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PubMed2001

Androgen metabolism in the brain of the green anole lizard (Anolis carolinensis): effects of sex and season.

Courtship behavior in male green anoles is partly mediated by the 5alpha-reductase enzyme, which converts testosterone (T) to 5alpha-dihydrotestosterone. This study aimed to determine whether the activity of 5alpha-reductase is enhanced in breeding males compared to females and nonbreeding males who do not normally display masculine behaviors. In some cases, aromatase, which converts T to 17beta-estradiol, also was assessed to determine whether the pattern of its activity in anoles is similar to that in other vertebrates. 5alpha-Reductase is greatest in the brainstem, so its activity was determined separately in homogenates of whole brain and brainstems. The following comparisons were done in different assays: (1) breeding males with breeding females, (2) nonbreeding males with nonbreeding females, and (3) breeding males with nonbreeding males. Aromatase activity was greater in breeding males (mean +/- SE, 0.61 +/- 0.06 fmol/min/mg protein) than in breeding females (0.41 +/- 0.08 fmol/min/mg protein). It was also greater in breeding males (0.84 +/- 0.16 fmol/min/mg protein) than in nonbreeding males (0.33 +/- 0.07 fmol/min/mg protein). In contrast, sex or seasonal differences did not exist in 5alpha-reductase activity. The results are consistent with those of other vertebrate species in which male-biased sex dimorphisms and seasonal differences occur in aromatase, but not in 5alpha-reductase activity. The greater levels of aromatase activity in breeding male anoles suggest that this enzyme might mediate male-specific functions. The equivalently high levels of 5alpha-reductase activity in both sexes suggests that, in addition to facilitating male courtship behavior, the enzyme has a basic function common to both sexes.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1993

Corticosterone during the annual reproductive cycle and in sexual behavior in the crested newt, Triturus carnifex.

To clarify the role of corticosterone in the male and female crested newt, Triturus carnifex, and the possible involvement of this hormone in the reproductive processes, we monitored the seasonal and daily pattern of this corticosteroid; in addition, corticosterone, testosterone, and 17 beta-estradiol plasma levels were evaluated during the various phases of courtship. In both sexes, the seasonal pattern of corticosterone in plasma showed two peaks: one in winter, at the beginning of the reproduction, and the other one in summer, when the newts leave the pond. The corticosterone daily pattern showed a peak at 05:00 PM. During courtship, corticosterone was lower and testosterone higher in "inactive" male newts than in the courting animals, while estradiol was highest during the approach; in the females corticosterone was lower in "nonreceptive" animals than in "receptive" ones, and sex steroids did not show any difference. These data suggest that corticosterone is involved in the reproductive processes in male and female crested newts.

Animals↗
PubMed1993

Effects of corticosterone on social behavior of male lizards.

Adrenal corticoid release is a major component of the stress response which can affect many body functions including behavior. The purpose of our studies was to examine the effects of corticosterone (B) on both the agonistic and courtship components of social behavior in male side-blotched lizards (Uta stansburiana). Of particular interest was the effect of B on plasma testosterone (T), a hormone known to influence aggression, and the importance of this action on the behavioral effects of B. Experiments included either castrated males, hormone (either B, T, or B + T)-implanted intact males, or sham males. Behavioral observations were recorded when these males were challenged with "immigrant" males; measurement of plasma steroids confirmed the efficacy of implants in elevating B and T. Castration, B implantation, and combined B and T implantation significantly reduced aggressive behavior to varying degrees, while T implants in intact animals had no effect. B implants significantly decreased plasma T levels (from 1.87 to 0.33 ng/ml), but this decrease was not essential for the inhibitory effect of B on aggression since B + T implantation also reduced aggression, even though plasma T was elevated above normal (67.6 ng/ml). In contrast, B implantation did not affect male courtship and copulatory behavior when males were presented with estrogenized females. These results suggest that the effect of B on social behavior is not through just a single route, that of decreasing plasma T, and that B can affect various intra- and intersexual behaviors differently.

