Sex and seasonal differences in hippocampal volume and neurogenesis in brood‐parasitic brown‐headed cowbirds (Molothrus ater)

Brown‐headed cowbirds (Molothrus ater) are one of few species in which females show more complex space use than males. Female cowbirds search for, revisit, and parasitize host nests and, in a previous study, outperformed males on an open field spatial search task. Previous research reported a female‐biased sex difference in the volume of the hippocampus, a region of the brain involved in spatial memory. Neurons produced by adult neurogenesis may be involved in the formation of new memories and replace older neurons that could cause interference in memory. We tested for sex and seasonal differences in hippocampal volume and neurogenesis of brood‐parasitic brown‐headed cowbirds and the closely related non‐brood‐parasitic red‐winged blackbird (Agelaius phoeniceus) to determine whether there were differences in the hippocampus that reflected space use in the wild. Females had a larger hippocampus than males in both species, but hippocampal neurogenesis, measured by doublecortin immunoreactivity (DCX+), was greater in female than in male cowbirds in the absence of any sex difference in blackbirds, supporting the hypothesis of hippocampal specialization in female cowbirds. Cowbirds of both sexes had a larger hippocampus with greater hippocampal DCX+ than blackbirds. Hippocampus volume remained stable between breeding conditions, but DCX+ was greater post‐breeding, indicating that old memories may be lost through hippocampal reorganization following breeding. Our results support, in part, the hypothesis that the hippocampus of cowbirds is specialized for brood parasitism. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1275–1290, 2016     

Vocal matching and intensity of begging calls are associated with a forebrain song circuit in a generalist brood parasite

Vocalizations produced by developing young early in life have simple acoustic features and are thought to be innate. Complex forms of early vocal learning are less likely to evolve in young altricial songbirds because the forebrain vocal‐learning circuit is underdeveloped during the period when early vocalizations are produced. However, selective pressure experienced in early postnatal life may lead to early vocal learning that is likely controlled by a simpler brain circuit. We found the food begging calls produced by fledglings of the brown‐headed cowbird (Molothrus ater), a generalist avian brood parasite, induced the expression of several immediate early genes and early circuit innervation in a forebrain vocal‐motor pathway that is later used for vocal imitation. The forebrain neural activity was correlated with vocal intensity and variability of begging calls that appears to allow cowbirds to vocally match host nestmates. The begging‐induced forebrain circuits we observed in fledgling cowbirds were not detected in nonparasitic passerines, including species that are close relatives to the cowbird. The involvement of forebrain vocal circuits during fledgling begging and its association with vocal learning plasticity may be an adaptation that provides young generalist brood parasites with a flexible signaling strategy to procure food from a wide range of heterospecific host parents. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 615–625, 2016     

Sex differences in humeral bilateral asymmetry in two hunter‐gatherer populations: California Amerinds and British Columbian Amerinds

This study uses two prehistoric Amerindian populations of hunter‐gatherer subsistence patterns to determine whether levels of sexual dimorphism in humeral bilateral cross‐sectional asymmetry are related to sex‐specific differences in activities among these populations. Results confirmed that males of the California Amerind population who engaged in the more unimanual activities of spear hunting and warfare were more asymmetrical than were their female counterparts who engaged in the more bimanual activities of grinding acorns. California Amerind males were also more asymmetrical than British Columbian Amerind males who rowed (using both arms) extensively. Sex differences within British Columbian Amerinds were not statistically significant, nor were female differences between populations. In general, levels of humeral asymmetry appear to be more dependent on sex and population‐specific behaviors rather than broad subsistence patterns. Am J Phys Anthropol 2009. © 2009 Wiley‐Liss, Inc.     

Isolation and characterization of 12 microsatellite loci from Golden‐winged Warblers (Vermivora chrysoptera) with broad cross‐taxon utility in emberizine songbirds

We describe 12 microsatellite loci from the Golden‐winged Warbler (Vermivora chrysoptera), a bird species of conservation concern owing to competition and hybridization with the Blue‐winged Warbler (V. pinus). Directional mitochondral DNA introgression from V. pinus into V. chrysoptera has been reported within the hybrid zone. Frequent hybrid phenotypes suggest that nuclear introgression is also prevalent, although this has not been demonstrated conclusively with molecular markers. These microsatellites will foster explorations of the genetic interactions between these avian congeners, and amplification tests suggest that they have high cross‐species utility for closely allied bird genera and families.     

