Sex reversal of pejerrey (Odontesthes bonariensis), a species with temperature-dependent sex determination, in a seminatural environment

DEL FRESNO, P. S.; GARCIA DE SOUZA, J. R.; COLAUTTI, D. C.; YAMAMOTO, Y.; YOKOTA, M.; STRUSSMANN, C. A.; MIRANDA, L. A.

JOURNAL OF FISH BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2022

0022-1112

This study examined the changes in sex ratios and sex reversal rates in pejerreyOdontesthes bonariensis that occur with the progression of the spawning season in aseminatural setting. Four groups of hatchery-produced pejerrey larvae were stockedin floating cages in La Salada de Monasterio lake (Pampas region), a natural habitat ofthis species, and reared from hatching beyond gonadal sex determination with minimumhuman interference. Cage 1 was stocked at the beginning of the spring spawningseason and the other cages were stocked with monthly delays until cage 4 inearly summer. The genotypic (amhy+, XY/YY; amhy, XX) and phenotypic (testis,male; ovary, female) sex ratios and proportions of genotype/phenotype mismatchedindividuals were estimated and their relation to water temperature and daylengthduring the experiment was analysed by generalized linear modelling. Water temperaturevaried between 11 and 30.5C, and daylength duration between 11 h 22 minand 14 h 35 min. Sex genotyping revealed nearly balanced sex ratios of XY/YY(46%–49.1%) and XX (50.9%–54%) fish in cages 2–4 whereas the genotypic sex ratioin cage 1 was clearly biased towards XY/YY fish (60.6%). Phenotypic males rangedfrom 42% to 54.4% in cages 1–3. Cage 4, in turn, had significantly more phenotypicmales (66%). The percentage of XX males (phenotypic male/genotypic female) was23.1% in cage 1, decreased to a minimum of 5.4% in cage 2 and gradually increasedin cages 3 and 4 to a maximum of 40.7% in the latter. The percentages of XY/YYfemales (phenotypic female/genotypic male) were highest in cage 1 (30%) anddecreased progressively in the other cages to a significantly lower value (4.3%) incage 4. These results generally support the findings of laboratory studies on theeffect of temperature on the sex determination of this species and also provide novelevidence of a XX genotype-specific masculinizing effect of short daylength.