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Typescript. / Bibliography: leaves 563-582. / xiii, 593 leaves ill. (some col.), map

Thesis (Ph. D.)--University of California, Los Angeles, 2003. / Vita. Includes bibliographical references (leaves 120-136).

1. The development of estuarine research in South Africa has been reviewed, and the present state of knowledge assessed. Little is known about many abundant estuarine species, and a previously unstudied prosobranch Nassarius kraussianus (Dunker), was selected for investigation. 2. The study area, a mudflat on the Bushmans River estuary, was divided into three habitat types: supratidal, intertidal and subtidal, each with a particular substratum and pattern of vegetation cover. The distribution of N. kraussianus is associated with the nature of the substratum and the degree of Zostera capensis Setchell cover. 3. A brief review of pertinent literature indicated the necessity of relating population parameters to environmental conditions. 4. The population biology of N. . kraussianus was investigated, and the size frequencies, sex ratios, and male/female size frequencies were recorded over three distinct periods: pre-flood, post-flood and recovery. 5. The Bushmans River flooded in July and August 1979, and the results of the flood have been described. The most immediate result was a period of low salinity, but the most persistant result was the deposition of silt, which had an important effect on the substratum and the Z. capensis beds. 6. The pre-flood population was characterised by patchy distribution, and by a large number of mature adults in relation to juveniles. Females were generally larger than males, and the sex ratio was 1:1. The presence of juveniles in consistantly low numbers indicated that reproduction may have been continuous, but that intraspecific adult/juvenile competition may have kept juvenile numbers low. 7. The post-flood period was characterised by extreme physical conditions, and the survival of a few adults. Juveniles were completely annihilated, and were absent until a few were spawned by the surviving adults towards the end of 1979 . Sex ratio was biased, and females predominated. 8. The recovery period began abruptly with the arrival of a large number of juveniles in the 2, 3 and 4 mm size classes. Recolonisation coincided with habitat recovery, and reqeneration of the Z. capensis cover. Recolonising juveniles grew quickly, reaching adult size in three months. After that, juveniles were spawned on the mudflat by the new population. During this period the sex ratio did not return to the pre-flood 1:1, but remained female biased. Males and females grew at the same rate over the period measured, but females were consistantly larger, indicating that at some stage female growth may be faster. 9. The recolonising juveniles arrived in a regenerated habitat, at a time when temperatures were high, and conditions for growth probably optimal. If intraspecific competition was a feature of the pre-flood population it would have been elimianted in the recovery phase, by the absence of adults. 10. N. kraussianus is apparently omnivorous and proabably not food limited. However, carrion, a limited resource, may be essential for growth to reproductive maturity. Adults and juveniles may compete for this resource, and any juveniles deprived of access to carrion may be stimulated to leave the parental habitat. 11. N. kraussianus is ovoviviparous, and carries up to 5 egg cases within the uterus. Each triangular egg case contains 1 egg which hatches after approximately 3 weeks, as a free swimming veliger. Yeligers metamorphose, and settle after 4-7 days, assuming a benthic mode of life. Ovoviviparity protects the developing embryo from the rigours of environmental extremes, and ensures that embryos are not swept out to sea . Additionally, veligers have a high probability of settling in the parental habitat. 12. This reproductive strategy has been compared with other prosobranchs, and the evolutionary trends within the Prosobranchia, and particularly the Nassariidae, have been related to their dispersal potential. 13. Developmental strategy is intimately related to recolonisation potential. Ovoviviparity, and the lack of pelagic larvae, did not limit the recolonisation potential of N. kraussianus, and recolonisation was probably effected by post-larval juveniles, which may disperse from neighbouring estuaries and coastal pools, by floating in coastal and tidal currents. Post-larval juveniles have two important advantages over larvae. They are less vulnerable to physical extremes, and they have a sturdy crennellated shell which probably affords them protection from predators. 14. Examples of larval recolonisation in estuarine populations have been reviewed, and the most fundamental conclusion of this work is that recolonisation is an important, and probably widespread, adaptation to estuarine conditions in South Africa.

viii, 73 leaves : map ; 28 cm Notes Typescript Thesis (M.S.)--University of Oregon, 1983 Includes vita and abstract Bibliography: leaves 68-73 Another copy on microfilm is located in Archives

