Female Pairs Research Articles

Imaging, Behavior and Endocrine Analysis of "Jealousy" in a Monogamous Primate.

Understanding the neurobiology of social bonding in non-human primates is a critical step in understanding the evolution of monogamy, as well as understanding the neural substrates for emotion and behavior. Coppery titi monkeys (Callicebus cupreus) form strong pair bonds, characterized by selective preference for their pair mate, mate-guarding, physiological and behavioral agitation upon separation, and social buffering. Mate-guarding, or the "maintenance" phase of pair bonding, is relatively under-studied in primates. In the current study, we used functional imaging to examine how male titi monkeys viewing their pair mate in close proximity to a stranger male would change regional cerebral glucose metabolism. We predicted that this situation would challenge the pair bond and induce "jealousy" in the males. Animals were injected with [18F]-fluorodeoxyglucose (FDG), returned to their cage for 30 min of conscious uptake, placed under anesthesia, and then scanned for 1 hour on a microPET P4 scanner. During the FDG uptake, males (n=8) had a view of either their female pair mate next to a stranger male ("jealousy" condition) or a stranger female next to a stranger male (control condition). Blood and cerebrospinal fluid samples were collected and assayed for testosterone, cortisol, oxytocin, and vasopressin. Positron emission tomography (PET) was co-registered with structural magnetic resonance imaging (MRI), and region of interest analysis was carried out. Bayesian multivariate multilevel analyses found that the right lateral septum (Pr(b>0)=93%), left posterior cingulate cortex (Pr(b>0)=99%), and left anterior cingulate (Pr(b>0)=96%) showed higher FDG uptake in the jealousy condition compared to the control condition, while the right medial amygdala (Pr(b>0)=85%) showed lower FDG uptake. Plasma testosterone and cortisol concentrations were higher during the jealousy condition. During the jealousy condition, duration of time spent looking across at the pair mate next to a stranger male was associated with higher plasma cortisol concentrations. The lateral septum has been shown to be involved in mate-guarding and mating-induced aggression in monogamous rodents, while the cingulate cortex has been linked to territoriality. These neural and physiological changes may underpin the emotion of jealousy, which can act in a monogamous species to preserve the long-term integrity of the pair.

A population based twin study of DSM-5 maladaptive personality domains.

Personality disorders (PDs) can be partly captured by dimensional traits, a viewpoint reflected in the most recent Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition (DSM-5) Alternative (Section III) Model for PD classification. The current study adds to the literature on the Alternative Model by examining the magnitude of genetic and environmental influences on 6 domains of maladaptive personality: negative emotionality, detachment, antagonism, disinhibition, compulsivity, and psychoticism. In a large, population-based sample (N = 2,293) of Norwegian male and female twin pairs, we investigated (a) if the domains demonstrated measurement invariance across gender at the phenotypic level, meaning that the relationships between the items and the latent factor were equivalent in men and women; and (b) if genetic and environmental influences on variation in these domains were equivalent across gender. Multiple group confirmatory factor modeling provided evidence that all 6 domain scale measurement models were gender-invariant. The best fitting biometric model for 4 of the 6 domains (negative emotionality, detachment, disinhibition, and compulsivity) was one in which genetic and environmental influences could be set invariant across gender. Evidence for sex differences in psychoticism was mixed, but the only clear evidence for quantitative sex differences was for the antagonism scale, with greater genetic influences found for men than women. Genetic influences across domains were moderate overall (19-37%), in line with previous research using symptom-based measures of PDs. This study adds to the very limited knowledge currently existing on the etiology of maladaptive personality traits. (PsycINFO Database Record

Attitudes to Gun Control in an American Twin Sample: Sex Differences in the Causes of Variation.

The genetic and social causes of individual differences in attitudes to gun control are estimated in a sample of senior male and female twin pairs in the United States. Genetic and environmental parameters were estimated by weighted least squares applied to polychoric correlations for monozygotic (MZ) and dizygotic (DZ) twins of both sexes. The analysis suggests twin similarity for attitudes to gun control in men is entirely genetic while that in women is purely social. Although the volunteer sample is small, the analysis illustrates how the well-tested concepts and methods of genetic epidemiology may be a fertile resource for deepening our scientific understanding of biological and social pathways that affect individual risk to gun violence.

