Academic literature on the topic 'Austrocochlea constricta'

An analysis of allele frequencies at five polymorphic enzyme loci of one mainland Australian and four Tasmanian populations of Austrocochlea constricta revealed that three readily distinguishable morphs were three species. These were identified as A. constricta, A. porcata and A. brevis sp. nov. In sympatric populations, two diagnostic loci separated A. constricta and A. brevis (PEP-A and AAT-2), two separated A. porcata and A. brevis (PEP-A and AAT-2), and one separated A. porcata and A. constricta (PEP-A). With the exception of the last, these loci were also diagnostic in allopatric populations. In addition, significant differentiation was observed at most non-diagnostic loci in sympatric populations.A. porcata and A. constricta, but not A. brevis, showed limited, although significant, interpopulation differentiation at two of the five loci, which was attributed to geographic isolation. Examination of genetic distance data showed the three species to have non-overlapping values, but variance overlap meant that the intraspecies population affinities were unresolved. Radulae of the three species were assessed qualitatively and quantitatively from scanning electron micrographs. Inter-specific comparisons of tooth dimensions revealed no significant differences and, despite a less variable tooth shape in A. constricta than in A. Porcata or A. brevis, no consistent features of radular morphology were found to distinguish any one species. Morphological descriptions of the shells and anterior soft body regions are given to enable ready field identification of the species, and their known distributions are outlined.

Patterns of genetic and morphological divergence were examined among Western Australian (Abrolhos Islands and Albany) and Tasmanian members of the highly variable 'Austrocochlea constricta' species complex. Analyses of allele frequencies at 13 enzyme loci confirmed the presence of three species within this complex in Tasmania, revealing additional diagnostic differences not previously detected. Where combinations of species sympatry were examined in Tasmania, seven diagnostic loci separated A. constricta and A. brevis, four separated A. porcata and A. brevis, and one separated A. porcata and A. constricta. Western Australian animals were genetically most similar to Tasmanian A. constricta populations, separated from them by genetic distances of just 0.018 (Albany) to 0.107 (Abrolhos), despite spatial isolation over ~3000 km. These genetic distances, in addition to that separating Abrolhos and Albany populations (0.138), are considered within the range possible for allopatric conspecifics. In comparison, genetic distances separating A. constricta from sympatric A. porcata (0.191) and A. brevis (0.803) in Tasmania were much larger. However, on the basis of a range of morphological traits, which were species-diagnostic in Tasmania, Abrolhos animals most closely resembled A. porcata, and Albany animals appeared intermediate to A. porcata and A. constricta. This suggests Australia-wide discordance among genetic and morphological characters of the 'A. constricta' complex.

Environmental Context. The pathways by which arsenic is accumulated, biotransformed and transferred in aquatic ecosystems are relatively unknown. Examination of whole marine ecosystems rather than individual organisms provides greater insights into the biogeochemical cycling of arsenic. Rocky intertidal zones, which have a high abundance of organisms but low ecological diversity, are an important marine habitat. This study examines the cycling of arsenic within intertidal ecosystems to further understand its distribution and transfer. Abstract. The present study reports total arsenic and arsenic species in a short rocky intertidal marine food chain in NSW, Australia. Total mean arsenic concentrations increased up the food chain in the following order: 4 ± 2 µg g–1 in attached rock microalgae, 31 ± 14 µg g–1 in Bembicium nanum Lamarck, 45 ± 14 µg g–1 in Cellana tramoserica Sowerby, 58 ± 14 µg g–1 in Nerita atramentosa Reeve, 75 ± 15 µg g–1 in Austrocochlea constrica Lamarck (a herbivore) and 476 ± 285 µg g–1 in the carnivore Morula marginalba Blainville. Significant differences in arsenic concentrations of B. nanum, N. atramentosa and M. marginalba were found among locations and may be related to food availability, spawning or differences in age and/or size classes of individuals. Significant differences in arsenic concentrations were also found within locations among species, and increased in the order: rock microalgae < B. nanum < C. tramoserica < N. atramentosa < A. constricta < M. marginalba. Although small differences in total arsenic concentrations were found among locations for some gastropod species, arsenic species proportions were very consistent within gastropod species across locations. The majority of arsenic in Homosira banksii (macroalgae) was oxo-arsenoribosides, with thio-arsenoribosides making up ~10% of the total methanol–water extractable arsenic. The rock microalgae contained arsenobetaine (AB) (59 ± 5%) and arsenoribosides (36 ± 15%). The AB content of the herbivores B. nanum, N. atramentosa and A. constricta ranged from 71 to 95%, and that of the carnivore M. marginalba was 98%. Most gastropods contained thio-arsenosugars (up to 13 ± 3% of total extractable arsenic), with C. tramoserica containing higher proportions of thio-phosphate arsenoriboside (7 ± 2%) and lower proportions of AB (69 ± 4%). Glycerol trimethylarsonioribosides (1.4 ± 0.1%) were also found in most of the herbivorous gastropods. Oxo-dimethylarsinoylethanol (oxo-DMAE) was found in N. atramentosa (<1%).

