Brain aromatase mRNA expression in two populations of the peacock blenny Salaria pavo with divergent mating systems

Abstract

Keywords:Aromatase Reproductive behavior Salaria pavo Peacock blenny Alternative reproductive tactics Sex-role reversal Aromatase, the key enzyme in the conversion of androgens to estrogens, regulates the availability of these hormones in tissues and controls many physiological and behavioral processes. In fish and other vertebrates, the regulation of aromatase expression in the brain has been implicated in the modulation of male sexual and aggressive behaviors. Here, the pattern of mRNA expression of the brain aromatase isoform (encoded by the CYP19A2 gene also referred as CYP19b) was quantified at the peak of spawning season in brain macroareas from males and females of the blenny Salaria pavo originated from two populations displaying male alternative reproductive tactics but differing in their mating systems. In Trieste (Adriatic) nesting males aggressively defend nests and take the initiative in courtship and perform sexual displays more often than females while in Ria Formosa (Southern Portugal) the pattern is reversed as a result of shortage of appropriate nesting sites. Nesting males from Ria Formosa had overall higher levels of brain aromatase mRNA expression than nesting males from Trieste, suggesting a higher brain estrogen synthesis in these males. Since in some fish species exogenous estradiol administration has been shown to decrease sexual and agonistic behaviors, the higher levels of brain aromatase in Ria Formosa nesting males may explain their reduced expression of sexual and aggressive displays when compared with nesting males from Trieste. Alternatively, the higher brain aromatase levels in nesting males from Ria Formosa could be a mechanism to decrease the putative androgen-induced activation of aggressive and sexual displays by reducing the local availability of androgens through their metabolization into estrogens. Although females and parasitic female-like males also differ in their displays between populations, the interpopulational pattern of brain aromatase mRNA expression was similar, suggesting that other neuroendocrine agents mediate the expression of female and female-like behaviors. In conclusion, brain aromatase availability seems like a probable mechanism to regulate the effects of steroids on the brain circuits underlying the expression of sexual and agonistic displays in S. pavo.

Temporal variation in brain transcriptome is associated with the expression of female mimicry as a sequential male alternative reproductive tactic in fish

“…A similar mechanism of brain feminization may be present in the peacock blenny. In this species, gonadal steroids regulate different aspects of reproductive behaviour in the different morphs (Gonçalves, Alpedrinha, Teles, & Oliveira, ; Gonçalves et al., ; Oliveira, Carneiro, Gonçalves, Canario, & Grober, ), and sneaker males have lower levels of brain aromatase mRNA (Gonçalves et al., ) and of brain aromatase activity (Gonçalves et al., ) than nest‐holder males. Thus, neuronal intracellular levels of E2 are expected to be low in sneakers in comparison with nest‐holder males, consistent with the observed upregulation of dnmt3a in sneakers.…”

Neural sensitivity to sex steroids predicts individual differences in aggression: implications for behavioural evolution

“…On the one hand, levels of gene expression may have a heritable component [21,46,72,73]. On the other hand, environmental and social conditions can affect transcription as well [25].…”

Neural and hormonal mechanisms of reproductive-related arousal in fishes

“…Nesting males of the peacock blenny, Salaria pavo , have higher brain aromatase activity than males that adopt a sneaking reproductive tactic (Goncalves et al, 2008). Sex differences in aromatase activity or expression in various brain regions including the POA of teleosts is found in several species (reviewed in Forlano et al, 2006; Goncalves et al, 2010; Goncalves et al, 2008), and thus similar levels of circulating testosterone between sexes could be seen very differently in brain areas where androgen metabolism is sexually dimorphic. It is interesting to note that while the vast majority of teleost fishes reproduce by external fertilization and estrogen does not appear necessary for female sexual behavior (Munakata and Kobayashi, 2010), guppies are internal fertilizers, and like mammals, female receptivity is regulated by estradiol (Liley, 1972).…”