Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 1997. / Thesis submitted for the degree of doctor of philosophy. Reprint from Records of Western Australian Museum of article entitled "Status of Anadara trapezie (Deshayes) (Bivalvia: Arcoida) from Oyster Harbour, Albany (Western Australia) as compared with east Australian populations" by M. Roseline Yardine and Barry J. Richardson bound in back. Includes bibliographical references (leaves 249-328).

This project investigated the genetic composition of natural populations of Anadara trapezia in Australia at three spatial scales : i) microgeographic (within an estuary, 50 metres to ~ 6 kilometres); ii) microgeographic (within populations, less than 50 metres); and, iii) macrogeographic (hundreds of kilometres along the coast of Australia). Allozyme polymorphism surveys using cellulose acetate strips have revealed, from 43 enzymes screened, 18 putative polymorphic loci. Comparisons of levels of heterozygosity among enzyme structural groups showed no significant differences, however, monomers were significantly more variable as a group than multimers. Significant differences in the level and distribution of polymorphism among functional groups of enzymes were observed. It appears that selection may be acting at the molecular level, not only on a particular locus, but on a group of functionally similar loci. At the macrogeographic scale, significant departures from random mating were observed in most populations. Significant differences in allele distribution among populations of A. trapezia along the east coast of Australia were found. At the macrogeographic scale, heterogeneity of allele frequencies may depend upon the distance separating the populations and surface water currents. Differentiation among population groups in this study is attributed to changes in the direction of the East Australian Current combined with onshore countercurrents. The systematic status of the disjunct western Australian population of A. trapezia was also evaluated as compared with the east coast populations. No evidence of genetic, hence evolutionary divergence was found. The results have serious implications in the management of fisheries as erroneous assumptions in fisheries management models may lead to depletion and near extinction of marine species. The research stresses the necessity of sampling at multiple scales and replication strategies. It also highlighted the complexities researchers are faced with in studies of marine bivalves, such as the presence of null alleles, deficiencies of heterozygotes, apparent inbreeding and the small geographic scales governing population structure. / Doctor of Philosophy (PhD)

This study examines the occurrence, distribution and storage of selenium in seagrass communities of Lake Macquarie, which is a heavily industrialised area of NSW, where notably high trace metal concentrations have been reported previously. Initially a suite of organisms was collected from a seagrass bed (Zostera capricornia) in the southeastern section of the lake to investigate the bioaccumulation and biomagnification of selenium. All organisms contained selenium, with sediment-dwelling organisms containing the highest Se concentrations. No consistent pattern of significant Se-metal correlations with Cu, Zn and Cd was found. Biomagnification of Se was evident, as concentrations increased from sediments and water to flora (algae and seagrass) to bivalves to Crustacea. However, this trend was not continued to the higher trophic groups of invertebrate predators and teleost fish. The bivalve Anadara trapezia was further studied. Intrinsic and extrinsic factors affecting the accumulation of Se were examined. Gender and mass were assessed in a single day study, followed by a temporal investigation of the effect of gender, reproductive cycle, temperature and salinity on Se accumulation. Gender had no effect on the accumulation of Se in A. trapezia. Se was present in all tissues (adductor, blood, foot, gills, intestine and mantle) and not immobilised or stored in a specific tissue, indicating that it plays a structural role in the tissues of A. trapezia. Se burden increased relative to size (shell length and dry mass) suggesting that Se is metabolically controlled within the organism. Se concentrations were found to fluctuate temporally because of: food availability in response to water temperatures; the reproductive cycle; and associated metabolic activities responding to temperature changes and food availability. Subcellular selenium associations in A. trapezia were examined to assist in the understanding of the fate of Se in marine tissues. Most of the Se was associated with proteins, suggesting that Se has a metabolic role in this marine organism. Proteins are intrinsically associated with the lipid bilayer of the cell membranes. A number of proteins (94, 85, 43, 36.5, 30, 23.4, 17.4 and 15 kDa) were separated by SDS PAGE from ethanol fractions. Determination of the Se concentration within individual proteins was not possible because the ratio of Se to protein was too low for further analysis. These findings indicated that Se plays a metabolic role in the tissues of the marine organism A. trapezia. The biochemical regulatory mechanism responsible for maintaining Se concentrations within the tissues is currently unknown.