Agonistic Behavior↗
PubMed1993

Reproductive behavior, endocrine state, and the distribution of GnRH-like immunoreactive mast cells in dove brain.

Previous studies indicate that there is an increase in the number of detectable mast cells expressing gonadotropin-releasing hormone-like immunoreactivity (GnRH-ir) in the medial habenular region of the brain in ring doves after a period of 2 hr of courtship. In the present experiment the overall distribution of GnRH-ir mast cells in the brain is described, and the influence of behavioral and endocrine state on brain mast cell distribution and detectable mast cell number is explored. Four groups of male birds were studied: (1) paired with a female and displaying courtship behavior, (2) paired with a squab and displaying aggressive behavior, (3) visually isolated from other doves, and (4) long-term castrates housed communally. In all four groups, GnRH-ir mast cells were observed in the following areas: the medial habenula, circumventricular organs, organum vasculosum lamina terminalis and organum subseptale, the pia mater, and blood vessels. Cell counting revealed differences among groups in numbers of habenular mast cells. Courted doves had the most habenular mast cells, followed by doves paired with squabs, and then visually isolated doves, while castrates had the fewest. One-way ANOVA indicates significant differences among groups. All pairwise comparisons show that the courting animals had significantly more detectable mast cells in the habenular area than did visually isolated and castrated groups. These results suggest that the appearance and/or detectability of GnRH-ir mast cells in the habenula is related to the behavioral state and possibly to the endocrine state of the animal and suggest a novel mechanism for interactions among the nervous, endocrine, and immune systems.

Aggression↗
PubMed1996

Social modulation of sex steroid concentrations in the urine of male cichlid fish Oreochromis mossambicus.

The relationship between urinary concentrations (free + sulfates + glucuronides) of the steroids testosterone (T), 11-ketotestosterone (11KT), 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17, 20 beta-P) and 17 alpha, 20 alpha-dihydroxy-4-pregnen-3-one (17, 20 alpha-P), and the social behavior of males of the cichlid fish Oreochromis mossambicus was investigated. After 8 days of isolation none of the steroids were good predictors of social dominance developed after subsequent formation of all-male groups. One day after group formation dominance indexes were good predictors of the urine concentrations of all sex steroids. Dominance indexes and androgen concentrations measured after all-male group formation were positively correlated with territoriality, courtship rate, and nest size. Similar relationships were found for progestins with the exception that they were not correlated with courtship rate. All-male group formation was also accompanied by an increase in urinary sex steroid concentrations in fish that became territorial and a decrease in non-territorial fish with the exception of T, which increased in both groups. Addition of ovulating females caused steroid concentrations to return to levels near isolation, except for 17, 20 alpha-P in territorials, which underwent a large increase. Thus, social interactions may have an important modulatory effect on sex steroid concentrations in O. mossambicus.

Animals↗
PubMed1996

Parental care and the prolactin secretion pattern in the King penguin: an endogenously timed mechanism?

The King penguin (Aptenodytes patagonicus) has been studied on Possession Island, Crozet Archipelago (46 degrees 25'S-51 degrees 45'E). It is an offshore feeder, but it breeds on land. Its breeding cycle is unusually long (about 14 months). It starts at the beginning of spring, is interrupted during 5 months of winter, and ends in the next spring. Furthermore, it is characterized by a long parental care period, of about 11 months, including the winter interruption. In fact, care given to the egg and the chick is biparental, which supposes that parental behavior includes both parents. Each parent alternates care given to the egg and to the chick on land and foraging bouts at sea. An incubation bout, or a chick care bout, is called a shift. Prolactin is the hypophyseal hormone known to be correlated with incubation and chick care. We studied the mechanism of the maintenance of prolactin during the parental care period in the King penguin, a period which is unusually long. In many species, prolactin secretion has been shown to be stimulated by the presence of eggs and/or chicks, but in the King penguin, prolactin secretion is observed throughout the entire period of parental care, despite the fact that the birds leave the egg and the chick repeatedly and for extended periods of time to feed. Prolactin levels rise significantly at the beginning of courtship; females have significantly higher prolactin levels than males during courtship, copulation, and the period of waiting for egg laying. In both sexes, prolactin levels remain high during incubation and the first part of chick rearing, before winter. Prolactin concentrations decline somewhat during the winter period of minimal parental care, but remain that level in spring when parental care starts again. The level returns to basal value during molt. Prolactin levels rise during the incubation shifts but not over the course of contact with young. Prolactin values remain high in unsuccessful breeders, possibly preventing the birds from relaying, but remain low in immature birds. These data raise questions about how prolactin secretion is controlled in this species. The hypothesis of a programmed secretion of prolactin is advanced.

