Monogamous Mating Research Articles

Sperm Storage in a Family-Living Lizard, the Tree Skink (Egernia striolata).

The ability to produce viable offspring without recently mating, either through sperm storage or parthenogenesis, can provide fitness advantages under a suite of challenging ecological scenarios. Using genetic analysis, we demonstrate that 3 wild-caught female Tree Skinks (Egernia striolata) reproduced in captivity with no access to males for over a year, and that this is best explained by sperm storage. To the best of our knowledge, this is the first time female sperm storage has been documented in any monogamous family-living reptile, including social Australian egerniine skinks (from the subfamily Egerniinae). Furthermore, by using paternal reconstruction of genotypes we show that captive-born offspring produced by the same females in the preceding year, presumably without sperm storage, were sired by different males. We qualitatively compared aspects of these females' mates and offspring between years. The parents of each litter were unrelated, but paternal and offspring genotypes from litters resulting from stored sperm were more heterozygous than those inferred to be from recent matings. Family-living egerniine skinks generally have low rates of multiple paternity, yet our study suggests that female sperm storage, potentially from outside social partners, offers the real possibility of benefits. Possible benefits include increasing genetic compatibility of mates and avoiding inbreeding depression via cryptic female choice. Sperm storage in Tree Skinks, a family-living lizard with a monogamous mating system, suggests that females may bet-hedge through extra-pair copulation with more heterozygous males, reinforcing the idea that females could have more control on reproductive outcomes than previously thought.

Early Neurodevelopmental Anomalies in Young Rats from Adult female Treated with Valproic Acid

Background: the influence of VPA on murine fertility, and on offspring is well documented: VPA decreases the fertility rate (by 25%) and the number of fÅ“tus. Furthermore, VPA causes behavioral alterations in rodents similar to the symptoms observed in autism.Objective: in this study we investigated the effects of exposure of non-pregnant adult rats to VPA in the offspring of these animals.Material and methods: non-pregnant adult rats were divided into 3 groups; (1) distilled water group, (2) VPA 200 mg / kg group and (3) VPA 400 mg/kg group. The products were administered orally daily for 30 days. At the end of treatments, all rats were put into monogamous mating with breeding males. The zootechnical characteristics (gestation period, litter size, mortality rate) were then noted. The young rats were then subjected to a battery of behavioral tests (reversal and anti-gravity reflexes, cliff avoidance, suspension, motor coordination and eye opening), carried out at different stages of life to assess sensorimotor development. Morphological abnormalities were also sought, as well as the mortality rate on the 28th day of life.Results: An increase in the mortality rate and a decrease in the mean lifespan were found in female rats exposed to VPA. Young rats from female rats exposed to VPA showed decreased success rates and performance in behavioral testing. Morphodevelopmental abnormalities such as adictalia or stump necrosis were found in the VPA groups. The offspring mortality rate of female rats exposed to VPA 200 mg/kg was 100%.Conclusion: VPA administered to non-pregnant adult rats causes developmental abnormalities, decreased success rates for performance testing, deformities and increased mortality in young rats from the treated rats by VPA. Â

Effects of Sex and Breeding Status on Skull Morphology in Cooperatively Breeding Ansell’s Mole-Rats and an Appraisal of Sexual Dimorphism in the Bathyergidae

African mole-rats of the genus Fukomys (Northern common mole-rats) combine a monogamous mating system and pronounced sexual size dimorphism; a pattern highly untypical for mammals. At the same time, they live in cooperatively breeding groups composed of reproductive and non-reproductive members of both sexes. How and to which degree sex and breeding status influence morphofunctional characters in eusocial mole-rats is not well characterized but essential to come to a comprehensive understanding of their peculiar social system. Here, we explore patterns of morphological differentiation in skulls of Ansell’s mole-rats (Fukomys anselli) by means of multivariate analysis of linear skull measurements combined with a 2D shape analysis of cranium and mandible. Compared to females, males display larger skulls relative to body size and show an expansion of the facial portion of the cranium, while reproductive status did not have an effect on any of the traits studied. We also show that species of Fukomys mole-rats display a scaling of relative sexual body size dimorphism in compliance to Rensch’s rule, which is deemed indicative of intense male intrasexual competition. For the bathyergid family as a whole, results of scaling analyses were more ambiguous, but also indicative of Rensch’s rule conformity. In line with genetic field data, our results point to a greater role of male-male conflicts in Fukomys than is traditionally assumed and support the notion that reproductive status does not correlate with morphofunctional segregation in these unusual rodents.