Reproductive biology of two species of Hyalella Smith, 1874 (Crustacea: Amphipoda: Hyalellidae) from southern Brazil

ABSTRACTReproduction is a critical event in the life cycle of animals, and a high amount of energy is allocated to it. The aim of this study was to characterize the reproductive biology of two recently described species of Hyalella from the north-east region of state of Rio Grande do Sul in southern Brazil. The specimens were collected during 12 months from a stream source (Hyalella georginae) and from a water reservoir (H. gauchensis), in Palmeira das Missões municipality, state of Rio Grande do Sul. Upon sampling, ovigerous females and pairs in precopulatory behaviour were separated into microtubes. In the laboratory, the cephalothorax length (CL in mm) of all specimens was measured. Male size at onset of sexual maturity was larger than that of the females, in both species. There was a correlation between the size of paired males and females: larger males carried larger females, in both Hyalella species. Precopulatory pairs were found throughout the year; however, H. georginae had a higher frequency in spring, and H. gauchensis in autumn. There was a positive correlation between the CL of ovigerous females and the number of eggs/juveniles. A reduction in the number of eggs throughout the embryonic development was observed in H. georginae. The average fecundity of H. georginae was significantly higher than H. gauchensis. The differences between the reproductive biology of these species may be related to the physical and environmental conditions at which they are exposed in their habitats.

Gender and autistic traits modulate implicit motor synchrony.

Interpersonal motor synchrony during walking or dancing is universally observed across cultures, and this joint movement was modulated by physical and social parameters. However, human interactions are greatly shaped by our unique traits, and self-related factors are surprisingly little studied in the context of interpersonal motor synchrony. In this study, we investigated two such factors known to be highly associated with motor coordination: gender and autistic traits. We employed a real-world task extending our understanding beyond laboratory tasks. Participants of the same gender were paired up to walk and chat in a natural environment. A cover story was introduced so that participants would not know their walking steps were being recorded and instead believed that their location was being tracked by a global positioning system (GPS), so they would ignore the motor recording. We found that the female pairs’ steps were more synchronized than those of the males, and higher autistic tendencies (measured by the autism-spectrum quotient) attenuated synchronous steps. Those who synchronized better had higher impression rating increase for their walking partners (measured by interpersonal judgement scale) than those who synchronized less well. Our results indicated that the participants’ joint movements were shaped by predisposed traits and might share similar mechanism with social functions such as empathy.

Immunohistochemical Staining for Uroguanylin, a Satiety Hormone, is Decreased in Intestinal Tissue Specimens From Female Adolescents With Obesity.

Gastrointestinal tract-secreted satiety hormones play a significant role in one of the largest health-care challenges for children and adults, obesity. Recent studies in mice identified a novel role for uroguanylin, the endogenous intestinal hormone that binds guanylyl cyclase C (GUCY2C), in regulating satiety via a gut-brain signaling pathway. Mice bred without GUCY2C receptors over-ate and developed obesity. We hypothesized that intestinal uroguanylin expression in pediatric patients with obesity would be lower than patients without obesity, and we attempted to examine the difference with immunohistochemistry. Retrospective chart review of gastrointestinal endoscopic procedures at an academic children's hospital identified patients with normal pathology findings on biopsy. Children aged 8-17 were included in the review; we analyzed biopsy samples from 20 matched pairs that differed only by body mass index (BMI)-for-age (average: 25%-75% vs. high: >95%). Biopsies of the duodenum, terminal ileum, ascending colon, and descending colon were subjected to immunohistochemistry for GUCY2C, uroguanylin, and the endogenous colonic hormone, guanylin. Intensity staining of all specimens was scored by a blinded pathologist. The overall staining intensity for females with high BMI-for-age was less for uroguanylin and guanylin as compared to average BMI-for-age females while GUCY2C staining was equal. Males did not exhibit different staining intensities for uroguanylin or guanylin. More matched female pairs had greater uroguanylin and guanylin staining in the average BMI-for-age cohort. The intestinal expression of uroguanylin, a key satiety hormone, appears to be diminished in female pediatric patients in the setting of obesity.