Neritina zebra à um gastrÃpode comum em bancos de lama e Ãguas salobras. Este estudo tem como objetivos revisar o conteÃdo da literatura especializada e acrescentar informaÃÃes sobre a anatomia de Neritina zebra. Foram analisados os animais coletados no estuÃrio do rio Cearà - CE, no Parque Estadual do rio Cocà â CE e os espÃcimes tombados na coleÃÃo MalacolÃgica "Prof. Henry Ramos Matthews" (CMPHRM) da Universidade Federal do Cearà (UFC) e na coleÃÃo de Moluscos do Museu de Zoologia da Universidade de SÃo Paulo (MZUSP). A rÃdula foi observada e fotografada atravÃs de microscÃpio Ãptico e microscÃpio eletrÃnico de varredura (MEV). A protoconcha foi observada e fotografada atravÃs do MEV. N. zebra apresenta concha globosa, protoconcha com 1,5 voltas, teleoconcha com 3,5 voltas, lÃbio interno denteado, espira baixa, abertura semilunar. Concha apresentando vÃrias cores e vÃrios padrÃes de âziguezagueâ. A columela forma um septo transversal. O opÃrculo à calcÃrio e liso, com apÃfise bifurcada. O mÃsculo columelar à bem desenvolvido, com duas partes de tamanhos diferentes. BrÃnquia bipectinada. O osfrÃdio encontra-se à frente da membrana suspensÃria da brÃnquia, do lado esquerdo do manto. O coraÃÃo apresenta um Ãtrio e um ventrÃculo. A rÃdula à do tipo rhipidoglossa, apresentando a fÃrmula geral .5.1.5.. EsÃfago e intestino longos. O intestino passa atravÃs da cavidade pericardial, estando envolvido pelo ventrÃculo. O sistema reprodutor masculino apresenta uma abertura genital, ducto espermÃtico longo e enrolado, glÃndula prostÃtica e pÃnis com formato laminar do lado direito da regiÃo cefÃlica. O sistema reprodutor feminino apresenta trÃs poros genitais (um vaginal, um âgonoporo principalâ e um âducto enigmÃticoâ), um saco de reforÃo, saco do espermatÃforo, ovÃrio com vÃrias vilosidades digitiformes paralelas, receptÃculo seminal e glÃndulas de albÃmen e da cÃpsula. / Neritina zebra is a common gastropod on mud bottom and brackish water. This study aims to review the literature and add information about the anatomy of Neritina zebra. We analyzed the animals collected in the estuary of the Cearà river â CE, in âParque Estadual do rio CocÃâ - CE and specimens deposited in âColeÃÃo MalacolÃgica Prof. Henry Ramos Matthews" (CMPHRM) of âUniversidade Federal do CearÃâ (UFC) and âColeÃÃo de Moluscos do Museu de Zoologia da Universidade de SÃo Pauloâ (MZUSP). The radula was observed and photographed through optic and scanning electron microscope (SEM). The protoconch was observed and photographed by SEM. N. zebra presents globose shell, protoconch with 1.5 whorls, teleoconch with 3.5 whorls, small teeth on inner lip, low spire, semilunar aperture. Shells present several different colors and patterns of zigzag. The columella forms a transversal septum. Operculum calcareous, smooth, with bifurcated apophysis. The columellar muscle is well developed, with two parts of different sizes. Bipectinate gill. The osphradium is in front of the suspensory membrane of the gill, on the left side of the mantle. The heart presents one auricle and one ventricle. The radula is rhipidoglossa type, presenting the general formula .5.1.5. . Long esophagus and intestine. The intestine passes through the pericardial cavity, enwrapped by the ventricle. The male reproductive system presents one genital opening, very long and coiled spermatic duct, prostate gland and penis with laminar shape on the right side of the cephalic region. The female reproductive system has three genital pores (vaginal pore, main female gonopore and enigmatic duct), a reinforcement sac, a spermatophore sac, an ovary with many small parallel digitiformes vilosities, a seminal receptacle and the albumen and capsule glands.

