Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 46 for “"urchins"”.
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David Gilmour Blythe's Street Urchins and American Nativism
David Gilmour Blythe's street urchin paintings created during the 1850s are disturbing and often grotesque. The image of childhood that he created was quite different from that of his American contemporaries who adapted the romantic notion of the child from eighteenth-century English painters. …
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Systematics and biodiversity of South African sea urchins
The South African Echinoidea (Echinodermata) were last reviewed by Clark & Courtman Stock (1976) and numerous unidentified specimens and records have accumulated since that time, plus there have been many taxonomic changes within the group. Therefore this study, which forms the first of its kind in …
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Hydrogen peroxide-induced genotoxicity and transgenerational implications in sea urchins
… degradation rates and genotoxicity in sea urchins exposed to environmentally-relevant concentrations of H<sub>2</sub>O<sub>2</sub>. The degradation rate of H<sub>2</sub>O<sub>2</sub> was 1% per day, slower than reported in previous studies which suggested limited environmental impact due to …
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COLLAGEN AND ANTIOXIDANTS FROM SEA URCHINS: WASTE VALORIZATION CHALLENGES TOWARDS REGENERATIVE MEDICINE
Sea urchins (mainly Paracentrotus lividus) are well known worldwide as a delicacy that is processed in the food industry or consumed directly in restaurants. The gonads are the only edible part of these marine animals, while the rest (more than 90-95% of their total mass) is discarded as waste. …
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Distributional relationships among subtidal algae, sea urchins and reef fish in northeastern New Zealand
Interactions among large brown macroalgae, sea urchins, and fishes were investigated in northeastern New Zealand during the period 1988 - 1993. The Cape Rodney to Okakari Point Marine Reserve was the site of many of these investigations. The patterns of abundance of large brown macroalgae and …
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Development of an embryo-larval chronic toxicity test using the sea urchins Tripneustes gratilla and Echinometra mathaei
… and ecologically relevant. Gametes of the sea urchins Echinometra mathaei and Tripneustes gratilla are used for acute toxicity testing purposes in South Africa through the fertilisation test (e.g. for testing effluents and seawater samples). However, this test has raised questions on the …
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Kelp forests in False Bay: urchins vs. macroalgae in South Africa's south-west coast biogeographical transition zone
… to grazing influence from species such as sea urchins. This study (1) explores the uniformity of these transition zone kelp forests along the western side of False Bay, with a focus on macroalgae and urchins, (2) identifies a threshold in urchin density above which algal abundance declines and …
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The primary structure of histones H2B from sperm of the sea urchins Parechinus angulosus and Psammechinus miliaris
Histones H2B have been purified from sperm of the sea urchin Parechinus angulosus and Psammechinus miliaris. Three H2B variants have been completely sequenced from P. angulosus and two H2B variants from P. miliaris have been partially sequenced. The sequences of the sperm histones H2B are compared …
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The feasibility of a commercial-scale recirculating aquaculture system integrating sea urchins (Tripneustes gratilla) and seaweed (Ulva)
… production parameters were compared between urchins stocked at various densities. The first trial was a three-month grow-out trial where only fresh Ulva lacinulata was supplied and the objective was to maximise urchin size. The subsequent trial focused on maximising gonad production where …
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Evaluating in situ Grazing Patterns of Lytechinus variegatus and their Effects on Seagrass Beds of Thalassia testudinum
… of these denudation events, the effects of sea urchins on seagrass are poorly understood. This study examines the effects of <em>L. variegatus</em> on <em>T. testudinum</em> in situ, to understand how sea urchins are affecting seagrasses <em>in situ</em>. Results indicate that urchins were found …
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Ecological interactions between abalone (Haliotis midae) juveniles and sea urchins (Parechinus angulosus), off the south-west coast of South Africa