Facultative polyandry protects females from compromised male fertility caused by heatwave conditions

Why is polyandry such a common mating behaviour when it exposes females to a range of significant fitness costs? Here, we investigated whether polyandry protects females against reduced male fertility caused by thermal stress from heatwave conditions. Sperm production and function are vulnerable to heat, and heatwave conditions are forecast to increase as our climate warms, so we examined these effects on female reproduction and mating behaviour in the flour beetle, Tribolium castaneum, a promiscuous ectotherm model in which fertility is damaged by environmental warming. We tested whether polyandrous matings, or polyandrous sperm stores, protect females against reduced male fertility caused by heatwave conditions, and whether females flexibly adjust their remating behaviour to enable fertility rescue. We found that polyandry protected females against reduced male fertility: monogamous matings with males exposed to heatwave conditions halved female offspring production, but opportunities to mate with five of these males allowed normal female reproductive output. By contrast with this fertility improvement following polyandrous mating opportunities, there was no protective benefit for females already carrying sperm stores from multiple males, which suffered similar heatwave damage within the female tract as monogamous sperm stores. Importantly, female polyandry was flexible to male condition, with females showing greater motivation to remate with new males if their previous mate had been damaged by heatwave exposure, enabling a rapid reproductive rescue. Our results reveal that flexible polyandry enables females to rescue their fertility when male reproductive function is compromised by heatwave conditions, a phenomenon that may become more prevalent under climate change.

The evolution of monogamy is associated with reversals from male to female bias in the survival cost of parasitism.

The extent to which parasites reduce host survival should depend upon how hosts balance trade-offs between reproduction and survival. For example, parasites are predicted to impose greater survival costs under polygynous or promiscuous mating systems in which competition for mates favours increased reproductive investment, particularly in males. We provide, to our knowledge, the first comparative test of the hypothesis that the mating system of the host is an important determinant of (i) the extent to which parasites reduce survival, and (ii) the extent to which males and females differ in the survival cost of parasitism. Using meta-analysis of 85 published estimates of the survival cost of parasitism from 72 studies of 64 species representing diverse animal lineages, we show that parasites impose a mean 3.5-fold increase in the odds of mortality on their hosts. Although this survival cost does not differ significantly across monogamous, polygynous and promiscuous mating systems, females incur a greater survival cost than males in monogamous species, whereas males incur a greater survival cost than females in polygynous and promiscuous species. Our results support the idea that mating systems shape the relative extent to which males and females invest in reproduction at the expense of defence against parasites.

Mating System of the Snapping Shrimp Synalpheus brevicarpus (Caridea, Alpheidae) Inhabiting Sponges Dysidea sp. (Demospongiae).

AbstractThe lifestyle of symbiotic species in the genus Synalpheus can vary from pair living to eusocial. A pair-living social system commonly implies the adoption of a monogamous mating system. In this study, we used the symbiotic shrimp Synalpheus brevicarpus in association with the sponge Dysidea sp. to test the hypothesis that heterosexual pairs of symbiotic shrimps can adopt a monogamous mating system when living in association with a morphologically complex host. We collected a total of 40 sponges, which were inhabited by 76 shrimps: 41 males, 33 females, and 2 juveniles. Synalpheus brevicarpus is sexually dimorphic, with males displaying proportionately larger weaponry (snapping claws) and a smaller average body size than females. Sponges were more often inhabited by a pair of heterosexual shrimps than expected by chance. Larger sponges were inhabited by more than one pair of shrimps in which the sex ratio did not differ significantly from 1∶1. Pairs of heterosexual shrimps were recorded, with females carrying embryos in all stages of embryonic development. Our results indicate that S. brevicarpus is a pair-living shrimp with a monogamous social and mating system that may also guard spaces or areas within its sponge host. Our hypothesis of monogamy is supported by the observations on pair living, sex ratio, and sexual dimorphism in body size and weaponry in this species.

