoides Pallary, 1912 from the Gulf of Gabès; and O. aegeensis n. sp. currently known from the Aegean Sea only. The new species is differentiated from the other taxa by very subtle morphological diagnostic features, although it is clearly identified by genetic distance and apomorphic DNA-sequence characters. The identity of Murex corallinus Scacchi, 1836 (type species of Ocinebrina Jousseaume, 1880) could not be defined with certainty, pending genetic comparison of specimens of the ‘large Tyrrhenian morphotype’ (corresponding to the neotype, but not assayed herein) with the assayed ‘small morphotype’.

Description: The occurrence and the intensity of specific behavioural defensive reactions were investigated in freshwater snails of the family Physidae, which vigorously shake their shells when attacked by invertebrate predators. Physella acuta and Physa fontinalis were exposed to two species of leeches with different hunting strategies—the molluscivorous Glossiphonia complanata and the opportunistic predator Erpobdella octoculata . Parameters of reaction were measured and compared between snails and leeches. Significant differences were found in the reactions of both snail species in 10 out of 11 measured parameters. Physa fontinalis reacted more intensively, with a higher number of shell movements triggered by both leech species. The study showed possible recognition by the prey of the predator species, followed by a specific defensive reaction. In general, G. complanata elicited more intensive reactions, especially in treatment with P. fontinalis .

Description: Large parts of the discovered diversity of sea slugs are still undescribed, despite their potential contribution to a better understanding of the evolution of the group. Here, we describe an enigmatic tiny sea slug that was discovered in the 1970s on subtidal reef flats on Guam (Mariana Islands, Indo-West Pacific). The slug presents a long, coiled visceral sac, unique within the highly diverse body plans of sea slugs, which are usually characterized by different degrees of external body symmetry, linked to the reduction of the shell. Its initial assignment to the order Acochlidiida is confirmed by our 3D-microanatomical study based on a histological section series. Helicohedyle dikiki n. gen., n. sp. shows a number of putative plesiomorphic characters such as a simple excretory system—including a sac-like kidney combined with a short nephroduct—and an androdiaulic, hermaphroditic reproductive system, which bears an unarmed copulatory organ. Based on external morphology and microanatomical data it can be assigned to the Hedylopsacea and shows affinities both with marine and brackish Pseudunelidae, and also with limnic Tantulidae. We discuss the different potential scenarios of the evolution of a helicoid visceral sac as a secondary adaptation to the benthic marine lifestyle vs its interpretation as a plesiomorphic character from a coiled and shell-bearing ancestor, predating the transition to the interstices of sandy habitats associated with (progenetic) modifications in body plans.