Browsing by Author "Oliveira, R. F."
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- 11-ketotestosterone inhibits the alternative mating tactic in sneaker males of the peacock blenny, Salaria pavoPublication . Oliveira, R. F.; Carneiro, L. A.; Gonçalves, D.; Canario, Adelino; Grober, M. S.In the peacock blenny, Salaria pavo, a species with courtship sex-role reversal, smaller, younger males mimic the courtship behavior and the nuptial coloration of females in order to get access to nests during spawning and to parasitize egg fertilization from nest-holder males. Later in their life, sneakers transform both morphologically and behaviorally into nest-holder males. In the present paper we investigate the activational role of 11-ketotestosterone (KT), the most potent androgen in most teleost species, to promote the switch between tactics in sneaker males of S. pavo. Sneakers were implanted either with KT or with control (i.e. castor oil) silastic implants. A week after implantation they were subjected to a set of behavioral tests and morphometric measurements. KT treatment promoted the differentiation of secondary sex characters, such as the anal glands, and inhibited the expression of female courtship behavior. KT-treated sneakers also showed a trend toward less frequent display of female nuptial coloration. There was no effect of KT treatment on the expression of typical nest-holder male behavior. Finally, there was no effect of KT treatment on the number or soma size of arginine vasotocin neurons in the preoptic area, which are often associated with the expression of vertebrate sexual behavior. Thus, KT seems to play a key role in mating tactic switching by inhibiting the expression of female courtship behavior and by promoting the development of male displaying traits (e.g. anal glands). The lack of a KT effect on behavior typical of nest-holding males and vasotocinergic preoptic neurons suggests that a longer time frame or other endocrine/social signals are needed for the initiation of these traits in males that are switching tactics.
- Androgen levels and energy metabolism in Oreochromis mossambicusPublication . Ros, A. F. H.; Becker, K.; Canario, Adelino V. M.; Oliveira, R. F.Two studies were conducted to test the relationship between androgens and routine metabolism in the Mozambique tilapia Oreochromis mossambicus. In the first study, endogenous levels of plasma levels of androgens and oxygen consumption rate were measured. In accordance with expectations routine metabolism corrected for metabolic body mass, was positively correlated with the behaviourally active metabolite of testosterone, 11-ketotestosterone, but not with testosterone itself.
- Androgen levels and social interactions in breeding males of the peacock blennyPublication . Oliveira, R. F.; Almada, V. C.; Gonçalves, E. J.; Forsgren, E.; Canario, Adelino V. M.Nest-holder male Salaria pavo have lower circulating concentrations of 11-ketotestosterone (KT) at the beginning of the breeding season than at its peak. At that peak density of nesting males was higher as were the number of visits of sneaker males to nests and of agonistic interactions between nest-holders and sneaker males. There was no difference between the two dates either in the frequency of male–male interactions or in the frequency of courtship episodes. Thus, higher plasma levels in nest-holders might be explained by a more intense sneaking pressure at the peak of the breeding season. At that peak, nest-holders had higher plasma levels of KT and a higher testosterone (T) to KT metabolization index in the gonads than did floater males. Both nest-holders and floaters had higher levels of KT and T in the testicular gland than in the testis. The levels of both androgens in the testicular gland, but not in the testis, were correlated with circulating concentrations of KT. These results suggest that the testicular gland is the major source of circulating KT in blenniids. Nest-holders had higher metabolization indexes than floaters both in the testis and in the testicular gland, which suggests that nest holding status promotes the conversion of T into KT.
- Androgen levels of reproductive competitors in a co-operatively breeding cichlidPublication . Oliveira, R. F.; Hirschenhauser, K.; Canario, Adelino V. M.; Taborsky, M.Androgen levels of family groups of Neolamprologus pulcher were assessed using non-invasive methods. There were no significant differences in the excretion rates neither of testosterone nor of 11-ketotestosterone between territorial and helper males.