Sex differences in the vocal repertoire of adult red‐capped mangabeys (Cercocebus torquatus): a multi‐level acoustic analysis

Sex differences in the vocal behavior of nonhuman primates can take various forms: sex‐specific call types, differential production of shared call types, or sex discrepancy in phonation. Also, a growing literature is evidencing that systematically analyzing the vocal repertoires of primates at the call level might lead to underestimating their communicative abilities. Here, we present an extensive multi‐level analysis of the still unknown vocal repertoire of adult red‐capped mangabeys (Cercocebus torquatus), with a special emphasis on sex differences. We collected recordings from seven adult males and seven adult females housed in captivity. We present a structurally‐based classification of mangabey calls that we cross‐validated by an analysis of the associated contexts of emission. We found 12 sound units (including six sex‐specific) that were concatenated to form eight call types (including four sex‐specific), which were produced either singularly or in sequences composed of one (“repetition”) or several (“combination”) call types. We extracted organizational principles that ruled call composition and calling patterns. This revealed a high degree of potentially meaningful variability in terms of semantics and syntax. Male–female discrepancy in terms of phonation could be related to morphological dimorphism and would enable listeners to behave appropriately according to the sex of the caller. Sex differences in repertoire size, structural gradation, and call usage could reflect specificities of male–female social roles. We discuss the pertinence of these sex differences according to social system and habitat quality. Am. J. Primatol. 72:360–375, 2010. © 2010 Wiley‐Liss, Inc.     

Production and perception of sex differences in vocalizations of Wied's black‐tufted‐ear marmosets (Callithrix kuhlii)

Males and females from many species produce distinct acoustic variations of functionally identical call types. Social behavior may be primed by sex‐specific variation in acoustic features of calls. We present a series of acoustic analyses and playback experiments as methods for investigating this subject. Acoustic parameters of phee calls produced by Wied's black‐tufted‐ear marmosets (Callithrix kuhlii) were analyzed for sex differences. Discriminant function analyses showed that calls contained sufficient acoustic variation to predict the sex of the caller. Several frequency variables differed significantly between the sexes. Natural and synthesized calls were presented to male–female pairs. Calls elicited differential behavioral responses based on the sex of the caller. Marmosets became significantly more vigilant following the playback of male phee calls (both natural and synthetic) than following female phee calls. In a second playback experiment, synthesized calls were modified by independently manipulating three parameters that were known to differ between the sexes (low‐, peak‐, and end‐frequency). When end‐frequency‐modified calls were presented, responsiveness was differentiable by sex of caller but did not differ from responses to natural calls. This suggests that marmosets did not use end‐frequency to determine the sex of the caller. Manipulation of peak‐and low‐frequency parameters eliminated the discrete behavioral responses to male and female calls. Together, these parameters may be important features that encode for the sex‐specific signal. Recognition of sex by acoustic cues seems to be a multivariate process that depends on the congruency of acoustic features. Am. J. Primatol. 71:324–332, 2009. © 2008 Wiley‐Liss, Inc.     

Sex differences in the effects of juvenile and adult diet on age‐dependent reproductive effort

Sexual selection should cause sex differences in patterns of resource allocation. When current and future reproductive effort trade off, variation in resource acquisition might further cause sex differences in age‐dependent investment, or in sensitivity to changes in resource availability over time. However, the nature and prevalence of sex differences in age‐dependent investment remain unclear. We manipulated resource acquisition at juvenile and adult stages in decorated crickets, Gryllodes sigillatus, and assessed effects on sex‐specific allocation to age‐dependent reproductive effort (calling in males, fecundity in females) and longevity. We predicted that the resource and time demands of egg production would result in relatively consistent female strategies across treatments, whereas male investment should depend sharply on diet. Contrary to expectations, female age‐dependent reproductive effort diverged substantially across treatments, with resource‐limited females showing much lower and later investment in reproduction; the highest fecundity was associated with intermediate lifespans. In contrast, long‐lived males always signalled more than short‐lived males, and male age‐dependent reproductive effort did not depend on diet. We found consistently positive covariance between male reproductive effort and lifespan, whereas diet altered this covariance in females, revealing sex differences in the benefits of allocation to longevity. Our results support sex‐specific selection on allocation patterns, but also suggest a simpler alternative: males may use social feedback to make allocation decisions and preferentially store resources as energetic reserves in its absence. Increased calling effort with age therefore could be caused by gradual resource accumulation, heightened mortality risk over time, and a lack of feedback from available mates.     