Mechanisms that ensure monogamous mating in Saccharomyces cerevisiae.

Haploid cells of the budding yeast Saccharomyces cerevisiae communicate using secreted pheromones and mate to form diploid zygotes. Mating is monogamous, resulting in the fusion of precisely one cell of each mating type. Monogamous mating in crowded conditions, where cells have access to more than one potential partner, raises the question of how multiple-mating outcomes are prevented. Here we identify mutants capable of mating with multiple partners, revealing the mechanisms that ensure monogamous mating. Before fusion, cells develop polarity foci oriented toward potential partners. Competition between these polarity foci within each cell leads to disassembly of all but one focus, thus favoring a single fusion event. Fusion promotes the formation of heterodimeric complexes between subunits that are uniquely expressed in each mating type. One complex shuts off haploid-specific gene expression, and the other shuts off the ability to respond to pheromone. Zygotes able to form either complex remain monogamous, but zygotes lacking both can re-mate.

Effect of Rotation Number on Parameter of Fertilisation of Poligamously Mating Domestic Pigeons (Columba Livia L.)

In the rotation method to break the monogamous mating habits, 24 male and 24 female racing pigeons were used. They were didved into three groups, each consisting of 8 male and 8 feamle pigeons put separated in three huts A, B, C. At the first rotation (second mating) female pigeons of hut a were moved to hut B; all female pigeons of hut B to hut C while female pigeons of hut C took the place of female pigeons of hut A. The females were rotated sequentially three times and the male pigeons three times also. With regard to percentage fertilization and productivity rate, there were no significant differences at 5% level (P>0.05) among the rotations. The regression (b - 0.72%) of percentage fertilization on rotation number and the regression (b - 0.89%) of productivity rate on rotation number were found not to be significantly different from zero. The correlation coefficients attached to both regressions (r 0.41 and r -0.34) respectively were not significant at 5% level. The rotational mating method did not depress the parameters of fertility tested and is, as such a useful tool to induce pigeons to sequential polygamy.

Sex and age-specific survival and life expectancy in a free ranging population of Indri indri (Gmelin, 1788)

The critically endangered indri (Indri indri) is the largest extant lemur species and its population size is projected to decline over the next three generations due to habitat loss, hunting and climate change. Accurate information on the demographic parameters driving the population dynamics of indri is urgently needed to help decision-making regarding the conservation of this iconic species. We monitored and followed the life histories of 68 individually recognizable indris in 10 family groups in the Maromizaha New Protected Area (Madagascar) for 12 years. We estimated age and sex-specific survival trajectories using a Bayesian hierarchical survival model and found that the survival curves for male and female indris show a similar pattern, consistent with what found typically in primates; i.e., a high infant mortality rate which declines with age in the juvenile phase and increases again for adults. Also, life expectancies at 2 years of age (e2), were found to be similar between the sexes (e2 females = 7.8 years; e2 males = 7.5 years). We suggest that the lack of strong differences in the survival patterns for male and female indris are related to the strictly monogamous mating system and the lack of sexual dimorphism in this species. Our study provides, for the first time, robust estimates for demographic parameters of indris and one of the very few datasets on survival trajectories available for primates.

Observations of life history traits of Typton carneus Holthuis, 1951 (Caridea, Palaemonidae): a poorly known sponge-dwelling shrimp

The objective of this study was to investigate some life history traits of the palaemonid shrimp Typton carneus collected from a reef in northeastern Brazil. Samples of the sponges Amphimedon compressa, A. viridis, Desmapsamma anchorata, Dysidea etheria, Haliclona implexiformis and Tedania ignis were analyzed and shrimps were removed from them. A total of 41 individuals were found in Te. ignis, three in H. implexiformis and one in D. etheria; the latter two sponges are new records of sponge hosts for Ty. carneus. Of the specimens associated with Te. ignis, 24 were males, 10 ovigerous females, six non-ovigerous females and one juvenile male. Fecundity varied between 19 to 56 eggs (37 ± 14) per female, and the mean egg volume was 0.033 ± 0.010 mm³. Eleven heterosexual pairs were obtained. Characteristics of the pairs suggest a monogamous mating system for the studied population, such as: the absence of sexual dimorphism in weaponry and body size and presence of paired non-brooding and brooding females carrying eggs in different development stages; and a sex ratio that does not differ from the expected 1:1. However, the lack of size-assortative pairing as well as the low proportion of pairs, compared to solitary individuals, have been observed in polygamous mating systems.

