{"id":{"repo_id":"cape-town","oai_identifier":"oai:open.uct.ac.za:11427/9669"},"canonical_url":"https://search.dev.ndltd.org/etd/cape-town/oai:open.uct.ac.za:11427/9669","repository":{"repo_id":"cape-town","name":"University of Cape Town","base_url":"https://open.uct.ac.za/oai/request"},"display":{"title":"Triploid induction in the South African abalone, Haliotis midae","abstract":"An investigation was undertaken to determine whether triploidy could be induced and improve the growth rate of the South African abalone, Haliotis midae. From the polar body counts at 17 °C the release times of polar body 1 and 2 were found to be at 12 - 15 min. post insemination (pi.) and 33-36 min. pi. respectively. Cytochalasin B (CB) (0.5mg. 1-¹ seawater) and elevated temperature (30 °C) were used as stresses to induce triploidy. CB induced 48.4% polar body 1 and 70.9 % polar body 2 triploid larvae at 20 hrs pi. At 120 hrs pi. induction rates were 55.5% and 62.4% respectively. Temperature induction was more successful, producing 92.9% polar body 1 and 86.4% polar body 2 triploid larvae at 20 hrs pi. This success was still evident at 120 hrs pi, where 71.1 % polar body 1 and 62.5% polar body 2 triploid larvae were produced. In the CB induction, where polar body 1 was retained, there was a pronounced production of tetraploid larvae (34. 2%). It appeared that CB affected the ova's resistance to polyspermy, which was found to be dependent on both CB concentration and the amount of excess sperm present. At 0.4 mg 1-¹ CB in seawater, 86.5% triploids and 0% tetraploids were produced. However, on the addition of sperm, 25.4% triploids and 69% tetraploids resulted. CB (0.5 mg 1-¹ ) in seawater produced 42.6%> tetraploids which, after the addition of sperm, increased even further to 50. l % pentaploids. Larval survival was found to be low overall with only 17% and 22% of control (diploid) animals surviving the rearing period, in the temperature and CB treatments respectively. The survival rates of the polar body 2 treatment were 11 % and 15% whilst those of the polar body 1 treatment were 7% and 11 %. Although these percentages indicated a difference in survival rates between the CB and temperature inductions, the actual numbers of larvae surviving were the same. The polar body 1 triploid larval survival was significantly less than both control and polar body 2 triploid animals.","abstract_html":"An investigation was undertaken to determine whether triploidy could be induced and improve the growth rate of the South African abalone, Haliotis midae. From the polar body counts at 17 °C the release times of polar body 1 and 2 were found to be at 12 - 15 min. post insemination (pi.) and 33-36 min. pi. respectively. Cytochalasin B (CB) (0.5mg. 1-¹ seawater) and elevated temperature (30 °C) were used as stresses to induce triploidy. CB induced 48.4% polar body 1 and 70.9 % polar body 2 triploid larvae at 20 hrs pi. At 120 hrs pi. induction rates were 55.5% and 62.4% respectively. Temperature induction was more successful, producing 92.9% polar body 1 and 86.4% polar body 2 triploid larvae at 20 hrs pi. This success was still evident at 120 hrs pi, where 71.1 % polar body 1 and 62.5% polar body 2 triploid larvae were produced. In the CB induction, where polar body 1 was retained, there was a pronounced production of tetraploid larvae (34. 2%). It appeared that CB affected the ova's resistance to polyspermy, which was found to be dependent on both CB concentration and the amount of excess sperm present. At 0.4 mg 1-¹ CB in seawater, 86.5% triploids and 0% tetraploids were produced. However, on the addition of sperm, 25.4% triploids and 69% tetraploids resulted. CB (0.5 mg 1-¹ ) in seawater produced 42.6%> tetraploids which, after the addition of sperm, increased even further to 50. l % pentaploids. Larval survival was found to be low overall with only 17% and 22% of control (diploid) animals surviving the rearing period, in the temperature and CB treatments respectively. The survival rates of the polar body 2 treatment were 11 % and 15% whilst those of the polar body 1 treatment were 7% and 11 %. Although these percentages indicated a difference in survival rates between the CB and temperature inductions, the actual numbers of larvae surviving were the same. The polar body 1 triploid larval survival was significantly less than both control and polar body 2 triploid animals.","abstract_has_math":false,"creators":["Stepto, Nigel Keith"],"institution":"Department of Biological Sciences","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Cook, Peter"],"committee_chairs":[],"committee_members":[],"year":1997,"date_issued":"1997","date_published":"1997","updated_at":"2026-07-22T22:23:27Z","subjects":[],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/11427/9669","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Cook, Peter"]},{"key":"dc:creator","label":"Author","values":["Stepto, Nigel Keith"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-11-15T19:43:48Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-11-15T19:43:48Z"]},{"key":"dc:date.issued","label":"Date","values":["1997"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Department of Biological Sciences"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cape Town"]},{"key":"dc:type","label":"Dc Type","values":["Master Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Masters"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["MSc"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/11427/9669"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Bibliography: leaves 72-80."]