REPRODUCTION, DEVELOPMENT, GROWTH AND EFFECT OF STEROID MASCULINIZATION IN TRIHYBRID CICHLID ON POSSIBLE RESTORATION OF MALE FERTILITY UPSTREAM OF GENETIC SEX DIFFERENTIATION

We already have evidence that estradiol treatment of zebrafish (polygenic fish species) triploids (all males) prior and during morphological sex differentiation does not act on restoring feminization (Delomas and Dabrowski, 2018. Mol.Reprod.Dev. 85:612), however, the mechanism of action of testosterone in other fish species might be different. In the present study the original trihybrid (Vieja melanura x Cichlasoma urophthalmus (female) were fertilized by 4 different males of Amphilophus citrinellum) and initially raised on formulated feeds (Otohime B1 and B2) or live Artemia nauplii (control). The third experimental treatment were fish exposed for 21 days to Otohime diet containing methyltestosterone (30 ppm). Progenies from all pairs of trihybrids in replicated groups were then fed control Otohime B2 diet. In the following period of 42 days significant differences in mean weight were found among treatments when different progenies, that were fed the same diet, were combined. Fish treated with MT continue to grow slower, 12 + 0.8 g in comparison to fish initially offered live food, 17.5 + 2.5 g, but not different from dry food (control, no MT), 14.8 + 2.1 g. Fish were then PIT-tagged and grown in "common garden" set up until 235 days post fertilization (dpf) (Fig. 1). At the time of submission only 12 fish out of 91 tagged had identifiable sizable "nuchial hump" (Fig. 2).