Rock pools are unique and complex habitats in intertidal areas. Quantitative studies of assemblages in pools are few. Abundances and distributions of species in pools on a rock platform near Sydney (Australia) were sampled for two years. Pools of four different depths (5, 15, 30 and 40 cm deep) and up to four strata within each pool (0–5, 5–15, 15–30 and 30–40 cm, from the top of the pool) were sampled, replicated at four sites. The abundances and distributions of most species of plants and animals in pools did not differ between strata nor at different depths in the pools. Abundances of only three species, the encrusting alga, Hildenbrandia prototypus Nardo, the trochid snail, Austrocochlea constricta (Lamarck) and the limpet, Cellana tramoserica (Sowerby) varied significantly between strata and depths. In contrast to other studies on rock pools, most species showed no significant temporal variations in mean abundances in the sites sampled. Significantly large, spatial and temporal, random fluctuations did, however, occur in abundances in individual pools. The consistency of abundances at larger spatial scales indicated that disturbance in these habitats may not be an important structuring process. The large variation between pools does, however, suggest that the history of each pool may have a more significant role in the character of its assemblage. Some implications of small-scale variability are discussed.

Zinc, copper and cadmium accumulation was measured in two herbivorous gastropod molluscs Austrocochlea constricta and Bembicium auratum from Lake Macquarie NSW an area with a history of trace metal pollution. The investigation consisted of three main parts. The first part examined the influence of organism mass and location within the Lake on whole body tissue metal concentrations. This part of the study also compared the distributions of tissue metal concentrations of populations from Lake Macquarie, a known polluted environment, with those of populations from Jervis Bay NSW, an unpolluted environment, to establish whether either species is a net accumulator of zinc copper or cadmium. The second part of the investigation examined a range of factors which may influence whole body metal concentrations. One location in Lake Macquarie was sampled monthly from August 1995 to July 1996. The factors examined were temporal variation, gender, breeding cycle, and tissue distribution. The final part of the investigation examined the detoxification and storage of excess metals in the gastropods from Lake Macquarie. The mechanisms studied were metallothioneins and granules. The tissue metal concentrations of both species were found to be independent of mass. Location within Lake Macquarie did not significantly influence tissue metal concentrations. Variation between individuals was the most significant contribution to overall variation, resulting in a positive skewing of sample trace metal distributions. B. auratum populations from Lake Macquarie had significantly higher copper and cadmium tissue concentrations and A. constricta populations had significantly higher zinc, copper and cadmium tissue concentrations than the populations from Jervis Bay. This suggests that regulation of these metals is not occurring. A. constricta may therefore be considered a net accumulator of zinc, copper and cadmium and B. auratum of copper and cadmium. Tissue metal concentrations did not vary significantly over time. It is suggested that the organisms are in equilibrium with their environment. B. auratum has higher natural equilibrium concentrations than A. constricta particularly for copper and cadmium, suggesting different routes of exposure, uptake or accumulation for the two species. Gender and breeding cycle did not significantly influence tissue metal concentrations. Most of the variability in total copper and cadmium concentrations of both species was explained by variability in gonad tissue metal concentration, while variability in the gonad and somatic tissues zinc concentration explained about an equal amount of the variability in total zinc concentration. A. constricta and B. auratum were both found to induce a cadmium binding protein which has some features in common with metallothionein. A protein of around 10 000 Da which binds approximately 60% of the soluble cadmium was isolated using gel filtration. This protein was further separated into two isoforms using anion exchange. The first isoform eluted at the same time as MT I and the second at the same time as MT II rabbit liver standard. Large cells containing granular material which stained positive for calcium were observed interspersed among the connective tissue immediately behind the columnar epithelial cells lining the gut wall in both species under a light microscope. Calcium positive granular particles were also observed within the columnar epithelial cells of B. auratum. These species have been shown to be net accumulators of the trace metals investigated, with the exception of zinc in B. auratum. It has also been established that organism mass, gender and reproductive state, the partitioning of metals between tissues, and temporal effects are not confounding factors for the purposes of comparing trace metal concentrations between populations. They should therefore be effective biomonitors of the trace metals investigated, with the exception of zinc in B. auratum.