Effects of Relatedness,Dominance, Age,and Association on Reciprocal Allogrooming by Captive Impala

Wild impala display a highly reciprocal allogrooming system that, by virtue of its frequency and high degree of reciprocity, is unique among ungulates. A herd of 35 free-ranging captive impala provided opportunity to examine the degree of reciprocity of allogrooming exchanges and the influence of relatedness, dominance, age and association on partner preferences and distribution of grooming between allogrooming partners. As in wild impala, the exchange of allogrooming bouts in the captive impala was highly reciprocal regardless of partners. Kinship and dominance had no influence on partner preference or distribution of grooming between partners. Although mothers showed a significant preference to allogroom with their unweaned offspring, this preference practically disappeared with older offspring. Age-mates (no greater than 6 mo apart) tended to associate with one another and spatial proximity was positively correlated with grooming partner preference. It was not clear whether impala actively sought out age-mates for grooming, or randomly chose grooming partners from nearby age-mates. The failure to find a role for kinship and dominance is counter to what has generally been found in most Old World terrestrial primate studies. The absence of pronounced social influences, coupled with the known effectiveness of grooming in removing ectoparasites, suggest that a utilitarian role, especially removal of ticks, is an important function of the impala reciprocal allogrooming system.     

Sex, but not maternal protein or folic acid intake, determines the fatty acid composition of hepatic phospholipids, but not of triacylglycerol, in adult rats

The aim of the study was to investigate whether the protein and folic acid content of the maternal diet and the sex of the offspring alter the polyunsaturated fatty acid content of hepatic phospholipids and triacylglycerol (TAG). Pregnant rats were fed diets containing 18% or 9% protein with either 1 or 5mg/kg folic acid. Maternal diet did not alter hepatic lipid composition in the adult offspring. Data from each maternal dietary group were combined and reanalysed. The proportion of 18:0, 20:4n-6 and 22:6n-3 in liver phospholipids was higher in females than in males, while hepatic TAG composition did not differ between sexes. Delta5 Desaturase expression was higher in females than in males. Neither Delta5 nor Delta6 desaturase expression was related to polyunsaturated fatty acid concentrations. These results suggest that sex differences in liver phospholipid fatty acid composition may reflect primary differences in the specificity of phospholipid biosynthesis.     

Why Wasp Foundresses Change Nests: Relatedness,Dominance, and Nest Quality

The costs and benefits of different social options are best understood when individuals can be followed as they make different choices, something that can be difficult in social insects. In this detailed study, we follow overwintered females of the social wasp Polistes carolina through different nesting strategies in a stratified habitat where nest site quality varies with proximity to a foraging area, and genetic relatedness among females is known. Females may initiate nests, join nests temporarily or permanently, or abandon nests. Females can become helpers or egglayers, effectively workers or queens. What they actually do can be predicted by a combination of ecological and relatedness factors. Advantages through increased lifetime success of individuals and nests drives foundresses of the social wasp Polistes from solitary to social nest founding. We studied reproductive options of spring foundresses of P. carolina by monitoring individually-marked wasps and assessing reproductive success of each foundress by using DNA microsatellites. We examined what behavioral decisions foundresses make after relaxing a strong ecological constraint, shortage of nesting sites. We also look at the reproductive consequences of different behaviors. As in other Polistes, the most successful strategy for a foundress was to initiate a nest as early as possible and then accept others as subordinates. A common feature for many P. carolina foundresses was, however, that they reassessed their reproductive options by actively monitoring other nests at the field site and sometimes moving permanently to new nests should that offer better (inclusive) fitness prospects compared to their original nests. A clear motivation for moving to new nests was high genetic relatedness; by the end of the foundress period all females were on nests with full sisters.     

Genetic deletion of microglial Panx1 attenuates morphine withdrawal,but not analgesic tolerance or hyperalgesia in mice

Opioids are among the most powerful analgesics for managing pain, yet their repeated use can lead to the development of severe adverse effects. In a recent study, we identified the microglial pannexin-1 channel (Panx1) as a critical substrate for opioid withdrawal. Here, we investigated whether microglial Panx1 contributes to opioid-induced hyperalgesia (OIH) and opioid analgesic tolerance using mice with a tamoxifen-inducible deletion of microglial Panx1. We determined that escalating doses of morphine resulted in thermal pain hypersensitivity in both Panx1-expressing and microglial Panx1-deficient mice. In microglial Panx1-deficient mice, we also found that acute morphine antinociception remained intact, and repeated morphine treatment at a constant dose resulted in a progressive decline in morphine antinociception and a reduction in morphine potency. This reduction in morphine antinociceptive potency was indistinguishable from that observed in Panx1-expressing mice. Notably, morphine tolerant animals displayed increased spinal microglial reactivity, but no change of microglial Panx1 expression. Collectively, our findings indicate microglial Panx1 differentially contributes to opioid withdrawal, but not the development of opioid-induced hyperalgesia or tolerance.     

