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PubMed2003

Context-dependent song amplitude control in Bengalese finches.

Estrildid finches have two song types: directed (courtship) and undirected (solo). These are acoustically identical and differ only in social context. Recent studies have shown that undirected singing is accompanied by strong activation of the basal ganglia pathway, whereas directed singing is not, which suggests a different degree of feedback control between the two. We examined whether the magnitude of the Lombard effect, i.e., vocal amplitude regulation in response to environmental noise, differed based on the song context. Our results indicate that Bengalese finches change the amplitude of undirected song based on background noise levels, but do not do so for directed song. This is the first behavioral evidence suggesting that feedback control of song output vary by social context.

Animals↗
PubMed2004

Socially induced sex change regulates forebrain isotocin in Lythrypnus dalli.

The neurohypophyseal peptides are evolutionarily conserved and their expression can be socially modulated. Our question was what effect will socially induced sex change have on forebrain isotocin, an oxytocin homologue? We removed males from social groups to induce dominant females to change sex and become males in Lythrypnus dalli. Fish in the late stages of sex change had fewer forebrain isotocin-immunoreactive (-ir) cells than early stage and unchanged females. When groups were consolidated into unequivocal males (control males and sex-changed new males) and unequivocal females (fish prior to courtship as a male), females had significantly more isotocin-ir cells than control males and recently sex-changed fish. This is the first study demonstrating the social regulation of forebrain isotocin.

Animals↗
PubMed2001

The paraphilic and hypersexual disorders: an overview.

In this article, the first of a two-part series, the authors present reasons for considering the paraphilic and hypersexual disorders together and provide an overview of these disorders. The DSM-IV diagnostic criteria for paraphilias are reviewed, and proposed criteria for hypersexual disorders are presented. The question of whether the paraphilic and hypersexual disorders should be considered within the spectrum of obsessive-compulsive disorders is considered. The authors then review the epidemiology of these disorders, and discuss some implications of recent sexual predator legislation. The authors discuss the etiology of the paraphilias and hypersexual disorders, and consider the role of endocrinological function, findings from brain imaging and neuropsychological testing, findings from primate research, the monoamine hypothesis, the imprinting hypothesis, social learning theory, the concept of courtship disorder, the role of obsessive-compulsive elements, psychodynamic theories, and genetic factors. The phenomenology of the paraphilias and hypersexual disorders is discussed, including the tendency for multiple paraphilias to co-occur, the lack of a specific offender profile, the predominance of males among those with paraphilias, the incidence of a history of victimization in individuals with paraphilias and compulsive sexual disorders, the onset and course of both types of disorders, and the lack of internal motivation for change in individuals with paraphilias and hypersexual disorders. The authors then discuss disorders that commonly co-occur with paraphilias and compulsive sexual disorders, including mood disorders, substance abuse and dependence disorders, attention-deficit/hyperactivity disorder, anxiety and impulse control disorders, and personality disorders. The second article in the series will discuss the clinical assessment and the behavioral and psychopharmacological treatment of these disorders. A guide for clinicians and patients on where and how to find specialized clinicians and treatment resources in the United States will also be provided.

Journal Article↗
PubMed2004

Effects of male sterility on female remating in the mediterranean fruitfly, Ceratitis capitata.

Mating-induced reductions in female receptivity are common in insects. These responses are of interest because of their utility in insect pest control. In addition, the control of receptivity is likely to be the subject of sexual conflict over remating frequency. We investigated the specific effect of male sterility on female receptivity in an important pest species, the Mediterranean fruitfly (medfly), in which sterile males are often used for population suppression. Sterile males performed less courtship, obtained significantly fewer first and second matings than fertile males, and reduced female receptivity significantly less effectively than did fertile males. We modelled the likelihood of fertile matings and show that the low mating success of sterile males represents a significant problem for medfly sterile insect technique (SIT) programmes.

Animals↗
PubMed2004

Possible role of female discrimination against 'redundant' males in the evolution of colour pattern polymorphism in guppies.

Multiple paternity of offspring can result from active preferences on the part of females or sexual harassment by males. We examined sexual responses of female guppies to a previous mate versus a novel male (experiment 1) or to a male with a colour pattern similar to that of the previous mate versus a novel male (experiment 2). Females showed significantly more sexual responses to courtship by novel males than to previous mates in experiment 1 or to males that resembled previous mates in experiment 2. These results suggest that females discriminate actively against previous mates, and extend this discrimination to males with similar colour patterns to previous mates. This could lead to negative frequency-dependent sexual selection against common colour patterns (a 'redundant male effect'), which could contribute to the maintenance of the extraordinarily high levels of genetic polymorphism in guppy colour patterns.

