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PubMed2006

Analysis of behavior-related excitatory inputs to a central pacemaker nucleus in a weakly electric fish.

Gymnotid electric fish explore their environment and communicate with conspecifics by means of rhythmic electric organ discharges. The neural command for each electric organ discharge arises from activity of a medullary pacemaker nucleus composed of two neuronal types: pacemaker and relay cells. During different behaviors as in courtship, exploration and agonistic interactions, these species display specific electric organ discharge frequency and/or waveform modulations. The neural bases of these modulations have been explained in terms of segregation of inputs to pacemaker or relay cells, as well as differential activation of the glutamate receptors of these cells. One of the most conspicuous electric organ discharge frequency modulations in Gymnotus carapo results from the activation of Mauthner cells, a pair of reticulospinal neurons that are involved in the organization of sensory-evoked escape responses in teleost fish. The activation of Mauthner cells in these animals produces a prolonged increase in electric organ discharge rate, whose neural mechanisms involves the activation of both N-methyl-D-aspartate (NMDA) and metabotropic glutamatergic receptors of pacemaker cells. Here we provide evidence which indicates that pacemaker cells are the only cellular target of the synaptic inputs responsible for the Mauthner cell initiated electric organ discharge modulation at the medullary pacemaker nucleus. Additionally, although pacemaker cells express both NMDA and non-NMDA ionotropic receptors, we found that non-NMDA receptors are not involved in this synaptic action which suggests that NMDA and non-NMDA receptor subtypes are not co-localized at the subsynaptic membrane. NMDA receptor activation of pacemaker cells seems to be an efficient neural strategy to produce long-lasting enhancements of the fish sampling capability during Mauthner cell-initiated motor behaviors.

Action Potentials↗
PubMed2004

Hormonal regulation of brain circuits mediating male sexual behavior in birds.

Male sexual behavior in both field and laboratory settings has been studied in birds since the 19th century. Birds are valuable for the investigation of the neuroendocrine mechanisms of sexual behavior, because their behavior can be studied in the context of a large amount of field data, well-defined neural circuits related to reproductive behavior have been described, and the avian neuroendocrine system exhibits many examples of marked plasticity. As is the case in other taxa, male sexual behavior in birds can be usefully divided into an appetitive phase consisting of variable behaviors (typically searching and courtship) that allow an individual to converge on a functional outcome, copulation (consummatory phase). Based primarily on experimental studies in ring doves and Japanese quail, it has been shown that testosterone of gonadal origin plays an important role in the activation of both of these aspects of male sexual behavior. Furthermore, the conversion of androgens, such as testosterone, in the brain to estrogens, such as 17beta-estradiol, is essential for the full expression of male-typical behaviors. The localization of sex steroid receptors and the enzyme aromatase in the brain, along with lesion, hormone implant and immediate early gene expression studies, has identified many neural sites related to the control of male behavior. The preoptic area (POA) is a key site for the integration of sensory inputs and the initiation of motor outputs. Furthermore, prominent connections between the POA and the periaqueductal gray (PAG) form a node that is regulated by steroid hormones, receive sensory inputs and send efferent projections to the brainstem and spinal cord that activate male sexual behaviors. The sensory inputs regulating avian male sexual responses, in contrast to most mammalian species, are primarily visual and auditory, so a future challenge will be to identify how these senses impinge on the POA-PAG circuit. Similarly, most avian species do not have an intromittent organ, so the projections from the POA-PAG to the brainstem and spinal cord that control sexual reflexes will be of particular interest to contrast with the well characterized rodent system. With this knowledge, general principles about the organization of male sexual circuits can be elucidated, and comparative studies relating known species variation in avian male sexual behaviors to variation in neural systems can be pursued.

Androgens↗
PubMed2006

Environmental, seasonal, and social modulations of basal activity in a weakly electric fish.