Sex differences in the level of Bcl‐2 family proteins and caspase‐3 activation in the sexually dimorphic nuclei of the preoptic area in postnatal rats

In developing rats, sex differences in the number of apoptotic cells are found in the central division of the medial preoptic nucleus (MPNc), which is a significant component of the sexually dimorphic nucleus of the preoptic area, and in the anteroventral periventricular nucleus (AVPV). Specifically, male rats have more apoptotic cells in the developing AVPV, whereas females have more apoptotic cells in the developing MPNc. To determine the mechanisms for the sex differences in apoptosis in these nuclei, we compared the expression of the Bcl‐2 family members and active caspase‐3 in postnatal female and male rats. Western blot analyses for the Bcl‐2 family proteins were performed using preoptic tissues isolated from the brain on postnatal day (PD) 1 (day of birth) or on PD8. In the AVPV‐containing tissues of PD1 rats, there were significant sex differences in the level of Bcl‐2 (female > male) and Bax (female < male) proteins, but not of Bcl‐xL or Bad proteins. In the MPNc‐containing tissues of PD8 rats, there were significant sex differences in the protein levels for Bcl‐2 (female < male), Bax (female > male), and Bad (female < male), but not for Bcl‐xL. Immunohistochemical analyses showed significant sex differences in the number of active caspase‐3‐immunoreactive cells in the AVPV on PD1 (female < male) and in the MPNc on PD8 (female > male). We further found that active caspase‐3‐immunoreactive cells of the AVPV and MPNc were immunoreactive for NeuN, a neuronal marker. These results suggest that there are sex differences in the induction of apoptosis via the mitochondrial pathway during development of the AVPV and MPNc. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006     

Tyrosine hydroxylase‐synthesizing cells in the hypothalamus of prairie voles (Microtus ochrogaster): Sex differences in the anteroventral periventricular preoptic area and effects of adult gonadectomy or neonatal gonadal hormones

The vertebrate hypothalamus and surrounding region contain a large population of cells expressing tyrosine hydroxylase (TH), the rate limiting enzyme for synthesis of dopamine and other catecholamines. Some of these populations are sexually dimorphic in rats. We here examined sex differences in TH‐immunoreactive populations in the forebrain of gonadally intact and gonadectomized prairie voles (Microtus ochrogaster), a species that sometimes shows unusual sexual differentiation of brain and behavior. A sex difference was found in the anteroventral periventricular preoptic area (AVPV; likely analogous to the rat rostral A14) only in gonadectomized subjects, which was due to a 50% reduction in the number of TH‐immunoreactive cells after castration in males. There was no significant sex difference or effects of gonadectomy on the number of TH‐immunoreactive cells in the anteroventral preoptic area (AVP), periventricular anterior hypothalamus (caudal A14), arcuate nucleus (A12), zona incerta (A13), or posterodorsal hypothalamus (A11). In a second experiment, testosterone propionate (TP; 500 μg), diethylstilbestrol (DES; 1 μg), or estradiol benzoate (EB; 30 μg) injected daily during the first week after birth each significantly reduced later TH expression in the AVPV of females by approximately 40–65% compared to oil‐treated controls. Unlike rats, therefore, a sex difference in TH expression in the prairie vole AVPV is found only after removal of circulating gonadal hormones in males. Furthermore, unlike our previous findings on the generation of sex differences in extra‐hypothalamic arginine‐vasopressin expression in prairie voles, TH expression in the AVPV of female prairie voles can be highly masculinized by neonatal exposure to either aromatizable androgens or estrogens. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2006     

Apolipoprotein A‐I possesses an anti‐obesity effect associated with increase of energy expenditure and up‐regulation of UCP1 in brown fat

