Effects of temperature manipulation on gamete development and reproductive activity in the farmed catfish Lophiosilurus alexandri.

ABSTRACT

Temperature is a critical factor for fish management, especially during breeding season. This study evaluated gametogenesis and gonadal maturation in the catfish Lophiosilurus alexandri under farming conditions in two temperatures. The fish were divided in the following experimental groups (S0) control group, before starting the experiment, (S1) 30 days at 23 °C, (S2) 70 days at 23 °C, (S3) 30 days at 27 °C, and (S4) 70 days at 27 °C. Gonad, liver, and blood samples were obtained to analyze reproductive and health parameters. In females, increased gonadosomatic index (GSI) was associated with a decreased proportion of perinucleolar follicles and increased diameter of vitellogenic follicles in S4. Postovulatory follicles were found only in fish kept at 27 °C, whereas atretic follicles were more frequent at 23 °C. In S4, females had higher hepatic levels of vitellogenin and lower levels of zona radiata proteins. In males, a lower proportion of spermatogonia was found at 27 °C (S4), whereas GSI and proportions of spermatocytes, spermatids, and spermatozoa were similar among the groups. Levels of cortisol were higher in females of group S3. Plasma 17ß-estradiol, 11-ketotestosterone and 17α-hydroxyprogesterone were significantly higher in S4. Hematocrit, erythrocytes, and glucose were higher at 27 °C. Together, the present study indicate that exposure of L. alexandri to 27 °C provides suitable conditions for germ cell development and gonadal maturation in captivity, promotes increase of sex steroids, follicular growth, and oocyte maturation, with onset of ovulation occurring at 30 days. At 23 °C, spermatogonia proliferation is favored in males, but it cannot be recommended for stimulating female maturation of L. alexandri in fish farming.