Group mating in Cretaceous water striders.

Fossilized mating insects are irreplaceable material for comprehending the evolution of the mating behaviours and life-history traits in the deep-time record of insects as well as the potential sexual conflict. However, cases of mating pairs are particularly rare in fossil insects, especially aquatic or semi-aquatic species. Here, we report the first fossil record of a group of water striders in copulation (including three pairs and a single adult male) based on fossils from the mid-Cretaceous of northern Myanmar. The new taxon, Burmogerris gen. nov., likely represents one of the oldest cases of insects related to the marine environment, such as billabongs formed by the tides. It exhibits conspicuous dimorphism associated with sexual conflict: the male is equipped with a specialized protibial comb as a grasping apparatus, likely representing an adaptation to overcome female resistance during struggles. The paired Burmogerris show smaller males riding on the backs of the females, seemingly recording a scene of copulatory struggles between the sexes. Our discovery reveals a mating system dominated by males and sheds light on the potential sexual conflicts of Burmogerris in the Cretaceous. It indicates the mating behaviour remained stable over long-term geological time in these water-walking insects.

Intra-horn insemination in the alpaca Vicugna pacos: Copulatory wounding and deep sperm deposition.

Alpacas (Vicugna pacos) are reported to be the rare mammal in which the penis enters the uterus in mating. To date, however, only circumstantial evidence supports this assertion. Using female alpacas culled for meat, we determined that the alpaca penis penetrates to the very tips of the uterine horns, abrading the tract and breaking fine blood vessels. All female alpacas sacrificed one hour or 24 hours after mating showed conspicuous bleeding in the epithelium of some region of their reproductive tract, including the hymen, cervix and the tips of each uterine horn, but typically not in the vagina. Unmated females showed no evidence of conspicuous bleeding. Histological examination of mated females revealed widespread abrasion of the cervical and endometrial epithelium, injuries absent in unmated females. Within one hour of mating, sperm were already present in the oviduct. The male alpaca's cartilaginous penis tip with a hardened urethral process is likely responsible for the copulatory abrasion. The entire female reproductive tract interacts with the penis, functioning like a vagina. Alpacas are induced ovulators, and wounding may hasten delivery of the seminal ovulation-inducing factor beta-NGF into the female's blood stream. There is no evidence of sexual conflict in copulation in alpaca, and thus wounding may also be one of a variety of mechanisms devised by mammals to induce a beneficial, short-term inflammatory response that stimulates blastocyst implantation, the uterine remodeling associated with placental development, and thus the success of early pregnancy.

An automatic system for recognizing fly courtship patterns via an image processing method.

Fruit fly courtship behaviors composed of a series of actions have always been an important model for behavioral research. While most related studies have focused only on total courtship behaviors, specific courtship elements have often been underestimated. Identifying these courtship element details is extremely labor intensive and would largely benefit from an automatic recognition system. To address this issue, in this study, we established a vision-based fly courtship behavior recognition system. The system based on the proposed image processing methods can precisely distinguish body parts such as the head, thorax, and abdomen and automatically recognize specific courtship elements, including orientation, singing, attempted copulation, copulation and tapping, which was not detectable in previous studies. This system, which has high identity tracking accuracy (99.99%) and high behavioral element recognition rates (> 97.35%), can ensure correct identification even when flies completely overlap. Using this newly developed system, we investigated the total courtship time, and proportion, and transition of courtship elements in flies across different ages and found that male flies adjusted their courtship strategy in response to their physical condition. We also identified differences in courtship patterns between males with and without successful copulation. Our study therefore demonstrated how image processing methods can be applied to automatically recognize complex animal behaviors. The newly developed system will largely help us investigate the details of fly courtship in future research.

Eye-tracking does not reveal early attention processing of sexual copulatory movement in heterosexual men and women.

Men and women respond differently when presented with sexual stimuli. Men's reaction is gender-specific, and women's reaction is gender-nonspecific. This might be a result of differential cognitive processing of sexual cues, namely copulatory movement (CM), which is present in almost every dynamic erotic stimulus. A novelty eye-tracking procedure was developed to assess the saliency of short film clips containing CM or non-CM sexual activities. Results from 29 gynephilic men and 31 androphilic women showed only small and insignificant effects in attention bias and no effects in attentional capture. Our results suggest that CM is not processed differently in men and women and, therefore, is not the reason behind gender-nonspecific sexual responses in women.

Mating dynamics of a sperm-limited drosophilid, Zaprionus indianus.

When males have large sperm, they may become sperm limited and mating dynamics may be affected. One such species is Zaprionus indianus, a drosophilid that is an introduced pest species in the Americas. We examined aspects of mating behavior in Z. indianus to determine the senses necessary for mating and measure female and male remating habits. We found that vision is necessary for successful copulation, but wings, which produce courtship song, are not needed. Males need their foretarsi to successfully copulate and although the foretarsi may be needed for chemoreception, their role in hanging on to the female during copulation may be more important for successful mating. Females that mate once run out of sperm in approximately five days, although mating a second time greatly increases offspring production. Females do not seem to exert pre-mating choice among males with respect to mating with a familiar versus a novel male. Males are not capable of mating continuously and fail to produce offspring in many copulations. Overall, females of this species benefit from polyandry, providing an opportunity to study sexual selection in females. In addition, the dynamics of male competition for fertilizing eggs needs to be studied.

Sniffing behavior of semi free-ranging Barbary macaques (Macaca sylvanus).