Insight Study on the Comparison between Zinc Oxide Nanoparticles and Its Bulk Impact on Reproductive Performance, Antioxidant Levels, Gene Expression, and Histopathology of Testes in Male Rats.

Background: Despite the beneficial effects of zinc oxide nanoparticles (ZnONPs) on different biomedical applications, including their antioxidant and anti-inflammatory ones, it might have cytotoxic and genotoxic impacts on the male reproductive system. Objective: The current study compares the effect of zinc oxide nanoparticles and their bulk form, at different doses, on male rats’ reproductive performance, testicular antioxidants, gene expression, and histopathology. Materials and Methods: Thirty male rats were randomly allocated equally in five groups. The control one was injected with Tween 80 (10%). The zinc oxide nanoparticle (ZnONP) groups received ZnONPs < 50 nm, specifically, 5 mg/kg (ZnONP-1) and 10 mg/kg (ZnONP-2). The bulk zinc oxide (BZnO) groups were administered 5 mg/kg (BZnO-1) and 10 mg/kg (BZnO-2), correspondingly. Rats were injected intraperitoneally with the respected materials, twice/week for eight consecutive weeks. Finally, the male rats’ sexual behavior and their pup’s performance were determined in a monogamous mating system. Rats were then anesthetized and sacrificed for semen characteristics evaluation and tissue collection for antioxidant and hormones analysis, gene expression, and histopathological examination. Results: It was shown that ZnONP-1 improved sexual behavior, semen characteristics, and pup’s performance compared to its bulk form. Similarly, the testicular antioxidants activity, glutathione (GSH), and superoxide dismutase (SOD) increased with a decrease in the malonaldehyde (MDA), interleukin 6 (IL-6), and tumor necrosis factor (TNF-α) levels. It also improves the reproductive hormone levels and mRNA expression of different steroidogenesis-associated genes and anti-apoptotic genes. Conclusion: It can be concluded that zinc oxide nanoparticles, administered at 5 mg/kg, had the most beneficial effect on male reproductive performance, while 10 mg/kg could have a detrimental effect.

Shorebird Reproductive Response to Exceptionally Early and Late Springs Varies Across Sites in Arctic Alaska

While increases in overall temperatures are widely reported in the Arctic, large inter-annual variation in spring weather, with extreme early and late conditions, is also occurring. Using data collected from three sites in Arctic Alaska, we explored how shorebird breeding density, nest initiation, nest synchrony, nest survival, and phenological mismatch varied between two exceptionally early (2015 and 2016) and late (2017 and 2018) springs. We assessed these differences in the context of long-term data from each site and whether species exhibited conservative or opportunistic reproductive strategies. Conservative shorebirds typically display nest-site fidelity and territoriality, consistent population densities, relatively even individual spacing, and monogamous mating systems with bi-parental incubation. In contrast, opportunistic shorebirds display the opposite traits, and a polygamous mating system with uniparental incubation. In this study, we evaluated 2,239 nests from 13 shorebird species, 2015–2018, and found that shorebirds of both strategies bred earlier and in higher numbers in early, warm springs relative to historic levels (based on 3,789 nests, 2005–2014); opposite trends were observed in late springs. In early springs, nests were initiated less synchronously than in late springs. Nest survival was unrelated to spring type, but was greater in earlier laid nests overall. Invertebrate food resources emerged earlier in early springs, resulting in a greater temporal asynchrony between invertebrate emergence and chick hatching in early than late springs. However, invertebrate abundance was quite variable among sites and years regardless of spring type. Overall, our results were generally consistent with predicted relationships between spring conditions and reproductive parameters. However, we detected differences among sites that could not be explained by other ecological factors (e.g., predators or alternative prey). Differences in shorebird community composition and other subtler methodological/ecological differences among sites highlight the difficulty of understanding the complex nature of these ecological systems and the importance of evaluating questions at multiple sites across multiple years. Our study demonstrates that shorebirds exhibit a high degree of behavioral flexibility in response to variable Arctic conditions, but whether this flexibility is enough to allow them to optimally track changing environmental conditions or if evolutionary adjustments will be necessary is unknown.

