11-Ketotestosterone Inhibits the Alternative Mating Tactic in Sneaker Males of the Peacock Blenny, &lt;i&gt;Salaria pavo&lt;/i&gt;

2005

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The occurrence of intra-sexual variation in reproduction is a widespread phenomenon in teleosts. One such form of variation consists in the occurrence of alternative male types: males that invest resources in mate attraction and males that exploit the investment of the former males, by trying to sneak fertilizations during spawning. These alternative reproductive tactics can be classified according to their plasticity during the life span of the individuals (i.e., fixed vs. sequential vs. reversible). Furthermore, the differences between morphs within a given species may involve a set of different traits, including reproductive behavior, the differentiation of male morphological traits, and the patterns of gonad tissue allocation and the differentiation of gonadal accessory glands. In this paper, we review the available data on four species exhibiting different types of intra-sexual plasticity in reproduction that have been studied in our lab. The data on the proximate mechanisms, androgens and forebrain arginine-vasotocin (AVT), underlying these alternative tactics suggest that between-morph differences in androgen levels, especially in 11-ketotestosterone, are especially present in species where the alternative male types have evolved morphological traits that are tactic-specific (i.e., sexual polymorphisms) and that differences in AVT appear to be related to between-morph differences in the expression of courtship behavior. Therefore, this comparative approach leads us to propose that the different endocrine systems are involved in the differentiation of different sets of traits that make up alternative phenotypes, and that the differentiation of alternative tactics is not controlled by a single endocrine system (e.g., androgens).

Section: Avt and Intra-sexual Variation In Reproductionsupporting

confidence: 62%

Section: Androgens and Intra-sexual Variation In Reproductionmentioning

confidence: 94%

Intra-sexual variation in male reproduction in teleost fish: a comparative approach

Oliveira

Ros

2005

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“…Administration of both T and 11KT to parasitic males decreases the frequency of the female-like sexual displays and promotes the development of male secondary sexual characters (Gonçalves et al, 2007;Oliveira et al, 2001). This is consistent with the fact that circulating levels of both T and 11KT are higher in nesting males than in parasitic males , and in fish species with male ART higher levels of 11KT (but not T) have consistently been found in nesting males (Brantley et al, 1993;Oliveira, 2006).…”

Section: Introductionsupporting

confidence: 81%

“…In S. pavo, levels of both 11KT and T are higher in nesting males , and, in general, in species with male ART nesting males have higher levels of 11KT, a non-aromatizable androgen, but not of T when compared with parasitic males (Brantley et al, 1993;Oliveira, 2006). The administration of both T and 11KT to parasitic males inhibited the expression of female-like displays, although it did not induce malelike sexual behaviors (Gonçalves et al, 2007;Oliveira et al, 2001). Those experiments only lasted for 8 days and it is possible that a longer time frame would be necessary for the putative masculinizing behavioral effects of androgens to be observed.…”

Section: Differences Between Morphotypesmentioning

confidence: 94%

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

Saraiva

Teles

et al. 2010

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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.

“…In species with alternative reproductive tactics (ART), males that follow a conventional tactic, investing resources in mate acquisition and monopolization ('bourgeois' males sensu Taborsky, 1997), have generally higher circulating levels of 11KT than those of parasitic males (sensu Taborsky, 1997) that exploit this investment using an alternative tactic, whereas T shows no clear pattern (Brantley et al, 1993b;Oliveira, 2006). Furthermore, the administration of 11KT to parasitic males promotes the appearance of SSCs and inhibits the expression of female-like behaviors (Oliveira et al, 2001c).…”

Section: Introductionmentioning

confidence: 99%

Environmental modulation of androgen levels and secondary sex characters in two populations of the peacock blenny Salaria pavo

Saraiva

Oliveira

2010

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Morphology and endocrinology were studied in two populations of the peacock blenny Salaria pavo, with different regimes of sexual selection imposed by differences in nest site availability. The peacock blenny is a small, sexually dimorphic benthic fish that presents exclusive paternal care of the clutch and inhabits rocky shores of the Mediterranean and adjacent Atlantic areas. In a population from the Gulf of Trieste (Northern Adriatic sea) inhabiting rocky shores where nest sites are abundant, male-male competition for nests is low, males court females and a low frequency of alternative reproductive tactics (small, parasitic femalemimicking sneaker males that change tactic into nest holders in subsequent breeding seasons) occurs. Conversely at Ria Formosa, a coastal lagoon in Southern Portugal, where nest sites are scarce and highly aggregated, male-male competition for nests is very high, there is sex-role reversal with female courtship and a high frequency of alternative reproductive tactics is observed. Concomitantly, at Ria Formosa nest holder males are larger and present more developed secondary sex characters and higher levels of 11KT than at the Gulf of Trieste. However, the gonads of nest holders and parasitic males were larger in the Gulf of Trieste population. Competition for nests at Ria Formosa seems to promote more developed secondary sex characters in nest site scarcity conditions, while competition for females at the Gulf of Trieste seems to be spurring sperm competition among males in populations where nest sites are more abundant. 11KT was thus associated with the development and expression of secondary sex characters in contrasting environments. These results exemplify how the modulation of behavioral plasticity and secondary sex characters by the social environment can be mediated by androgens.