The electric organ discharge (EOD) of weakly electric fish encodes information about species, sex, behavioral, and physiological states throughout the lifetime. Its central command is crucial for sensory-motor coordination, and is therefore the target of plastic mechanisms that adapt fish to environmental and social challenges. The EOD waveform of Brachyhypopomus pinnicaudatus is modulated by environmental factors and the neuroendocrine system. In this study we investigate the effects of water temperature and day-night cycle upon EOD rate in this species during the breeding and non-breeding seasons. During the non-breeding season, EOD rate is a linear function of water temperature and exhibits counterclockwise hysteresis. During breeding, a thermal resistance strategy prevents the decrease of EOD rate to cooling. A nocturnal increase of EOD basal rate independent of water temperature and locomotor activity was demonstrated in isolated non-breeding adults and in male-female dyads all year round. An additional increase of nocturnal EOD rate, probably acting as a social courtship signal, was found in breeding dyads. This additional increase of nocturnal EOD rate could not be fully explained by gonadal maturation and was modulated by social stimuli. This study provides novel data on the complex interactions between environment, reproductive cycle, social behavior, and electromotor output in an advantageous model of the vertebrate central nervous system.

Activity Cycles↗
PubMed2004

Schizophrenia as one extreme of a sexually selected fitness indicator.

Schizophrenia remains an evolutionary paradox. Its delusions, hallucinations and other symptoms begin in adolescence or early adulthood and so devastate sexual relationships and reproductive success that selection should have eliminated the disorder long ago. Yet it persists as a moderately heritable disorder at a global 1% prevalence--too high for new mutations at a few genetic loci. We suggest that schizophrenia persists and involves many loci because it is the unattractive, low-fitness extreme of a highly variable mental trait that evolved as a fitness ("good genes") indicator through mutual mate choice. Here we show that this hypothesis explains many key features of schizophrenia and predicts that some families carry modifier alleles that increase the indicator's neurodevelopmental sensitivity to heritable fitness and condition. Such alleles increase the extent to which high-fitness family members develop impressive courtship abilities and achieve high reproductive success, but also increase the extent to which low-fitness family members develop schizophrenia. Here we introduce this fitness indicator model of schizophrenia, discuss its explanatory power, explain how it resolves the evolutionary paradox, discuss its implications for gene hunting, and identify some empirically testable predictions as directions for further research.

Biological Evolution↗
PubMed2005

From mandatory to voluntary testing: balancing human rights, religious and cultural values, and HIV/AIDS prevention in Ghana.

This paper examines efforts by some churches in Ghana to reduce the spread of HIV/AIDS. The analysis is based on focus group discussions with two groups of men and two groups of women, along with in-depth interviews with 13 pastors and marriage counsellors in the churches studied. In response to government and public criticisms about human rights violations, churches that previously imposed mandatory HIV testing on members planning to marry now have voluntary testing programmes. However, the results suggest that what the churches refer to as voluntary testing may not be truly voluntary. Cultural values and traditional practices, including traditional courtship and marriage rites (which are performed before church weddings), not only clash with considerations about pre-marital HIV testing but also complicate the contentious issue of confidentiality of information on HIV testing. Associated with these complexities and issues of confidentiality is a reluctance among participants, particularly those from northern Ghana, to test for HIV. The results reveal how broader social impacts of HIV testing for those planning to marry may extend beyond individuals or couples in different cultural contexts. The findings also support the general view that there are no perfect or easy solutions to combating the HIV/AIDS pandemic. Practical solutions and programs for Ghana cannot be neutral to cultural values and need to be tailored for particular (ethnic) populations.

Adult↗
PubMed2004

Occurrence of flehmen in male buffaloes (Bubalus bubalis) with special reference to estrus.

