A new sabellid that infests the shells of molluscs and its implications for abalone mariculture

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dc.contributor.advisorCook, Peteren_ZA
dc.contributor.authorRuck, Kevinen_ZA
dc.date.accessioned2014-08-13T14:07:38Z
dc.date.available2014-08-13T14:07:38Z
dc.date.issued2000en_ZA
dc.descriptionBibliography: leaves 76-87.en_ZA
dc.description.abstractInfestations of sabellid polychaetes were found in South African farmed abalone in 1994. Growth experiments confirmed that infested abalone had reduced growth rates. Surveys of both the intertidal and subtidal region at various locations around the South African coastline revealed that the sabellid was endemic to the region. It occurred in a range of mollusc species, but some species were more susceptible than others. The fact that some molluscan species became infested with worms only when exposed to them in the laboratory suggests that environmental factors may play a role in controlling natural levels of infestation. Different host selection on the East Coast of South Africa suggests that there may be more than one species of worm. Larvae disperse by crawling and settle at the growing edge of the shell underneath the mantle. Although the larvae are benthic, there is limited transfer of larvae through the water column, which can result in export of larvae from infested tanks. The risks of dispersal are discussed in a farm management context. Abalone kept in more hygienic laboratory conditions tended to grow faster than in farm tanks and had lower levels of infestation by sabellid larvae. This was attributed to the sabellids being less fecund under these conditions. This was probably caused by lack of food as evidenced in a separate starvation experiment. Based on experimental observations and farm experience it was possible to make management recommendations to limit the effect of the sabellid Quantitative measurement taols to assess the impact and productivity of sabellid infestations were developed Management of infestations on a farm requires a combination of inhibiting transfer and productivity of the worm and also promoting growth of the abalone. However, the constant risk of exposure to natural populations of sabellids necessitates the development oJ a treatment to eradicate sabellid infestations. The use of microcapsules as a drug delivery mechanism was explored and holds promise. Gelatin microcapsules, oil immulsions and liposomes were experimented with. All formulations were successfully produced in the desired size range of 2-30 μm. In all cases the sabellid'l readily ingested the capsules. Various toxins were successfully added to the formulations, but none of the treatments were able to harm the sabellids. The problem appeared to be the short passage time within the guts and the inability of the sabellids to digest the outer encapsulating layers to expose the toxins. More research is required to find the correct combination of toxin and delivery mechanism.en_ZA
dc.identifier.apacitationRuck, K. (2000). <i>A new sabellid that infests the shells of molluscs and its implications for abalone mariculture</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/6178en_ZA
dc.identifier.chicagocitationRuck, Kevin. <i>"A new sabellid that infests the shells of molluscs and its implications for abalone mariculture."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2000. http://hdl.handle.net/11427/6178en_ZA
dc.identifier.citationRuck, K. 2000. A new sabellid that infests the shells of molluscs and its implications for abalone mariculture. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Ruck, Kevin AB - Infestations of sabellid polychaetes were found in South African farmed abalone in 1994. Growth experiments confirmed that infested abalone had reduced growth rates. Surveys of both the intertidal and subtidal region at various locations around the South African coastline revealed that the sabellid was endemic to the region. It occurred in a range of mollusc species, but some species were more susceptible than others. The fact that some molluscan species became infested with worms only when exposed to them in the laboratory suggests that environmental factors may play a role in controlling natural levels of infestation. Different host selection on the East Coast of South Africa suggests that there may be more than one species of worm. Larvae disperse by crawling and settle at the growing edge of the shell underneath the mantle. Although the larvae are benthic, there is limited transfer of larvae through the water column, which can result in export of larvae from infested tanks. The risks of dispersal are discussed in a farm management context. Abalone kept in more hygienic laboratory conditions tended to grow faster than in farm tanks and had lower levels of infestation by sabellid larvae. This was attributed to the sabellids being less fecund under these conditions. This was probably caused by lack of food as evidenced in a separate starvation experiment. Based on experimental observations and farm experience it was possible to make management recommendations to limit the effect of the sabellid Quantitative measurement taols to assess the impact and productivity of sabellid infestations were developed Management of infestations on a farm requires a combination of inhibiting transfer and productivity of the worm and also promoting growth of the abalone. However, the constant risk of exposure to natural populations of sabellids necessitates the development oJ a treatment to eradicate sabellid infestations. The use of microcapsules as a drug delivery mechanism was explored and holds promise. Gelatin microcapsules, oil immulsions and liposomes were experimented with. All formulations were successfully produced in the desired size range of 2-30 μm. In all cases the sabellid'l readily ingested the capsules. Various toxins were successfully added to the formulations, but none of the treatments were able to harm the sabellids. The problem appeared to be the short passage time within the guts and the inability of the sabellids to digest the outer encapsulating layers to expose the toxins. More research is required to find the correct combination of toxin and delivery mechanism. DA - 2000 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2000 T1 - A new sabellid that infests the shells of molluscs and its implications for abalone mariculture TI - A new sabellid that infests the shells of molluscs and its implications for abalone mariculture UR - http://hdl.handle.net/11427/6178 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/6178
dc.identifier.vancouvercitationRuck K. A new sabellid that infests the shells of molluscs and its implications for abalone mariculture. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2000 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/6178en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Biological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherZoologyen_ZA
dc.titleA new sabellid that infests the shells of molluscs and its implications for abalone maricultureen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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