Browsing by Author "Grober, M. S."
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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.
- 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.
- Effects of androgens on social behavior and morphology of alternative reproductive males of the Azorean rock-pool blennyPublication . Oliveira, R. F.; Carneiro, L. A.; Canario, Adelino V. M.; Grober, M. S.In the Azorean rock-pool blenny Parablennius sanguinolentus parvicornis two sequential reproductive tactics occur. Larger and older males establish breeding territories, while some of the smaller males become attached to nest-holder territories, acting as satellites on these territories, which they help to defend while trying parasitic fertilizations when females go in the nests to spawn. In the present paper we tested the effects of the androgens 17a-methyltestosterone (MT) and 11-ketotestosterone (KT) in the expression of male secondary sex characters and bourgeois behavior in satellite males. One week after satellites were implanted with Silastic tubes containing MT, KT, or castor oil (control), androgen-treated satellites had developed male secondary sex traits such as longer and wider male-type genital papilla and anal glands that secrete a sex pheromone, both traits being less expressed or absent, respectively, in satellite males. Androgen treatment had no effect on the gonadosomatic index or on the development of the testicular gland. KT treatment had a positive effect on relative liver weight. In terms of behavior, androgen-implanted individuals were less aggressive both in a mirror test and toward females when these were introduced into their tanks. MT-treated individuals spend more time inside the provided nests. Only androgen-implanted satellites managed to have the females entering their nests. When given a chance in a group tank either to try to attract females to their own nest or to act as satellites of an already established nest-holder’s nest, MT-implanted males spent significantly more time in their own nest than near the nest-holder nest. These data suggest that androgens, particularly testosterone testosterone, may be involved in mating tactic switching in this species.
- 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.
- Reproduction in context: field testing a laboratory model of socially controlled sex change in Lythrypnus dalli (Gilbert)Publication . Black, M. P.; Moore, B.; Canario, Adelino V. M.; Ford, D.; Reavis, R. H.; Grober, M. S.Social interactions can have profound effects on reproduction and the proximate mechanisms involved are just beginning to be understood. Lythrypnus dalli, the bluebanded goby, is an ideal organism for analyzing the dynamics of socially controlled sex change both in the laboratory and field. As with most research species, the majority of its behavioural and physiologic study has been performed in the laboratory. The goal of our study was to induce sex change of L. dalli in a more natural environment and compare field dynamics with our laboratory-based model. Groups of L. dalli, composed of one large male and three females of varying sizes, were introduced into artificial habitats in the field. After male removal, the dominant, largest female underwent protogynous sex change in the majority of the groups. Within 15 days, 9 of 15 of the dominant females (focal fish) successfully fertilized eggs as males, compared to 13 of 17 in the laboratory. Focal fish displayed the distinctive temporal sequence of behaviour changes consisting of a dominance, quiescent, and courtship phase. In addition, focal fish had gonads, genital papillae, and accessory gonadal structures with morphology in between that of females and males. Those fish that fertilized eggs had this transitional morphology, but were functionally male. Steroids of focal fish were assayed by water sample, and morning samples of free 11-ketotestosterone (11-KT) positively correlated with the percent of male tissue in the gonad, with the size of the accessory gonadal structure but not the genitalia (genital papilla), and with aggressive displacement behaviour on the last day before the fish were sacrificed. These morphological, physiological, and behavioural patterns parallel those seen in the laboratory. Lower rates of behaviour and the dramatic effects of ambient temperature in the field provide insights as to how the environmental context modifies the behaviour and, subsequently, the reproductive function of individuals within a social group.
- Sound production by the Lusitanian toadfish, Halobatrachus didactylusPublication . Santos, Manuel Eduardo dos; Modesto, Teresa; Matos, Ricardo; Grober, M. S.; Oliveira, R. F.; Canario, Adelino V. M.Several batrachoidids have been known to produce sounds associated with courtship and agonistic interactions, and their repertoires have been studied acoustically and behaviourally. In contrast, sound production of the Lusitanian toadish Halobatrachus didactylus, although often noted, has not been acoustically studied. This sedentary predator of Northeastern Atlantic coastal waters is usually found in sandy and muddy substrates, under rocks or crevices. Sound recordings were made in Ria Formosa, a lagoon complex in southern Portugal. The sound producing apparatus was studied in adult individuals of both sexes captured by local fishermen. It is shown that this species produces acoustic emissions similar to other batrachoidids. It produces a long, rhythmical, tonal sound, often in choruses, which is comparable to the boatwhistle or hum signals of Opsanus and Porichthys, and a complex of signals that were classified as grunts, croaks, double croaks and mixed calls ('grunt-croak’). As in other toadfishes, H. didactylus presents sonic muscles connected to a bi-lobed swimbladder. Asynchronous contractions of the sonic muscles were detected when massaging the ventral surface of the fish.
- The effect of arginine vasotocin on courtship behaviour in a blenniid fish with alternative reproductive tacticsPublication . Carneiro, L. A.; Oliveira, R. F.; Canario, Adelino V. M.; Grober, M. S.In a sex-role reversed population of the peacock blenny, Salaria pavo, two alternative male types are present: (a) older and larger nest-holder males that defend nests in which females come to spawn, and (b) younger and smaller sneaker males that mimic female-courtship behaviour and nuptial colouration in order to try to sneak fertilizations during spawning episodes. In this study the effects of exogenous administration of arginine vasotocin (AVT, 3 μg/g body weight) on the behaviour of nest-holder males, sneakers and females was tested. AVT induced the expression of female courtship behaviour in sneakers and female nuptial colouration in sneakers and in females, but failed to promote the expression of male courtship behaviour in both male types.
- The interaction of social and steroidal influences in regulating transitons between adult sexual phenotypes.Publication . Grober, M. S.; Rodgers, E. W.; Denman, H. N.; Canario, Adelino V. M.Variation in adult sexual expression is common in a variety of vertebrate species and early exposure to steroid hormones mediates the development of sexual phenotype. For many fish species, social cues regulate transitions between adult alternative reproductive states, and changing levels of estrogens and androgens are thought to be key components of this process.