Pheromonal cues present in the urine and vaginal mucus during the estrus period elicit courtship behaviour in mammals including the characteristic flehmen behaviour. In the present study, the flehmen behaviour was assessed in male buffaloes by exposing them to heifers for three consecutive estrous cycles. Behavioural observations revealed that the bulls sniffed the female's external genitalia, responded to the chemical signal(s) and exhibited the flehmen behaviour similar to those reported in other ungulates. The flehmen behaviour was recorded daily during 15-min contact with females for three consecutive estrous cycles. Out of 180 observations during five days estrus periods (-3 to +1 days) which included high frequency of flehmen behaviour and out of 637 observations with or without flehmen behaviour during diestrus periods, the bull displayed 365 and 441 flehmen behaviour, respectively. Average numbers of all (2.03 +/- 0.66) and repeated flehmen (1.05 +/- 0.64) behaviour during estrus periods were significantly higher than those of diestrus periods of all (0.69 +/- 0.25) and repeated flehmen (0.11 +/- 0.10). The statistical significance was higher (P < 0.001) in repeated flehmen behaviour of estrus as compared to that in diestrus. In case of all flehmen behaviour, the statistical significance was higher (P < 0.01) in estrus when compared to that in diestrus. The occurrence of flehmen behaviour in male buffaloes clearly indicates that the specific pheromonal compound(s) present in the urine/vaginal mucus during estrus significantly influence the flehmen behaviour.

Animals↗
PubMed2004

Reproductive traits in the spur-thighed tortoise (Testudo graeca terrestris): new tools for the enhancement of reproductive success and survivorship.

The Mediterranean tortoise (Testudo graeca) is listed as "Vulnerable" on the IUCN Red List. Reproductive characteristics and means to increase offspring production were studied in T. graeca terrestris in a semi-natural environment. Courtship and mating occurred during early spring for about 4 weeks, followed by a laying season of approximately 2 months, with a second, shorter mating period in the fall. During the first mating, calcified eggs were already present in the uterus; we inferred that sperm from both mating seasons were stored in the oviduct for fertilization of eggs of the second laying cycle and of the following year. Average egg production was 3.8+/-0.3 eggs/year. Most females laid all of their eggs in a single clutch, but 18% laid in a second clutch, 11-21 days later. X-ray radiography revealed calcified eggs in the uterus about 4 weeks before oviposition. All eggs in the uterus were calcified simultaneously and were laid in a single clutch; if a second clutch developed, those eggs were also calcified simultaneously. Based on endoscopic examinations, ovaries were active throughout the entire year. Plasma progesterone concentrations in females were very low and were detected only soon after oviposition ( 440 +/-141 pg/ml). Plasma estradiol concentrations in females varied from 4.1 +/-1.5 pg/ml to 70.2 +/-29.4 pg/ml, with no clear seasonal pattern. Maintaining tortoises at a low environmental temperature (9 +/-1 degrees C versus 28 +/- 1 degrees C) reduced plasma estradiol concentrations. Giving 2mg/kg tamoxifen (TAM) increased plasma estradiol to 220 +/-33 pg/ml when treatment was given in September but not in late October, winter or spring. Treatment with TAM increased the number of eggs laid during the following laying season to 7.3 +/- 1.0 eggs/year, laid in one to three clutches. In males, plasma testosterone concentrations had a seasonal pattern with the onset of a rise in July from 2 to >4ng/ml, a continued increase to a peak of 12.8+/-5.3 ng/ml during November and a decline thereafter. Artificial incubation in sand at 29 +/-1 degrees C shortened the natural incubation time of 103+/-3.1 days to 83.5 +/- 1.3 days, increased hatching rate from 28 to 53%, and increased survival rate from 51 to 71% at 40 weeks of age. In summary, this study provides options for increasing reproductive performance, hatchability and offspring survival in captive Mediterranean tortoises, and may offer new tools for conservation of animals that are on the verge of extinction.

Animals↗
PubMed2005

Effect of breed and age on sexual behaviour of rams.