Subclinical Primary Psychopathy,but Not Physical Formidability or Attractiveness,Predicts Conversational Dominance in a Zero-Acquaintance Situation

The determinants of conversational dominance are not well understood. We used videotaped triadic interactions among unacquainted same-sex American college students to test predictions drawn from the theoretical distinction between dominance and prestige as modes of human status competition. Specifically, we investigated the effects of physical formidability, facial attractiveness, social status, and self-reported subclinical psychopathy on quantitative (proportion of words produced), participatory (interruptions produced and sustained), and sequential (topic control) dominance. No measure of physical formidability or attractiveness was associated with any form of conversational dominance, suggesting that the characteristics of our study population or experimental frame may have moderated their role in dominance dynamics. Primary psychopathy was positively associated with quantitative dominance and (marginally) overall triad talkativeness, and negatively associated (in men) with affect word use, whereas secondary psychopathy was unrelated to conversational dominance. The two psychopathy factors had significant opposing effects on quantitative dominance in a multivariate model. These latter findings suggest that glibness in primary psychopathy may function to elicit exploitable information from others in a relationally mobile society.     

Sex differences in lizard escape decisions vary with latitude,but not sexual dimorphism

Sexual selection is a powerful evolutionary mechanism that has shaped the physiology, behaviour and morphology of the sexes to the extent that it can reduce viability while promoting traits that enhance reproductive success. Predation is one of the underlying mechanisms accounting for viability costs of sexual displays. Therefore, we should expect that individuals of the two sexes adjust their anti-predator behaviour in response to changes in predation risk. We conducted a meta-analysis of 28 studies (42 species) of sex differences in risk-taking behaviour in lizards and tested whether these differences could be explained by sexual dichromatism, by sexual size dimorphism or by latitude. Latitude was the best predictor of the interspecific heterogeneity in sex-specific behaviour. Males did not change their escape behaviour with latitude, whereas females had increasingly reduced wariness at higher latitudes. We hypothesize that this sex difference in risk-taking behaviour is linked to sex-specific environmental constraints that more strongly affect the reproductive effort of females than males. This novel latitudinal effect on sex-specific anti-predator behaviour has important implications for responses to climate change and for the relative roles of natural and sexual selection in different species.     

Castration Lowers Aggression but not Social Dominance in Male Haplochromis burtoni (Cichlidae)

Adult males of the African cichlid fish Haplochromis burtoni are either territorial or nonterritorial. In nature and aquaria, only territorial males breed and they have markedly more developed testes than do nonterritorial males. Territorial males are clearly dominant over nonterritorial males of the same age and size, and also exhibit higher levels of aggression. In this study, territorial males were gonadectomized in order to assess the effects of lowered androgen levels on their aggression and dominance status. Completely castrated males showed a pronounced reduction in both testosterone and 11-ketotestosterone, as well as significantly lower aggression scores than sham-operated males. Partially castrated males (> 0.005 g gonadal tissue remaining at autopsy) exhibited intermediate levels of both androgen levels and aggression. Surprisingly, in dyadic encounters with normal nonterritorial males of the same size, castrated territorial males retained their dominance despite decreased androgen levels and aggression.     

Genetic dissimilarity between mates, but not male heterozygosity, influences divorce in schistosomes

Background

Correlational studies strongly suggest that both genetic similarity and heterozygosity can influence female mate choice. However, the influence of each variable has usually been tested independently, although similarity and heterozygosity might be correlated. We experimentally determined the relative influence of genetic similarity and heterozygosity in divorce and re-mating in the monogamous endoparasite Schistosoma mansoni.

Methodology/Principal Findings

We performed sequential infections of vertebrate hosts with controlled larval populations of parasites, where sex and individual genetic diversity and similarity were predetermined before infection. Divorce rate increased significantly when females were given the opportunity to increase genetic dissimilarity through re-mating with a new partner, independently of the intensity of male-male competition. We found however no evidence for females attempting to maximize the level of heterozygosity of their reproductive partner through divorce.

Conclusions/Significance

Female preference for genetically dissimilar males should result in more heterozygous offspring. Because genetic heterozygosity might partly determine the ability of parasites to counter host resistance, adaptive divorce could be an important factor in the evolutionary arms race between schistosomes and their hosts.     

