Termination of reproduction in nonhuman and human female primates

We examined demographic records from 13 captive primate species and a human population to determine age-related changes in female reproduction. In most species age-specific fertility declined and interbirth intervals increased with age. Using an operational definition of termination of reproduction based on individual variance in interbirth intervals, a proportion of females in most nonhuman species had terminated reproduction before death. Compared to other primates, a greater proportion of chimpanzees and human females ceased reproduction, and humans, in particular, were reproductively inactive for relatively longer than would be expected from their body weight. These empirical data quantify the extent of reproductive termination and thereby extend hitherto anecdotal accounts of this phenomenon in primates.     

Termination of reproduction in nonhuman and human female primates

We examined demographic records from 13 captive primate species and a human population to determine age-related changes in female reproduction. In most species age-specific fertility declined and interbirth intervals increased with age. Using an operational definition of termination of reproduction based on individual variance in interbirth intervals, a proportion of females in most nonhuman species had terminated reproduction before death. Compared to other primates, a greater proportion of chimpanzees and human females ceased reproduction, and humans, in particular, were reproductively inactive for relatively longer than would be expected from their body weight. These empirical data quantify the extent of reproductive termination and thereby extend hitherto anecdotal accounts of this phenomenon in primates.     

Reproductive suppression in female primates: A review

Reproductive performance is the currency of evolution. All things being equal, an organism should reproduce as often as possible. The puzzling questions in evolutionary biology, therefore, are not how and why an organism does reproduce, but rather how and why an organism does not reproduce. It is difficult to understand why any individual, particularly a female, might forestall reproduction when one of the biggest limitations for female mammalian reproduction is time (that is, reproductive lifespan). 1 The answer, now widely cited throughout behavioral ecology is quite simple: Reproductive suppression can be an adaptive strategy. 2     

Behaviourally mediated crypsis in two nocturnal moths with contrasting appearance

The natural resting orientations of several species of nocturnal moth on tree trunks were recorded over a three-month period in eastern Ontario, Canada. Moths from certain genera exhibited resting orientation distributions that differed significantly from random, whereas others did not. In particular, Catocala spp. collectively tended to orient vertically, whereas subfamily Larentiinae representatives showed a variety of orientations that did not differ significantly from random. To understand why different moth species adopted different orientations, we presented human subjects with a computer-based detection task of finding and ‘attacking’ Catocala cerogama and Euphyia intermediata target images at different orientations when superimposed on images of sugar maple (Acer saccharum) trees. For both C. cerogama and E. intermediata, orientation had a significant effect on survivorship, although the effect was more pronounced in C. cerogama. When the tree background images were flipped horizontally the optimal orientation changed accordingly, indicating that the detection rates were dependent on the interaction between certain directional appearance features of the moth and its background. Collectively, our results suggest that the contrasting wing patterns of the moths are involved in background matching, and that the moths are able to improve their crypsis through appropriate behavioural orientation.     

Orgasm in female primates

The major genital responses of arousal in women are vasocongestion, resulting in tumescence of the vaginal walls, and vaginal lubrication, facilitating penile intromission and thrusting. During orgasm, several involuntary muscular reactions occur, the most adaptive being in the outer third of the vagina and the uterus. Uterine suction of the ejaculate seems to occur when the reproductive apparatus is functioning at full efficiency. Coitus may result in reflex ovulation. Indices of female nonhuman primate orgasm thus far proposed include rhythmic vaginal and anal contractions, hyperventilation, involuntary muscle tension, arm and leg spasms, grimacing, and uterine contractions. Orgasm in our species may exist as a result of phylogenetic inertia, not as a novel response selected during protohominid or hominid evolution. A theory for the evolutionary nature of orgasm in women states that the orgasmic vaginal contractions stimulate ejaculation. Reasons for the common asynchrony of this adaptive pattern are the usually lowered ejaculatory threshold because of non-species-typical orgasmic frequency in the male, and the frequently delayed female orgasm because of psychological inhibition and/or inadequate control and development of the pubococcygeus.     