The objective of this study was to highlight the problems that arise during the reproduction between thin-tailed rams and fat-tailed ewes. At the same time, particular emphasis laid on the influence of sheep breed, sheep age, time after ram introduction and day of the ewe estrus cycle on ram and ewe sexual behaviour. Rams were subjected to sexual performance tests by being individually exposed to 12 ewes for 3 h daily, 19 consecutive days. The 16 rams of the experiment were separated according to their age (9 and 21 months old) and breed (Chios and Karagouniki), and the 96 ewes of Chios fat-tailed breed, were divided by age (9 and 21 months old). The main characteristics of courtship behaviour, like sniffing, nudging, flehmen response and following were recorded and studied in detail. Mature Chios rams, which were the only one with previous experience of Chios ewes, exhibited higher rates of sexual interest per ewe than the other rams (P < 0.05). On the other hand, rams sniffed and nudged more young than mature ewes (P < 0.05), probably due to the fact that young ewes did not express intense symptoms of estrus. Young rams exhibited substandard sexual interest towards mature ewes, when they first came in contact with them (P < 0.05). In general, Karagouniki thin-tailed rams exhibited reduced rates of mating behaviour when they courted with Chios fat-tailed ewes in comparison with Chios rams (P < 0.05). Moreover, as the time after ram introduction passed, the frequency and duration of sexual behaviour components decreased (P < 0.001). Finally, the effect of the day of the experiment was only significant in the case of sniffing, which increased during the first 2 days and then declined and stabilized (P < 0.01). As it was demonstrated, ram age and ram breed played a fundamental role in the exhibition of sexual interest elements.

Age Factors↗
PubMed2004

Bacterial linguistic communication and social intelligence.

Bacteria have developed intricate communication capabilities (e.g. quorum-sensing, chemotactic signaling and plasmid exchange) to cooperatively self-organize into highly structured colonies with elevated environmental adaptability. We propose that bacteria use their intracellular flexibility, involving signal transduction networks and genomic plasticity, to collectively maintain linguistic communication: self and shared interpretations of chemical cues, exchange of chemical messages (semantic) and dialogues (pragmatic). Meaning-based communication permits colonial identity, intentional behavior (e.g. pheromone-based courtship for mating), purposeful alteration of colony structure (e.g. formation of fruiting bodies), decision-making (e.g. to sporulate) and the recognition and identification of other colonies - features we might begin to associate with a bacterial social intelligence. Such a social intelligence, should it exist, would require going beyond communication to encompass unknown additional intracellular processes to generate inheritable colonial memory and commonly shared genomic context.

Adaptation, Physiological↗
PubMed2003

Octopamine receptor OAMB is required for ovulation in Drosophila melanogaster.

Octopamine is a major monoamine in invertebrates and affects many physiological processes ranging from energy metabolism to complex behaviors. Octopamine binds to receptors located on various cell types and activates distinct signal transduction pathways to produce these diverse effects. We previously identified one of the Drosophila octopamine receptors named OAMB that produces increases in cAMP and intracellular Ca2+ upon ligand binding. It is expressed at high levels in the brain. To explore OAMB's physiological roles, we generated deletions in the OAMB locus. The resultant oamb mutants were viable without gross anatomical defects. The oamb females displayed normal courtship and copulation; however, they were impaired in ovulation with many mature eggs retained in their ovaries. RT-PCR, in situ hybridization, and expression of a reporter gene revealed that OAMB was also expressed in the thoracicoabdominal ganglion, the female reproductive system, and mature eggs in the ovary. Moreover, analysis of various alleles pinpointed the requirement for OAMB in the body, but not in the brain, for female fecundity. The novel expression pattern of OAMB and its genetic resource described in this study will help advance our understanding on how the neuromodulatory or endocrine system controls reproductive physiology and behavior.

Animals↗
PubMed2004

Effect of estradiol implants on reproductive behavior of female Lapland longspurs (Calcarius lapponicus).

