On sex differences in sexual imprinting

Several studies have reported sex differences in the relation between early experience and later pair formation. These differences are usually ascribed to sex differences in ‘imprintability’. This interpretation has given rise to various functional explanations. In this article the evidence for both the existence of sex differences in imprintability (i.e. learning of plumage characteristics during juvenile life) and the functional explanations of these differences are critically examined. It is concluded that the existence of sex differences in imprintability has not been proved. Recent studies indicate that sex differences may be the result of a difference in the way both sexes weigh multiple criteria on which mate choice is based. It is suggested that more attention should be given to a causal and ontogenetic analysis of these criteria for an understanding of sex differences in mate choice. The function of sex differences found in imprinting studies seems not to be related to plumage differences between sexes but may be related to sex differences in optimal mate choice.     

Departures from neutrality induced by niche and relative fitness differences

Breaking the core assumption of ecological equivalence in Hubbell’s “neutral theory of biodiversity” requires a theory of species differences. In one framework for characterizing differences between competing species, non-neutral interactions are said to involve both niche differences, which promote stable coexistence, and relative fitness differences, which promote competitive exclusion. We include both in a stochastic community model in order to determine if relative fitness differences compensate for changes in community structure and dynamics induced by niche differences, possibly explaining neutral theory’s apparent success. We show that species abundance distributions are sensitive to both niche and relative fitness differences, but that certain combinations of differences result in abundance distributions that are indistinguishable from the neutral case. In contrast, the distribution of species’ lifetimes, or the time between speciation and extinction, differs under all combinations of niche and relative fitness differences. The results from our model experiment are inconsistent with the hypothesis of “emergent neutrality” and support instead a hypothesis that relative fitness differences counteract effects of niche differences on distributions of abundance. However, an even more developed theory of interspecific variation appears necessary to explain the diversity and structure of non-neutral communities.     

Female preference functions drive interpopulation divergence in male signalling: call diversity in the bushcricket Ephippiger diurnus

Female preferences play a major role in the elaboration and diversification of male traits: as a selective pressure on males, variation in female preferences can generate population divergence and ultimately, speciation. We studied how interpopulation differences in the shape of female mate preference functions may have shaped male advertisement signals in the bushcricket Ephippiger diurnus. This species is distributed as geographically isolated populations with striking interpopulation variation in male acoustic signals, most notably in the number of syllables per call. Here, we asked whether differences in the shape of preference functions exist among populations and whether those differences may have driven male signal evolution resulting in the observed differences in syllable numbers. Our results reveal fundamental differences in female preferences among populations, with differences in the overall preference function shape corresponding to differences in male signals. These differences in female preferences best explain the major differences in male signals among populations. The interpopulation variation in signals and preferences potentially reflects the evolutionary history of the species and may contribute to further divergence among populations and subsequent speciation.     

Sex‐specific aging in animals: Perspective and future directions

Sex differences in aging occur in many animal species, and they include sex differences in lifespan, in the onset and progression of age‐associated decline, and in physiological and molecular markers of aging. Sex differences in aging vary greatly across the animal kingdom. For example, there are species with longer‐lived females, species where males live longer, and species lacking sex differences in lifespan. The underlying causes of sex differences in aging remain mostly unknown. Currently, we do not understand the molecular drivers of sex differences in aging, or whether they are related to the accepted hallmarks or pillars of aging or linked to other well‐characterized processes. In particular, understanding the role of sex‐determination mechanisms and sex differences in aging is relatively understudied. Here, we take a comparative, interdisciplinary approach to explore various hypotheses about how sex differences in aging arise. We discuss genomic, morphological, and environmental differences between the sexes and how these relate to sex differences in aging. Finally, we present some suggestions for future research in this area and provide recommendations for promising experimental designs.     

Prenatal influences on Aboriginal-white Australian differences in neonatal irritability

Recent research with the Brazelton Neonatal Behavioral Assessment Scale in Australia has shown significant Aboriginal-white Australian group differences in neonatal irritability. These differences are best accounted for by individual differences in maternal age and maternal blood pressure during pregnancy. These data do not support the theory that ethnic/racial differences in neonatal behavior are due to gene pool differences but argue instead for a more complex model of gene-environment interaction during pregnancy.     

