8 resultados para BRYOZOANS

em Deakin Research Online - Australia


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Examination of samples of bryozoans from the south- eastern slope sediments of Australia ("Franklin" SLOPE Stations 6, 7), has revealed the presence of many specimens of several genera with species which have minute, rooted colony forms. Among these are new species of the genera Batopora Reuss (B. problematica) and Lacrimula Cook (L. affinis). The structure of colonies is briefly described. The family Batoporidae is considered to contain only these two genera, although they have relationships with the discoidal genus Orbitulipora, and similarities in colony form to the genera assigned to the Conescharellinidae.

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The genus Adeona is a characteristic and common part of the Australian shelf fauna, extending to the tropical Indo-West Pacific. The genus first appears in the fossil record of the Miocene of south-eastern Australia. Zooid dimorphism has been recognised initially from subtle differences in the external appearance, which have not been described previously. Detailed examination has shown enlarged brooding zooids with marked differences from autozooids in the internal structure of the peristomes and in the occurrence of a primary calcified orifice.

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The family Conescharellinidae Levinsen is defined and is regarded as comprising seven cheilostome genera (Conescharellina, Bipora, Trochosodon, Flabellopora, Zeuglopora, Crucescharellina and Ptoboroa). The astogeny of colonies, that consists of frontally budded zooids with "reversed" orientation, is briefly described and compared between genera. The morphology of zooids and heterozooids is defined and keys to genera and Australian species are provided. Taxa that were first described from Australia or from reliable subsequent records are redescribed and illustrated where possible. Australian specimens that have been identified as non-Australian species, have generally been found to be distinct and are here redescribed as new species. Some non-Australian records of specimens previously assigned to Australian species have also been re-examined. These are described and sometimes referred to other taxa. Altogether, eight previously described species that have not been found in the present material are discussed and 27 taxa are described from collections, principally from the eastern and southern coasts of Australia and from the Tertiary of Victoria. Eighteen of these are considered to be new species. Where possible, type or at least topotype material of previously described species has been examined. Colonies from the collections of Museum Victoria (NMV) and the Natural History Museum, London (BMNH), have been examined. New species from Australia described here are: Conescharellina cognata, C. ecstasis, C. diffusa, C. obscura, C. stellata, C. plana, C. perculta, C. pustulosa, C. ocellata, C. macgillivrayi, C. humerus; Trochosodon fecundus, T. asymmetricus, T. diommatus, T. aster, T. anomalus, T. praecox and Crucescharellina australis. In addition, the New Zealand bryozoan Trochosodon multiarmatus (Gordon, 1989) (not Bipora multiarmata Maplestone, 1909) is described as Trochosodon gordoni sp. nov.

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Recent sediment samples recovered from the mid-latitude South West Shelf (SWS) of Western Australia (23°- 32° S) by a scientific team aboard the RV Franklin have produced large numbers of free-living, lunulitiform bryozoans. Among these are three undescribed species, Otionellina boneae sp. nov., Selenaria kayae sp. nov., and Selenaria meganae sp. nov. The Australasian lunulite fauna is both diverse and abundant and the new species bring the total of described taxa to sixty (P. Cook unpub.). Twelve lunulite species have been recorded from the SWS. These findings have extended the known geographical range of several lunulite species.

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Members of the bryozoan family Petraliellidae share the capacity to develop basal rhizoids, which anchor the unilaminar, semi-repent parts of the colonies above the substratum, and enable them to overgrow other, competing sessile forms. Little is known of the larval behaviour and settlement, or the early astogeny of species. Ancestrulate colonies of the Australian Tertiary lunulitiform species Smittia biincisa are referred to the genus Riscodopa , and together with Riscodopa paucipora sp. nov. are described and compared with the Recent species R. cotyla and R. parva from New Zealand, and with R. hyalina sp. nov. from New South Wales, Australia. All the Recent species are known to develop basal rhizoids, and an early astogeny similar to that of many other small, rooted bryozoans, comprising the post-metamorphosis development of a binary complex, including rhizoid and feeding elements, is inferred for Riscodopa . Observations on living Hippopetraliella magna from Queensland suggest that both the ancestrular morphology and early astogeny show a capacity for semi-repent growth, even though they do not include rhizoid development. Larvae metamorphose without direct attachment, and the ancestrula develops elongated, partially calcified supporting processes, which raise the early stages of growth above the substratum. A similar kind of ancestrula has been found in preserved specimens of Mucropetraliella ellerii .