Behaviourally mediated indirect effects: interference competition increases predation mortality in foraging redshanks

1. The effect of competition for a limiting resource on the population dynamics of competitors is usually assumed to operate directly through starvation, yet may also affect survival indirectly through behaviourally mediated effects that affect risk of predation. Thus, competition can affect more than two trophic levels, and we aim here to provide an example of this. 2. We show that the foraging success of redshanks Tringa totanus (L.) foraging on active prey was highest in the front of flocks, whereas this was not the case for redshanks foraging on inactive prey. Also, when foraging on active prey, foraging success in a flock decreased as more birds passed through a patch, while overall foraging success was not lower on subsequent visits to the same patch. Thus, redshanks foraging on active prey suffered from interference competition, whereas this was not the case for redshanks foraging on inactive prey. 3. This interference competition led to differences in activity: redshanks attaining a lower foraging success had a higher walking rate. Greater activity was associated with wider flock spacing and shorter distances to cover, which has previously been shown to increase predation risk and mortality from sparrowhawks Accipiter nisus (L.). 4. We conclude that behavioural adaptations of prey species can lead to interference competition in foraging redshanks, and thus can affect their predation risk and mortality through increased activity. This study is one of the first to show how interference competition can be a mechanism for behaviourally mediated indirect effects, and provides further evidence for the suggestion that a single species occupying an intermediate trophic level may be simultaneously top-down controlled by a predator and bottom-up controlled by a behavioural response of its prey.     

Adolescent exaggeration in female catarrhine primates

Adolescent females of 11 primate species display exaggerated versions of the cues to sexual cycle state or fertility which are displayed by adult females: anubis baboons; geladas; Assamese, Barbary, crab-eating, Japanese, and stump-tailed macaques; patas monkeys; gorillas; and humans. These cases are briefly described and a variety of hypotheses is presented and evaluated to account for the adolescent exaggeration. Such exaggeration may be a super-normal sexual stimulus, a barrier to cross-species hybridization, a helpful prop in female:female competition, a passport for transfers, an insurance policy where unpredictable changes of circumstance are likely, or a non-adaptive side-effect of some other phenomenon. The transfer and unpredictability hypotheses seem to apply to the largest number of species, including humans.     

Postcanine tooth size in female primates

The results of many allometric studies of postcanine tooth size in mammals have not corresponded to expectations of tooth size based on energy requirements and dental function. The purpose of this study is to investigate the relationship between postcanine occlusal surface area, body size, and the metabolic demands of pregnancy and lactation in female primates. Tooth and body sizes from 38 primate species were taken from the literature to test two hypotheses: 1) females should have relatively larger teeth than males in order to masticate additional food for the energetic costs of reproduction; 2) taxa with the largest neonatal size (a measure of average metabolic costs of pregnancy and lactation) should have females with a greater degree of relative dental enlargement. The results show that relatively large female teeth are not found consistently in primate species. Females have less occlusal surface area than expected on the basis of the male tooth and body size regression in 21% of the species, and there is no correlation between relative female tooth size and relative newborn size across higher primate taxa. The degree of female dental enlargement is most closely related to degree of sexual dimorphism in body weight. The correlation between degree of body weight dimorphism and relatively larger postcanine teeth in females than in males is 0.87 in the 38 species. Species that are monomorphic in weight tend to be monomorphic in tooth size even though females apparently require more food than males.(ABSTRACT TRUNCATED AT 250 WORDS)     

Involvement of copper in female reproduction

Copper (Cu) is one of the essential trace metals which are necessary in maintaining the functioning of living organisms. The current knowledge on the role of copper in animal reproduction is presented in the article. Our studies have shown that complexes of copper (Cu(2+)) with gonadotropin-releasing hormone (GnRH) are even more effective in the release of LH than native GnRH. Moreover, Cu-GnRH is more potent in inducing in vivo release of FSH than LH. Copper complexes with GnRH interact with GnRH receptors (GnRHR) and modulate intracellular signaling in the gonadotrope cells of the anterior pituitary. Copper plays also a significant role in maintaining normal fetus development in mammals.     