},{"key":"dc:description.abstract","label":"Abstract","values":["An investigation was undertaken to determine whether triploidy could be induced and improve the growth rate of the South African abalone, Haliotis midae. From the polar body counts at 17 °C the release times of polar body 1 and 2 were found to be at 12 - 15 min. post insemination (pi.) and 33-36 min. pi. respectively. Cytochalasin B (CB) (0.5mg. 1-¹ seawater) and elevated temperature (30 °C) were used as stresses to induce triploidy. CB induced 48.4% polar body 1 and 70.9 % polar body 2 triploid larvae at 20 hrs pi. At 120 hrs pi. induction rates were 55.5% and 62.4% respectively. Temperature induction was more successful, producing 92.9% polar body 1 and 86.4% polar body 2 triploid larvae at 20 hrs pi. This success was still evident at 120 hrs pi, where 71.1 % polar body 1 and 62.5% polar body 2 triploid larvae were produced. In the CB induction, where polar body 1 was retained, there was a pronounced production of tetraploid larvae (34. 2%). It appeared that CB affected the ova's resistance to polyspermy, which was found to be dependent on both CB concentration and the amount of excess sperm present. At 0.4 mg 1-¹ CB in seawater, 86.5% triploids and 0% tetraploids were produced. However, on the addition of sperm, 25.4% triploids and 69% tetraploids resulted. CB (0.5 mg 1-¹ ) in seawater produced 42.6%> tetraploids which, after the addition of sperm, increased even further to 50. l % pentaploids. Larval survival was found to be low overall with only 17% and 22% of control (diploid) animals surviving the rearing period, in the temperature and CB treatments respectively. The survival rates of the polar body 2 treatment were 11 % and 15% whilst those of the polar body 1 treatment were 7% and 11 %. Although these percentages indicated a difference in survival rates between the CB and temperature inductions, the actual numbers of larvae surviving were the same. The polar body 1 triploid larval survival was significantly less than both control and polar body 2 triploid animals."]},{"key":"dc:title","label":"Title","values":["Triploid induction in the South African abalone, Haliotis midae"]}]}],"canonical_facts":{"dc:contributor.advisor":["Cook, Peter"],"dc:creator":["Stepto, Nigel Keith"],"dc:date.accessioned":["2014-11-15T19:43:48Z"],"dc:date.available":["2014-11-15T19:43:48Z"],"dc:date.issued":["1997"],"dc:description":["Bibliography: leaves 72-80."],"dc:description.abstract":["An investigation was undertaken to determine whether triploidy could be induced and improve the growth rate of the South African abalone, Haliotis midae. From the polar body counts at 17 °C the release times of polar body 1 and 2 were found to be at 12 - 15 min. post insemination (pi.) and 33-36 min. pi. respectively. Cytochalasin B (CB) (0.5mg. 1-¹ seawater) and elevated temperature (30 °C) were used as stresses to induce triploidy. CB induced 48.4% polar body 1 and 70.9 % polar body 2 triploid larvae at 20 hrs pi. At 120 hrs pi. induction rates were 55.5% and 62.4% respectively. Temperature induction was more successful, producing 92.9% polar body 1 and 86.4% polar body 2 triploid larvae at 20 hrs pi. This success was still evident at 120 hrs pi, where 71.1 % polar body 1 and 62.5% polar body 2 triploid larvae were produced. In the CB induction, where polar body 1 was retained, there was a pronounced production of tetraploid larvae (34. 2%). It appeared that CB affected the ova's resistance to polyspermy, which was found to be dependent on both CB concentration and the amount of excess sperm present. At 0.4 mg 1-¹ CB in seawater, 86.5% triploids and 0% tetraploids were produced. However, on the addition of sperm, 25.4% triploids and 69% tetraploids resulted. CB (0.5 mg 1-¹ ) in seawater produced 42.6%> tetraploids which, after the addition of sperm, increased even further to 50. l % pentaploids. Larval survival was found to be low overall with only 17% and 22% of control (diploid) animals surviving the rearing period, in the temperature and CB treatments respectively. The survival rates of the polar body 2 treatment were 11 % and 15% whilst those of the polar body 1 treatment were 7% and 11 %. Although these percentages indicated a difference in survival rates between the CB and temperature inductions, the actual numbers of larvae surviving were the same. The polar body 1 triploid larval survival was significantly less than both control and polar body 2 triploid animals."],"dc:identifier.uri":["http://hdl.handle.net/11427/9669"],"dc:language.iso":["eng"],"dc:publisher.department":["Department of Biological Sciences"],"dc:publisher.institution":["University of Cape Town"],"dc:title":["Triploid induction in the South African abalone, Haliotis midae"],"dc:type":["Master Thesis"],"dc:type.qualificationlevel":["Masters"],"dc:type.qualificationname":["MSc"]},"updated_at":"2026-07-22T22:23:27Z"}