Animals↗
PubMed2004

Long-term effects of flipper bands on penguins.

Changes in seabird populations, and particularly of penguins, offer a unique opportunity for investigating the impact of fisheries and climatic variations on marine resources. Such investigations often require large-scale banding to identify individual birds, but the significance of the data relies on the assumption that no bias is introduced in this type of long-term monitoring. After 5 years of using an automated system of identification of king penguins implanted with electronic tags (100 adult king penguins were implanted with a transponder tag, 50 of which were also flipper banded), we can report that banding results in later arrival at the colony for courtship in some years, lower breeding probability and lower chick production. We also found that the survival rate of unbanded, electronically tagged king penguin chicks after 2-3 years is approximately twice as large as that reported in the literature for banded chicks.

Animal Identification Systems↗
PubMed2004

Uncoupling the links between male mating tactics and female attractiveness.

Because not all females are equally attractive, and because mating reduces the chances of getting further copulations, males should prefer better-quality mates. In this paper, we use the Trinidadian guppy (Poecilia reticulata) to explore the effects of two non-correlated measures of female quality--size and reproductive status--on male mating decisions. All male guppies employ two alternative mating tactics. We found that large females, particularly those from a high predation site, were the target of most sneaky mating attempts. The response persisted in fish raised under standard conditions over several generations in the laboratory. In addition, non-pregnant females received more courtship displays. We conclude that males can discriminate among females and that they uncouple their mating tactics to track different axes of quality.

Analysis of Variance↗
PubMed2005

Effects of Hurricane Charley on fish chorusing.

Hurricane Charley, a category 4 hurricane, passed through Charlotte Harbor, Florida, directly over an autonomous underwater acoustic datalogger used to record sound production by fishes associated with courtship and spawning. Acoustic recordings made on 9 days prior to the storm, during and 3 days after the storm provided unprecedented documentation of the hurricane's passage and its effect on fishes' calling behaviour. The hurricane did not inhibit nightly chorusing events of spawning fish. Sound levels produced by spawning fish on the night of and 3 days after the hurricane were higher and lasted longer than any of the 9 days recorded prior to the hurricane.

Animal Communication↗
PubMed2005

Ultraviolet vision and foraging in dip and plunge diving birds.

Many fishes are sensitive to ultraviolet (UV) light and display UV markings during courtship. As UV scatters more than longer wavelengths of light, these signals are only effective at short distances, reducing the risk of detection by swimming predators. Such underwater scattering will be insignificant for dip and plunge diving birds, which prey on fishes just below the water surface. One could therefore expect to find adaptations in the eyes of dip and plunge diving birds that tune colour reception to UV signals. We used a molecular method to survey the colour vision tuning of five families of dip or plunge divers and compared the results with those from sister taxa of other foraging methods. We found evidence of extended UV vision only in gulls (Laridae). Based on available evidence, it is more probable that this trait is associated with their terrestrial foraging habits rather than piscivory.

Animals↗
PubMed2006

Death feigning in the face of sexual cannibalism.

Pre-copulatory sexual cannibalism by females affects male and female reproductive success in profoundly different ways, with the females benefiting from a meal and the male facing the risk of not reproducing at all. This sexual conflict predicts evolution of traits to avoid cannibalism and ensure male reproductive success. We show that males of the nuptial gift-giving spider Pisaura mirabilis display a remarkable death feigning behaviour--thanatosis--as part of the courtship prior to mating with potentially cannibalistic females. Thanatosis is a widespread anti-predator strategy; however, it is exceptional in the context of sexual selection. When the female approached a gift-displaying male, she usually showed interest in the gift but would sometimes attack the male, and at this potentially dangerous moment the male could 'drop dead'. When entering thanatosis, the male would collapse and remain completely motionless while retaining hold of the gift so it was held simultaneously by both mates. When the female initiated consumption of the gift, the male cautiously 'came to life' and initiated copulation. Death feigning males were more successful in gaining copulations, but did not have prolonged copulations. We propose that death feigning evolved as an adaptive male mating strategy in conjunction with nuptial gift giving under the risk of being victimized by females.