Apolipoprotein A‐I (ApoA‐I) is the most abundant protein constituent of high‐density lipoprotein (HDL). Reduced plasma HDL and ApoA‐I levels have been found to be associated with obesity and metabolic syndrome in human beings. However, whether or not ApoA‐I has a direct effect on obesity is largely unknown. Here we analysed the anti‐obesity effect of ApoA‐I using two mouse models, a transgenic mouse with overexpression of ApoA‐I and the mice administered with an ApoA‐I mimetic peptide D‐4F. The mice were induced to develop obesity by feeding with high fat diet. Both ApoA‐I overexpression and D‐4F treatment could significantly reduce white fat mass and slightly improve insulin sensitivity in the mice. Metabolic analyses revealed that ApoA‐I overexpression and D‐4F treatment enhanced energy expenditure in the mice. The mRNA level of uncoupling protein (UCP)1 in brown fat tissue was elevated by ApoA‐I transgenic mice. ApoA‐I and D‐4F treatment was able to increase UCP1 mRNA and protein levels as well as to stimulate AMP‐activated protein kinase (AMPK) phosphorylation in brown adipocytes in culture. Taken together, our results reveal that ApoA‐I has an anti‐obesity effect in the mouse and such effect is associated with increases in energy expenditure and UCP1 expression in the brown fat tissue.     

Compositional differences between near‐isogenic GM and conventional maize hybrids are associated with backcrossing practices in conventional breeding

Here, we show that differences between genetically modified (GM) and non‐GM comparators cannot be attributed unequivocally to the GM trait, but arise because of minor genomic differences in near‐isogenic lines. Specifically, this study contrasted the effect of three GM traits (drought tolerance, MON 87460; herbicide resistance, NK603; insect protection, MON 89034) on maize grain composition relative to the effects of residual genetic variation from backcrossing. Important features of the study included (i) marker‐assisted backcrossing to generate genetically similar inbred variants for each GM line, (ii) high‐resolution genotyping to evaluate the genetic similarity of GM lines to the corresponding recurrent parents and (iii) introgression of the different GM traits separately into a wide range of genetically distinct conventional inbred lines. The F1 hybrids of all lines were grown concurrently at three replicated field sites in the United States during the 2012 growing season, and harvested grain was subjected to compositional analysis. Proximates (protein, starch and oil), amino acids, fatty acids, tocopherols and minerals were measured. The number of statistically significant differences (α = 0.05), as well as magnitudes of difference, in mean levels of these components between corresponding GM variants was essentially identical to that between GM and non‐GM controls. The largest sources of compositional variation were the genetic background of the different conventional inbred lines (males and females) used to generate the maize hybrids and location. The lack of any compositional effect attributable to GM suggests the development of modern agricultural biotechnology has been accompanied by a lack of any safety or nutritional concerns.     

Standing genetic diversity and selection at functional gene loci are associated with differential invasion success in two non‐native fish species

Invasive species are expected to experience a unique combination of high genetic drift due to demographic factors while also experiencing strong selective pressures. The paradigm that reduced genetic diversity should limit the evolutionary potential of invasive species, and thus, their potential for range expansion has received little empirical support, possibly due to the choice of genetic markers. Our goal was to test for effects of genetic drift and selection at functional genetic markers as they relate to the invasion success of two paired invasive goby species, one widespread (successful) and one with limited range expansion (less successful). We genotyped fish using two marker types: single nucleotide polymorphisms (SNPs) in known‐function, protein‐coding genes and microsatellites to contrast the effects of neutral genetic processes. We identified reduced allelic variation in the invaded range for the less successful tubenose goby. SNPs putatively under selection were responsible for the observed differences in population structure between marker types for round goby (successful) but not tubenose goby (less successful). A higher proportion of functional loci experienced divergent selection for round goby, suggesting increased evolutionary potential in invaded ranges may be associated with round goby's greater invasion success. Genes involved in thermal tolerance were divergent for round goby populations but not tubenose goby, consistent with the hypothesis that invasion success for fish in temperate regions is influenced by capacity for thermal tolerance. Our results highlight the need to incorporate functional genetic markers in studies to better assess evolutionary potential for the improved conservation and management of species.     

Dickkopf‐1‐promoted vasculogenic mimicry in non‐small cell lung cancer is associated with EMT and development of a cancer stem‐like cell phenotype