… of a strong positive relationship between the urchins Parechinus angulosus and juveniles of the abalone Haliotis midae. Both species occupied primarily hard substrates, showing preferences for encrusting corallines. Of the juvenile abalone sampled, > 98% were found beneath sea urchins. All …
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Phenotypic and Genetic Diversity in the Sea Urchin Lytechinus Variegatus
… and throughout the Gulf of Mexico and Caribbean. Urchins in each of the 5 regions sampled (Beaufort, Gulf, Keys, Panama and Brazil) have a distinct phenotypic composition despite the presence of similar color morphs. The two regions at the extremes--Beaufort and Brazil--demonstrate the most …
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Aspects of the community structure and reproductive ecology of the common sea-urchin Parechinus angulosus Leske around the Cape Peninsula, South Africa
… (Zululand) to Luderitz Bay (Day, 1974). The urchins are therefore adapted to a wide range of temperatures. Maximum fluctuations probably occur along the stretches of coastline affected by upwelling, the South-West, and west coasts, with differentials of twelve degrees Centigrade and more. …
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The use of ULVA as a feed supplement in the development of an artificial diet and feeding regimes to produce export quality roe from the sea urchin Tripneustes gratilla (Linnaeus)
… FCR was significantly higher (p < 0.05) for urchins fed artificial feeds supplemented with Ulva, when compared to urchins fed non-supplemented feeds, suggesting that the inclusion of Ulva into the artificial diets acts as a feeding stimulant.Increased palatability and consumption subsequently …
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Chemosensory properties of different Ulva extracts and their effects on Tripneustes gratilla
Identifying the chemical compounds that attract urchins to seaweeds will increase sea urchin aquaculture efficiency as these compounds can be utilized in the production of artificial feeds enhancing their attractiveness and palatability. This study investigated the chemosensory preferences of the …
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Aspects of the community structure and reproductive ecology of the common sea-urchin Parechinus angulosus Leske around the Cape Peninsula, South Africa
… (Zululand) to Luderitz Bay (Day, 1974). The urchins are therefore adapted to a fairly wide range of temperatures. Maximum fluctuations probably occur along the stretches of coastline affected by upwelling, the south-west and west coasts, with differentials of twelve degrees Centigrade and …
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ECOLOGY OF ROCKY SUBTIDAL COMMUNITIES: THE ROLE OF MODIOLUS MODIOLUS (L) AND THE INFLUENCE OF DISTURBANCE, COMPETITION, AND MUTUALISM
… The hypothesis that by grazing kelp off mussels urchins decrease the risk of mussel dislodgement was tested by an urchin removal experiment. The removal of urchins from mussel beds led to exponential kelp recruitment, resulting in a 30-fold increase of mussel mortality (via kelp-induced …
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A MARINE PATHOGENIC PROTIST ACROSS SCALES: HOST-MICROBIOME INTERACTION, PROVENANCE, MORPHOLOGY AND TAXONOMICAL CHARACTERIZATION OF THE SCUTICOCILIATE PARASITE OF DIADEMATIDAE
… for mass mortality in Diadematidae sea urchins across the Caribbean and Indo-Pacific impacts its host, the pathogens provenance, and its taxonomic placement based on morphological and genetic variables. Combining molecular techniques, bacterial and archaeal microbiome profiling, 18S rRNA …
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Determining larval settlement, post-settlement and weaning substrates and regimes for the sea urchin Tripneustes gratilla in intensive aquaculture
Sea urchins gonads are a highly valued and priced seafood. Demand is stable and unlikely to decline in the future. Successful echinoculture is limited by the ability to produce large enough quantities of viable larvae and/or juveniles economically and efficiently due to a bottleneck in production …
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Ecosystem effects of a rock-lobster 'invasion': comparitive and modelling approaches
… reflected their previouslyrecorded dependency on urchins and the effects of rampant poaching. Floral species diversity was on average greater at invaded sites and increased with depth, whereas faunal species diversity was greater at non-invaded sites but also increased with depth. The depths in …
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