Cover Caption

Behavioral strategies and mechanisms by which some animals maintain monogamous mating systems are not well understood. Here, using the bark beetle Dendroctonus valens, we deciphered cues contributing in monogamy. Field and laboratory observations suggest the bark beetle commonly form permanent bonds. A second female was shown to perceive the resident's presence by physical contact and to form a separated gallery. During gallery constructing, females released acoustic signals and volatiles to attract males. When a male joined a female, the male emitted aggressive sounds and volatiles to deter other males. Thus, D. valens has evolved multifaceted mechanisms contributing to single pairings that confer benefits to both sexes (see pages 1285‐1297). Photo provided by Zhu‐Dong Liu.

Genetic parameter and genetic trend estimates for reproductive traits in Wistar rats

ABSTRACT The aim of this study was to estimate genetic parameters and genetic trends for reproductive traits in Wistar rats. A total of 1,167 data records from 283 females over six generations of monogamous mating pairs was used. Heritability and genetic correlation were estimated through Bayesian inference and genetic trends were calculated by linear regression of breeding values over generations. Heritability estimates for litter size at birth (LS), calving interval (CI), pup mortality (PM) and maternal cannibalism (CAN) presented low magnitude, ranging from 0.01 to 0.13. CAN presented high and positive genetic correlation with LS and PM (0.77 and 0.78, respectively). On the other hand, all the other estimated genetic correlations were not significant. Genetic trend was positive for LS (+0.0900 pups per generation), and negative for PM and CAN (-1.0085 and -0.5217 pups per generation, respectively). For CI the genetic trend was not significant. It is recommended to increase selection intensity on dams in this Wistar rat population in order to accelerate the genetic progress.

Simplified Method to Measure Mouse Fertility.

Estimating breeding performance from mouse mating trials has focused on lifetime mating trials, which are too slow and costly for characterizing the many novel genetic mouse lines produced in fertility research, an underpinning of reproductive pathophysiology research. This study introduces the fertility index, defined as the slope of the regression of cumulative number of pups produced by a female over elapsed time in a monogamous mating trial. By using a robust resampling technique, the Theil-Sen estimator (widely available in free or niche statistical software), to estimate the fertility index, the present study of 410 mating trials of mice from 7 genotypes lasting a median of 10 litters shows that it is possible to estimate the fertility index reliably over as few as 4 litters.

Minding your own business: low pair cohesion in a territorial, monogamous mammal

Social interactions among individuals play a central role in behavioural ecology and studying cohesion of monogamous pairs is important to understand their social relationships. Here, we tested five hypotheses to investigate patterns of pair cohesion in an obligate monogamous mammal, the Eurasian beaver, Castor fiber. We hypothesized that pair cohesion is related to the spatial structure of the territory, territory defence, resource competition, offspring provisioning and the age difference between pair members. We analysed GPS data of 14 beaver pairs and calculated the distance between pair members, and the proportion of territory and core area overlap. While overall territory size was similar between partners and overlap was high, the distance between pair members was large, averaging 500 m, and increased with increasing territory size. Moreover, the proportion of core area overlap was comparatively low and decreased with territory size, also indicating low pair cohesion. Pair members were closest at the beginning and end of their nightly activity periods, suggesting that variation in pair cohesion was caused by the spatial structure of territories with the lodge serving as a central place. We found no support for the other hypotheses, but the overall low pair cohesion might nevertheless serve to increase territory defensibility and reduce intrapair competition for resources. Ultimately, low pair cohesion might be caused by the obligate monogamous mating system of beavers, leading to the defence of spatially structured territories rather than the defence of a partner.

Mating patterns influence vulnerability to the extinction vortex.