Animals↗
PubMed1991

Another battle of the sexes: the consequences of sexual asymmetry in mating costs and predation risk in the guppy, Poecilia reticulata.

The risk of predation and cost or benefit of a mating attempt are rarely the same for both sexes. An excellent example is provided by the guppy. Poecilia reticulata, a species that has a promiscuous mating system in which female choice plays an important role. Male engage almost continuously in courtship behaviour but, as females are sexually receptive for short periods only, most male displays are ignored and sneaky mating attempts avoided. Experiments on guppies from wild Trinidad populations reveal that females appear to perceive themselves to be at a greater risk of predation and devote more time to antipredator behaviour, for example, schooling when threatened. Inspections of the predator are also mainly initiated and led by female guppies. Males exploit this behavioural switch by increasing their sneaky mating attempts. A game theoretical analysis is used to explore the sexual asymmetry in mating cost and predation risk. Together these approaches show that there is no intersexual cooperation during predator inspection behaviour in this species, and may explain the paradoxical increase in mating activity by male guppies under threat.

Animals↗
PubMed1996

Selective phonotaxis by males in the Majorcan midwife toad.

Males are expected to exhibit mating preferences when there is high variance in the quality of females or when males are limited to a small number of matings. In the Majorcan midwife toad, Alytes muletensis, the male performs parental care by carrying the eggs wrapped in a string around his hind legs. Both sexes possess courtship vocalizations which they use to advertise receptivity. We looked for evidence of male mating preferences in a phonotaxis arena in which males were presented with two alternative synthetic female calls. We predicted that males should prefer to mate with large females because of maternal effects on egg size, and that this preference would be manifest by selective phonotaxis toward low frequency calls. We also predicted that males should prefer high intensity calls as indicators of the energetic or motivational state of the female. Contrary to our prediction, males did not exhibit a preference for low frequency calls. The results suggest that there is stabilizing selection on call frequency and directional selection on call intensity.

Animals↗
PubMed1998

Parasite-induced risk of mortality elevates reproductive effort in male Drosophila.

A trade-off between sex and somatic maintenance is fundamental to life-history theory. Tests of this trade-off usually emphasize deleterious consequences of increased reproduction on life span. Here we show the reverse effect, that reductions in the expected life span elevate sexual activity. Experimentally parasitized male Drosophila nigrospiracula lived shorter lives, but before dying, they courted females significantly more than unparasitized controls. This greater courtship resulted in increased mating speed, and potentially greater reproductive success than parasitized males would have achieved otherwise. The results show that an environmental reduction in life span increases reproductive effort, and support the hypothesis of a trade-off between these key life-history traits.

Animals↗
PubMed2000

Testosterone treatment is immunosuppressive in superb fairy-wrens, yet free-living males with high testosterone are more immunocompetent.

The immunocompetence handicap hypothesis proposes that the immunosuppressive effect of testosterone enforces honesty of sexual signalling via a physiological trade-off between signal intensity and immunocompetence. However, evidence that testosterone is immunosuppressive is scant, particularly in birds. I studied the correlation between immunocompetence and testosterone in superb fairy-wrens (Malurus cyaneus), a species with intense intersexual selection. Males are seasonally dichromatic and testosterone increases during the moult from dull brown eclipse plumage into bright nuptial plumage. I determined the primary antibody response to immunization with sheep red blood cells (SRBCs) in (i) control and testosterone-implanted males in captivity, and (ii) a cross-section of free-living males with basal and elevated testosterone (in eclipse plumage, moulting and in nuptial plumage). Experimental treatment with testosterone decreased the likelihood of an antibody response to SRBCs in captive birds. In contrast, free-living males which had acquired the nuptial plumage and had naturally elevated testosterone were more likely to respond to SRBCs than males in eclipse plumage with basal testosterone levels. The association between higher immunocompetence and higher immunosuppressive testosterone could arise if both are positively correlated with male phenotypic quality In addition, the association could result if males compensate for potential immunosuppression by enhancing their humoral immune responses, particularly since high testosterone is linked to other demanding activities such as moulting and courtship displays.

Animals↗
PubMed2001

Patterns of sperm precedence and predictors of paternity in the Trinidadian guppy.

