Female-specific target sites for both oestrogen and androgen in the teleost brain

To dissect the molecular and cellular basis of sexual differentiation of the teleost brain, which maintains marked sexual plasticity throughout life, we examined sex differences in neural expression of all subtypes of nuclear oestrogen and androgen receptors (ER and AR) in medaka. All receptors were differentially expressed between the sexes in specific nuclei in the forebrain. The most pronounced sex differences were found in several nuclei in the ventral telencephalic and preoptic areas, where ER and AR expression were prominent in females but almost completely absent in males, indicating that these nuclei represent female-specific target sites for both oestrogen and androgen in the brain. Subsequent analyses revealed that the female-specific expression of ER and AR is not under the direct control of sex-linked genes but is instead regulated positively by oestrogen and negatively by androgen in a transient and reversible manner. Taken together, the present study demonstrates that sex-specific target sites for both oestrogen and androgen occur in the brain as a result of the activational effects of gonadal steroids. The consequent sex-specific but reversible steroid sensitivity of the adult brain probably contributes substantially to the process of sexual differentiation and the persistent sexual plasticity of the teleost brain.     

Sex-role reversal is reflected in the brain of African black coucals (Centropus grillii)

In most bird species males compete over access to females and have elevated circulating androgen levels when they establish and defend a breeding territory or guard a mate. Testosterone is involved in the regulation of territorial aggression and sexual display in males. In few bird species the traditional sex-roles are reversed and females are highly aggressive and compete over access to males. Such species represent excellent models to study the hormonal modulation of aggressive behavior in females. Plasma sex steroid concentrations in sex-role reversed species follow the patterns of birds with "traditional" sex-roles. The neural mechanisms modulating endocrine secretion and hormone-behavior interactions in sex-role reversed birds are currently unknown. We investigated the sex differences in the mRNA expression of androgen receptors, estrogen receptor alpha, and aromatase in two brain nuclei involved in reproductive and aggressive behavior in the black coucal, the nucleus taeniae and the bed nucleus of the stria terminalis. In the bed nucleus there were no sex differences in the receptor or aromatase expression. In the nucleus taeniae, however, we show for the first time, that females have a higher mRNA expression of androgen receptors than males. These results suggest that the expression of agonistic and courtship behavior in females does not depend on elevated blood hormone levels, but may be regulated via increased steroid hormone sensitivity in particular target areas in the brain. Hence, aggression in females and males may indeed be modulated by the same hormones, but regulated at different levels of the neuroendocrine cascade.     

Neural steroid sensitivity and aggression: comparing individuals of two songbird subspecies

Hormones coordinate the expression of complex phenotypes and thus may play important roles in evolutionary processes. When populations diverge in hormone‐mediated phenotypes, differences may arise via changes in circulating hormones, sensitivity to hormones or both. Determining the relative importance of signal and sensitivity requires consideration of both inter‐ and intrapopulation variation in hormone levels, hormone sensitivity and phenotype, but such studies are rare, particularly among closely related taxa. We compared males of two subspecies of the dark‐eyed junco (Junco hyemalis) for territorial aggression and associations among behaviour, circulating testosterone (T), and gene expression of androgen receptor (AR), aromatase (AROM) and oestrogen receptor α in three behaviourally relevant brain regions. Thus, we examined the degree to which evolution may shape behaviour via changes in plasma T as compared with key sex steroid binding/converting molecules. We found that the white‐winged junco (J. h. aikeni) was more aggressive than the smaller, less ornamented Carolina junco (J. h. carolinensis). The subspecies did not differ in circulating testosterone, but did differ significantly in the abundance of AR and AROM mRNA in key areas of the brain. Within populations, both gene expression and circulating T co‐varied significantly with individual differences in aggression. Notably, the differences identified between populations were opposite to those predicted by the patterns among individuals within populations. These findings suggest that hormone–phenotype relationships may evolve via multiple pathways, and that changes that have occurred over evolutionary time do not necessarily reflect standing physiological variation on which current evolutionary processes may act.     