Animals↗
PubMed1996

Androgenic effects on hypothalamic asymmetry in a sexually differentiated nucleus related to vocal behavior in Mongolian gerbils.

The relationship between courtship ultrasound emission rates and the volume of a discrete, sex-related, hypothalamic nucleus, the sexually dimorphic area, pars compacta (SDApc), in male and neonatally androgenized female gerbils is lateralized. Unbiased stereological estimates of neuron number and nuclear and neuropil volume are also laterally asymmetric in male SDApcs. In this study sexual differentiation and lateral asymmetry of stereologically assessed cytoarchitectural SDApc components, and their relationship to male-typical behaviors, including vocal emission, were examined in masculinized females. Female neonates received a single injection of testosterone propionate (TP) or control vehicle (Control) and were then implanted with silastic cannulae of testosterone at 65 days of age. Total SDApc volume, neuron number, nuclear volume, and neuropil volume had significantly greater values in TP compared to Control females. Neuron number was laterally asymmetric in TP females, since the left SDApc contained a greater number of smaller neurons, possibly interneurons, than the right. Courtship vocal emission and two other behaviors were masculinized in TP females. Left SDApc total volume and, most significantly, left neuron number, were correlated with vocal rates. No other lateralized correlations between behaviors and stereological estimates were found. It was concluded that various stereological parameters and the lateralization of vocal behavior and brain asymmetry depend on the early sexually differentiating effects of androgens. It is suggested that in gerbils, androgens have a role in the survival of interneurons in a laterally asymmetric hypothalamic nucleus which is an index of vocal control.

Androgens↗
PubMed2002

Fat is sexy for females but not males: the influence of body reserves on reproduction in snakes (Vipera aspis).

Reproduction is energetically expensive for both sexes, but the magnitude of expenditure and its relationship to reproductive success differ fundamentally between males and females. Males allocate relatively little to gamete production and, thus, can reproduce successfully with only minor energy investment. In contrast, females of many species experience high fecundity-independent costs of reproduction (such as migration to nesting sites), so they need to amass substantial energy reserves before initiating reproductive activity. Thus, we expect that the relationship between energy reserves and the intensity of reproductive behavior involves a threshold effect in females, but a gradual (or no) effect in males. We tested this prediction using captive vipers (Vipera aspis), dividing both males and females into groups of high versus low body condition. Snakes from each group were placed together and observed for reproductive behavior; sex-steroid levels were also measured. As predicted, females in below-average body condition had very low estradiol levels and did not show sexual receptivity, whereas males of all body condition indices had significant testosterone levels and displayed active courtship. Testosterone levels and courtship intensity increased gradually (i.e., no step function) with body condition in males, but high estradiol levels and sexual receptivity were seen only in females with body reserves above a critical threshold.

Adipose Tissue↗
PubMed2000

Evidence for the involvement of two areas of the zebra finch forebrain in sexual imprinting.