A gene expression atlas of adult Schistosoma mansoni and their gonads

RNA-Seq has proven excellence in providing information about the regulation and transcript levels of genes. We used this method for profiling genes in the flatworm Schistosoma mansoni. This parasite causes schistosomiasis, an infectious disease of global importance for human and animals. The pathology of schistosomiasis is associated with the eggs, which are synthesized as a final consequence of male and female adults pairing. The male induces processes in the female that lead to the full development of its gonads as a prerequisite for egg production. Unpaired females remain sexually immature. Based on an organ-isolation method we obtained gonad tissue for RNA extraction from paired and unpaired schistosomes, with whole adults included as controls. From a total of 23 samples, we used high-throughput cDNA sequencing (RNA-Seq) on the Illumina platform to profile gene expression between genders and tissues, with and without pairing influence. The data obtained provide a wealth of information on the reproduction biology of schistosomes and a rich resource for exploitation through basic and applied research activities.

Hallux Valgus, By Nature or Nurture? A Twin Study.

To evaluate the contributions of shared but unmeasured genetic and environmental factors to hallux valgus (HV). Between 2011 and 2012, 74 monozygotic (MZ) and 56 dizygotic (DZ) female twin pairs self-reported HV and putative risk factors, including footwear use across their lifespan. Estimates of casewise concordance (PC ), correlation (ρ), and odds ratios (ORs) were calculated, adjusting for age and other risk factors, and compared between MZ and DZ pairs using logistic regression, generalized estimating equations, and a maximum likelihood-based method, respectively. A total of 70 participants (27%) reported HV, with 12 MZ and 7 DZ pairs being concordant. After adjusting for age, twins were correlated (ρ = 0.27 [95% confidence interval (95% CI) 0.08, 0.46]) and concordant (PC = 0.45 [95% CI 0.29, 0.61]; mean age 58 years), with no difference between MZ and DZ pairs (P = 0.7). HV was associated with regularly wearing footwear with a constrictive toe-box during the fourth decade (adjusted OR 2.73 [95% CI 1.12, 6.67]). This risk factor was correlated in MZ (ρ = 0.38 [95% CI 0.15, 0.60]) but not DZ (ρ = -0.20 [95% CI -0.43, 0.03]) pairs. These correlations were significantly different (P = 0.002). Twins are correlated for HV, but we found no evidence that correlation was due to shared genetic factors. We identified an environmental risk factor, footwear with a constrictive toe-box, that is not shared to the same extent by MZ and DZ pairs, contrary to the assumption of the classic twin model. Footwear, and possibly genetic factors and unknown shared environmental factors, could contribute to developing HV.

Major depressive disorder, suicidal thoughts and behaviours, and cannabis involvement in discordant twins: a retrospective cohort study