- Androgens and Mating Systems in Fish: Intra- and Inter-specific AnalysisPublication . Oliveira, R. F.; Ros, A. F. H.; Hirschenhauser, K.; Canario, Adelino V. M.One of the predictions of the ‘challenge hypothesis’ (Wingfield et al., 1990) is that androgen patterns during the breeding season should vary among species according to the parenting and mating system. Here we assess this prediction of the challenge hypothesis both at the intra- and at the inter-specific level. To test the hypothesis at the inter-specific level, a literature survey on published androgen pat- terns from teleost fish with different mating systems was carried out. The results confirm the predicted effect of mating system on andro- gen levels. To test the hypothesis at an intra-specific level, a species with flexible reproductive strategies (i.e. monogamy vs. polygyny), the Saint Peter’s fish was studied. Polygynous males had higher 11- ketotestosterone levels. However, males implanted with methyl-tes- tosterone did not became polygynous and the variation of the ten- dency to desert their pair mates was better explained by the repro- ductive state of the female partner. This result stresses the point that the effects of behaviour on hormones cannot be considered without respect to the social context.
- Behavioural endocrinology: no hormonal response in tied fightsPublication . Oliveira, R. F.; Carneiro, L. A.; Canario, Adelino V. M.Fish androgens may start to surge only when there seems to be a good chance of winning a contest. Duel action: a cichlid attacks its reflection. Androgens are the principal sex steroids controlling reproduction and aggression in male fish1, but their production can also be affected by social interactions2, 3. Here we show that androgen concentrations are not significantly increased in cichlid fish (Oreochromis mossambicus) that are fighting their own image in a mirror, despite their aggressive behaviour towards the virtual intruder. Our results indicate that the hormonal response normally triggered in male contests is not induced under these circumstances by the act of fighting itself, and that it may therefore depend on some indicator of relative fighting ability that cannot be delivered by a mirror-image challenger.
- Brain aromatase activity and mRNA expression in a fish with male alternative reproductive tactics.Publication . Gonçalves, D.; Domingues, A.; Alpedrinha, J.; Teodósio, H. R.; Canario, Adelino V. M.; Oliveira, R. F.In southern Portugal, a population of the peacock blenny Salaria pavo inhabits a mudflat area where there is a scarcity of hard-substrate necessary for nesting. Males compete strongly for the access to the few available nest sites and only large males are able to acquire nests.
- Brain aromatase mRNA expression in two populations of the peacock blenny Salaria pavo with divergent mating systemsPublication . Gonçalves, D.; Saraiva, J. L.; Teles, Magda; Teodósio, H. R.; Canario, Adelino V. M.; Oliveira, R. F.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.
- Do cleaning organisms reduce the stress response of client reef fish?Publication . Bshary, Redouan; Oliveira, R. F.; Oliveira, T.; Canario, Adelino V. M.Marine cleaning interactions in which cleaner fish or shrimps remove parasites from visiting 'client' reef fish are a textbook example of mutualism. However, there is yet no conclusive evidence that cleaning organisms significantly improve the health of their clients. We tested the stress response of wild caught individuals of two client species, Chromis dimidiata and Pseudanthias squamipinnis, that had either access to a cleaner wrasse Labroides dimidiatus, or to cleaner shrimps Stenopus hispidus and Periclimenes longicarpus, or no access to cleaning organisms. For both client species, we found an association between the presence of cleaner organisms and a reduction in the short term stress response of client fish to capture, transport and one hour confinement in small aquaria, as measured with cortisol levels. It is conceivable that individuals who are more easily stressed than others pay a fitness cost in the long run. Thus, our data suggest that marine cleaning mutualisms are indeed mutualistic. More generally, measures of stress responses or basal levels may provide a useful tool to assess the impact of interspecific interactions on the partner species.
- Effects of 11-ketotestosterone on genital papilla morphology in the sex changing fish Lythrypnus dalliPublication . Carisle, S. L.; Marxer-Miller, S. K.; Canario, Adelino V. M.; Oliveira, R. F.; Carneiro, L. A.; Grober, M. S.Five days after implantation with 11-ketotestosterone (KT) female Lythrypnus dalli exhibited elevated urinary KT levels and male-like genital papilla morphology. Papilla length increased, width decreased, and length : width ratio increased. Control fish exhibited increases in papilla length, and length : width ratio on day 3, but not on day 5. Changes in the total area of the papilla were not statistically significant. It is suggested that KT mediates genital papilla morphology rapidly and thus may be a useful indicator of circulating KT in L. dalli.
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