Sexual imprinting in male zebra finches is a two-step process, including an acquisition period early in life and a stabilization process normally occuring during the first courtship attempts of the male. During the acquisition period, a young male learns about its social environment. During stabilization, which can be delayed experimentally until day 100, it develops a preference for the appropriate object for courtship behavior on the basis of its previous and acute experience. Thereafter, this preference cannot be altered again. Exploring the physiological basis for imprinting, we have previously shown that the neurons of two forebrain areas (ANC and HAD) increase their spine density in the course of the stabilization process, while in two other areas (MNH and LNH) a decrease of spine density can be observed. With the present experiments, we tested the idea that the spine density decrease in MNH and LNH is the anatomical manifestation of the imprinting process. Previous behavioral experiments have shown that exposure to a nestbox after 100 days of age stabilizes the sexual preference of a zebra finch male as well as does exposure to a female. The present study shows that nestbox exposure also reduces the spine density in MNH and LNH, but has no effect on ANC and HAD. It has also been shown previously that treating males with an antiandrogen between days 40 and 100 affects the final preference of a male. The present experiment indicates that the same treatment affects spine growth during development in MNH and LNH and prevents the increase of spine density within HAD and ANC normally induced by exposure to a female. The results are interpreted as strong evidence for the involvement of MNH and LNH in sexual imprinting.

Androgen Antagonists↗
PubMed1994

Sound production evoked by electrical stimulation of the forebrain in the oyster toadfish.

In mammals, birds and amphibians the neural pathways controlling sound production descend from higher centers in the forebrain, whereas in fishes only brainstem and spinal centers have been explicitly implicated in sound production. We now report that electrical stimulation of the forebrain of the oyster toadfish (Opsanus tau) readily evokes both the agonistic grunt and the courtship boatwhistle. Boatwhistles are more realistic than ones previously evoked from lower centers. Positive stimulation sites are localized in the preoptic area (nucleus preopticus parvocellularis anterior) and the supra-commissural nucleus of the ventral telencephalon, a likely homologue of the amygdala. Both sites contain gonadal steroid-concentrating neurons and play a central role in fish courtship behavior. Evoked sounds form a continuum from knock grunts, burst grunts, transition boatwhistles to complete boatwhistles; sound pressure level (SPL), fundamental frequency and duration increase consistently within the continuum. For all sound types, SPLs exhibit the smallest variation (coefficients of variation of 2.7 to 5.7%), fundamental frequency is intermediate (5 to 13%) and durations vary most widely (18 to 60%). Boatwhistles, with the smallest variation and greatest amplitude, are likely generated by a maximal output of the CNS and sonic muscles. Grunt SPLs however, vary over a range of 26 dB for all fish and by as much as 18 dB in an individual; suggesting recruitment of variable numbers of motor units despite electrical coupling within the sonic motor nucleus.

Animals↗
PubMed1996

Effects of ovariectomy and estrogen replacement on attractivity and receptivity in the red-sided garter snake (Thamnophis sirtalis parietalis).

Activation of courtship behavior in male red-sided garter snakes, Thamnophis sirtalis parietalis, is independent of the presence of sex steroids. The only consistent treatment that stimulates courtship behavior in males is prolonged exposure to low temperature followed by subsequent warming, mimicking the emergence from hibernation. We investigated whether attractivity and receptivity in female red-sided garter snakes is similarly steriod independent. Female red-sided garter snakes are attractive when they emerge from hibernation and are courted by males; most mate within an hour of emergence. In a series of experiments, groups of females were either ovariectomized (OVEX) in the late spring, fall or while in hibernation. They were tested for attractivity and receptivity upon emergence from hibernation. Females OVEX in the spring were unattractive whereas those OVEX in fall or while in hibernation were attractive. Thus, attractivity appears determined the year before emergence and is dependent on the presence of the ovaries. All OVEX females were unreceptive upon emergence. OVEX females were also given replacement estradiol (E) treatment (either in Silastic capsules or single injections) at various points of their annual cycle. The only treatment that resulted in reinstating receptivity in OVEX females was the injection of E (20 micrograms) one hour prior to emergence. The effectiveness of E in reinstating receptivity was time dependent: the longer the period between emergence and injection, the less effective the same dosage was in stimulating receptive behavior. These experiments suggest that sexual behavior in female red-sided garter snakes is, unlike males, dependent on the presence sex steroid hormones. Although E is naturally at its lowest seasonal level upon emergence, the concentration is sufficient to stimulate receptivity. However, it appears that temperature regulates a time-limited window of sensitivity to E.