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The “Levipustula fauna” is a relatively diverse fossil assemblage composed of brachiopods, bivalves, bryozoans, gastropods and crinoids that appears in glaciomarine sequences related to the Carboniferous glacial event that affected the central-western Argentinean basins. Brachiopods that characterize this fauna have been studied in some of the classical localities of the Argentine Precordillera in San Juan province.

In the Hoyada Verde Formation, the “Levipustula fauna” is usually located immediately above the glacial diamictite horizons and appears to be associated with the mudstones facies of the postglacial transgression. From a palaeoecological study, three brachiopod subfaunas are distinguished in this formation: the lower “Neospirifer” (“Trigonotretidae” gen. nov.) subfauna, above which the more diversified Kitakamithyris subfauna occurs, and the upper Levipustula subfauna, with the dominant species being attributed to Levipustula levis Maxwell. The Hoyada Verde fauna, as well those identified in the La Capilla Formation (Cerro El Morado locality), have been proposed as the typical “Levipustula fauna”. However, in the Leoncito Formation, the “Levipustula fauna” occurs in sandstones horizons located below the glacial diamictite beds. This fauna is poorly diversified and the brachiopods are characterized by “Neospirifer” (“Trigonotretidae” gen. nov.)-Septosyringothyris assemblage and Levipustula is not abundant. This fauna has been considered a colder “pre-interglacial fauna”.

The significant taxonomic, palaeoecologic and taphonomic variations of the “Levipustula fauna”, as well as its position in the glacial sequences, suggest an important palaeoenvironmental control related to Carboniferous glacial dynamics. From the palaeobiogeographic viewpoint, this fauna shows the highest affinity with the Eastern Australian basins from where it was previously described.

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The objective of the work reported in this thesis was to design and implement an ecological effects environmental monitoring program which would: 1) Collect baseline biological information on sessile epibiotic fouling communities from an area adjacent to a petroleum refinery located on Corio Bay, Victoria, to allow comparison with results of future monitoring for the assessment of long term temporal water quality trends. 2) Detect and — if possible - estimate the magnitude of any influence on epibiotic fouling communities within the Corio Bay marine ecosystem attributable to operations at the Shell Petroleum Refinery. 3) Investigate the extent of thermal stratification and rate of dispersal of the petroleum refinery main cooling-water outfall plume (discharging up to 350,000 tonnes of warmed seawater per day), and its effect on epibiotic communities within the EPA-defined mixing zone. A major component of the work undertaken was the design and development of artificial-substrate biological sampling stations suitable for use under the conditions prevailing in Corio Bay, and the development of appropriate quantitative underwater photographic sampling techniques to fulfil the experimental criteria outlined above. Experimental and other constraints imposed on the design of the stations precluded the simple suspension of frames from jetties or pylons, a technique widely used in previous work of this type. Artificial substrate panels were deployed along three radial transects centred within and extending beyond the petroleum refinery main cooling-water mixing zone. Identical substrate panels were deployed at a number of control sites located throughout Corio Bay, each chosen for differences in their degree of exposure to such factors as water movement, depth, shipping traffic and/or comparable industrial activity. The rate of colonisation (space utilisation) and the development of epibiotic fouling communities on artificial substrate panels was monitored over two twelve-month sampling periods using quantitative underwater photographic sampling techniques. Sampling was conducted at 4-8 week intervals with the rate of panel colonisation and community structure determined via coverage measurements. Various species of marine algae, polychaete tubeworms, hydroids, barnacles, simple and colonial ascidians, sponges, bivalve molluscs and encrusting bryozoans were all detected growing on panels. Communities which established on panels within the cooling-water mixing-zone and those at control sites were compared using statistical procedures including agglomerative hierarchical cluster analysis. A photographic sample archive has been established to allow comparison with similar future studies.