BackgroundEarly-onset and frequent cannabis use are associated with an increased likelihood of major depressive disorder (MDD) as well as suicidal thoughts and behaviours. We identify associations between aspects of cannabis use and MDD as well as suicidal thoughts and behaviours and examine whether such associations persist after accounting for those predisposing factors, including genetic liability and early family environment, that are shared by identical twins who are discordant for cannabis exposure. Any residual association in such identical pairs might be indicative of individual – specific pathways that may be of a causal nature.MethodsWe did a logistic regression analysis of cannabis use from retrospective data on same-sex male and female twin pairs drawn from 3 studies that had recruited twins from the Australian Twin Registry, 1992–93 (sample 1), 1996–2000 (sample 2), and 2005–09 (sample 3). We studied associations between early use and frequent use of cannabis and MDD, suicidal ideation (ever and persistent), and suicide plan and attempt in the full sample as well as in pairs of monozygotic and dizygotic twins that were discordant for each measure of cannabis involvement at a single timepoint. Significant monozygotic associations were further adjusted for covariates, such as early alcohol or nicotine use, early dysphoric or anhedonic mood, conduct disorder, and childhood sexual abuse. Interactions between each cannabis measure and sex, sample or study effects, and birth year category were also examined as covariates.FindingsIn 13 986 twins (6181 monozygotic and 7805 dizygotic), cannabis use ranged from 1345 (30·4%) of 4432 people in sample 1 to 2275 (69·0%) of 3299 in sample 3. Mean age of first cannabis use ranged from 17·9 years (SD 3·3) in sample 3 to 21·1 years in sample 1, and frequent use (≥100 times) was reported by 214 (4·9%) people in sample 1 and 499 (15·2%) in sample 3. The prevalence of suicidal ideation ranged from 1102 (24·9%) in sample 1 to 1644 (26·3%) of 6255 people in sample 2 and 865 (26·2%) people in sample 3. Prevalence of MDD ranged from 901 (20·3%) people in sample 1 to 1773 (28·5%) people in sample 2. The monozygotic twin who used cannabis frequently was more likely to report MDD (odds ratio 1·98, 95% CI 1·11–3·53) and suicidal ideation (2·47, 1·19–5·10) compared with their identical twin who had used cannabis less frequently, even after adjustment for covariates. For early cannabis use, the monozygotic point estimate was not significant but could be equated to the significant dizygotic estimate, suggesting a possible association with suicidal ideation.InterpretationThe increased likelihood of MDD and suicidal ideation in frequent cannabis users cannot be solely attributed to common predisposing factors.FundingNational Institutes of Health

Phylogeographic structure without pre-mating barriers: Do habitat fragmentation and low mobility preserve song and chorus diversity in a European bushcricket?

When animal species have a strong phylogeographic structure questions arise on the origin, maintenance and future evolutionary trajectory of that structure. One prediction is that phenotypic differences among populations serve as pre-mating barriers should secondary contact occur. Post-mating barriers may also function and ensure further separation of the populations. We tested these predictions in an acoustic insect, the European bushcricket Ephippiger diurnus, that is geographically distributed in separated, genetically isolated populations distinguished by pronounced differences in male songs and chorusing and female preferences for song. We staged mixed-population choruses to examine how males sing when in the company of other populations, and we released females in these choruses to assess their preference for or aversion toward males of their own population versus a different one. We also paired males and females of the same and different populations to test mating success, spermatophore transfer, and oviposition in the various pairings. In most cases males sang as effectively when accompanied by males from another population as when in a single-population chorus, and females overall expressed little aversion toward males from a different population. Inter-population pairs did not mate less frequently, transfer smaller spermatophores, or deposit fewer or smaller eggs than pairs of males and females from the same population. We infer that pre-mating barriers play little role in maintaining phylogeographic structure despite the acoustic differences between populations. Rather, the structure probably reflects the fragmented distribution of suitable habitat and the low mobility of both juveniles and adults. Thus, if secondary contact does occur, and we predict that it will in several key locations owing to ongoing environmental change, coalescence of populations and reduction of genetic and acoustic diversity may follow.

The complexity of mating decisions in stalk-eyed flies.

All too often, studies of sexual selection focus exclusively on the responses in one sex, on single traits, typically those that are exaggerated and strongly sexually dimorphic. They ignore a range of less obvious traits and behavior, in both sexes, involved in the interactions leading to mate choice. To remedy this imbalance, we analyze a textbook example of sexual selection in the stalk‐eyed fly (Diasemopsis meigenii). We studied several traits in a novel, insightful, and efficient experimental design, examining 2,400 male–female pairs in a “round‐robin” array, where each female was tested against multiple males and vice versa. In D. meigenii, females exhibit strong mate preference for males with highly exaggerated eyespan, and so we deliberately constrained variation in male eyespan to reveal the importance of other traits. Males performing more precopulatory behavior were more likely to attempt to mate with females and be accepted by them. However, behavior was not a necessary part of courtship, as it was absent from over almost half the interactions. Males with larger reproductive organs (testes and accessory glands) did not make more mating attempts, but there was a strong tendency for females to accept mating attempts from such males. How females detect differences in male reproductive organ size remains unclear. In addition, females with larger eyespan, an indicator of size and fecundity, attracted more mating attempts from males, but this trait did not alter female acceptance. Genetic variation among males had a strong influence on male mating attempts and female acceptance, both via the traits we studied and other unmeasured attributes. These findings demonstrate the importance of assaying multiple traits in males and females, rather than focusing solely on prominent and exaggerated sexually dimorphic traits. The approach allows a more complete understanding of the complex mating decisions made by both males and females.

