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Browsing CCMAR by Subject "11-ketotestosterone"
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- 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.
- Endocrine correlates of intra-specific variation in the mating system of the St. Peter's fish (Sarotherodon galilaeus)Publication . Ros, A. F. H.; Canario, Adelino V. M.; Couto, Elsa; Zeilstra, IIja; Oliveira, R. F.The Challenge Hypothesis postulates that androgen levels are a function of the social environment in which the individual is living. Thus, it is predicted that in polygynous males that engage in social interactions, androgen levels should be higher than in monogamous animals that engage in parental care. In this study, we tested this hypothesis at the intra-specific level using a teleost species, Sarotherodon galilaeus, which exhibits a wide variation in its mating system. Experimental groups of individually marked fish were formed in large ponds with different operational sex-ratios (OSR) to study the effects of partner availability on blood plasma levels of sex steroids [11-ketotestosterone (11-KT), testosterone (T), and 17,20B-dihydroxy-4-pregnen-3-one (17,20B-P)] and gonadosomatic index (GSI). Polygyny mostly occurred in the female biased OSR groups. 17,20B-P and gonadosomatic index did not differ among OSR groups. However, 11-KT was high in male biased OSR and positively correlated with aggressive challenges, thereby supporting the central postulate of the Challenge Hypothesis. The results of T were the inverse of those of 11-KT, probably because 11-KT is metabolized from T. 11-KT levels of polygynous males did not differ neither from those of monogamous males, nor from those of males that participated in parental care. These results do not support the expected relationships between polygyny, parental care, and androgen levels. The differences from expectations for 11-KT may be related to the fact that in S. galilaeus, the mating and the parenting phase are not clearly separated and thus, males may still fight and court while they are brooding.
- Endocrine correlates of male polymorphism and alternative reproductive tactics in the Azorean rock-pool blenny, Parablennius sanguinolentus parvicornisPublication . Oliveira, R. F.; Canario, Adelino V. M.; Grober, M. S.; Santos, Ricardo SerrãoIn the Azorean rock-pool blenny male sexual polymorphism occurs. Larger and older males (M1 males) fully express male secondary sex characters (SSC), particularly an anal gland that produces a sex pheromone, whereas smaller and younger sexually active males do not express SSC (M2 males). Two mating tactic types can be identified among M1 males: nest-holders that establish nests and court females and floaters that move around in the breeding area and try to achieve parasitic fertilizations and/or to take over nests. Two behavioral tactic types can also be identified within M2 males: satellites that are associated with particular nests and actively participate in territorial defense (when females go inside the nest to spawn they try to enter to fertilize some of the eggs) and sneakers that do not help nest holders (when spawning occurs they also try to enter the nest to fertilize eggs). It was found that M1 males have significantly higher levels of 11-ketotestosterone (KT), but not testosterone (T), than M2 males [M1 male androgen levels (mean 6 SE): total T 5 11.6 6 3.0 ng ml21, total KT 5 4.5 6 1.1 ng ml21; M2 male androgen levels (mean 6 SE): total T 5 9.6 6 1.0 ng ml21, total KT 5 2.5 6 1.1 ng ml21]. There were no differences in plasma T or KT among individuals using different mating tactics within the same male morph; that is, among M1 males, nest-holders did not differ in androgen levels from floaters [nest-holder androgen levels (mean 6 SE): total T 5 12.3 6 4.4 ng ml21, total KT 5 4.3 6 1.4 ng ml21; floater androgen levels (mean6SE): total T55.960.8 ng ml21, total KT 5 3.4 6 0.3 ng ml21], and among M2 males, satellites did not differ in androgen levels from sneakers [satellite androgen levels (mean 6 SE): total T 5 7.7 6 1.5 ng ml21, total KT51.360.3 ng ml21; sneaker androgen levels (mean6SE): total T58.361.6 ng ml21, total KT 5 1.4 6 0.3 ng ml21]. Thus, the observed differences appear to be correlated with the expression of different male morphotypes and not with the expression of different behavioral tactics within the morphotype. Androgen levels were not correlated with the behavior activity of nest-holders, except for a negative correlation between KT levels and parental behavior. Furthermore, nestholder males that succeeded in having females spawn in their nests during the observation period had significantly lower KT levels than unsuccessful males. Since behavioral observations preceded blood sampling in time, it is suggested that these results indicate a negative relationship between KT and parental care, since successful males were parenting when blood samples were collected. Male SSC were better correlated with KT than with T and the use of total blood levels (i.e., free 1 conjugates) yielded higher correlation coefficients than when only the free fraction of each steroid was considered. Since conjugates are nonactive metabolites of the free androgen they should reflect active free steroids in a previous time. Thus, their incorporation into the hormonal measurements increases the time frame captured, and because steroids are released in a pulsatile way, this time-integrated measure can be more meaningful than the free steroids, which represent a snapshot of the hormone levels at a given point in time.
