ALBERT

Description: Periphyton was grown on transparent plastic substrata in the Kiel Fjord and used for short-term laboratory experiments to study the feeding selectivity of the periwinkle Littorina littorea in response to the vertical structure of the periphyton. The susceptibility of algae to periwinkle grazing was assessed by comparing the species-specific biomass within the grazing tracks of the snails to the biomass outside the tracks. After 3 weeks of incubation, the periphyton consisted of a scattered monolayer of algal cells without vertical structure. No apparent grazing could be found. After 6 weeks of incubation, periphyton consisted of a tightly attached undergrowth (mainly Cocconeis scutellum, Bacillariophyceae, and Myrionema sp., Phaeophyceae) and canopy of filamentous (Melosira moniliformis, Bacillariophyceae) and stalked forms (Achnanthes longipes, Bacillariophyceae). The unicellular diatoms Fragilaria tabulata and Stauroneis constricta grew partly on the primary substratum and partly as epiphytes on the canopy species. The canopy species and the epiphytes were decimated inside the grazing tracks, while the tightly attached undergrowth species appeared ungrazed.

Description: The filaria Litomosoides sigmodontis, which develops a patent infection in BALB/c mice, was used to determine the fate of a challenge inoculum following immunization of mice with irradiation attenuated infective larvae (3 subcutaneous inoculations at weekly intervals with 25 L3 irradiated at 60 krad, and challenge with 25 L3 two weeks after the final immunization). The adult worm burden of vaccinated mice was reduced to 50% of that of controls although the pattern of larval migration and microfilaraemia were not affected. Necropsies showed that the increased killing of the filariae of the challenge inoculum occurred at the L3 stage within the first 2 days of challenge. This result draws attention on the protective mechanisms operating very early and probably in the subcutaneous region.

Description: Oxides of Fe and Mn in soils are capable of sorbing large amounts of trace metal ions and can therefore be important in controlling trace metal concentrations in soil solution, and hence trace metal bioavailability in soils. There is, however, relatively little information on the rates of desorption of trace metals from oxide materials or on the factors affecting desorption rates. The objective of this study was to examine the kinetics of desorption of Cd and Co from two Fe oxides, goethite and ferrihydrite, and from two Mn oxides, hausmannite and cryptomelane. The concentrations of Cd and Co specifically sorbed by the oxides at pH 6.0 were greater for the Mn oxides than for the Fe oxides. The metals were also much less readily desorbed from the Mn than the Fe oxides and, in general, Cd was more readily desorbed than Co from all four oxides. Increasing the initial sorption period from 1 to 15 wk substantially decreased the proportion of sorbed Cd or Co subsequently desorbed from goethite, with a similar but much smaller effect also observed with the Mn oxides. Desorption kinetics for both Cd and Co were found to be described well by assuming either the occurrence of two simultaneous first-order desorption reactions, or by a continuous distribution of reaction sites, distributed lognormally with respect to desorption first-order rate constant. With increasing initial sorption period, the parameters obtained from fitting either type of kinetic equation to the experimental data could be interpreted as indicating a movement of metal ions to sites with slower desorption reactions.

Description: Microsatellite DNA markers were applied for the first time in a population genetic study of a cephalopod and compared with previous estimates of genetic differentiation obtained using allozyme and mitochondrial DNA (mtDNA) markers. Levels of genetic variation detected with microsatellites were much higher than found with previous markers (mean number of alleles per locus=10.6, mean expected heterozygosity (HE)=0.79; allozyme HE=0.08; mtDNA restriction fragment length polymorphism (RFLP) HE=0.16). In agreement with previous studies, microsatellites demonstrated genetic uniformity across the population occupying the European shelf seas of the North East Atlantic, and extreme genetic differentiation of the Azores population (RST/FST=0.252/0.245; allozyme FST=0.536; mtDNA FST=0.789). In contrast to other markers, microsatellites detected more subtle, and significant, levels of differentiation between the populations of the North East Atlantic offshore banks (Rockall and Faroes) and the shelf population (RST=0.048 and 0.057). Breakdown of extensive gene flow among these populations is indicated, with hydrographic (water depth) and hydrodynamic (isolating current regimes) factors suggested as possible barriers to migration. The demonstration of genetic subdivision in an abundant, highly mobile marine invertebrate has implications for the interpretation of dispersal and population dynamics, and consequent management, of such a commercially exploited species. Relative levels of differentiation indicated by the three different marker systems, and the use of measures of differentiation (assuming different mutation models), are discussed.

Description: A 3 year study of the diets of breeding royal Eudyptes schlegeli and rockhopper E. chrysocome penguins was carried out at two nearby colonies on Macquarie Island. Diets of both species were dominated by euphausiids and myctophid fish, in particular Euphausia vallentini and Krefftichthys anderssoni. Prey items were those found in the region of the Polar Frontal Zone, confirming the importance of this zone to these penguins. Diets of both species before hatching of the chicks were variable between years, and differences in quantity of food brought ashore and degree of digestion of prey suggested inter-annual variation in distribution of prey resources. No dietary differences were detected in either penguin species across the breeding season, which reflected variability in diet at all stages, indicating that individual penguins foraged in separate areas. Significant differences between the two species were found, royal penguins consuming more myctophid fish and rockhopper penguins consuming more euphausiids. Differences were also found in the size class of prey items taken and the degree of digestion of food by both penguin species, indicating that prey were taken from different sectors of the ocean. It is concluded that the overlap in diet is small in individuals from these two spatially close colonies and, contrary to previous studies, indicates a separation in the resources used by both species. The contrast with previous studies is most likely a reflection of the different methods used to assess overlap and, to a lesser extent, the years and colonies in which the comparisons were made.