Three gastropods occupy a range of habitats along gradients in hydrothermal flux at Juan de Fuca Ridge vents. I examined how these species co-exist and identified mechanisms driving their abundances. First, I measured temperatures and spatial patterns in adult densities of the three species at three distances from vents to test if thermal regime relates to their habitat selection. Lepetodrilus fucensis and Depressigyra globulus were most dense in-vent (0-25 cm) at variable temperatures (10+5°C): 2100 and 240 incl. dm -2 (respectively). Provanna variabilis was most abundant far-vent (51-75 cm: 60 ind. dm 2) at stable temperatures (3±0.5°C). Thermal conditions are key in their habitat selection: behavioural experiments showed that these gastropods select fluid temperatures<18°C. L.fucensis and D. globulus preferred 5-15°C, while P. variabilis preferred 4-12°C. The next studies sought to explain how Lepetodrilus fucensis reaches order of magnitude higher densities in comparison to other gastropods. First. I quantified L. fucensis recruitment and sex ratio patterns to identify innovative life history traits. I meaured size structure and density at in- and far-vent locations. Early postlarval juveniles occupied far-vent at remarkable densities (2419 ind. dm-2). To test for sex ratio biases, I sexed animals from different habitats and sizes. Populations nearest vents hosted the largest females (>6.0 mm), while peripheral habitats were male-biased. A transplant experiment showed that female survivorship and gonad fullness were significantly lower than males in far-vent locations. Sex ratio biases are driven by two mechanisms: females maximize their reproductive output by selecting optimal habitats and suffer relatively higher mortality in low flux. Next, I hypothesized that the Lepetodrilus fucensis gill symbiosis is a key adaptation. I used multiple approaches to determine if the prevalence of the association and relationship to the limpets condition support this hypothesis. FISH probes specific to the 16S rRNA molecule of a gamma-Proteobacteria hybridized where bacteria were present. Direct sequencing using symbiont-specific primers gave a single unambiguous sequence. indicating high specificity. Light and TEM micrographs of gill tissue from a range of species also showed that the symbiosis is ubiquitous. In addition, the gills of in-vent animals had high surface area. dense symbiont populations and healthy tissues, while far-vent animals showed the reverse trend, suggesting that the symbiosis benefits L. fucensis. Carbon fixation by gill tissues was stimulated by inorganic sulfide and related to the abundance of bacteria on the gill. These data indicate a persistent and specific symbiosis that is dependent on access to sulphide. I further examined feeding by Lepetodrilus fucensis to determine if the bacteria contribute to their host's nutrition. The morphology of feeding structures were compared among Lepetodrilus species. L. fucensis exhibited specialized features: the gill is enlarged. the lamellae are free of the mantle. do not narrow and are stabilized by ciliary junctions. The radula and stomach of L. fucensis are also reduced. Shipboard observations confirmed suspension feeding by L. fucensis. In addition, the symbiont may be ingested because its phylotype was well-represented in food material on the gill. The limpet's morphological specializations are consistent with dependence on suspension feeding and/or symbiont farming; however, L. fucensis also grazes. a mechanism likely important in peripheral locations. Lepetodrilus fucensis populations are partitioned by size and sex along environmental gradients near vents. Peripheral populations are dominated by recruits and adults tend to be male: grazing is likely their primary feeding mode. Larger animals form stacks in venting fluids and are female-biased. These populations access suspended particles for food and sulphide, which generates dense symbiont populations for ingestion. Multiple feeding modes sustain high L. fucensis densities in a space-limited environment and may be an innovative strategy that drives its remarkable abundances.