From lynx spiders to cotton: Behaviourally mediated predator effects over four trophic levels

Food web studies often examine density and behaviourally mediated effects of predators on herbivores, but are less likely to assess the plant targeted by the herbivore. We conducted a study that incorporated four trophic levels examining the effect of two generalist predators (damsel bugs, Nabis kinbergii Reuter; and lynx spiders, Oxyopes molarius L. Koch) on damage to cotton bolls caused by green mirids (Creontiades dilutus (Stål)). First we tested whether lynx spiders and damsel bugs could control mirid numbers and cotton boll damage in field cages. We found that in cages containing mirids and only lynx spiders, lynx spiders reduced both mirid numbers and boll damage. However, in cages which contained mirids and both predators (lynx spiders and damsel bugs) only mirid numbers were reduced. To explain the negative effect of damsel bugs on boll damage, we examined the interactions between lynx spiders, damsel bugs and mirids. We found that lynx spiders were better mirid predators than damsel bugs, and that lynx spiders attacked damsel bugs, but not vice versa. Behaviourally, mirids responded to increasing predator pressure regardless of whether the predators were lynx spiders or damsel bugs. However, damsel bugs seemed to alter the behaviour of lynx spiders because in their presence, a higher proportion of lynx spiders moved to the top of the plant, towards the damsel bugs but away from the bolls found lower on the plant. These results suggest that the most likely explanation for the increase in boll damage in the presence of damsel bugs was that lynx spiders moved to the top of the plant in the presence of damsel bugs, which then exposed the bolls lower down on the plant to mirid attack. This work emphasizes the importance of behaviourally mediated effects in food webs extending over four trophic levels.     

Hormonal regulation of female reproduction

Reproduction is an event that requires the coordination of peripheral organs with the nervous system to ensure that the internal and external environments are optimal for successful procreation of the species. This is accomplished by the hypothalamic-pituitary-gonadal axis that coordinates reproductive behavior with ovulation. The primary signal from the central nervous system is gonadotropin-releasing hormone (GnRH), which modulates the activity of anterior pituitary gonadotropes regulating follicle stimulating hormone (FSH) and luteinizing hormone (LH) release. As ovarian follicles develop they release estradiol, which negatively regulates further release of GnRH and FSH. As estradiol concentrations peak they trigger the surge release of GnRH, which leads to LH release inducing ovulation. Release of GnRH within the central nervous system helps modulate reproductive behaviors providing a node at which control of reproduction is regulated. To address these issues, this review focuses on several critical questions. How is the HPG axis regulated in species with different reproductive strategies? What internal and external conditions modulate the synthesis and release of GnRH? How does GnRH modulate reproductive behavior within the hypothalamus? How does disease shift the activity of the HPG axis?     

The evolution of social philopatry in female primates

The transition from solitary life to sociality is considered one of the major transitions in evolution. In primates, this transition is currently not well understood. Traditional verbal models appear insufficient to unravel the complex interplay of environmental and demographic factors involved in the evolution of primate sociality, and recent phylogenetic reconstructions have produced conflicting results. We therefore analyze a theoretical model for the evolution of female social philopatry that sheds new light on the question why most primates live in groups. In individual-based simulations, we study the evolution of dispersal strategies of both resident females and their offspring. The model reveals that social philopatry can evolve through kin selection, even if retention of offspring is costly in terms of within-group resource competition and provides no direct benefits. Our model supports the role of predator avoidance as a selective pressure for group-living in primates, but it also suggests that a second benefit of group-living, communal resource defense, might be required to trigger the evolution of sizable groups. Lastly, our model reveals that seemingly small differences in demographic parameters can have profound effects on primate social evolution.     

Role of corticosteroids in female reproduction.

