Environmental and endocrine control of reproduction and its manipulation in the rabbitfish siganus canaliculatus (Park 1797)
| Author | Shams, Abdulredha Jassim. | |
|---|---|---|
| metadata.dc.contributor.department | UNIVERSITY OF WALES | |
| metadata.dc.date.accessioned | 2026-09-20T15:52:47Z | |
| Publication date | 1998 | |
| Degree level | Doctoral | |
| Abstract | Abstract : A detailed description is given of the normal seasonal changes in ovarian morphology and oocyte histology in Siganus canaliculatus from the previtellogenic stages to the time of completion of vitellogenesis. A histological description is given of the maturational stages observed in oocytes from gonadotropin-treated hatchery fish. Atresia is described for most stages of oocyte development and was observed in both hatchery and wild fish. Seasonal changes in serum oestradiol levels, which correlated closely with vitellogenesis in both hatchery and wild fish, ranged from less than 0.2 ng ml"1 from June to November to a peak of approximately 1.0 ng ml"1 in the early part of the normal spawning season in April. Broodstock fish subjected to handling stressors typical of hatcheries (netting, biopsy and blood sampling), can accommodate to moderate levels of stressors. Effects caused by stressors may not be evident until the later stages of oocyte or larval development. Lunar regimes, including simulated constant full and constant new moon conditions, simulated normal and reversed lunar cycles, did not promote oocyte maturation or spawning in hatchery fish. Reproduction can be advanced by manipulation of the photoperiod. Photoperiodic regimes which advanced reproduction were those involving a switch to long days prior to or soon after the winter solstice. The extent of the advance (up to 3 months) was not correlated with the date on which the switch occurred. Reproduction was not delayed by any of the photoperiodic regimes which artificially delayed the winter solstice. A single injection of human Chorionic gonadotropin (hCG) induced final oocyte maturation and spawning in fish which had completed vitellogenesis. The optimum dose was approximately 1.0 IU g'1 body weight. There was some evidence that higher and lower doses caused deterioration in gamete and larval quality. Domperidone, a dopamine antagonist, which had no effect alone, potentiated some of the effects of hCG, including a reduction in the interval between injection and spawning. The use of comparatively high doses of either salmon- or mammalian gonadotropin releasing hormone analogues, given as a single injection with and without Domperidone, did not reliably induce spawning. | |
| metadata.dc.identifier.other | Drupal node 4246 | |
| metadata.dc.identifier.other | https://digitalrepository.uob.edu.bh/en/dar/environmental-and-endocrine-control-reproduction-and-its-manipulation-rabbitfish-siganus | |
| metadata.dc.identifier.uri | http://165.227.56.122/handle/123456789/7365 | |
| Language | en | |
| Link | https://digitalrepository.uob.edu.bh/en/_flysystem/fedora/2025-08/001650_environmental_and_endocrine_control_of_reproduction_and_its_manipulation_in_the_rabbitfish_siganus_canaliculatus_park_1797.pdf | |
| Subject | Paleontology--Eocene | |
| Subject | Algae, Fossil | |
| Subject | Siganidae. | |
| Title | Environmental and endocrine control of reproduction and its manipulation in the rabbitfish siganus canaliculatus (Park 1797) | |
| Type | Doctoral Dissertation |
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