Temperature-dependent sex determination in Clarias gariepinus
Posted: 19 Jan 2016, 06:47
Santi, S., Gennotte, V., Toguyeni, A., Mélard, C., Antoine, N., & Rougeot, R. 2016. Thermosensitivity of the sex differentiation process in the African catfish, Clarias gariepinus: Determination of the thermosensitive period. Aquaculture. Accepted date: 14 January 2016. Available online 15 January 2016. doi:10.1016/j.aquaculture.2016.01.009
Cheers, Eric
Significant conclusions from this paper: The most thermosensitive period extended from 6 to 8 days post-hatching. Fish batches exposed to 36°C during this period showed a sex-ratio skewed towards the male phenotype, ranging from 58 to 100% between families. Variability in sex-ratios between families suggests a role of minor genetic factors and interactions between these genetic factors and the environmental (thermal) conditions.Santi et al. wrote:ABSTRACT:
Gonadal sex differentiation in gonochoristic fish is generally labile and under the control of two interacting processes: genetic sex determination (GSD) and environmental sex determination (ESD). Numerous experimental studies deal with temperature induced-sex differentiation in teleosts, but none focused on the African catfish . The aim of this study was to confirm the thermosensitivity of the sex differentiation process and to determine the thermosensitive period during the African catfish development. Fish were exposed to high temperature (36°C) for 3 days at different periods during ontogenesis. The treatment was applied every 3 days from fertilization until 29 days post-hatching (dph). Before and after the thermal treatment, fish were reared at 28°C. Gonadal development was histologically characterized on fish sampled at 10, 15, 20, 25, 35, 45, 55 and 70 dph. Our results demonstrated that the African catfish displays a thermosensitivity of the sex differentiation process, with a masculinizing effect of high temperature (36°C). The most thermosensitive period extended from 6 to 8 dph. Fish batches exposed to 36°C during this period showed a sex-ratio skewed towards the male phenotype, ranging from 58 to 100% (high inter-familial variability). The African catfish gonads (male and female) stayed histologically undifferentiated until 20 dph. Obvious signs of gonadal differentiation clearly appeared at 25 dph in females and at 45 dph in males.
Variability in sex-ratios between progenies and in the response to thermal treatment suggests a role of minor genetic factors and interactions between genomic and environmental determinants in the expression of the sexual phenotype.
Statement of Relevance
- This paper provide novel methods to control African catfish Clarias gariepinus sex differentiation through high temperature and then to produce all male population.
- Our work underline the possibility to significantly reduce high temperature (masculinizing effect) treatment period to 3 days and then increase survival rate of progenies after treatment.
- This study also show the variability of thermosensitivity on sex differentiation process according to the family in Clarias gariepinus.
Cheers, Eric