Corticosteroids, ACTH, and stress can exert inhibitory and facilitory effects on reproduction. The purpose of this review is to reconcile the divergent effects of corticosteroids on gonadotropin secretion based on recent work in the area. Whether stimulation or inhibition of gonadotropin secretion is observed appears to depend on two important variables: 1) length of exposure, and 2) background of estrogen priming. The acute administration of ACTH and certain corticosteroids to estrogen-primed animals brings about the release of LH and FSH. Corticosteroids have also been shown by some investigators to cause selective release of follicle-stimulating hormone (FSH) both in vitro and in vivo. This selective facilitation of FSH release by corticosteroids may explain many deleterious effects on reproduction observed after adrenalectomy, and it may have relevance in explaining the beneficial effects of corticosteroids in inducing ovulation in anovulatory patients suffering from polycystic ovarian syndrome. Finally, evidence is presented which suggests that adrenal steroids may participate in initiation and synchronization of the preovulatory LH and FSH surge, as well as the secondary FSH surge seen on estrus in the rat.     

Role of oxidative stress in female reproduction

In a healthy body, ROS (reactive oxygen species) and antioxidants remain in balance. When the balance is disrupted towards an overabundance of ROS, oxidative stress (OS) occurs. OS influences the entire reproductive lifespan of a woman and even thereafter (i.e. menopause). OS results from an imbalance between prooxidants (free radical species) and the body's scavenging ability (antioxidants). ROS are a double-edged sword – they serve as key signal molecules in physiological processes but also have a role in pathological processes involving the female reproductive tract. ROS affect multiple physiological processes from oocyte maturation to fertilization, embryo development and pregnancy. It has been suggested that OS modulates the age-related decline in fertility. It plays a role during pregnancy and normal parturition and in initiation of preterm labor. Most ovarian cancers appear in the surface epithelium, and repetitive ovulation has been thought to be a causative factor. Ovulation-induced oxidative base damage and damage to DNA of the ovarian epithelium can be prevented by antioxidants. There is growing literature on the effects of OS in female reproduction with involvement in the pathophsiology of preeclampsia, hydatidiform mole, free radical-induced birth defects and other situations such as abortions. Numerous studies have shown that OS plays a role in the pathoysiology of infertility and assisted fertility. There is some evidence of its role in endometriosis, tubal and peritoneal factor infertility and unexplained infertility. This article reviews the role OS plays in normal cycling ovaries, follicular development and cyclical endometrial changes. It also discusses OS-related female infertility and how it influences the outcomes of assisted reproductive techniques. The review comprehensively explores the literature for evidence of the role of oxidative stress in conditions such as abortions, preeclampsia, hydatidiform mole, fetal embryopathies, preterm labour and preeclampsia and gestational diabetes. The review also addresses the growing literature on the role of nitric oxide species in female reproduction. The involvement of nitric oxide species in regulation of endometrial and ovarian function, etiopathogenesis of endometriosis, and maintenance of uterine quiescence, initiation of labour and ripening of cervix at parturition is discussed. Complex interplay between cytokines and oxidative stress in the etiology of female reproductive disorders is discussed. Oxidant status of the cell modulates angiogenesis, which is critical for follicular growth, corpus luteum formation endometrial differentiation and embryonic growth is also highlighted in the review. Strategies to overcome oxidative stress and enhance fertility, both natural and assisted are delineated. Early interventions being investigated for prevention of preeclampsia are enumerated. Trials investigating combination intervention strategy of vitamin E and vitamin C supplementation in preventing preeclampsia are highlighted. Antioxidants are powerful and there are few trials investigating antioxidant supplementation in female reproduction. However, before clinicians recommend antioxidants, randomized controlled trials with sufficient power are necessary to prove the efficacy of antioxidant supplementation in disorders of female reproduction. Serial measurement of oxidative stress biomarkers in longitudinal studies may help delineate the etiology of some of the diosorders in female reproduction such as preeclampsia.     