Animals↗
PubMed1994

Male polymorphism in Limia perugiae (Pisces: Poeciliidae).

The male-polymorphic poeciliid fish, Limia perugiae, a small teleostean endemic to the southeast of the Caribbean island Hispañola, consists of three male size morphs with uniform females. Large males differentiate at a size varying between 25 and 38 mm; intermediate males, between 21 and 25 mm. Under competition, large males exhibit an elaborate courtship display, whereas small males show only a sneak-chase behavior. Intermediate males adapt their tactics to the respective competitors. However, all male morphs can switch from courtship display to sneak-chase behavior. In large mating groups with four males of different size and five or six virgin females, large dominant alpha-males as well as small subordinate delta-males did not produce any offspring. Unexpectedly, all progeny were sired exclusively by the intermediate subordinate beta- and gamma-males. Breeding experiments with the three male morphs can best be explained by a model of Y-linked genes for small and large size which are both suspended by the activity of an autosomal recessive repressor responsible for the development of intermediate males. The dominant allele of the recessive repressor, in either its homoorits heterozygous state, activates the Y-chromosomal genes for large or small size, respectively. Accordingly, intermediate males may produce male offspring of all size classes, depending on the presence of either the Y-linked gene or the autosomal repressor.

Agonistic Behavior↗
PubMed1977

Behavioral role of the sexcombs in Drosophila melanogaster and Drosophila simulans.

The sexcombs were amputated from males of three strains of Drosophila melanogaster and one strain of D. simulans in order to assess the importance of these structures in the sexual behavior of these species. In D. melanogaster the sexcombs are important in attempts to copulate with the female. Their removal delays copulation but does not suppress it entirely. Other aspects of courtship are not influenced by removal of the sexcombs. Strain differences in quanitative aspects of courtship were found, and also in the insemination rates of females by males without sexcombs. The present evidence suggests that the sexcombs are primarily structures adapted to grasping the female securely during the act of intromission.

Animals↗
PubMed2001

Adaptations for rapid and forceful contraction in wing muscles of the male golden-collared manakin: sex and species comparisons.

The courtship display of the male golden-collared manakin (Manacus vitellinus) of Panamanian rainforests is noteworthy for several types of whip-crack-like sounds created by a rapid overhead flip of the wings. We have hypothesized that this courtship behavior. which is not performed by females, is associated with steroid-sensitive and sexually dimorphic neuromuscular systems. Presumably, muscles creating the motion of the wingsnap in males are specialized for greater force generation and speed of contraction. We tested this hypothesis by examining mass, fiber diameter, metabolic enzyme activity, and myosin isoform expression in several muscles of male and female manakins and in both sexes of a non-wingsnapping bird, the zebra finch (Taenopygia guttata). We have identified three wing muscles, the scapulohumeralis caudalis, the supracoracoideus, and the pectoralis major, that differ in one or more of these characteristics across sex and species, suggesting they are specialized for faster contraction and greater force production in male manakins. These muscles normally function to raise and lower the wings during flight. As this movement is the principal motion of the wingsnap, these adaptations presumably underlie the performance of the wingsnap display.

Adaptation, Physiological↗
PubMed2006

Behavioural evidence of UV sensitivity in jumping spiders (Araneae: Salticidae).