Despite its widespread occurrence in animals, sperm competition has been studied in a limited range of taxa. Among the most neglected groups in this respect are internally fertilizing fish in which virtually nothing is known about the dynamics of sperm competition. In this study, we examined the outcome of sperm competition when virgin female guppies mated with two males. Behavioural cues were used to ensure that each male mated once (with female cooperation) and that sperm were successfully inseminated at copulation. Two polymorphic microsatellite loci were used to estimate the proportion of offspring sired by the second male (P2) and the results revealed a bimodal distribution with either first or (more often) second male priority The observed P2 distribution differed from that expected under the 'fair raffle' model of sperm competition. Random sperm mixing is therefore unlikely to account for the observed variance in P2 in this study. A further aim of our study was to identify predictors of male reproductive success. Using logistic linear modelling, we found that the best predictors of paternity were time to remating and the difference in courtship display rate between first and second males. Males that mated quickly and performed relatively high numbers of sigmoid displays obtained greater parentage than their slower and less vigorous counterparts. Since females are attracted to high-displaying males, our results suggest that female choice may facilitate sperm competition and/or sperm choice in guppies.

Animals↗
PubMed2001

Disruptive sexual selection against hybrids contributes to speciation between Heliconius cydno and Heliconius melpomene.

Understanding the fate of hybrids in wild populations is fundamental to understanding speciation. Here we provide evidence for disruptive sexual selection against hybrids between Heliconius cydno and Heliconius melpomene. The two species are sympatric across most of Central and Andean South America, and coexist despite a low level of hybridization. No-choice mating experiments show strong assortative mating between the species. Hybrids mate readily with one another, but both sexes show a reduction in mating success of over 50% with the parental species. Mating preference is associated with a shift in the adult colour pattern, which is involved in predator defence through Müllerian mimicry, but also strongly affects male courtship probability. The hybrids, which lie outside the curve of protection afforded by mimetic resemblance to the parental species, are also largely outside the curves of parental mating preference. Disruptive sexual selection against F(1) hybrids therefore forms an additional post-mating barrier to gene flow, blurring the distinction between pre-mating and post-mating isolation, and helping to maintain the distinctness of these hybridizing species.

Animals↗
PubMed2002

Female choice depends on size but not symmetry of dorsal eyespots in the butterfly Bicyclus anynana.

The eyespots on the ventral wings of Bicyclus anynana butterflies are exposed when at rest and interact with predators. Those on the dorsal surface are not exposed in this way, and may be involved in courtship and mate choice. In this study, we examined whether the size and fluctuating asymmetry (FA) of dorsal eyespots are reliable signals of male quality. High developmental stability is considered to result in low FA, and to be associated with high quality. Individuals of high quality are predicted to produce sexually selected traits that are large and symmetrical, at a relatively low cost. In this study, we manipulated eyespot development to uncouple eyespot size and FA in order to examine their independent roles in signalling to the female. Individual females in cages were given the choice between two or three males differing in eyespot traits. The results indicate that although size per se of the eyespots is used as a signal, FA and wing size are not. We discuss the use of FA in studies of sexual selection and aspects of sexual selection on dorsal eyespot size.

Animals↗
PubMed2003

Evolution of sexual dimorphism in the olfactory brain of Hawaiian Drosophila.

In the fruitfly, Drosophila melanogaster, mate choice during courtship depends on detecting olfactory cues, sex pheromones, which are initially processed in the antennal lobe (AL), a primary olfactory centre of the brain. However, no sexual differences in the structure of the AL have been found in Drosophila. We compared the central brain anatomy of 37 species of Drosophilidae from the islands of the Hawaiian archipelago, uncovering an extreme sexual dimorphism within the AL in which two out of the 51 identifiable glomeruli were markedly enlarged in males. A phylogeny indicated that the sexual dimorphism of the homologous glomeruli arose 0.4-1.9 Myr ago independently in two species groups of Hawaiian endemic Drosophilidae. The corresponding glomeruli in D. melanogaster were also found to be sexually dimorphic. The formation of glomeruli of male size is prevented by the ectopic expression of female-type transformer (tra) cDNA in males, indicating that the glomerular sexual dimorphism is under the control of the sex-determination cascade of genes. It is suggested that a defined set of glomeruli in Drosophila can enlarge in response to sex-determination genetic signals, the mutations of which may result in species differences in sexual dimorphism of the brain.

Animals↗