Effect of high temperature during larval and juvenile stages on masculinization of common carp (Cyprinus carpio, L)

Abstract

Temperature can influence sex differentiation in gonochoristic fish with a genetic sex-determination system (GSD). The precise effect of high temperature on sex remains unknown in a eurythermal carp (Cyprinus carpio). The present study aimed to identify the critical thermosensitive period and the effect of temperature on sex differentiation in common carp, C. carpio. Our results demonstrated the lower and upper limits of the lethal maximum temperature (LTmax) of C. carpio juveniles (42 dph) were 37.2 and 39.7 °C, respectively in the present study condition. The confidence limit of the median lethal time (LT50) of the juveniles was 38.87 °C. To de- termine the thermosensitivity of sex differentiation, the larvae were exposed to a high temperature (36 °C) for 7- day durations, starting from hatching until 69 dph. The period of critical thermosensitivity for sex differentiation towards the male phenotype was 7 to 13 dph. The sex proportions and thermosensitivity of sex differentiation illustrated high inter-familial variability of sex ratio skewed towards male phenotype ranged from 69 to 100% in the 10 full-sib families exposed to 36 °C. Exposure of juveniles to the high temperatures (34 °C and 36 °C) significantly altered the sex ratios and produced 63 to 82 % male phenotype even during the transition of sex differentiation. This study demonstrates that sex differentiation in common carp is seriously influenced by the environmental process. Also, it explores a temperature-induced method of skewing sex ratio towards the male phenotype irrespective of morphological gonad differentiation in common carp.