Phenotypic sex differentiation of blue tilapia under constant and fluctuating thermal regimes and its adaptive and evolutionary implications |
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Authors: | E. Baras,C. Prignon,,G. Gohoungo, C. Mé alard |
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Affiliation: | University of Liège, Laboratory of Fish Demography and Aquaculture, 10 Chemin de la Justice, 4500 Tihange, Belgium |
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Abstract: | Oreochromis aureus exposed during the first 28 days of exogenous feeding to constant 35° C, or fluctuating temperatures (day at 35° C, night at 27° C, and vice versa) showed significantly ( P <0·05) faster growth, least size heterogeneity and better survival rates than siblings under constant 27° C. Constant high temperatures had a strong masculinizing effect (M: F sex ratios of 7·33–19·00: 1·00 v . 0·75–0·82: 1·00 in controls reared at 27° C). Fluctuating temperatures had less masculinizing potential but still produced sex ratios significantly skewed to the detriment of females (M: F sex ratios of 2·33–11·50: 1·00). This suggests that ambient temperature may have represented a sufficient environmental pressure for the selection of thermolabile sex-determinism in this species, and presumably in other Oreochromis spp. The evolutionary advantage of thermosensitivity in Oreochromis spp. is discussed, considering a framework where individual advantages oppose, to some degree, to the population or species interest. |
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Keywords: | sex determinism thermosensitivity evolution growth survival Oreochromis tilapia |
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