Aspects of reproduction and their implications for the conservation of the endangered limpet,Patella ferruginea

Summary

The protandric limpet, Patella ferruginea G., is the most endangered marine species in the Western Mediterranean and is at serious risk of extinction. Nevertheless, its biology and ecology are little known. In the present work, several reproductive aspects are studied. Recruitment take place in June and the largest individuals are the most scarce. The sex ratio is slanted towards the largest sizes, and the species seems to show sex change at sizes from 60 mm upwards, although males can be observed up to 80 mm. There is no correlation between size of oocytes and shell length; however, the larger females contribute greatly to the reproductive event, with high fecundity and GSI values. The mean diameter of oocytes was observed to be 149.78 μm, whereas the heads of spermatozoa were 3.78 μm long. The results of the present study increase the maximum length for males by double that cited in previous literature and highlight the importance of strictly protecting females (i.e., most of the largest individuals, >60 mm), since their population percentage is very low, in order to develop adequate strategies to preserve the species.     

Emotions as infectious diseases in a large social network: the SISa model

Human populations are arranged in social networks that determine interactions and influence the spread of diseases, behaviours and ideas. We evaluate the spread of long-term emotional states across a social network. We introduce a novel form of the classical susceptible–infected–susceptible disease model which includes the possibility for ‘spontaneous’ (or ‘automatic’) infection, in addition to disease transmission (the SISa model). Using this framework and data from the Framingham Heart Study, we provide formal evidence that positive and negative emotional states behave like infectious diseases spreading across social networks over long periods of time. The probability of becoming content is increased by 0.02 per year for each content contact, and the probability of becoming discontent is increased by 0.04 per year per discontent contact. Our mathematical formalism allows us to derive various quantities from the data, such as the average lifetime of a contentment ‘infection’ (10 years) or discontentment ‘infection’ (5 years). Our results give insight into the transmissive nature of positive and negative emotional states. Determining to what extent particular emotions or behaviours are infectious is a promising direction for further research with important implications for social science, epidemiology and health policy. Our model provides a theoretical framework for studying the interpersonal spread of any state that may also arise spontaneously, such as emotions, behaviours, health states, ideas or diseases with reservoirs.     

Individual variation and the endocrine regulation of behaviour and physiology in birds: a cellular/molecular perspective

Investigations of the cellular and molecular mechanisms of physiology and behaviour have generally avoided attempts to explain individual differences. The goal has rather been to discover general processes. However, understanding the causes of individual variation in many phenomena of interest to avian eco-physiologists will require a consideration of such mechanisms. For example, in birds, changes in plasma concentrations of steroid hormones are important in the activation of social behaviours related to reproduction and aggression. Attempts to explain individual variation in these behaviours as a function of variation in plasma hormone concentrations have generally failed. Cellular variables related to the effectiveness of steroid hormone have been useful in some cases. Steroid hormone target sensitivity can be affected by variables such as metabolizing enzyme activity, hormone receptor expression as well as receptor cofactor expression. At present, no general theory has emerged that might provide a clear guidance when trying to explain individual variability in birds or in any other group of vertebrates. One strategy is to learn from studies of large units of intraspecific variation such as population or sex differences to provide ideas about variables that might be important in explaining individual variation. This approach along with the use of newly developed molecular genetic tools represents a promising avenue for avian eco-physiologists to pursue.     

Reproductive cycle and sex inversion in razor fish, a protogynous labrid in the southern Mediterranean Sea

The reproductive biology of the Mediterranean razor fish Xyrichthys novacula was investigated by demographic data and histological analysis of the female, intersexual and male gonads. Specimens were collected by bottom trawl on a monthly basis between June 2000 and July 2001 in a sandy bay in southern Thyrrenian. Gonad histology confirmed that the Mediterranean razor fish is a monandric, protogynous hermaphrodite. Females reached first sexual maturity at 100 mm ( L _T) and the estimated mean L _T at first maturity ( L ₅₀) was 125 mm. Females exhibited asynchronous ovarian development and multiple ovulations occurred over the spawning period. Vitellogenesis started in early May and spawning occurred from late May until late September. Sexual transition involved a large‐scale atresia of all oocyte stages and a massive degeneration of ovarian tissue followed by primordial germ cells proliferation. Sex change began at spawning time (June) but transitional individuals tended to cluster at the end of the reproductive period (September). They accounted for 17·1% of the population sampled and were found in a broad size range (105–150 mm L _T).     