Estrogen regulation of protein expression and signaling pathways in the heart

Sex differences in cardiovascular disease and cardiac physiology have been reported in humans as well as in animal models. Premenopausal women have reduced cardiovascular disease compared to men, but the incidence of cardiovascular disease in women increases following menopause. Sex differences in cardiomyocytes likely contribute to the differences in male–female physiology and response to disease. Sex differences in the heart have been noted in electrophysiology, contractility, signaling, metabolism, and cardioprotection. These differences appear to be due, at least in part, to differences in gene and protein expression as well as in posttranslational protein modifications. This review will focus primarily on estrogen-mediated male–female differences in protein expression and signaling pathways in the heart and cardiac cells. It should be emphasized that these basic differences are not intrinsically beneficial or detrimental per se; the difference can be good or bad depending on the context and circumstances.     

Parental alleles of an imprinted mouse transgene replicate synchronously

Molecular features of imprinted genes include differences in expression, methylation, and the timing of DNA replication between parental alleles. Whereas methylation differences always seem to be associated with differences in expression, differences in the timing of replication between parental homologs are not always seen at imprinted loci. These observations raise the possibility that differences in replication timing may not be an essential feature underlying genomic imprinting. In this study, we examined the timing of replication of the two alleles of the imprinted RSVIgmyc transgene in individual embryonic cells using fluorescence in situ hybridization (FISH). The cis-acting signals for RSVIgmyc imprinting are within RSVIgmyc itself. Thus, allele-specific differences in replication, if they indeed govern RSVIgmyc imprinting, should be found in RSVIgmyc sequences. We found that the parental alleles of RSVIgmyc, which exhibit differences in methylation, replicated at the same time. Synchronous replication was also seen in embryonic cells containing a modified version of RSVIgmyc that exhibited parental allele differences in both methylation and expression. These findings indicate that maintenance of expression and methylation differences between alleles does not require a difference in replication timing. The differences in replication timing of endogenous imprinted alleles detected by FISH might therefore reflect structural differences between the two alleles that could be a consequence of imprinting or, alternatively, could be unrelated to imprinting. Dev. Genet. 23:275–284, 1998. © 1998 Wiley-Liss, Inc.     

The Biochemistry of Drug Metabolism – An Introduction

This review is part of a series of review articles on the metabolism of drugs and other xenobiotics published in Chemistry & Biodiversity. After a thorough discussion of metabolic reactions and their enzymes, this article focuses on genetically determined differences in drug and xenobiotic metabolism. After a short introduction on the causes for genetic differences, the first focus is on species differences in drug and xenobiotic metabolism. A major chapter is then dedicated to clinically relevant genetic polymorphisms in human drug metabolism and resultant ethnic differences. The last two chapters deal with sex‐dependent differences in drug metabolism and personalized pharmacotherapy related to inter‐individual differences in drug metabolism.     

Characterization of genetic differences in hormone-induced ovulation rate in mice

Major genetic differences in hormone-induced ovulation rate were not explained by strain differences in age at puberty, by maturation and ovulation of follicles by endogenous gonadotrophins, or by differential responses to gonadotrophins at different ages. The major genetic differences in hormone-induced ovulation rate were explained by strain differences in ovarian responsiveness to exogenous gonadotrophins.     

Sex differences in opioid analgesia, hyperalgesia, tolerance and withdrawal: Central mechanisms of action and roles of gonadal hormones

This article reviews sex differences in opiate analgesic and related processes as part of a Special Issue in Hormones and Behavior. The research findings on sex differences are organized in the following manner: (a) systemic opioid analgesia across mu, delta and kappa opioid receptor subtypes and drug efficacy at their respective receptors, (b) effects of the activational and organizational roles of gonadal steroid hormones and estrus phase on systemic analgesic responses, (c) sex differences in spinal opioid analgesia, (d) sex differences in supraspinal opioid analgesia and gonadal hormone effects, (e) the contribution of genetic variance to analgesic sex differences, (f) sex differences in opioid-induced hyperalgesia, (g) sex differences in tolerance and withdrawal-dependence effects, and (h) implications for clinical therapies.     