Individual recognition of opposite sex vocalizations in the zebra finch

Individual vocal recognition plays an important role in the social lives of many vocally active species. In group-living songbirds the most common vocalizations during communal interactions are low-intensity, soft, unlearned calls. Being able to tell individuals apart solely from a short call would allow a sender to choose a specific group member to address, resulting in the possibility to form complex communication networks. However, little research has yet been carried out to discover whether soft calls contain individual identity. In this study, males and females of zebra finch pairs were tested with six vocalization types - four different soft calls, the distance call and the male song - to investigate whether they are able to distinguish individuals of the opposite sex. For both sexes, we provide the first evidence of individual vocal recognition for a zebra finch soft unlearned call. Moreover, while controlling for habituation and testing for repeatability of the findings, we quantify the effects of hitherto little studied variables such as partners’ vocal exchange previous to the experiment, spectral content of playback calls and quality of the answers. We suggest that zebra finches can recognize individuals via soft vocalizations, therefore allowing complex directed communication within vocalizing flocks.

Overweight is associated with lower resting state functional connectivity in females after eliminating genetic effects: A twin study.

Obesity is related to altered functional connectivity of resting state brain networks that are involved in reward and motivation. It is unknown to what extent these associations reflect genetic confounding and whether the obesity-related connectivity changes are associated with differences in dietary intake. In this study, resting state functional MRI was performed after an overnight fast in 16 female monozygotic twin pairs (aged 48.8 ± 9.8 years) with a mean BMI discordance of 3.96 ± 2.1 kg/m2 (range 0.7-8.2). Functional connectivity of the salience, basal ganglia, default mode and anterior cingulate-orbitofrontal cortex networks was examined by independent component analysis. Dietary intake was assessed using 3-day 24-hour recalls. Results revealed that within the basal ganglia network, heavier versus leaner co-twins have decreased functional connectivity strength in bilateral putamen (P < 0.05, FWE-corrected). There were no differences in connectivity in the other networks examined. In the overall group, lower functional connectivity strength in the left putamen was correlated with higher intake of total fat (P < 0.01). It was concluded that, after eliminating genetic effects, overweight is associated with lower resting state functional connectivity in bilateral putamen in the basal ganglia network. The association between lower putamen connectivity and higher fat intake suggests an important role of the putamen in appetitive mechanisms. The cross-sectional nature of our study cannot discriminate cause and consequence, but the findings are compatible with an effect of lower putamen connectivity on increased BMI and associated higher fat intake. Hum Brain Mapp 38:5069-5081, 2017. © 2017 Wiley Periodicals, Inc.

Shared familial risk between bulimic symptoms and alcohol involvement during adolescence.