黄河兰州段鱼类多样性与保护

兰州市是黄河唯一穿城而过的省会城市, 是黄河流域综合治理与高质量发展的重要区域, 了解其鱼类多样性现状及变化趋势对黄河流域水生态保护尤为重要。本文于2020年7-10月对黄河干流兰州段及其4条支流(庄浪河、大通河、湟水河和宛川河)开展了鱼类多样性、分布及影响因素调查, 以Shannon-Wiener多样性指数、Pielou均匀度指数、Simpson优势度指数、Cody和Routledge指数、Bray-Curtis相异性系数对黄河兰州段5条河流鱼类群落进行评估, 同时通过相对多度(relative abundance, RA)判定优势种, 利用非度量多维标度排序(non-metric multidimensional scaling, NMDS)展示物种空间分布格局。本次调查获得鱼类20种, 隶属于4目6科15属。其中, 国家II级重点保护野生动物1种, 受威胁鱼类4种, 中国特有鱼类7种, 黄河特有鱼类4种。区系组成属青藏高原区高原西北亚区, 其中鲤形目种类占绝对优势, 优势种为东方高原鳅(Triplophysa orientalis)、粗壮高原鳅(T. robusta)、鲫(Carassius auratus)和麦穗鱼(Pseudorasbora parva)。庄浪河和黄河干流的α多样性较高。β多样性分析结果表明, 黄河干流与庄浪河、大通河、湟水河和宛川河间的鱼类物种明显不相似; 大通河与湟水河之间以及黄河干流与宛川河之间的鱼类物种组成相似性较高。NMDS分析表明, 黄河兰州段鱼类被划分为地理空间上相近的4个地理群。水利设施建设、外来物种和水体污染可能影响了黄河兰州段鱼类多样性和分布。本研究为黄河兰州段鱼类多样性保护和科学管理以及黄河流域生态保护和高质量发展提供了基础调查数据。     

A model for genomic imprinting in the social brain: elders

Genomic imprinting refers to the process whereby genes are silenced when inherited via sperm or egg. The most widely accepted theory for the evolution of genomic imprinting-the kinship theory-argues that conflict between maternally inherited and paternally inherited genes over phenotypes with asymmetric effects on matrilineal and patrilineal kin results in self-imposed silencing of one of the copies. This theory was originally developed in the context of fitness interactions within nuclear families, to understand intragenomic conflict in the embryo and infant, but it has recently been extended to encompass interactions within wider social groups, to understand intragenomic conflict over the social behavior of juveniles and adults. Here, we complete our model of genomic imprinting in the social brain by considering age-specific levels of expression in a society were generations overlap, to determine how intragenomic conflict plays out in older age. We determine the role of sex bias in juvenile dispersal, reproductive success, and adult mortality in mediating the direction and intensity of conflict over the competing demands of parental and communal care as the individual ages. We discover that sex-specific asymmetries in these demographic parameters result in intragenomic conflict at early age but this conflict gradually decays with age. Although individuals are riven by internal conflict in their youth and middle age, they put their demons to rest in later life.     

Androgen receptor immunoreactivity in the male and female Syrian hamster brain

To investigate potential mechanisms for sex differences in the physiologic response to androgens, the present study compared the hormonal regulation of intracellular androgen receptor partitioning and the distribution of androgen receptor immunoreactivity in select brain regions from male and female hamsters. Androgen receptors were visualized on coronal brain sections. Two weeks after castration, androgen receptor immunoreactivity filled the neuronal nuclei and cytoplasm in males and females. In gonad‐intact males and females, androgen receptor immunoreactivity was limited to the cell nucleus. Whereas exogenous dihydrotestosterone prevented cytoplasmic immunoreactivity, estrogen at physiologic levels did not. These results suggest that nuclear androgen receptor immunoreactivity in gonad‐intact females is maintained by endogenous androgens, and that androgens have the potential to influence neuronal activity in either sex. However, sex differences in the number and staining intensity of androgen‐responsive neurons were apparent in select brain regions. In the ventral premammillary nucleus, ventromedial nucleus of the hypothalamus, and medial amygdaloid nucleus, androgen receptor staining was similar in gonadectomized males and females. In the lateral septum, posteromedial bed nucleus of the stria terminalis (BNSTpm), and medial preoptic nucleus, the number of androgen receptor–immunoreactive neurons was significantly lower in females (p < .05). Moreover, the integrated optical density/cell in BNSTpm was significantly less in females (1.28 ± 0.3 units) than in males (2.21 ± 0.2 units; p < .05). These sex differences in the number and staining intensity of androgen‐responsive neurons may contribute to sex differences in the behavioral and neuroendocrine responses to androgens. © 1999 John Wiley & Sons, Inc. J Neurobiol 39: 359–370, 1999     