Egg phenotype matching by cuckoos in relation to discrimination by hosts and climatic conditions

Although parasites and their hosts often coexist in a set of environmentally differentiated populations connected by gene flow, few empirical studies have considered a role of environmental variation in shaping correlations between traits of hosts and parasites. Here, we studied for the first time the association between the frequency of adaptive parasitic common cuckoo Cuculus canorus phenotypes in terms of egg matching and level of defences exhibited by its reed warbler Acrocephalus scirpaceus hosts across seven geographically distant populations in Europe. We also explored the influence of spring climatic conditions experienced by cuckoos and hosts on cuckoo-host egg matching. We found that between-population differences in host defences against cuckoos (i.e. rejection rate) covaried with between-population differences in degree of matching. Between-population differences in host egg phenotype were associated with between-population differences in parasitism rate and spring climatic conditions, but not with host level of defences. Between-population differences in cuckoo egg phenotype covaried with between-population differences in host defences and spring climatic conditions. However, differences in host defences still explained differences in mimicry once differences in climatic conditions were controlled, suggesting that selection exerted by host defences must be strong relative to selection imposed by climatic factors on egg phenotypes.     

Sexual differences in habitat use by small mammals: evolutionary strategy or reproductive constraint?

Summary This study examines the hypothesis that intersexual differences in habitat use by small mammals is an adaptive strategy. Specifically, I evaluate the occurrence of sexual differences in habitat by Peromyscus and Microtus, and test possible adaptive mechanisms which may lead to such differences.White-footed mice and meadow voles were live-trapped and microhabitat quantified in four habitats. Sexual differences in microhabitat use were found in three of 12 comparisons. These differences may be related to density dependent resource subdivision and habitat heterogencity, but neither of these can account completely for the observed patterns. Sexual differences in habitat do not appear to be an evolutionary strategy maximizing reproductive effort by females, or reducing predation. These sexual differences may reduce intraspecific resource overlap, or may simply reflect reproductive constraints limiting female habitat use to suitable nesting areas.     

Sex‐specific foraging behaviour in tropical boobies: does size matter?

Sex differences in the foraging behaviour of adults have been observed in a number of sexually size-dimorphic birds, and the usual inference has been that these sex-specific differences are driven primarily by differences in body size. An alternative explanation is that foraging differences result from sex differences unrelated to size, such as sex-specific nutritional requirements. To examine these alternative hypotheses, the foraging behaviour of parents was compared between two sympatric and congeneric species of seabird, the Brown Booby Sula leucogaster , which is highly sexually size-dimorphic (females 38% larger) and the Red-footed Booby S. sula , in which sex differences in body size are less marked (females 15% larger). Using temperature and depth loggers, we found that there were highly significant differences in the foraging trip durations and diving behaviour of male and female Brown Boobies. These sex differences were less marked in Red-footed Boobies. Thus, our interspecies comparison revealed that the magnitude of the difference between the sexes matched the sexual size dimorphism of the species, providing support for the size hypothesis.     

The relation between cell size, ploidy level and nitrate concentration in lettuce

In two experiments the relation between cell size, ploidy level and nitrate concentration of genotypes of lettuce ( Lactuca saliva L.) was investigated. Artificial increase of cell size by application of gibberellic acid to young plants decreased the percentage dry weight and the concentration of organic acids in the plant sap and increased the nitrate concentration of the shoot. Application of chlormequat chloride caused the opposite effects. Tetraploid genotypes of lettuce had larger cells, a lower nitrate concentration and a higher concentration of organic solutes than diploid genotypes. Genotypical differences in nitrate concentration could not be explained by differences in cell size, but were consistently related to differences in concentration of organic acids in plant sap. The percentage dry weight of genotypes was positively correlated with the concentration of organic acids in plant sap. However, differences in nitrate concentration were also found among genotypes with comparable dry matter content. These differences could be caused by differences in partitioning of photosynthates over structural components and organic acids in the vacuoles. Mono-saccharides seem to be less important than organic acids for explaining genotypical differences in nitrate level, because the concentration of monosaccharides was much lower than that of organic acids and because a negative relation between the concentration of monosaccharides and of nitrate was not found in every case. Genotypical differences in nitrate accumulation were not related to differences in osmolarity.     

