TEMPERATURE EFFECT ON SEX DETERMINATION IN PEJERREY (ODONTESTHES BONARIENSIS) IN THE WILD

Miranda, L. A.¹, del Fresno, P.¹, García de Souza, J.², Colautti D. C. ², Berasain, G. E. ³, Yamamoto, Y.⁴, Strüssmann, C. A.⁴

¹Instituto Tecnológico de Chascomús, ² Instituto de Limnología de la Plata

³Estación Hidrobiológica de Chascomús

⁴Tokyo University of Marine Science and Technology.

lmiranda@intech.gov.ar

O. bonariensis has a strong temperature sex determination (TSD), however recently studies have shown that this species has the testis-determining gene amhy (Y-chromosome-linked anti-Müllerian hormone), which plays a role in sex determination at intermediate temperatures. In this study it was analyzed the effect of water temperature (WT) on sex ratio in 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). After three months, 50 juveniles of each cage were sacrificed, and the phenotypic (P, gonads observation) 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+) and 10% sex-reversed males (male/amhy-). In October, the proportion of males was 43% (mean WT: 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 G proportion 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 being 2% sex-reversed females and 22% sex-reversed males. These results showed that the proportion 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.

Palabras clave: PEJERREY, TEMPERATURE, SEX DETERMINATION