The role of estrogens in reproductive behavior of free-living birds has been little investigated, despite the importance of estrogens in coordinating reproductive behavior and the need for information on potential effects of estrogenic contaminants on wildlife. We gave subcutaneous implants of estradiol (E2) to 15 female Lapland longspurs (Calcarius lapponicus), an arctic bird with a six-week breeding season. Controls were 9 females with empty implants and 14 unimplanted females. After implantation, E2 females had greater E2 levels and greater body mass than controls. We did not detect any increases in, or prolongation of, sexual or nest-building behavior. The incubation period was longer for E2 nests than for control nests. Nest videotapes showed that E2 females and their mates exhibited normal nestling care, and nestling growth, fledging success, and overwinter survival were also unaffected. However, whenever the males arrived at the nests, E2 females showed a significantly greater likelihood of begging from the male rather than leaving the nest. Courtship or incubation feeding have been considered atypical for this species, and it is not clear what role E2 normally plays in promoting begging behavior. Overall, elevated E2 levels did not result in any obvious costs for the female, save perhaps for slightly reduced incubation efficiency. The weak response to hormonal implants is similar to patterns seen in male Lapland longspurs, and may be related to the short breeding season. However, since little is presently known about the role of estrogens in behavior of wild female birds, it remains to be seen whether these patterns are typical of female passerines in general, or of short-season breeders. Further research on effects of estrogens (both exogenous and endogenous) on free-living female birds is needed.

Animals↗
PubMed2004

The role of olfaction during mating in the southern temperate spiny lobster Jasus edwardsii.

Chemosensory communication may be crucial during mate choice and mating in the southern temperate spiny lobster Jasus edwardsii to ensure that females mate with large males capable of supplying adequate numbers of sperm during the short mating window. To clarify the role of pheromones during this process, three laboratory experiments were carried out. In an experiment where the output of urine, which contains sex-specific pheromones, from large and small catheterized males was switched, large post-molt females did not make a clear choice of mate. This indicates that while females distinguish among females, males, and juveniles using their chemosensory sense, they distinguish among males using visual and tactile senses in combination with olfaction. Further, two antennule-ablation experiments were carried out to determine if detection of pheromones by the antennules of females or males was critical for mate selection, courting, or mating. In both cases, we observed a (nonsignificant) trend of slightly delayed mating of treatment females. We found that disruption of female olfaction causes less impact on courtship or mating than ablation of male antennules which increased the variance in the length of the period between molting and mating and resulted in a systematic reduction in clutch size. This lesser impact of female ablation may be because females can still respond to their own internal cues about egg ripeness whereas males cannot. In J. edwardsii, unlike the American clawed lobster, Homarus americanus, one fully functional partner of either sex appears sufficient to initiate mating.

Animals↗
PubMed2004

The role of androgens in the trade-off between territorial and parental behavior in the Azorean rock-pool blenny, Parablennius parvicornis.

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.

Absorbable Implants↗
PubMed2004

Visual sex discrimination in goldfish: seasonal, sexual, and androgenic influences.

The olfactory signals used by goldfish for sexual and aggressive communication have been studied extensively, but little work has addressed the role of other sensory modalities in social communication in this species. We therefore investigated the role that visual stimuli play in sex discrimination and the ability of androgens, which masculinize courtship behavior, to affect behavioral responses toward female visual stimuli. We found that males selectively orient toward female visual stimuli during the breeding season but not outside it, whereas prostaglandin F2-alpha (PGF2alpha)-injected females do not differentially approach male and female visual stimuli, even during the breeding season. Implanting adult females with testosterone (T) and 11-ketotestosterone (KT), however, induced orientation responses toward female visual stimuli similar to those observed in males. These results indicate that visual sexual stimuli are likely important for reproductive signaling in goldfish, potentially helping males identify ovulating females from a distance in a shoal of fish, and that androgens can influence mechanisms associated with orientation responses toward such stimuli.

Androgens↗
PubMed2004

Exogenous vasotocin alters aggression during agonistic exchanges in male Amargosa River pupfish (Cyprinodon nevadensis amargosae).