Twin studies show the established relation between bulimic symptoms and problematic alcohol involvement in adult females is partly due to shared familial factors, specifically shared genetic effects. However, it is unclear if similar shared etiological factors exist during adolescence or in males. We examined the familial overlap (i.e., genetic and common environmental correlations) between bulimic symptoms and various levels of alcohol involvement in 16- to 17-year-old female and male same-sex twin pairs using sex-specific biometrical twin modeling. Bulimic symptoms were assessed with the Eating Disorder Inventory-2. Alcohol involvement included alcohol use in the last month, having ever been intoxicated, and alcohol intoxication frequency. Results revealed 3 distinct patterns. First, in general, phenotypic correlations indicated statistically similar associations between bulimic symptoms and alcohol involvement in girls and boys. Second, common environmental overlap was significant for the bivariate associations including having ever been intoxicated. Third, moderate genetic correlations were observed between all bulimic symptoms and alcohol involvement in girls and moderate common environmental correlations were observed in boys for the more risky/deviant levels of involvement. Similar to adults, there is familial overlap between bulimic symptoms and alcohol involvement in adolescent girls and boys. These results could inform symptom- and sex-specific, developmentally targeted prevention and intervention programs for the comorbidity between bulimic symptoms and alcohol involvement. (PsycINFO Database Record

Anthropometric Profile in Different Event Categories of Acrobatic Gymnastics.

There is a specific anthropometric profile for each sport, which may be differentiated even in relation to the position, role or event category within each sport discipline. However, there are few studies on acrobatic gymnastics, and the goal of this work was to determine the anthropometric profile depending on the event category, as well as factors that predisposed to performance in these categories. The sample consisted of 150 gymnasts from Spain, divided into 8 groups according to the event category and the role played. The kinanthropometric measurements were taken through the procedures established by the International Society for the Advancement of Kineantropometry. The anthropometric characteristics, including body mass index, somatotype, body composition and proportionality using the Phantom stratagem were analyzed, and the results obtained from the different groups were compared. A regression analysis was performed with particular groups of gymnasts. No significant differences (p < 0.05) were observed between groups of female tops or male bases, although differences were found between female group bases and female pair bases. It could be suggested that higher values of body height, sitting height, the minimum abdominal circumference, percentage of fat and low biliocristal breadth predispose female bases to work in pairs rather than in groups. The conclusion is that the anthropometric measurements are not decisive when guiding a gymnast toward choosing one event category or another, except for female bases.

Identifying individual male reproductive consistency in Drosophila melanogaster: The importance of controlling female behaviour

Work on the repeatability of reproductive behaviour has mainly focused on the consistency of female preferences. We characterised the consistency of individual male Drosophila melanogaster reproductive behaviour in two experiments. In the first experiment, we allowed males to interact with a pair of live females that differed in body size. We then controlled female behaviour in a second experiment by examining the courtship behaviour of individual males interacting with a pair of decapitated females that varied in body size. In both experiments, we examined the consistency of individual male reproductive behaviour across two repeated trials on the same day. Males did not exhibit a courtship preference for the larger female in either experiment, but, in experiment 1, males did exhibit post-copulatory choice by copulating for longer durations with the large female, and males that mated with the same type of female in both trials exhibited repeatable behaviour. In general, we found weak evidence of consistent male courtship behaviour in the presence of behaving females. However, when female behaviour was controlled in experiment 2, we found that male courtship behaviour was highly repeatable. These results indicate that individual male D. melanogaster exhibit consistent reproductive behaviour and demonstrate the importance of controlling female behaviour when attempting to characterise the repeatability of male reproductive behaviour.

Brain reward responses to food stimuli among female monozygotic twins discordant for BMI

Obese individuals are characterized by altered brain reward responses to food. Despite the latest discovery of obesity-associated genes, the contribution of environmental and genetic factors to brain reward responsiveness to food remains largely unclear. Sixteen female monozygotic twin pairs with a mean BMI discordance of 3.96 ± 2.1 kg/m2 were selected from the Netherlands Twin Register to undergo functional MRI scanning while watching high- and low-calorie food and non-food pictures and during the anticipation and receipt of chocolate milk. In addition, appetite ratings, eating behavior and food intake were assessed using visual analog scales, validated questionnaires and an ad libitum lunch. In the overall group, visual and taste stimuli elicited significant activation in regions of interest (ROIs) implicated in reward, i.e. amygdala, insula, striatum and orbitofrontal cortex. However, when comparing leaner and heavier co-twins no statistically significant differences in ROI-activations were observed after family wise error correction. Heavier versus leaner co-twins reported higher feelings of hunger (P = 0.02), cravings for sweet food (P = 0.04), body dissatisfaction (P < 0.05) and a trend towards more emotional eating (P = 0.1), whereas caloric intake was not significantly different between groups (P = 0.3). Our results suggest that inherited rather than environmental factors are largely responsible for the obesity-related altered brain responsiveness to food. Future studies should elucidate the genetic variants underlying the susceptibility to reward dysfunction and obesity.Clinical Trial Registration Number: NCT02025595.

