Includes bibliographical references (41 leaves). / 3 v. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The systematics of the hyperiidean amphipod infraorder Physocephalata is investigated with particular emphasis on the higher classification of the superfamily Platysceloidea. / Thesis (Ph.D.)--University of Adelaide, Dept. of Environmental Biology, 2000?

Thesis (Ph.D.)--University of Adelaide, Dept. of Environmental Biology, 2000? / Includes bibliographical references (41 leaves).

Thesis (M. Sc. (Zoology and Entomology))--Rhodes University, 2006.

The population structure and feeding dynamics of the hyperiid amphipod, Themisto gaudichaudii, was investigated during two cruises of the South African National Antarctic Programme conducted in the Indian sector of the Polar Frontal Zone during austral autumn (April) 2004 and 2005. During the 2004 cruise the frontal features that delimit the PFZ converged to form a single distinctive feature. In 2005, the research cruise was conducted in the vicinity of a cold-core eddy which was spawned from the Antarctic Polar Front. Total mesozooplankton abundance and biomass during the 2004 study ranged from 55.19 to 860.57 ind. m⁻³, and from 2.60 to 38.42 mg dwt m⁻³, respectively. In 2005 the abundance and biomass ranged from 23.1 to 2160.64 ind. m⁻³, and from 0.76 to 35.16 mg dwt m⁻³, respectively. The mesozooplankton community was numerically dominated by copepods, pteropods, and ostracods during both surveys. The abundance and biomass of Themisto gaudichaudii in the region of investigation was < 0.2 ind. m⁻³ (range 0.01 to 0.15 ind. m⁻³) and < 0.06 mg dwt m⁻³ (range 0.02 to 0.06 mg dwt m⁻³) during 2004, while in 2005 the abundance and biomass of the amphipod ranged from < 0.01 to 0.2 ind. m⁻³ and < 0.01 to 0.04 mg dwt m⁻³, respectively. These values correspond to < 1% of the total mesozooplankton abundance and biomass during both surveys. T. gaudichaudii exhibited no significant spatial patterns in abundance, biomass and total length during both 2004 and 2005 (p > 0.05 in all cases). A key feature of the two investigations was the virtual absence of juveniles (total length < 15 mm) among the amphipod population, supporting the suggestion that they exhibit strong seasonal patterns in reproduction. Gut content analysis during both years indicated that for both the male and female amphipods’, copepods were the most prevalent prey species found in stomachs, followed by chaetognaths and pteropods. Results of electivity studies indicate that T. gaudichaudii is an opportunistic predator, generally feeding on the most abundant mesozooplankton prey. Results of in vitro incubations indicated that the total daily feeding rate of T. gaudichaudii during 2004 ranged from 11.45 to 20.90 ind. m⁻³ d⁻¹, which corresponds to between 0.12 and 1.64% of the total mesozooplankton standing stock. In 2005, the feeding rate ranged between 0.1 and 1.73% of the total mesozooplankton standing stock. The low predation impact of T. gaudichaudii during this study can be related to their low abundances and high interannual variability throughout the region of investigation.

The plankton community of the Gulf of California exist in a transition region from oceanic to neritic habitats, tropical to warm-temperature waters that is strongly influenced by a complex hydrography and bathymetry. Hyperiid Amphipods were chosen as a focus of this study to elucidate the various forces that shape the distributions of the entire community. To test how strongly hyperiids select water of a particular type (the "Water Mass" hypothesis), multiple regression analysis was applied to species' distributions and station hydrography. The quantitative results indicate that there is a strong relation between the distribution of a given hyperiid and the location of discrete water bodies in the Gulf of California. Three linked gyral currents, powered by a tidally-driven interval wave have been hypothesized to influence phytoplankton distributions in the Gulf. Through both qualitative and quantitative statistical analysis, these gyres are shown to be quite important in structuring species' distributions and have a strong effect on the character of the Gulf hydrography. Significant change in community diversity are found to occur only at the boundaries of these gyres. Many authors consider hyperiid amphipods as obligate parasites upon gelatinous zooplankton, and not worthy of distributional analyses. Both qualitative and quantitative test of this hypothesized relationship between hyperiid and "host" offer little support for the concept of hyperiid amphipods as parasites. Instead, there is considerable evidence that hyperiids are "substrate-bound," as are most amphipods, and use gelatinous zooplankton as facultative, transient hosts. Being able to switch hosts as desired, hyperiids can select for optimum conditions, and can serve to model the zooplankton community as a whole.