Earth's biodiversity is undergoing mass extinction due to anthropogenic compounding of environmental, demographic and genetic stresses. These different stresses can trap populations within a reinforcing feedback loop known as the extinction vortex, in which synergistic pressures build upon one another through time, driving down population viability. Sexual selection, the widespread evolutionary force arising from competition, choice and reproductive variance within animal mating patterns could have vital consequences for population viability and the extinction vortex: (a) if sexual selection reinforces natural selection to fix 'good genes' and purge 'bad genes', then mating patterns encouraging competition and choice may help protect populations from extinction; (b) by contrast, if mating patterns create load through evolutionary or ecological conflict, then population viability could be further reduced by sexual selection. We test between these opposing theories using replicate populations of the model insect Tribolium castaneum exposed to over 10years of experimental evolution under monogamous versus polyandrous mating patterns. After a 95-generation history of divergence in sexual selection, we compared fitness and extinction of monogamous versus polyandrous populations through an experimental extinction vortex comprising 15 generations of cycling environmental and genetic stresses. Results showed that lineages from monogamous evolutionary backgrounds, with limited opportunities for sexual selection, showed rapid declines in fitness and complete extinction through the vortex. By contrast, fitness of populations from the history of polyandry, with stronger opportunities for sexual selection, declined slowly, with 60% of populations surviving by the study end. The three vortex stresses of (a) nutritional deprivation, (b) thermal stress and (c) genetic bottlenecking had similar impacts on fitness declines and extinction risk, with an overall sigmoid decline in survival through time. We therefore reveal sexual selection as an important force behind lineages facing extinction threats, identifying the relevance of natural mating patterns for conservation management.

Group structure and putative mating system of three hermaphrodite gobiid fish, Priolepis akihitoi, Trimma emeryi, and Trimma hayashii (Actinopterygii: Gobiiformes)

We investigated the mating system of three sex changing gobiid fishes: Priolepis akihitoi, Trimma emeryi, and Trimma hayashii by underwater observation or specimen collection. P. akihitoi were found in pairs or were solitary. As the pair bond persisted for at least two months, and pair individuals seemed to mate with each other repeatedly, a monogamous mating system was suggested in P. akihitoi. In contrast, the harem-like group (living in a group composed of one largest male and some smaller females and/or immature individuals) of T. hayashii and T. emeryi suggested that these species have harem polygyny.

Steroidal regulation of the aromatase gene and dominant behavior in the false clown anemonefish Amphiprion ocellaris

The interaction between cortisol and aromatase may be a critical factor in sex determination or sex changes in teleost species. High cortisol concentrations inhibit transcription of the aromatase gene, resulting in masculinization. Anemonefish (Amphiprion spp.) are socially controlled, protandrous sex-changing fish, with a monogamous mating system. Females are the largest and most dominant members of social groups, second-ranking individuals become males, and other individuals remain nonreproductive. Individuals that change from male to female display high plasma cortisol concentrations, contrary to a previously established mechanism of masculinization. We investigated the effects of exogenous steroids on gene expression in the brain and gonads and on the occurrence of dominant behavior in the sexually immature ambisexual false clown anemonefish Amphiprion ocellaris. Transcription of the cyp19a1a aromatase gene increased in the gonads of estradiol pellet-fed fish but decreased in cortisol pellet-fed fish. Dominant behavior intensity significantly increased in estradiol pellet-fed fish, but decreased in cortisol pellet-fed fish. Methyltestosterone had no apparent effect on gene transcription or behavior. These results suggest that the masculinization mechanism induced by cortisol is common among teleost species, including protandrous sex-changing fish, and that behavioral changes induced by steroid supplements reflect social status in A. ocellaris.

Withdrawn: Mating system drives the mate selection in aphidophagous ladybird, Menochilus sexmaculatus.

Mate competition and selection of mates is strongly influenced by the organism's mating system. Earlier it was considered the monogamous matings provide more benefits as compared to polygamous matings. However, later studies have proven that in polygamous system, females gain resources and, genetic benefits from the males, thereby indulging in multiple mating, leading males to access maximum females. In ladybird, Menochilus sexmaculatus, mate choice has been studied on several pre-and postcopulatory factors. However, mate choice on the basis of mating system is still remains untouched. In the present study, we hypothesised that mating system modulates the mate selection of beetles either in isolation or in combination. Adults were isolated on the basis of different mating systems and then males and females were subjected to mate choice trials. In second experiment we have also included relatedness as combining factor and its effect was observed on mate choice. This effect of mating system was not confined only to mate choice but was also observed on mating and reproductive parameters.