Male vigilance and presence are important for foraging by female Chinese grouse in the pre-incubation period

In some monogamous birds, males invest more time in vigilance than females, especially during the pre-incubation period. As behaviors are time costly, there is a tradeoff between vigilance and feeding behavior. Male vigilance can be regarded as a male investment in their mates and may benefit the female by reducing the danger of predation, increasing her probability of survival, and allowing more time for her to forage to obtain more resources for egg production and incubation. In this study, we documented the proportion of time spent in vigilance and feeding by Chinese grouse Tetrastes sewerzowi with their mates and alone during the pre-incubation period, and then estimated male vigilance under more severe predation pressures through predator call playback. Our results indicated that paired male Chinese grouse spend more time in vigilance than unpaired males and paired females and could alter their activity budgets in response to the social context (i.e. with and without their mate) and an experimental e...

The role of the model in mate‐choice copying in female zebra finches

AbstractPrevious studies have shown that zebra finch females copy the mate choice of other females by choosing a mate of the same phenotype as the one chosen by another female (model). Little is known about the influence of the model female on the mate choice of the observing female. Therefore, we investigated the role of the model female in mate‐choice copying by manipulating her phenotype. Test females could choose between an unadorned male and an artificially adorned male, that is, wearing a red feather on the forehead. During a 2h observation period, test females could observe a single male in one cage and a male–female pair in another cage. In treatment one, the single male was unadorned and both the male and the female of the pair (model female) were adorned. In treatment two, the single male was adorned, the male of the pair unadorned and the model female adorned. Afterwards, test females could again choose between two new males, one adorned and one unadorned. In treatment one, test females first showed no preference for one of the two males, but avoided adorned males after the observation period. In treatment two, test females lost an initial preference for unadorned males after the observation period. In both treatments, test females did not copy the mate choice of the adorned model female. Adorned model females seemed to have a negative influence on the attractiveness of their mates' phenotype. Test females might have recognised model females as females of a different phenotype within their species which are adapted to different environmental conditions, or even have recognised model females as a female of another species. Our study demonstrates the important role of the model female in the complex public information network in zebra finches.

Genetic analysis of age at onset variation in spinocerebellar ataxia type 2.

Objective:To examine heritability of the residual variability of spinocerebellar ataxia type 2 (SCA2) age at onset (AO) after controlling for CAG repeat length.Methods:From 1955 to 2001, dates of birth, CAG repeat lengths, AO, sex, familial inheritances, and clinical manifestations were collected for a large Cuban SCA2 cohort of 382 affected individuals, including 129 parent-child pairs and 69 sibships. Analyses were performed with log-transformed AO in the GENMOD procedure to predict AO using repeat length, taking into account family structure. Because all relationships were first degree, the model was implemented with an exchangeable correlation matrix. Familial correlations were estimated using the Pedigree Analysis Package to control for similarity due to genetic relatedness.Results:For the entire sample, the mutant CAG repeat allele explained 69% of AO variance. When adjusted for pedigree structure, this decreased to 50%. Evidence for imprinting or sex-specific effects of the CAG repeat on AO was not found. For the entire sample, we determined an upper bound for heritability of the residual variance of 33% (p = 0.008). Heritability was higher in sib-sib pairs, especially in female sib-sib pairs, than in parent-child pairs.Conclusions:We established that a large proportion of AO variance in SCA2 was determined by genetic modifiers in addition to CAG repeat length. The genetic structure of heritability of the residual AO variance was surprisingly similar to Huntington disease, suggesting the presence of recessive modifying alleles and possibly X-chromosome–linked modifiers.