Pupfishes in the Death Valley region have rapidly differentiated in social behaviors since their isolation in a series of desert streams, springs, and marshes less than 20,000 years ago. These habitats can show dramatic fluctuations in ecological conditions, and pupfish must cope with the changes by plastic physiological and behavioral responses. Recently, we showed differences among some Death Valley populations in brain expression of arginine vasotocin (AVT). As AVT regulates both hydromineral balance and social behaviors in other taxa, these population differences may indicate adaptive changes in osmoregulatory and/or behavioral processes. To test whether AVT is relevant for behavioral shifts in these fish, here we examined how manipulations to the AVT system affect agonistic and reproductive behaviors in Amargosa River pupfish (Cyprinodon nevadensis amargosae). We administered exogenous AVT (0.1, 1, and 10 microg/g body weight) and an AVP V1 receptor antagonist (Manning compound, 2.5 microg/g body weight) intraperitoneally to males in mixed-sex groups in the laboratory. We found that AVT reduced the initiation of aggressive social interactions with other pupfish but had no effect on courtship. The effects of AVT were confirmed in males in the wild where AVT (1 microg/g body weight) reduced the aggressive initiation of social interactions and decreased aggressive responses to the behavior of other males. Combined, these results show that AVT can modulate agonistic behaviors in male pupfish and support the idea that variation in AVT activity may underlie differences in aggression among Death Valley populations.

Aggression↗
PubMed2005

Testosterone, reproductive stage, and territorial behavior of male and female European stonechats Saxicola torquata.

We investigated territorial behavior and circulating testosterone (T) levels in a multiple-brooded population of the European stonechat, a socially monogamous passerine bird with biparental care. Between arrival at and departure from the breeding territories, we (1) quantified behavior of both sexes in response to a simulated territorial intrusion (STI) of a male conspecific and (2) measured plasma T concentrations in males and females. Male response scores to a STI and male T concentrations varied with phase, but there was no temporal association between plasma T levels and the intensity of territorial behavior. During both two sexual and two parental phases, at least half of the tested males showed aggressive responses. About 20% of the tested males responded with courtship prior to laying of the first clutch, but none of the males courted during later phases. Age had a positive overall effect on male plasma T. Females also reacted to the STI of a male, but their responses did not vary with breeding phase. Female plasma T varied with phase, being elevated during production of the first but not of the second clutch. As with males, female responses to the STI were not correlated with T levels. Responses of pair partners were positively correlated with each other. We conclude that modulation of male territorial aggression with breeding phase is not regulated by changes of plasma T concentrations. In light of other studies showing reduced male aggression by pharmacological inhibition of cellular actions of T, we propose that T is permissive for male territorial aggression, but does not mediate short-term changes associated with breeding phase. The function of the high female plasma T concentrations during formation of first clutches could be related to the production of eggs with high concentrations of androgens.

Age Factors↗
PubMed2005

Current research on the behavioral neuroendocrinology of reptiles.

Selected reptilian species have been the targets of investigations in behavioral neuroendocrinology for many years. Reptiles offer a particularly powerful set of traits that facilitate comparisons at multiple levels, including those within and between individuals of a particular species, between different environmental and social contexts, as well as across species. These types of studies, particularly as they are considered within the framework of results from other vertebrates, will enhance our understanding of the genetic and hormonal influences regulating changes in the structure and function of the nervous system. Work on the hormonal and environmental factors influencing courtship and copulatory behaviors in green anoles, including the development and maintenance of the neuromuscular structures critical for their display, is highlighted. Some very recent work on other model systems is also discussed to provide a context for suggested future research directions.

Animals↗
PubMed2005

Historical contributions of research on reptiles to behavioral neuroendocrinology.

Some of the first experiments in behavioral endocrinology in the 1930s were conducted with lizards, but events led to a hiatus that lasted for 30 years. In the 1960s, research resumed using techniques current at the time, but it was not until the mid-1970s that behavioral neuroendocrinology "discovered" reptiles as animal model systems. This historical review summarizes this period of work, illustrating an enormous increase in research that have led to conclusions such as (1) the phenomenon of dissociated reproductive strategies and hormone-independent behaviors, which have aided our understanding of how the "memory" of sex steroid actions is maintained. (2) Progesterone plays an important role in the organization and activation of sexual behavior in males. Progesterone also synergizes with T to control male courtship much as does estrogen and progesterone to control sexual receptivity in females. Thus, progesterone is as much a "male" hormone as it is a "female" hormone. (3) Use of cytochrome oxidase histochemistry to study the role of experience over the long term in modifying brain activity. (4) Hormone manipulations as a powerful tool to test hypotheses about the evolution of behavior in free-living animals.

Aggression↗