The influence of behavioral context and social characteristics on the physical aspects of social grooming in rhesus monkeys

The extent to which dominance status and sex can influence the physical act of grooming was examined in two groups of rhesus monkeys. Both the sex and the dominance status of the groomee, but not of the groomer, were found to affect the body sites groomed and the positions assumed by the animals during the grooming bout. Females were groomed more on the back and head and less on the tail, rump, upper leg, and lower arm than males. Females with infants tended to face away from the groomer. Higher-ranking groomees were groomed more on the tail and rump and less on the upper leg and back than lower-ranking groomees. Higher-ranking groomees spent more time lying down during grooming than lower-ranking groomees, while lower-ranking groomees faced away from the groomer more then higher-ranking groomees. The behavioral interactions just prior to and immediately after grooming were also recorded. Although the onset of grooming was preceded by social interactions between the partners, the end of grooming was followed by a complete break in interactions. Particular types of social signals displayed by the groomee just prior to grooming were highly correlated with the grooming of specific body sites. These results suggest that the groomee controls the behavior of the groomer by the social signals it displays and the positions it maintains during the grooming bout. Thus, the grooming act itself may play an important role in the social relationships between group members.     

Distributions and habitat associations of the bridled monocle bream Scolopsis bilineatus (Nemipteridae): a demographic approach

This study focussed on the demography and ecology of Scolopsis bilineatus at three locations on the Great Barrier Reef: the Lizard Island Group, Orpheus Island and One Tree Island. Scolopsis bilineatus lived for up to 16 years and had four distinct life‐history stages, which varied in their distribution patterns, habitat use and reproductive behaviour. Pre‐maturational sex change occurred whereby all males were derived from immature females, and males grew faster and larger than females. Small females and larger males generally formed pairs, which influenced their spatial distributions at small scales. Distributions of S. bilineatus were influenced by depth and exposure within reefs, particularly for juveniles, and most fish were found in shallow, sheltered habitats. Abundance was influenced by benthic cover, and was higher in areas of high coral cover and low where algae were abundant. Habitat associations were stronger at the microhabitat scale, and shelter sites were important for adults. Ontogenetic changes in microhabitat associations were found: juveniles occupied sand and rubble, and adults occupied shelters such as caves and overhangs. Adults showed site fidelity for shelter sites over a period of 4 days and returned to specific shelter sites repeatedly. These findings illustrate the importance of understanding the spatial ecology and habitat use of coral reef fishes, particularly with reference to size‐based changes within species.     

Grazing as a mediator for maintenance of offspring diversity: Sexual and clonal recruitment in alpine grassland communities

To understand the effects of grazing on grassland plants sexual and clonal recruitment, we conducted a demographic field investigation of species recruitment along a grazing gradient in the Tibetan alpine grassland. Grazing intensity had significant effects on quantity and diversity of sexual and clonal recruitment. Sexual recruitment increased significantly, but clonal offspring production decreased significantly with increased grazing intensity. Grazing intensity had different, significant effects on offspring recruitment of the various functional groups in the community, grasses (GG), sedges (SG), legumes (LG) and forbs (FG). Higher grazing intensity reduced offspring recruitment of GG and SG; it increased offspring recruitment of LG and FG. Seedlings were significantly more abundant in lightly grazed, moderately grazed and heavily grazed meadows than in non-grazed grasslands. Offspring diversity from sexual recruitment was significantly higher than that from clonal recruitment in grazed than in non-grazed grasslands. Our studies indicate that moderate grazing had positive effects on seedling recruitment and offspring diversity, but heavy gazing may alter community succession by affecting recruitment patterns among the four plant functional groups.     

