Browsing by Author "Grober, Matthew S."
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- Effects of 11-ketotestosterone on genital papilla morphology in the sex changing fish Lythrypnus dalliPublication . Carlisle, S. L.; Marxer-Miller, S. K.; Canário, Adelino V. M.; Oliveira, Rui Filipe; Carneiro, Luís Alberto; Grober, Matthew 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, Rui Filipe; Carneiro, Luís Alberto; Canário, Adelino V. M.; Grober, Matthew 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, 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, Rui Filipe; Canário, Adelino V. M.; Grober, Matthew S.; Santos, Ricardo SerrãoIn the Azorean rock-pool blenny male sexual polymorphism occurs, Larger and older males (M+ 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 (M- males). Two mating tactic types can be identified among M+ 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 M- males: satellites that are associated with particular nests and ac tively 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 M+ males have significantly higher levels of 11-ketotestosterone (KT), but not testosterone (T), than M- males [M+ male androgen levels (mean +/- SE): total T = 11.6 +/- 3.0 ng ml(-1), total KT = 4.5 +/- 1.1 ng ml(-1); M- male androgen levels (mean +/- SE): total T = 9.6 +/- 1.0 ng ml(-1), total KT 2.5 +/- 1.1 ng ml(-1)]. There were no differences in plasma T or KT among individuals using different mating tactics within the same male morph; that is, among M+ males, nest-holders did not differ in androgen levels from floaters [nest-holder androgen levels (mean It SE): total T = 12.3 +/- 4.4 ng ml(-1), total KT = 4.3 +/- 1.4 ng ml(-1); neater androgen levels (mean +/- SE): total T = 5.9 +/- 0.8 ng ml(-1), total KT = 3.4 +/- 0.3 ng ml(-1)], and among M- males, satellites did not differ in androgen levels from sneakers [satellite androgen levels (mean +/- SE): total T = 7.7 +/- 1.5 ng ml(-1), total KT = 1.3 +/- 0.3 ng ml(-1); sneaker androgen levels (mean +/- SE): total T = 8.3 +/- 1.6 ng ml(-1), total KT = 1.4 +/- 0.3 ng ml(-1)]. 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, nest holder 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 + 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.
- Forebrain AVT and courtship in a fish with male alternative reproductive tacticsPublication . Grober, Matthew S.; George, Andrew A.; Watkins, Kelly K.; Carneiro, Luís Alberto; Oliveira, Rui FilipeIn this paper, we present the results of cellular and molecular studies on the neuroendocrine correlates of male sexual polymorphism in a population of the blenniid fish Salaria pavo (Risso). Bigger and older males defend nests, whereas smaller and younger males mimic female nuptial coloration and behavior to gain access to nests and sneak fertilizations. In this population, sex-role reversal in courtship also occurs (i.e., females are the courting sex). Immunocytochemistry and in situ hybridization were used to examine the production of arginine vasotocin (AVT) peptide and messenger RNA, respectively. The expression of AVT mRNA on a per-cell basis was correlated with mating behavior, rather than with sex morphotype, which suggests that the greater level of AVT mRNA expression in females and sneakers is correlated with the production of courtship behavior. On the other hand, the number and size of AVT peptide-producing cells in both male types is higher or larger, respectively, than in females, which suggests that it is correlated with sex morphotype, rather than with mating behavior.
- Male mating success in the Azorean rock-pool blenny: The effects of body size, male behaviour and nest characteristicsPublication . Oliveira, Rui Filipe; Miranda, Jason; Carvalho, Natacha; Gonçalves, Emanuel João; Grober, Matthew S.; Santos, Ricardo Serrãofemale visits, were courted more often by females and received more spawnings. Larger males also received a higher number of male intrusions, attacked more conspecifics and defended larger territories. Larger males showed more nest cleaning behaviour and a marginally non-significant trend for higher egg fanning rate. Male courtship, male attack rate against conspecifics and parental behaviour were all correlated with the frequency of female spawnings received by each male even when controlling for male size, suggesting that these behaviour patterns influence male mating success. On the other hand, a positive partial correlation was found between female courtship and the frequency of female spawnings, controlling for the number of female visits, which suggests a role for female mate choice on male mating success. Finally, males nesting in chambers in the bottom of pools received more spawnings than males nesting either in crevices or under boulders. However, nest opening area was associated significantly negatively with male mating success, when controlling for male size. Thus, the present data suggest strongly that male characteristics overrule nest characteristics in determining male mating success in the Azorean rock-pool blenny.
- Male sexual polymorphism, alternative reproductive tactics, and androgens in combtooth blennies (Pisces: Blenniidae)Publication . Oliveira, Rui Filipe; Canário, Adelino V. M.; Grober, Matthew 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.
- Neurochemical correlates of male polymorphism and alternative reproductive tactics in the Azorean rock-pool blenny, Parablennius parvicornisPublication . Miranda, Jason; Oliveira, Rui Filipe; Carneiro, Luís Alberto; Santos, Ricardo Serrão; Grober, Matthew S.In the common Azorean rock-pool blenny, Parablennius parvicornis, males exhibit alternative reproductive morphologies: (1) larger males defend nest sites, provide parental care, have anal glands (involved in pheromone release), testicular glands, and low gonad:body weight ratio (GSI) and (2) smaller, younger, males do not defend nests, have reduced glands and high GSI. These smaller non-nesting males behave as satellites (associated with nests) or sneakers (moving among nests), attempting to achieve parasitic fertilizations via sperm competition. In non-mammals, arginine vasotocin (AVT) is a key hypothalamic peptide involved in the control of reproductive behavior and physiology, and several fish species that exhibit alternative male reproductive morphs show polymorphism in AVT brain chemistry. We conducted an immunocytochemical study to generate comparative data on this intertidal blenny. Our analysis showed no difference in AVT-immunoreactive cell number or size between the male morphs, which is consistent with studies on other fish, including blennies. The number of AVT cells was positively correlated to fish body mass, while cell size showed no such relation. If corrected for body mass, the smaller non-nesting males have significantly more cells than the large nesting males. Our data suggest that the size and number of forebrain AVT cells develops initially to allow for reproduction in the young non-nesting males and this pattern does not appear to change when males take on the nesting morphotype later in life. This result appears to be consistent in many fishes with alternative male morphotypes.
- Sound production by the lusitanian toadfish Halobatrachus didactylusPublication . Santos, Manuel Eduardo dos; Modesto, Teresa; Matos, Ricardo Jorge S.C.; Grober, Matthew S.; Oliveira, Rui Filipe; Canário, 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, Luís Alberto; Oliveira, Rui Filipe; Grober, Matthew 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.