Jumping spiders are known to possess ultraviolet (UV) receptors in the retinas of their large-principal eyes. The existence of UV visual cells, however, does not prove that jumping spiders can see into the UV part of spectrum (300-400 nm) or whether such an ability plays any role in salticid intra-specific interactions. In the study reported herein, we performed behavioural experiments to test whether a UV-reflecting jumping spider, Cosmophasis umbratica, is sensitive to UV wavelengths and whether UV cues are important in intra-specific communication. The absence of UV cues not only affected intra-specific behaviour by significantly reducing the frequency of agonistic displays, but also elicited unprecedented courtship displays in males towards their own mirror images and conspecific opponents. Furthermore, C. umbratica males were able to respond rapidly to changes in UV cues of conspecific mirror images by switching between agonistic and courtship displays. These findings clearly demonstrate that C. umbratica males are capable of seeing UV wavelengths and that UV cues are necessary and sufficient for this species to enable the agonistic displays. Hence, UV light may have an important role to play in intra-specific communication in jumping spiders.

Animal Communication↗
PubMed2002

Patterns of lipid storage and mobilisation in the female green sea turtle ( Chelonia mydas).

Reproductive data from southern Queensland indicate that vitellogenesis in female Chelonia mydas takes approximately 8 months and is followed by a migration to a breeding area. At Heron Island, females lay multiple clutches over approximately 3 months. To investigate how females mobilise and store lipid during the breeding season we collected plasma, yolk, and fat tissue samples from females at a variety of stages during the nesting season. In breeding females, concentrations of plasma triglyceride increased seasonally. They reached peak concentrations during vitellogenesis and courtship, remained high throughout the nesting season, and then declined to a nadir after the last clutch. Plasma protein concentration increased throughout the breeding season, peaking following the last clutch for the season. Yolk lipids were highest during courtship and were similar throughout the nesting season, suggesting that uptake of lipid by ovarian follicles is completed prior to the beginning of the nesting season. Plasma triglyceride decreases in females with prolonged periods of unsuccessful nesting, and total lipid levels in adipose tissue and follicle yolks were significantly lower in atretic females. It appears that: (1) endogenous energy reserves can be reduced by stochastic environmental events (such as those reducing nesting success), and (2) a metabolic shift signalling the end of the nesting season is characterised by a drop in plasma triglycerides and slight increase in total plasma protein.

Adipose Tissue↗
PubMed2004

Reduction in testosterone concentration and its effect on the reproductive output of chronic malaria-infected male mice.

An experimental host-parasite association involving BALB/c male mice infected with Plasmodium chabaudi chabaudi was used in order to investigate the influence of the parasite on the sexual physiology and behavior of infected hosts. Infected males displayed complete courtship behavior leading to ejaculation and sired litters on several occasions. A weekly assay of testosterone and corticosterone plasma concentrations revealed a twofold decrease in the testosterone level at 4 and 5 weeks post-injection, during recrudescence. This imbalance was accompanied by a decrease in the overall duration of the social investigation contacts occurring during courtship and by a reduction in the fertilization rate of the infected animals. These physiological perturbations can be regarded as an adaptive response of the host to the recrudescing parasites, which illustrates the rodents' capacity for regulating the testosterone profiles needed to balance the competing demands of immunity and reproduction.

Animals↗
PubMed2002

Novel genes expressed in subsets of chemosensory sensilla on the front legs of male Drosophila melanogaster.

Detection of courtship-activating female pheromones by contact chemoreceptors on the front legs of male Drosophila melanogaster is thought to play an important role in triggering courtship behavior. However, the chemosensory organs, cells, and molecules responsible are not known. We have isolated two genes, CheA29a and CheB42a, expressed in nonneuronal auxiliary cells within two nested subsets of chemosensory sensilla on the front legs of sexually mature, adult males. The proteins encoded by the CheA29a and CheB42a genes have no sequence similarity to each other or any other known protein, but they belong to two novel families of proteins encoded by the D. melanogaster genome. Members of the two families are predicted to have a single transmembrane domain at their amino terminus, probably to serve as a signal peptide, suggesting that they are soluble and secreted. Finally, in addition to CheA29a and CheB42a, other genes within each family are expressed preferentially in appendages where chemosensory organs are concentrated, in several cases in a male-specific manner. Our data suggest that CheA29a and CheB42a and other members of these two protein families are involved in male-specific chemical senses, perhaps pheromone response.

Amino Acid Sequence↗