Induction of sex inversion in juvenile grouper, Epinephelus suillus, (Valenciennes) by injections of 17α-Methyltestosterone
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Four groups of two-year old juvenile groupers (Epinephelus suillus), each with 8-9 individuals of mean body weight (BW) 1.2 kg, were treated with 17α-methyltestosterone (MT). MT was injected intramuscularly within the range of 0.5-5.0 mg kg-1 BW every 15 days. Gonadal biopsy and stripping of the abdomen was done every 15 days, the fish being sacrificed after six or twelve injections. Initial controls had immature ovaries containing primary oocytes in lamellae that extended into the central lumen. After six injections, proliferation of stromal and gonial cells were observed in all fish sampled. Regardless of treatment, gonad sections of fish with a minimum BW of 1.2 kg showed degeneration of primary oocytes and the presence of spermatogenic cells. Milt was also present in larger-sized fish (BW: 1.5 kg) given 0, 0.5 and 1.0mg MTkg-1 BW, after such fish had received an accumulated dose of 5 or 12mg MTkg-1 BW. However, gonad sections of smaller-sized fish following these treatments contained only primary oocytes and gonial cells after six (BW: 0.7-1.0kg) or twelve (BW: 0.6-1.3 kg) injections. In contrast, all fish treated with 5 mg MT kg-1 BW had testes in active spermatogenesis after six (BW: 1.2-1.6 kg) or twelve (BW: 0.8 kg) injections. Gonad weight and gonadosomatic index values decreased during consecutive sampling. Induction of female-to-male sex inversion in juvenile E. suillus by MT was probably synergistic with age and size.
CitationTan-Fermin, J. D., Garcia, L. M. B., & Castillo Jr., A. R. (1994). Induction of sex inversion in juvenile grouper, Epinephelus suillus, (Valenciennes) by injections of 17α-Methyltestosterone.
PublisherThe Ichthyological Society of Japan
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Dietary administration of dehydroepiandrosterone hormone influences sex differentiation of hybrid red tilapia (O. niloticus x O. mossambicus) larvae AH Mohamed, RFM Traifalgar, AE Serrano Jr., JP Peralta & FL Pedroso -
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.
ArticleGF Quinitio, JD Tan-Fermin & A Nagai -
Fisheries Science, 2001 - Japanese Society of Fisheries ScienceThirty immature juvenile grouper Epinephelus coioides (19-168 g bodyweight, BW) were randomly stocked in four units 6 t tanks to determine if mibolerone can be used to induce sex inversion in groupers. After acclimatization and weaning to artificial feed, the feed given daily (4% BW/day) was supplemented with 0, 50, 100, and 200 μg mibolerone/kg feed for about 18 weeks. Thereafter, the hormone treatment was withdrawn and the experiment was terminated at Week 24. Ten fish were killed for gonad histology at stocking to serve as an initial control while about three to five fish were killed every 8 weeks. In general, ovaries of initial controls showed the presence of moderate stromal cells and gonia and few primary oocytes. At Weeks 8 and 16, ovaries of the control fish (0 μg/kg) were similar to that of the initial control except that primary oocytes increased at Week 24. Gonads of fish fed diets containing 100 and 200 μg/kg had none to moderate spermatocytes and few spermatids at Week 8 and 16, although spermatozoa were not observed, indicating that the fish were undergoing spermatogenesis. Spermatogenesis at 50 μg/kg was not as advanced since only few spermatocytes occurred at Weeks 8 followed by moderate gonia and no spermatocytes and spermatids at Week 16. However, the presence of few primary oocytes was observed when mibolerone was withdrawn suggesting that sex-inversed fish reverted back to a female condition. These results show that sex inversion in juvenile grouper can be induced by oral administration of mibolerone and may have possible application on mature females to produce functional males.
Conference paperAC Fermin - In JV Juario & LV Benitez (Eds.), Seminar on Aquaculture Development in Southeast Asia, 8-12 September 1987, Iloilo City, Philippines, 1988 - Aquaculture Department, Southeast Asian Fisheries Development CenterBighead (Aristichthys nobilis) and silver (Hypophthalmichthys molitrix) carps were reared in ponds, pens and floating cages in Laguna Lake until maturity. Spontaneous gonadal maturation and rematuration of carp broodstock occurred within 2-2.5 years with average weight of 3-4 kg. Under lake conditions, broodstock were not given supplemental feeds. Induced spawning of gravid females was done by intraperitoneal injections using HCG combined with either common carp pituitary homogenates or LHRH-A. Stripping and dry-fertilization of eggs were done 6-8 hr after the final injection. Eggs were incubated in water containing 300-500 ppm Total Hardness. Fertilization and hatching rates were 23-88% and 7-36%, respectively. Post-larval carps were reared in tanks and fine-meshed nylon net cages installed in manured ponds. Tank-reared post-larvae were fed with Brachionus plicatilis and subsequently with Moina macrocopa in combination with powered formulated feeds containing 40% crude protein. Fry were harvested and stocked in nursery cages after 30-45 days of rearing in tanks. Four-month old 50-100 g tilapia (Oreochromis niloticus) stocked in hapa net cages, tanks or ponds were used for breeding. Egg and fry production was significantly high at 4 females/m2 stocking density Different sex ratios, however, did not affect fry production. Spawning frequency and total growth of broodstock was highest in fry fed formulated diets containing 50% crude protein. Harvesting of fry was done every 15 days during summer months and every 21 days during cold months. Fry were reared in tanks and hapa cages and fed diets containing 35% crude protein. Supplemental feeding in the lake was suspended when productivity reached 3 gC/m2 /day.