M.Sc. (Zoology) / Please refer to full text to view abstract

Gastropods are one of the most diverse species groups in mangrove habitats, however, many of their specific roles in relation to ecological patterns and processes are currently largely unknown. The overall aim of this research project was to provide basic ecological information for key gastropod species from subtropical mangroves within a protected area. South African mangroves cover relatively small areas and are restricted to estuaries, these habitats therefore present unique opportunities and challenges to the species that occur in them. Three gastropod species, Terebralia palustris, Cerithidea decollata, and Melanoides tuberculata, all occur at their natural southernmost range limit within South Africa and were selected based on their prominence and occurrence in mangrove habitats of the iSimangaliso Wetland Park, a UNESCO World Heritage Site. Trophic linkages and resource partitioning, resource utilization rates, and ecological resilience were investigated respectively using: 1) a stable isotope (δ15N and δ13C) approach; 2) an experimental approach to quantify feeding dynamics (ingestion rate, consumption/digestion efficiency and grazing impact); and 3) a mixed-effects modelling approach to relate population responses to environmental variables. The diet of T. palustris was seasonally variable and a number of sources were incorporated by different sized snails, but their grazing impact on microphytobenthos was not significant. The results also indicated an ontogenetic shift in the dietary niche for T. palustris through robust partitioning of resources between different size classes. The diets of C. decollata and M. tuberculata were dominated by different primary resources as a function of where they occurred in the mangroves. Melanoides tuberculata consumed a wide variety of primary resources, a typical trait of an opportunistic generalist species. The ingestion rate of M. tuberculata was not dependent on the availability of microphytobenthos, and was highest when conditions were oligotrophic. The resilience of C. decollata was related to the tree-climbing behaviour of this species and its occurrence was best explained by sediment conductivity. These responses were considered in conjunction to what has previously been reported on the resilience of the mangrove trees. The results of this research project have provided new basic ecological information for all three gastropod species in this data-deficient subtropical region. This information can potentially be used in comparative studies for these species in other regions or in broader scale ecological studies. Terebralia palustris has recently experienced a range contraction along the South African coastline. This research project has shown that the diet of this species is highly variable and that food limitation and competition for resources should be considered as potential drivers of the local decline. Cerithidea decollata has in contrast expanded its distributional range in this region. This research project has shown that this species has a generalist diet and exhibits traits in relation to tolerance that are expected to have facilitated its expansion into temperate saltmarsh habitats that occur in dynamic estuaries. Melanoides tuberculata is a globally invasive species, and as South African populations are within its native range, ecological information from this region is valuable as it can be used to investigate the potential ecological effects following introduction into new habitats beyond the native range. Biological drivers have a significant impact on mangrove ecosystem functioning, particularly in relation to recycling and the retention of organic carbon generated through primary productivity. Understanding the ecological linkages that maintain ecological functioning and stability is therefore an important step towards conserving and sustainably managing threatened ecosystems such as mangrove forests.

Graphite furnace and hydride generation atomic absorption, GFAA and HGAA, techniques have been developed and applied to the determination of arsenic concentrations in some marine invertebrates, mainly bivalves and gastropods, of British Columbia. Total arsenic concentrations in bivalves vary with species, ranging from 0.6-9.1 μg g⁻¹ (wet weight basis). Arsenic concentrations in the bivalve shells show a wider range of 0.1 to 26.3 μg g⁻¹ (dry weight basis). Gastropods show relatively higher arsenic concentrations in the soft tissues, 17.3-48.4 fig μg g⁻¹, and concentrations in the shells range from 1.4 to 16.3 fig μg g⁻¹. There is no correlation between arsenic levels in the soft-tissues and shells. There is also no correlation between arsenic levels in the organisms and the surrounding sediments and sediment pore waters. HPLC-GFAA techniques have been developed and used for the separation and quantitation of-arsenite, arsenate, methylarsonic acid, dimethylar-sinic acid, arsenobetaine, arsenocholine iodide and tetramethylarsonium iodide. This technique together with TLC, NMR, FAB and thermospray LCMS were employed for the detection of water-soluble arsenic compounds in 5 species of clams - Butter clam Saxidomus giganteus. Horse clam Schizothoerus nuttalli. Soft-shelled clam Mva arenaria. Native-littleneck clam Protothaca staminea and Manila clam Venerupis laponica. Varying amounts of arsenobetaine and tetramethylarsonium ion are found in all the clams. Butter clams show the pres ence of a third compound which appears to be trimethylarsine oxide. Small amounts of unknown arsenic containing compounds are present which are yet to be characterized . Arsenic speciation in 3 gastropods was also examined. The Northwest neptune Neptunea lvrata. the Thick-ribbed whelk Berinpius crebriscotata and Phoenician whelk Neptunea phoenicius all contain arsenobetaine and at least two unidentified arsenicals. / Science, Faculty of / Chemistry, Department of / Graduate