To characterize the contributions of Dickkopf‐1 (DKK1) towards the induction of vasculogenic mimicry (VM) in non‐small cell lung cancer (NSCLC), we evaluated cohorts of primary tumours, performed in vitro functional studies and generated xenograft mouse models. Vasculogenic mimicry was observed in 28 of 205 NSCLC tumours, while DKK1 was detected in 133 cases. Notably, DKK1 was positively associated with VM. Statistical analysis showed that VM and DKK1 were both related to aggressive clinical course and thus were indicators of a poor prognosis. Moreover, expression of epithelial‐mesenchymal transition (EMT)‐related proteins (vimentin, Slug, and Twist), cancer stem‐like cell (CSC)‐related proteins (nestin and CD44), VM‐related proteins (MMP2, MMP9, and vascular endothelial‐cadherin), and β‐catenin‐nu were all elevated in VM‐positive and DKK1‐positive tumours, whereas the epithelial marker (E‐cadherin) was reduced in the VM‐positive and DKK1‐positive groups. Non‐small cell lung cancer cell lines with overexpressed or silenced DKK1 highlighted its role in the restoration of mesenchymal phenotypes and development of CSC characteristics. Moreover, DKK1 significantly promotes NSCLC tumour cells to migrate, invade and proliferate. In vivo animal studies demonstrated that DKK1 enhances the growth of transplanted human tumours cells, as well as increased VM formation, mesenthymal phenotypes and CSC properties. Our results suggest that DKK1 can promote VM formation via induction of the expression of EMT and CSC‐related proteins. As such, we feel that DKK1 may represent a novel target of NSCLC therapy.     

Influences of Relatedness,Food Deprivation,and Sex on Adult Behaviors in the Group‐living Insect Forficula auricularia

The evolution of group living is generally associated with the emergence of social behaviors that ensure fitness benefits to group members. However, the expression of these behaviors may depend on group composition, which can vary over time with respect to sex, starvation status, and relatedness. Here, we investigated (1) whether adults of the group‐living European earwig, Forficula auricularia, show cooperative behaviors toward conspecifics and (2) whether sex, food availability, and relatedness shape the nature and frequency of these behaviors. We conducted a full‐factorial experiment using 108 unisexual pairs of adults, in which we manipulated these three factors and video‐recorded the earwig behaviors for 45 min. Our results revealed that adults mostly expressed self‐directed and aggressive behaviors. Nevertheless, they also showed allogrooming, a social behavior that offers scope for cooperation. Pairs of males displayed longer bouts of aggression and allogrooming (when it occurred) than pairs of females. Food deprivation had no effect on male behaviors, but females spent less time self‐grooming and walking when they were food deprived. Finally, low relatedness between adults did not influence any of the measured behaviors, but exacerbated frass production, possibly due to social stress. Overall, these results indicate the limited role of cooperation among F. auricularia adults during their group‐living phase.     

Social context affects testosterone‐induced singing and the volume of song control nuclei in male canaries (Serinus canaria)

The contribution of social factors to seasonal plasticity in singing behavior and forebrain nuclei controlling song, and their interplay with gonadal steroid hormones are still poorly understood. In many songbird species, testosterone (T) enhances singing behavior but elevated plasma T concentrations are not absolutely required for singing to occur. Singing is generally produced either to defend a territory or to attract a mate and it is therefore not surprising that singing rate can be influenced by the sex and behavior of the social partner. We investigated, based on two independent experiments, the effect of the presence of a male or female partner on the rate of song produced by male canaries. In the first experiment, song rate was measured in dyads composed of one male and one female (M‐F) or two males (M‐M). Birds were implanted with T‐filled Silastic capsules or with empty capsules as control. The number of complete song bouts produced by all males was recorded during 240 min on week 1, 2, 4, and 8 after implantation. On the day following each recording session, brains from approximately one‐fourth of the birds were collected and the volumes of the song control nuclei HVC and RA were measured. T increased the singing rate and volume of HVC and RA but these effects were affected by the social context. Singing rates were higher in the M‐M than in the M‐F dyads. Also, in the M‐M dyads a dominance‐subordination relationship soon became established and dominant males sang at higher rates than subordinates in T‐treated but not in control pairs. The differences in song production were not reflected in the size of the song control nuclei: HVC was larger in M‐F than in M‐M males and within the M‐M dyads, no difference in HVC or RA size could be detected between dominant and subordinate males. At the individual level, the song rate with was positively correlated with RA and to a lower degree HVC volume, but this relationship was observed only in M‐M dyads, specifically in dominant males. A second experiment, carried out with castrated males that were all treated with T and exposed either to another T‐treated castrate or to an estradiol‐implanted female, confirmed that song rate was higher in the M‐M than in the M‐F condition and that HVC volume was larger in heterosexual than in same‐sex dyads. The effects of T on singing rate and on the volume of the song control nuclei are thus modulated by the social environment, including the presence/absence of a potential mate and dominance status among males. 2006 Wiley Periodicals, Inc. J Neurobiol, 2006