Temperature effect on sex determination in pejerrey (Odontesthes bonariensis) in the wild.

MIRANDA LA; DEL FRESNO PS; GARCÍA DE SOUZA JR; COLAUTTI DC; BERASAIN GE; YAMAMOTO Y; CARLOS STRUSSMANN

Bariloche

Simposio; VI Simposio Argentino de Ictiología; 2019

0px; ">O. bonariensis has a strong temperature sex determination (TSD), however recently studieshave shown that this species has the testis-determining gene amhy (Y-chromosome-linkedanti-Müllerian hormone), which plays a role in sex determination at intermediatetemperatures. In this study it was analyzed the effect of water temperature (WT) on sex ratioin pejerrey in the wild. Newly hatched larvae were stocked in floating cages in September,October, November and December of 2015 in La Salada de Monasterio lake (Bs. As). Afterthree months, 50 juveniles of each cage were sacrificed, and the phenotypic (P, gonadsobservation) and the genotypic (G) sex (identification of amhy by PCR) were determined.For September, the proportion of males was 52% (mean WT during TSD window: 13.9° C),the G proportion of males was 60%, being 18% sex-reversed females (female/amhy+) and10% sex-reversed males (male/amhy-). In October, the proportion of males was 43% (meanWT: 18.6°C), the G proportion of males was 47%, being 7 % sex-reversed females and 3%sex-reversed males. For November the proportion of males was 54% (22.1± 1.5° C), the Gproportion of males was 48%, being 2% sex-reversed females and 8% sex-reversed males.Finally, in juveniles of December 65% were males (25.7 ± 1.9° C), 45% were G males being2% sex-reversed females and 22% sex-reversed males. These results showed that theproportion of males at low WT did not match with the reported in previous laboratory assays where all females were observed. On the other hand, the proportions of males at higher WT were like to the observed experimentally. Besides, the G analysis revealed that at low WT there were more inversions to females and when the WT increased, there were more inversions to males. These findings lead us to conclude that in the wild and especially at low WT, another factors (food availability, thermal fluctuation, etc) could be related to sexual determination in O. bonariensis.