- Male sexual polymorphism, alternative reproductive tactics, and androgens in combtooth blennies (Pisces : Blenniidae)Publication . Oliveira, R. F.; Canario, Adelino V. M.; Grober, M. S.In species in which intense intermale competition for the access to females is present males of lower competitive ability may adopt alternative reproductive tactics (ART) to get access to mates. These ART translate in many cases into male sexual polymorphism, with individuals following distinctly different tactics. Usually two alternative male morphs can be recognized in species with ART: (1) bourgeois males that compete for access to mates invest in typically male behaviors, such as building elaborated nests or displaying ornaments; and (2) parasitic males that take advantage of the success of the bourgeois males in attracting females and attempt “sneaker” fertilizations (e.g., sneaker and satellite males). In combtooth blennies (Blenniidae) the co-occurrence of ART and male sexual polymorphism has been described for two temperate species: the peacock blenny, Salaria pavo, and the Azorean rock-pool blenny, Parablennius sanguinolentus parvicornis. Interestingly, while in the peacock blenny the alternative male morph adopts a sneaker tactic, in the rock-pool blenny parasitic males act as satellites to nest-holder males. Thus, this variation in the ART expressed in these two closely related species allows for a comparative study of the proximate and ultimate factors affecting the expression of the two ART. In this article we summarize the available information on androgen levels in bourgeois and parasitic males of natural populations of the two species and of recent studies on the effect of exogenous administration of androgens on tactic switching in parasitic males of the two species. The information is discussed within the frame of the relative plasticity hypothesis, which predicts that plastic alternative morphs should show differences in hormone levels and that the administration of sex steroids should be effective in promoting the switch from the parasitic to bourgeois tactic. The evidence is only partly consistent with this hypothesis. Alternatively, a social transduction hypothesis that better fits the available data on androgens and ART in teleost is proposed. It states that the observed differences in androgen levels between alternative morphs should not be interpreted as an organization vs activation effect of steroids, but rather as the limited vs lifelong responsiveness of the neuroendocrine axis to social regulation.
- The effect of estrogen on the gnads and on in vitro conversion of androstenedione to testosterone, 11-ketotestosterone, and estradiol-17ß in Sparus aurata (Teleostei, Sparidae)Publication . Condeça, João B.; Canario, Adelino V. M.The effects of estrogen on gonad morphology and steroidogenesis of sea bream, Sparus aurata, a protandrous hermaphrodite teleost, were investigated. Fish were treated in winter/spring for different periods with 17aethynylestradiol (ethE2; experiment 1) and in summer with two doses of estradiol-17b (E2; experiment 2). Estrogen was more effective in summer. Its main effect on the gonad was inhibition of testicular growth and of male germ cell development beyond the spermatogonia stage, including mitosis. The effect of estrogen on ovarian development was slight and only apparent at the end of experiment 2 in the higher dose group. Gonadal fragments were incubated at different times during treatment with androstenedione and the output of testosterone (T), estradiol (E2), and 11-ketotestosterone (11KT) was measured by radioimmunoassay. T and E2 production was inversely correlated with the proportion of testicular tissue (and positively with ovarian tissue) in the gonad in experiment 2. However, the production of 11KT was not correlated with any type of tissue, possibly because of further metabolism. Inhibition of testicular development by estrogen was also associated with higher output of steroid conjugates.
- The role of androgens in the trade-off between territorial and parental behavior in the Azorean rock-pool blenny, Parablennius parvicornisPublication . Ros, A. F. H.; Bruintjes, R.; Santos, Ricardo Serrão; Canario, Adelino V. M.; Oliveira, R. F.Androgen hormones have been shown to facilitate competitive ability in courtship and territorial behavior, while suppressing paternal behavior. The rock-pool blenny, Parablennius parvicornis, provides an excellent model to study the proximate regulation of such a trade-off between territorial and parental behavior, because nest-holder males of this species display these behaviors simultaneously. A field study was carried out in which territorial nest holder males were either treated with long-lasting implants filled with 11-ketotestosterone (11-KT) or with control implants. Males treated with 11-KT showed a higher frequency of aggressive behavior, were more responsive to aggressive challenges, and were more persistent in aggressive behavior than control males. In addition, territories were larger in males treated with 11-KT than in controls. We found evidence for incompatibility between defense of a large territory and high levels of parental behavior. However, contrary to expectation, 11-KT did not suppress parental behavior. We suggest that trade-offs between territorial and parental behavior may not be regulated by androgen hormones but may result from a time constraint in the individual’s activity budget.