Inter-familiar differences in sprint speed of hatchling Sceloporus occidentalis (Reptilia: Iguanidae)

Hatchling Sceloporus occidentalis from the same dam had more similar sprint speeds than did hatchlings from different dams. Families (e.g. siblings from the same dam) of hatchlings differ significantly in body size. However, family differences in sprint speed remain significant when the size differences are removed statistically. Genetic differences among the families of lizards may account for most of the family differences in speed, although environmental or maternal effects may also contribute to family differences in sprint speed.     

Colony-dependent sex differences in protozoan communities of the lower termite <Emphasis Type="Italic">Reticulitermes speratus</Emphasis> (Isoptera: Rhinotermitidae)

In many animals, sex differences in hormones, behavior, and immunity lead to differences in their gut microbial communities. One of the best-known examples of mutualistic symbiosis is that between lower termites and their intestinal protozoa. Although differences in the protozoan communities of different castes have been studied in lower termites, nothing is known about the sex differences in protozoan communities in neuter castes. Here, we show that termite workers have different protozoan communities according to sex depending on the colony. We investigated the communities of symbiotic protozoa living in lower termites, Reticulitermes speratus, and how they are affected by sex and caste. Workers had the largest numbers of protozoa, followed by soldiers, whereas reproductives (primary kings and secondary queens) had no protozoa. Workers showed colony-dependent sex differences in the total abundance of protozoa, whereas soldiers showed no such sex differences. There were significant sex effect and/or interaction effect between colony and sex in abundances of five species of protozoa in workers. Workers also showed significant sex differences and/or colony-dependent sex differences in proportion of six species of protozoa. These may result in sex differences in the host–symbiont interaction due to physiological or behavioral sex differences in workers that have not been recognized previously. This study has an important implication: although workers are not engaged in reproduction, their potential sex difference may affect various aspects of social interactions.     

Immunoblot patterns of Giardia duodenalis isolates from different hosts and geographical locations

Eighteen isolates of Giardia duodenalis from animal and human sources were studied for protein differences by polyacrylamide gel electrophoresis and for antigenic differences by immunoblot analysis. The polyacrylamide gels showed that whilst the isolates were for the most part homogeneous in their protein banding patterns, some isolates did show some differences. The immunoblot analysis yielded many bands, including prominent bands of 32 and 66 kilodaltons. Five of the six isolates that showed differences in protein banding pattern also showed differences in antigenic reactivity. Our findings suggest that differences can be seen with the use of immunoblotting and that this technique is a tool that may be useful for isolate differentiation when used in conjunction with other techniques.     

1.2A分辨率胰岛素二体中两个分子间的构象差异

以1.2A分辨率的胰岛素精细结构模型为基础,分析并确定了三方二锌猪胰岛素晶体中二体分子的构象差异。构象差异不仅表现于侧链残基,也涉及到主链构象的变化。二体分子的构象差异带来的不对称性也明显地表现在二体分子的氢键体系和结合水的差异。局部微环境的不同是维持二体分子构象差异的稳定因素。文中对有重要差异的残基作了较详细的分析和讨论。     

Regional variation in tooth size and pathology in fossil hominids.

Tooth size and dental pathology in fossil hominids were studied to test for regional differences in these parameters. The results showed little regional variation in tooth size for the Middle and Upper Pleistocene sites compared (except for Krapina) but considerable differences in the severity of attrition and dental pathology. These differences were considered indicative of regional differences in the functional load borne by the teeth, and in view of the similar technological status of the groups studied, were attributed to environmental differences in the diet. Since, in all regions, reduction in tooth size appeared to continue at the same rate for the periods investigated, no association can be established between presumed selective pressures related to differences in functional demands made on the dentition, and tooth reduction.