Cost of reproduction, T-lymphocyte mediated immunocompetence and health status in female and nestling barn swallows Hirundo rustica

We investigate the trade-off between reproductive effort, health status and T-lymphocyte acquired immunity in female and nestling barn swallows Hirundo rustica using a brood size manipulation experiment. Maternal and total feeding effort increased with experimental brood size. Parents did not fully compensate for the increased food demand of the enlarged broods and as a consequence the per capita feeding rate of nestlings decreased with increasing experimental brood size. Body mass and a measure of T-cell mediated immunity in 12 days old nestlings also decreased with increasing experimental brood size. Different leucocyte concentrations and the heterophile/lymphocyte ratio – an index of stress – of nestlings did not change in relation to experimental brood size, suggesting that within brood competition did not affect stress to nestlings. The brood size manipulation had a significant effect on maternal T-cell mediated immunity, measured by the phytohemagglutinin skin test, but not on maternal body mass, haematocrit or differential or total white blood cell counts. Our results seem to support the prediction that under mild work stress females respond first by reducing the energetically expensive acquired immunity. Different leucocyte types and the heterophile/lymphocyte ratio appear less sensitive to parental workload.     

The value of grooming to female primates

Current socioecological models suggest that the structure of female-bonded primate groups is predicated on the need for coalitionary support in competitive interactions. Social grooming is thought to be the means by which females ensure support from other individuals, either by the direct exchange of grooming for aid or by using grooming as a means of strengthening social bonds. Since these relationships are valuable, they must be regularly serviced and must be repaired if they become damaged. We question this position and show that empirical evidence to support these theoretical arguments is lacking. We then go on to present a new framework in which the inconsistencies regarding grooming and relationship negotiation are interpreted in the context of individual decision-making processes. In this framework, primate groups represent biological markets in which individuals either trade grooming in a reciprocal manner for the direct benefits that grooming itself offers, or exchange it for tolerance by more powerful animals. A number of testable predictions are derived from this hypotheses. The need for socioecological studies to focus on the dynamics of individual relationships rather than using summary measures is emphasized since only a detailed knowledge of serial interaction will provide the key to understanding the complexities of individual decision-making processes.     

Molecular cytotaxonomy of primates by chromosomal in situ suppression hybridization

A new strategy for analyzing chromosomal evolution in primates is presented using chromosomal in situ suppression (CISS) hybridization. Biotin-labeled DNA libraries from flow-sorted human chromosomes are hybridized to chromosome preparations of catarrhines, platyrrhines, and prosimians. By this approach rearrangements of chromosomes that occurred during hominoid evolution are visualized directly at the level of DNA sequences, even in primate species with pronounced chromosomal shuffles.     

An evolutionary model of female dominance relations in primates

Though a few authors have provided individual selection explanations for the existence of dominance hierarchies, no unitary functional model exists which is capable of accounting for specific forms of dominance hierarchies. The framework of a model of female dominance relations in primates is developed and should be applicable to other species exhibiting overlapping generations, iteroparity, low female dispersal, and high parental investment. This model is based on the principles of individual selection, kin selection, reproductive value, and evolutionarily stable strategies. Three functional hypothesis are presented concerning female dominance relations. These hypotheses are tested using life table data for Macaca mulatta. Sister-sister, mother-daughter, and other rank relations are analyzed in detail taking into account self interest, conflicts of interest, and the interest of supporters in rank relations. One of the hypothesis satisfactorily accounts for the principal elements of the female dominance hierarchy in Macaca mulatta.     

Hormonal controls on reproduction in female heteroptera

A survey of the literature related to hormonal control of reproduction in female heteropterans reveals many common features. Juvenile hormone secreted by the corpus allatum is the principal hormone governing vitellogenesis. Feeding and nutrition affects egg development via juvenile hormone secreted by the corpus allatum, which is under inhibitory control from the brain. Information about feeding reaches the brain via a humoral route. Similarly, mating increases egg production by altering the degree of inhibition of the corpus allatum by the brain, although the nature of the mating stimulus and the route by which the stimulus reaches the brain remains uncertain. There may be one or more stimulatory factors acting on the corpus allatum. Progress in identifying controls on the corpus allatum is hindered by our ignorance of the identity of the juvenile hormone(s) acting in Heteroptera. Ovulation and oviposition are under the control of a myo-active peptide from the brain, and its release is governed by hormonal inputs from both mating and the ovary. The ovarian input appears to consist of ecdysteroid. A role for ovarian ecdysteroid in controlling the corpus allatum remains uncertain. Arch. Insect Biochem. Physiol. 35:443–453, 1997. © 1997 Wiley-Liss, Inc.