Submitted by Alberto Vieira (martins_vieira@ibest.com.br) on 2018-01-12T19:50:57Z No. of bitstreams: 1 552181.pdf: 40720142 bytes, checksum: 2e2fd4a9a7712d037db2df32bd963581 (MD5) / Made available in DSpace on 2018-01-12T19:50:58Z (GMT). No. of bitstreams: 1 552181.pdf: 40720142 bytes, checksum: 2e2fd4a9a7712d037db2df32bd963581 (MD5) Previous issue date: 2001 / CAPES / Estudo da ocorrência e distribuição das espécies da subordem Hyperiidea encontradas na área compreendida entre 02º e 40ºS, preenchendo uma lacuna no Oceano Atlântico Sul Ocidental, com escassos trabalhos sobre o grupo. As quatro coleções selecionadas, abrangendo as áreas: Nordeste, Central, Sudeste e Sul reuniram uma densidade média de 132,87 ind. L00m^-3. A coleção FINEP XI da área Sudeste, teve a maior representatividade em densidade, refletindo a sua amostragem exclusiva na zona costeira, onde normalmente uma maior abundância de organismos é encontrada. A maior diversidade e riqueza de espécies foi encontrada nas estações oceânicas. A área de estudo, ocupada pelas zonas tropical, subtropical e temperada, com a predominância das águas tropicais oligotróficas da Corrente do Brasil, é limitada ao norte pela região equatorial e ao sul pela Convergência Subtropical. Foram identificadas 107 espécies nas 279 amostras estudadas, sendo Lestrigonus bengalensis Giles, Themisto gaudichaudii Guérin e Themisto australis (Stebbing), as espécies mais abundantes e Lestrigonus bengalensis, Brachyscelus crusculum Bate e Hyperietta vosseleri (Stebbing), as espécies com as maiores frequências de ocorrência. Lestrigonus bengalensis é destacadamente a espécie responsável pela maior abundância do material estudado. A segunda espécie mais abundante, Themisto gaudichaudii, com ocorrência apenas na área Sul, tem uma grande representatividade e importância na cadeia trófica das regiões temperadas e polares. Foram encontrados também, 15 instantes de associação entre os Hyperiidea e organismos gelatinosos do tipo, salpas e sifonópforos. / Study of the occurrence and distribution of the species of suborder Hyperiidea found in the area between 02º and 40°S, thus filling a gap in the Western South Atlantic Ocean, with bore scant work on the group. The four collections selected, comprising the Northeastern, Center, Southeastern and Southern areas, displayed an average density of 132.87 ind. l00m^-3. The FINEP XI collection, from the Southeast area was the most representative in density, reflecting its exclusive sampling in the coastal zone, where normally a great abundance of organisms is found. The greatest diversity and wealth of species was found at ocean stations. The study area, taken up by the tropical, subtropical and temperate zones, with the predominance of the oligotrophic tropical waters of the Brazil Current is limited, in the north by the equatorial region, and in the south by the Subtropical Convergence. One hundred and seven (107) species were identified in the two hundred and seventy-nine (279) samples studied, the most abundant species being Lestrigonus bengalensis Giles, Themisto gaudichaudii Guérin e Themisto australis (Stebbing), while Lestrigonus bengalensis, Brachyscelus crusculum Bate and Hyperietta vosseleri (Stebbing), were the species with the highest frequencies of occurrence. Lestrigonus bengalensis is pointedly the species responsible for the greatest abundance of the material studied. The second most abundant species, Themisto gaudichaudii, with occurrence only in the Southern area bears great representative and importance in the trophic chain of the temperate and polar regions. Fifteen (15) instances of associations between the Hyperiidea and gelatinous organisms of the salp and siphonophore types have also been found.