Influence of sexual genotype on the behaviour of females (genotype WZ) and pseudofemales (genotype ZZ) in the tilapia Oreochromis aureus

Abstract

Abstract17α-ethynylestradiol sex-reversed males of Oreochromis aureus (pseudofemales, ∆F, genotype ZZ) are used in aquaculture to produce a male monosex population by crossing with ZZ homogametic normal males. When placed with males (M) and females (F) in the same spawning tank, the spawning rate of F is higher than for ∆F. In order to understand this phenomenon, comparisons were made between the behaviour of 18 F (446 ± 96 mm) and 18 ∆F (401 ± 59 mm). ∆F showed a more aggressive behaviour and were significantly more dominant than normal F in fighting pair experiments (F × ∆F) or in fighting group experiments in four different stocking densities (8, 12, 16 and 83 fish 10 -3 l with F/∆F ratio = 1). ∆F were also more aggressive towards males than F were. The results support the idea that behavioural differences exist between F and ∆F. These differences are probably due to the effect of the sexual genotype on behaviour. © 2002 Ifremer/CNRS/Inra/IRD/Cemagref/Éditions scientifiques et médicales Elsevier SAS. All rights reserved. RésuméInfluence du génotype sexuel sur le comportement de femelles (génotype WZ) et de pseudofemelles (génotype ZZ) chez le tilapia Oreochromis aureus. En aquaculture, l'inversion du sexe de mâles Oreochromis aureus au moyen d'un traitement hormonal à la 17α-ethynylestradiol est utilisée pour produire des pseudofemelles (∆F, génotype ZZ) qui croisées avec un mâle homogamétique (ZZ) donneront une progéniture constituée de 100% de mâles. Cependant, lorsque des femelles (F) et des pseudofemelles (∆F) sont placées dans un même bassin avec des mâles (M), la fréquence de ponte de femelles est supérieure à celle des pseudofemelles. Dans le but de comprendre ce phénomène, nous avons étudié le comportement de 18 F (446 ± 96 mm) et 18 ∆F (401 ± 59 mm). Dans les expériences de combat par paire (F × ∆F) et en groupes (8, 12, 16 et 83 poissons 10 -3 l avec une proportion F/∆F de 1) les ∆F se sont montrées plus agressives que les F. D'autres expériences ont montré que les ∆F se montrent plus agressives que les F vis-à-vis de mâles. Ces expériences montrent qu'il existe des différences comportementales entre F et ∆F qui sont le résultat de l'effet du génotype sexuel sur le comportement. © 2002 Ifremer/CNRS/Inra/Cemagref/Éditions scientifiques et médicales Elsevier SAS. Tous droits réservés.

Atypical feminized male's agonistic behavior relative to males and females of Nile tilapia (Oreochromis niloticus L.)

“…This is supported by the fact that AFM were not shown to be more aggressive than normal females or males with respect to frequency of aggressive behavior but did prove to be so in terms of intensity level. This result contrasts with that observed by Ovidio et al (2002), who reported that aggressive behavior in feminized males was higher when compared to that observed in normal females, a result based only on the frequency of confrontations and not, as was observed in our study, on the differential occurrence of certain behavioral acts.…”

“…This produces a phenotypic transformation, i.e. the morphology and function of adult females from male fingerlings (Vera & Mair, 2000;Ovidio et al, 2002;Desprez et al, 2003).…”

Do sex reversal procedures differentially affect agonistic behaviors and sex steroid levels depending on the sexual genotype in Nile tilapia?

“…The first one is a direct influence of sexual chromosomes on behavior through brain sexual differentiation, or on activation of neural mechanisms related to aggressiveness expression, as proposed by Desprez and Mélard () and Ovidio et al. () to explain the higher aggressiveness level observed in sex‐reversed ZZ females compared to ZW females in O. aureus . Brain organizational or activational modifications would be under control of genetic factors linked to the Y chromosome or induced by the absence of a twin copy of factors carried on the X chromosome.…”

“…On the contrary, particular biological traits were reported in sex‐reversed females of blue tilapia ( O. aureus ), a closely related species with a ZZ/ZW sex determination system. In this species, when ZZ females competed with ZW females for reproduction, the spawning rate of ZZ females was lower (Desprez & Mélard, ) and related to a higher level of dominance and aggressiveness than in ZW females (Ovidio, Desprez, Mélard, & Poncin, ). Desprez and Mélard () hypothesized that the phenotypic sex reversal could be incomplete, particularly in the brain, and that the interaction of genotypic and endocrine factors could modify the expression of behavior.…”

Genes involved in sex determination and the influence of temperature during the sexual differentiation process in fish: A review

“…Some studies show the sex determination system behavior as reported in zebrafish (Uchida et al, 2004), sole marble (Goto et al, 2000), gold (Kazeto- Goto et al, 2006) Japanese flounder (Yamamoto, 1999) and tilapia (Baroiller et al, 1995;Ovidio et al, 2002). These species also have a XX-XY sex determination system and the high temperature induces the XX fish masculinization.…”