No Sex or Age Difference in Dead-Reckoning Ability among Tsimane Forager-Horticulturalists

Sex differences in reproductive strategy and the sexual division of labor resulted in selection for and maintenance of sexual dimorphism across a wide range of characteristics, including body size, hormonal physiology, behavior, and perhaps spatial abilities. In laboratory tasks among undergraduates there is a general male advantage for navigational and mental-rotation tasks, whereas studies find female advantage for remembering item locations in complex arrays and the locations of plant foods. Adaptive explanations of sex differences in these spatial abilities have focused on patterns of differential mate search and routine participation in distinct subsistence behaviors. The few studies to date of spatial ability in nonindustrial populations practicing subsistence lifestyles, or across a wider age range, find inconsistent results. Here we examine sex- and age-based variation in one kind of spatial ability related to navigation, dead-reckoning, among Tsimane forager horticulturalists living in lowland Bolivia. Seventy-three participants (38 male) aged 6–82 years pointed a handheld global positioning system (GPS) unit toward the two nearest communities and the more distant market town. We find no evidence of sex differences in dead reckoning (p?=?0.47), nor do we find any evidence of age-related decline in dead-reckoning accuracy (p?=?0.28). Participants were significantly more accurate at pointing toward the market town than toward the two nearest villages despite its being significantly farther away than the two nearest communities. Although Tsimane do show sexual dimorphism in foraging tasks, Tsimane women have extensive daily and lifetime travel, and the local environment lacks directional cues that typically enhance male navigation. This study raises the possibility that greater similarity in mobility patterns because of overlapping subsistence strategies and activities may result in convergence of some male and female navigation abilities.     

LYST Affects Lysosome Size and Quantity,but not Trafficking or Degradation Through Autophagy or Endocytosis

Mutations in the large BEACH domain‐containing protein LYST causes Chediak–Higashi syndrome. The diagnostic hallmark is enlarged lysosomes and lysosome‐related organelles in various cell types. Dysfunctional secretion of enlarged lysosome‐related organelles has been observed in cells with mutations in LYST, but the capacity of the enlarged lysosomes to degrade endogenous proteins has not been studied. Here, we show for the first time that small interfering RNA‐depletion of LYST in human cell lines recapitulates the LYST mutant phenotype of enlarged lysosomes. We found no evidence for an effect of LYST depletion on autophagy or endocytic degradation. Autophagosomes are formed in normal size and quantities and are able to fuse to the enlarged lysosomes, leading to normal rates of degradation. Degradation of the epidermal growth factor receptor (EGFR) was similarly not affected, indicating that the enlarged lysosomes are fully functional in degrading endogenous proteins. Retrograde trafficking of toxins as well as the localization of transporters of lysosomal proteins, adaptor protein‐3 (AP‐3) and cation‐independent mannose‐6‐phosphate receptor (CI‐MPR), were all found to be unaffected by LYST. Quantitative analysis of the enlarged lysosomes shows that LYST depletion causes a reduction in vesicle quantity per cell, while the total enzymatic content and vesicular pH are unaffected, supporting a role for LYST in lysosomal fission and/or fusion events.      

Dominance is not always an honest signal of male quality,but females may be able to detect the dishonesty

Females prefer dominant males as mating partners in numerous species. Male dominance rank is considered as an honest signal of male quality, because only healthy males in good condition are thought to be able to win fights with other males. Here, we tested whether activation of the immune system influences the success of males in male–male competition and mating in the field cricket, Gryllus integer. We activated the immune system of males with a nylon monofilament (to mimic a parasitoid larva), and arranged fights between male pairs to assess male dominance and associated mating success. Activation of the immune system with nylon monofilament substantially enhanced the fighting success of males during male–male competition but had no effect on mating success. However, sham-manipulation (a wound only) did not have any effect on fighting success although females mated more often with dominant males. Our study suggests that when male crickets meet an apparent survival threat they may behave more dominantly, probably owing to terminal investment. Male success during male–male competition is not always an honest signal of males’ quality, but females may be able to detect this dishonesty.     

Cisplatin disrupts mammalian spermatogenesis, but does not affect recombination or chromosome segregation

Meiotic recombination is initiated by a series of double-strand breaks (DSBs) in areas of the genome that generally contain promoters and feature an open chromatin configuration [T.D. Petes, Meiotic recombination hot spots and cold spots, Nat. Rev. Genet. 2 (2001) 360-369]. To investigate whether induced DSBs likewise lead to recombinational repair and whether the placement of new exchange events alters normal patterns of recombination, we used the chemotherapeutic drug cisplatin (CP) to generate additional DSBs throughout the mouse genome. Treatment with CP impaired spermatogenesis, as exhibited by reductions in sperm counts, reductions in both testicular size and weight, changes in the distribution of cells at various prophase I substages, prolonged increases in germ cell apoptosis, and an increased incidence of synaptic abnormalities. Unexpectedly, however, no obvious effect on genome-wide recombination levels in CP-treated animals was observed, nor was the level of aneuploidy increased in sperm from exposed males.