Advancement of sexual maturation and spawning of sea bass, Lates calcarifer (Bloch), using pelleted luteinizing hormone-releasing hormone analogue and 17α-methyltestosterone.
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The ability of luteinizing hormone-releasing hormone analogue [(D-Ala6, Pro9-NEt)LHRH], 17α-methyltestosterone (MT), and their combination to advance gonadal maturation and spawning in captive sea bass (Lates calcarifer Bloch) broodstock was tested. Several hormonal therapies were tested including monthly implantations of a low dose (100 μg/kg body weight) of each hormone and a high dose (200 μg/kg) implanted to sexually-quiescent sea bass at 45-day intervals. A high dose of LHRHa alone or in combination with MT induced a significant number of mature females (43–71%) in April, 45 days after a single implantation in early March. A lower dose of pelleted LHRHa and LHRHa plus MT was found effective (78–80%) only in May following three monthly implantations. Two and three monthly implantations of a low dose of MT failed to stimulate oocyte growth in April and May whereas a less frequent mode of application of a high dose of the androgen inhibited ovarian growth in April only. A low dose of MT alone significantly increased the number of mature males in April (90%) and May (100%) after two and three monthly implantations. All male sea bass which received three monthly implantations of a low dose of LHRHa and LHRHa plus MT were sexually mature in May. Sexually mature sea bass obtained from these experiments spawned in early May after a single intramuscular injection of LHRHa. These results demonstrate the potential use of pelleted LHRHa and MT to significantly advance gonadal development and spawning in sea bass earlier than the annual breeding season.
Presented in part at the Second Asian Fisheries Forum in Tokyo, Japan, 17–21 April 1989 (Abstract No. 227).
CitationGarcia, L. M. B. (1990). Advancement of sexual maturation and spawning of sea bass, Lates calcarifer (Bloch), using pelleted luteinizing hormone-releasing hormone analogue and 17α-methyltestosterone.
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Milt production of sea bass Lates calcarifer Bloch administered an analogue of luteinizing hormone-releasing hormone and 17α-methyltestosterone GV Hilomen-Garcia, RB Baldevarona & F Lacanilao -
The Israeli Journal of Aquaculture-Bamidgeh, 2002 - Society of Israeli Aquaculture and Marine BiotechnologyThe milt production responses of sexually mature sea bass Lates calcarifer to (D-Ala6, Pro9-N- ethylamide) luteinizing hormone-releasing hormone (LHRHa) and 17α-methyltestosterone injections were examined. At 24 h after injection of a low dose of LHRHa (20 μg/kg BW), the sperm count decreased significantly compared to saline-treated fish, but it returned to pre-treatment levels 48 h after injection, suggesting a possible hydration of the milt. Other milt parameters (milt volume, spermatocrit, sperm production) in LHRHa-treated fish did not vary from their controls at 24 or 48 h after injection but the overall pattern suggested a reduction in milt viscosity. Total expressible milt and spermatozoa collected over the 48-h experiment was approximately three-fold higher in LHRHa-injected fish than in saline-injected fish, indicating a stimulation of spermatozoa production, not merely milt dilution due to hydration. In a second experiment, sperm count and spermatocrit were significantly lower than those of saline-injected fish at 17 and 48 h after a single injection of a high dose of LHRHa (80 μg/kg BW). A methyltestosterone injection combined with the LHRHa injection also resulted in a significantly lower sperm count, but the spermatocrit remained comparable to the control group, suggesting a suppression of the LHRHa-induced milt hydration response. Results demonstrate that LHRHa stimulates milt hydration and spermatozoa production in milting sea bass and that a simultaneous methyltestosterone injection partially suppresses this response.
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Journal of Fisheries and Aquatic Science, 2012 - Academic Journals, New YorkEffects of a steroid hormone Dehydroepiandrosterone (DHEA) on sex differentiation of hybrid red Tilapia Oreochromis niloticus x O. mossambicus larvae were investigated. Three day-old tilapia larvae were fed diets supplemented with varying concentrations of DHEA (0, 20, 40, 80 and 160 mg kg-1 feed) for 24 days. A positive control group fed with diet containing 60 mg kg-1 of 17α-methyl testosterone was also included in the experimental run. Results indicate that among the DHEA treatment groups, larvae fed with 160 mg kg-1 DHEA showed the highest percentage of males that is comparable to the number of differentiated male fish observed in treatment group receiving the 17α-methyl testosterone as the positive control group. DHEA supplementation also improves weight gain and enhances feed conversion ratio. These findings suggest that DHEA can be used as a dietary supplement to induce masculinization and can improve the growth performance of tilapia larvae.
Effect of season on oocyte development and serum steroid hormones in LHRHa and pimozide-injected catfish Clarias macrocephalus (Günther) JD Tan-Fermin, CL Marte, H Ueda, S Adachi & K Yamauchi -
Fisheries Science, 1999 - Japanese Society of Fisheries ScienceOocyte and blood samples were taken from gravid female catfish Clarias macrocephalus at 4-h intervals to monitor the stage of oocyte development and serum steroid hormone profiles after injection of luteinizing hormone-releasing hormone analogue (LHRHa) and pimozide (PIM) during the off-season (February) and the peak of the natural breeding period (August). Results showed that the onset of final oocyte maturation (12h) and ovulation (16h), and levels of serum estradiol-17β (E2) did not vary with season in LHRHa+PIM-injected fish. In February, ovulated eggs were stripped from three and two hormone-treated fish at 16h and 20h post-injection, respectively. In August, ovulation was observed in all hormone-treated females (n=5) at 16h post-injection but stripping of the eggs was possible only 4h thereafter. Serum E2 levels were significantly different only with varying time post-injection; a marked increase occurred at 12h, but the elevation was higher in fish induced to ovulate during the peak (16.8ng/ml) than off-season (7.7ng/ml). Hormone-treated fish showed higher serum testosterone (T) levels during the peak season (17-23ng/ml) than those injected during the off-season (10-20ng/ml) at 4-12h post-injection. Serum 17α, 20β-dihydroxy-4-pregnene-3-one (DHP) levels of hormone-treated fish during the off-season were only about half the level (0.29 and 0.52 ng/ml) of those treated with the same hormones during the peak season (0.54 and 0.9ng/ml) at 8 and 12h postinjection, respectively. Development of oocytes and serum steroid hormone profiles after LHRHa+PIM-induced ovulation provide basic understanding of the processes that mediate final oocyte maturation and ovulation in captive C. macrocephalus.