Effect of season on oocyte development and serum steroid hormones in LHRHa and pimozide-injected catfish Clarias macrocephalus (Günther)

Tan-Fermin, Josefa D.; Marte, Clarissa L.; Ueda, Hiroshi; Adachi, Shinji; Yamauchi, Kohei

Ovarian development and serum steroid hormone profiles in hatchery-bred female catfish Clarias macrocephalus (Gunther) during an annual reproductive cycle

Tan-Fermin, Josefa D.; Ijiri, Shigeho; Ueda, Hiroshi; Adachi, Shinji; Yamauchi, Kohei (Japanese Society of Fisheries Science, 1997)

Ovarian development e.g. gonadosomatic index, oocyte diameter, fecundity, histology, and related steroid hormones e.g. testosterone (T), estradiol-17 β (E₂), 17α, 20 β-dihydroxy-4-pregnen-3-one (DHP), were examined in captive female catfish Clarias macrocephalus during an annual cycle to establish the optimum season for its artificial propagation. Results showed that captive C. macrocephalus had a group-synchronous pattern of ovarian development, as indicated by the presence of oocytes at all stages of development throughout the annual cycle. Mean gonadosomatic index (GSI; 11-13%), oocyte diameter (1.54-1.56 mm), fecundity (80-110 eggs/g body weight), and serum T levels (36-37 ng/mL) were lowest in January-April, suggesting that it is not the optimum season to induce C. macrocephalus to spawn during these months. Serum E₂ levels were lowest in January (7 ng/mL), and highest in December (20 ng /mL). Serum DHP levels were below detectable limits (<0.02 ng/mL) throughout the year, supporting the observation that final maturation and ovulation do not occur in this species under captive conditions. Changes in various reproductive parameters and steroid hormone levels indicate that January-March, April-June, July-September and October-December correspond to the refractory, preparatory, spawning and post-spawning periods, respectively, of the annual cycle. The results of the present investigation can be used as a guide for the controlled breeding and commercial aquaculture of C. mucrocephalus in the Philippines.

Dietary administration of dehydroepiandrosterone hormone influences sex differentiation of hybrid red tilapia (O. niloticus x O. mossambicus) larvae

Mohamed, Asaad H.; Traifalgar, Rex Ferdinand M.; Serrano, Augusto E., Jr.; Peralta, Jose P.; Pedroso, Fiona L. (Academic Journals, New York, 2012)

Effects 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.

Serum steroid hormones, reproductive and larval performance of the Asian catfish Clarias macrocephalus (Gunther) during the off- and peak reproductive seasons

Tan-Fermin, Josefa D.; Marte, Clarissa L.; Adachi, Shinji; Yamauchi, Kohei (Institute of Zoology, Academia Sinica, Taipei, Taiwan, R.O.C., 2001)

Serum samples were taken from gravid female catfish 0 to 24 h after injection of luteinizing hormone releasing hormone analogue (LHRHa) and pimozide (PIM) to monitor the serum steroid hormone levels during the off seasons (February) and the peak of the natural breeding period (August). A parallel study was also conducted to compare egg production, fertilization, hachuring and larval rates upon yolk resorption from spawn’s of hormone-treated fish. Serum E₂ levels were significantly different only with varying times after injection (PI); a marked increase occurred at 13 h, but the elevation was higher in fish induced to ovulate during the peak (16.8 ng/ml) than off season(7.7ng/ml). Hormone-treated fish showed higher serum testosterone (T) levels during the peak season (17-23 ng/ml) than those injected during the off season (10-20 ng/ml) at 4-12 h PI. Serum 17¤, 20ß-dihydroxy-4-pregnene-3-one (DHP) levels og hormone-treated fish during the off season were only about half the level (0.29 and 0.52ng/ml) of those treated with the same hormones during the peak season (0.54 and 0.9 ng/ml) at 8 and 12 h PI, respectively. Initial eggs size was larger in fish induced to spawn in August (1.54 mm) than in fish induced in February (1.49 mm). All fish ovulated when induced to spawn during the peak of the natural breeding period, but ovulation rate was only 60% when were injected during the off season. Egg production, fertilization, hatchery and survival rates were similarly much higher when gravid females were induced to spawn in August (88 eggs/g body weight, 97%, 73%, and 95%, respectively) than those spawned in February (20 eggs/g BW,36%, 20%, and 47%, respectively). Results indicate that more eggs and of better quality, higher levels of T and DHP were produced during the peak season.