Life‐history traits of the common snook Centropomus undecimalis in a Caribbean estuary and large‐scale biogeographic patterns relevant to management

The ecology of common snook Centropomus undecimalis in Amatique Bay, a tropical estuary in eastern Guatemala, was investigated and life‐history traits were used to conduct a meta‐analysis of the species from Florida to Brazil. The reproduction cycle of C. undecimalis in Amatique was strongly related to the precipitation cycle, with a lag of 2 months. Spawning occurred from April to November with a peak spawning after the onset of the summer rains. Protandric sex reversal occurred early in the dry season (December) before somatic recovery from spawning. The growth cycle preceded that of body condition by c. 1 month, and was out of phase with the reproductive cycle. Growth was fast, as many individuals reached >70% of the maximum observed total length (L_T, 102 cm) after 3 years. Sex transition occurred within a relatively narrow L_T range (70–79 cm), but over a wide range of ages, indicating plasticity in this respect. The meta‐analysis indicated a latitudinal‐temperature gradient in life‐history traits, as well as different seasonal patterns relative to temperature and hydrographical cycles. Centropomus undecimalis from cooler winter waters (e.g. Florida) reach larger maximum L_T and L_T at sex change, as well as greater gonado‐somatic indices and longer life spans. Further, increased fishing mortality results in younger age at sex reversal and male predominance in the populations compared. Recognition of large‐scale biogeographic patterns in this important, but little studied, fish species helps in the formulation of management advice in other areas of its occurrence.     

Social Reversal of Sex‐Biased Aggression and Dominance in a Biparental Cichlid Fish (Julidochromis marlieri)

In biparental species, aggression, dominance, and parental care are typically sexually dimorphic. While behavioral dimorphism is often strongly linked to gonadal sex, the environment—either social or ecological—may also influence sex‐biased behavior. In the biparental cichlid fish Julidochromis marlieri, the typical social environment for breeding pairs consists of large females paired with smaller males. While both sexes are capable of providing territory defense and parental care, the larger female provides the majority of defense for the pair, while the smaller male remains in the nest guarding their offspring. We examine the contributions of sex and relative mate size to these sex‐biased behaviors in monogamous J. marlieri pairs. Both female‐larger and male‐larger pairs were formed in the laboratory and were observed for territorial aggression (against conspecifics and heterospecifics), dominance, and parental care. In female‐larger pairs, territorial aggression and intra‐pair dominance were female‐biased, while in male‐larger pairs this bias was reversed. For both pairing types, the presence of an intruder amplified sex differences in territorial aggression, with the larger fish always attacking with greater frequency than its mate. Though less robust, there was evidence for plasticity of sex‐bias for some egg care related behaviors in the inverse direction. Our study suggests that relative mate size strongly influences the sex bias of aggression and dominance in J. marlieri and that this aspect of the social environment can override the influence of gonadal sex on an individual's behavior. The remarkable plasticity of this species makes Julidochromis an exciting model that could be used to address the relationship between proximate and ultimate mechanisms of behavioral plasticity.     

Gates and oscillators: a network model of the brain clock

The suprachiasmatic nuclei (SCN) control circadian oscillations of physiology and behavior. Measurements of electrical activity and of gene expression indicate that these heterogeneous structures are composed of both rhythmic and nonrhythmic cells. A fundamental question with regard to the organization of the circadian system is how the SCN achieve a coherent output while their constituent independent cellular oscillators express a wide range of periods. Previously, the consensus output of individual oscillators had been attributed to coupling among cells. The authors propose a model that incorporates nonrhythmic "gate" cells and rhythmic oscillator cells with a wide range of periods, that neither requires nor excludes a role for interoscillator coupling. The gate provides daily input to oscillator cells and is in turn regulated (directly or indirectly) by the oscillator cells. In the authors' model, individual oscillators with initial random phases are able to self-assemble so as to maintain cohesive rhythmic output. In this view, SCN circuits are important for self-sustained oscillation, and their network properties distinguish these nuclei from other tissues that rhythmically express clock genes. The model explains how individual SCN cells oscillate independently and yet work together to produce a coherent rhythm.