The high temperature sex reversal process leading to functional phenotypic masculinization during development has been widely described in Nile tilapia (Oreochromis n iloticus) under laboratory or aquaculture conditions and in the wild. In this study, we selected five wild populations of O. niloticus from different river basins in Benin and produced twenty full-sib families of mixed-sex (XY and XX) by natural reproduction. Progenies were exposed to room temperature or high (36.5°C) temperatures between 10 and 30 days post-fertilization (dpf). In control groups, we observed sex ratios from 40% to 60% males as expected, except for 3 families from the Gobé region which showed a bias towards males. High temperature treatment significantly increased male rates in each family up to 88%. Transcriptome analysis was performed by RNA-sequencing (RNA-seq) on brains and gonads from control and treated batches of six families at 15 dpf and 40 dpf. Analysis of differentially expressed genes, differentially spliced genes, and correlations with sex reversal was performed. In 40 dpf gonads, genes involved in sex determination such as dmrt1, cyp11c1, amh, cyp19a1b, ara, and dax1 were upregulated. In 15 dpf brains, a negative correlation was found between the expression of cyp19a1b and the reversal rate, while at 40 dpf a negative correlation was found between the expression of foxl2, cyp11c1, and sf1 and positive correlation was found between dmrt1 expression and reversal rate. Ontology analysis of the genes affected by high temperatures revealed that male sex differentiation processes, primary male sexual characteristics, autophagy, and cilium organization were affected. Based on these results, we conclude that sex reversal by high temperature treatment leads to similar modifications of the transcriptomes in the gonads and brains in offspring of different natural populations of Nile tilapia, which thus may activate a common cascade of reactions inducing sex reversal in progenies.

In order to investigate the breeding performances of five F1 populations of Oreochromis niloticus originated from wild broodstock of Nangbéto, Sohoumè and Togbadji in the Mono basin, Gobé in the Ouémé basin and Gbassa in the Niger basin, breeding tests were conducted for 10 weeks in an ongrowing experimental system. All tested populations were checked daily in order to collect spawn and to compare the reproductive performances. Compared with others, Sohoumè, Togbadji, and Gobé populations significantly (P < .05) displayed the best breeding performances in terms of rate of multi-spawning females (89.3 ± 15.2–92.3 ± 10.8%); mean relative fecundity (4 ± 2–6 ± 3 eggs/g of female), mean gonadosomatic index (3.1 ± 2–4.8% ± 2.6); mean absolute fecundity rates (865 ± 339–989 ± 547 eggs); mean fertilization rates (98 ± 4.3–99.3 ± 1.1%); and mean hatching rates (83.7 ± 10–88.9 ± 9.1%).

Growth Performance of Clarias gariepinus (Burchell, 1822) fed with Local Feed without Fish Meal