Description: Mastigophora brevipinnis Owen, 1856, is a ‘fossil teuthid’ presently considered to be a member of the coleoid cephalopod Suborder Loligosepiina Jeletzky, which in turn has been placed by various authors in or near the Vampyromorpha Grimpe. Recent morphological and biochemical analyses indicate that vampyromorphs are more closely related to the Octopoda than to the Decapodiformes. Fossils of Mastigophora from the Oxford Clay (Jurassic: Callovian) show soft-tissue preservation and evidence of arm crown specialization. Some of these fossils have up to eight short, thick arms with circular sucker-like structures and filiform distal extensions, plus what appear to be the bases of two thinner ventrolateral arms. The latter lack proximal suckers and curve medially to insert into the arm crown, similar to the tentacles that are the modified ventrolateral arms of living squids and cuttlefishes. This suggests that the thinner structures were decapod-like tentacles. If Mastigophora had tentacles homologous with those of modern decapods, then it was a decapod, because this synapomorphy defines the Decapodiformes. This indication of decapod affinities for Mastigophora brings into question the relationships of the other ‘fossil teuthids’. The inferred relationship of the Loligosepiina, including Mastigophora, with the Vampyromorpha, based largely on similarities of gladius morphology with that of living Vampyroteuthis, may reflect shared plesiomorphic characters.

Description: Within the Australian-Antarctic Discordance (AAD), a boundary exists between isotopically defined “Pacific-type” and “Indian-type” mid-ocean ridge basalt (MORB) erupted along the Southeast Indian Ridge (SEIR). This boundary has migrated westward beneath the easternmost AAD spreading segment at a minimum rate of 25 mm/yr since 4 Ma; however, its long-term history remains a matter of speculation. To determine if Pacific-type upper mantle has migrated westward beneath the eastern Indian Ocean basin as Australia and Antarctica drifted apart during the last 70 m.y., we present new Sr-Nd-Pb isotope data, combined with trace element and 40Ar-39Ar radiometric age determinations, for samples from Legs 28 and 29 of the Deep Sea Drilling Project (DSDP). Basaltic basement at these DSDP sites provides a record of their upper mantle source composition and shows regional variations consistent with upper mantle flow in this region. East of the South Tasman Rise, all DSDP basalts have 87Sr/86Sr (0.7025–0.7029) and 206Pb/204Pb (18.80–19.48) ratios typical of Pacific-type MORB indicating that Pacific-type upper mantle existed east of the Australian-Antarctic continental margin and beneath the Tasman Sea during the early stages of seafloor spreading in this region. Basalts from DSDP sites west of the AAD have high 87Sr/86Sr (0.7030–0.7035), low 206Pb/204Pb (17.99–18.10) and trace element characteristics typical of present day Indian-type SEIR MORB. Between these two regions, DSDP basalts recovered along the western margin of the South Tasman Rise have isotopic characteristics that are, in one case consistent with an Indian-type MORB source (Site 280A) and, in the second case, transitional between Pacific-type and Indian-type mantle sources. The occurrence of seafloor basalts with transitional or Indian-type isotopic characteristics well to the east of the present Indian-Pacific MORB isotopic boundary within the AAD strongly implies that Pacific-type upper mantle has migrated westward into the region since the South Tasman Rise separated from Antarctica circa 40 Ma.

Description: 1. Monthly series of abundance indexes for the English Channel squid stock, based on fishery statistics of the United Kingdom (1980–93) and France (1986–96), were compared with water temperature data. The two objectives of the study were to test empirical predictive models and to analyse the stock–environment relationship at various time scales; both correlation and time-series statistical techniques were applied. Sea surface temperature (SST) showed inter-annual fluctuations and month-to-month auto-correlation in addition to the annual cycle. 2. Trends in squid landings and temperature at the annual scale were found to be related, whatever the statistical method used (moving averages, cumulative functions or regression using averaged data). 3. Variable selection applied in a ‘multi-month’ model suggested that fishing season indexes could be predicted from temperatures observed in the previous winter. The link between mild winter conditions and cohort success in winter/spring spawning species suggested that early life survival (and/or growth) was involved. This empirical model is a first step in the development of environment-predicted recruitment indexes useful for management advice. 4. Seasonal decomposition was performed on both the squid resource data and SST data in search of short-term relationships. In spite of the flexibility of the loliginid life-cycle, no significant relationship was found between squid seasonally adjusted indexes and temperature anomalies in the previous months. This underlined the conclusion that temperature effect on cohort success was not constant throughout the year.