Olfaction is one of the evolutionarily oldest senses and plays a fundamental role in foraging and social interactions across mammals. In primates, the role of olfaction is now well recognized, but better investigated in strepsirrhine and platyrrhine primates than in catarrhines. We observed the sniffing behavior of semi-free ranging Barbary macaques, Macaca sylvanus, at Affenberg Salem, Germany, to assess how frequently macaques sniff and in which contexts, and how sniffing is affected by sex and age. Focal observations of 24 males and 24 females aged 1-25 years showed that Barbary macaques sniffed, on average, 5.24 times per hour, with more than 80% of sniffs directed at food. Irrespective of the context, younger individuals sniffed more often than older ones. Females' sniffs were more often directed at food than male sniffs, while males sniffed more often than females in a social context. Sniffs at conspecifics occurred primarily in a sexual context, with 70% of social sniffs directed at female anogenital swellings performed by males. Of the observed 176 anogenital inspections, 51 involved sniffing of the swelling. Olfactory inspections were followed by copulation significantly less often than merely visual inspections, suggesting that anogenital odors may play a role in male mating decisions, but the role of olfaction in sexual interactions warrants further investigations. In sum, results show that Barbary macaques routinely use olfaction during feeding, but also in a socio-sexual context, corroborating the relevance of the olfactory sense in the lives of catarrhine primates.

Long-term neuropeptide modulation of female sexual drive via the TRP channel in Drosophila melanogaster.

Connectomics research has made it more feasible to explore how neural circuits can generate multiple outputs. Female sexual drive provides a good model for understanding reversible, long-term functional changes in motivational circuits. After emerging, female flies avoid male courtship, but they become sexually receptive over 2 d. Mating causes females to reject further mating for several days. Here, we report that pC1 neurons, which process male courtship and regulate copulation behavior, exhibit increased CREB (cAMP response element binding protein) activity during sexual maturation and decreased CREB activity after mating. This increased CREB activity requires the neuropeptide Dh44 (Diuretic hormone 44) and its receptors. A subset of the pC1 neurons secretes Dh44, which stimulates CREB activity and increases expression of the TRP channel Pyrexia (Pyx) in more pC1 neurons. This, in turn, increases pC1 excitability and sexual drive. Mating suppresses pyx expression and pC1 excitability. Dh44 is orthologous to the conserved corticotrophin-releasing hormone family, suggesting similar roles in other species.

Sox21b underlies the rapid diversification of a novel male genital structure between Drosophila species.

The emergence and diversification of morphological novelties is a major feature of animal evolution.1,2,3,4,5,6,7,8,9 However, relatively little is known about the genetic basis of the evolution of novel structures and the mechanisms underlying their diversification. The epandrial posterior lobes of male genitalia are a novelty of particular Drosophila species.10,11,12,13 The lobes grasp the female ovipositor and insert between her abdominal tergites and, therefore, are important for copulation and species recognition.10,11,12,14,15,16,17 The posterior lobes likely evolved from co-option of a Hox-regulated gene network from the posterior spiracles10 and have since diversified in morphology in the D. simulans clade, in particular, over the last 240,000 years, driven by sexual selection.18,19,20,21 The genetic basis of this diversification is polygenic but, to the best of our knowledge, none of the causative genes have been identified.22,23,24,25,26,27,28,29,30 Identifying the genes underlying the diversification of these secondary sexual structures is essential to understanding the evolutionary impact on copulation and species recognition. Here, we show that Sox21b negatively regulates posterior lobe size. This is consistent with expanded Sox21b expression in D. mauritiana, which develops smaller posterior lobes than D. simulans. We tested this by generating reciprocal hemizygotes and confirmed that changes in Sox21b underlie posterior lobe evolution between these species. Furthermore, we found that posterior lobe size differences caused by the species-specific allele of Sox21b significantly affect copulation duration. Taken together, our study reveals the genetic basis for the sexual-selection-driven diversification of a novel morphological structure and its functional impact on copulatory behavior.

Contrasting the form and strength of pre- and postcopulatory sexual selection in a flatworm.

Sexual traits may be selected during multiple consecutive episodes of selection, occurring before, during, or after copulation. The overall strength and form of selection acting on traits may thus be determined by how selection (co-)varies along different episodes. However, it is challenging to measure pre- and postcopulatory phenotypic traits alongside variation in fitness components at each different episode. Here, we used a transgenic line of the transparent flatworm Macrostomum lignano expressing green fluorescent protein (GFP) in all cell types, including sperm cells, enabling in vivo sperm tracking. We assessed the mating success, sperm-transfer efficiency, and sperm fertilizing efficiency of GFP(+) focal worms in which we measured 13 morphological traits. We found linear selection on sperm production rate arising from pre- and postcopulatory components and on copulatory organ shape arising from sperm fertilizing efficiency. We further found nonlinear (mostly concave) selection on combinations of copulatory organ and sperm morphology traits arising mostly from sperm-transfer efficiency and sperm fertilizing efficiency. Our study provides a fine-scale quantification of sexual selection, showing that both the form and strength of selection can change across fitness components. Quantifying how sexual selection builds up along episodes of selection allows us to better understand the evolution of sexually selected traits.

Intraspecific body size variation and allometry of genitalia in the orb-web spider-Argiope lobata.

The current consensus is that sexual selection is responsible for the rapid and diverse evolution of genitalia, with several mutually exclusive mechanisms under debate, including non-antagonistic, antagonistic and stabilizing mechanisms. We used the orb-web spider, Argiope lobata (Araneidae), as a study model to quantify the allometric relationship between body size and genitalia, and to test for any impact of genital structures on male mating success or outcome in terms of copulation duration, leg loss or cannibalism. Our data do not support the 'one-size-fits-all' hypothesis that predicts a negative allometric slope between genitalia and body size. Importantly, we measured both male and female genitalia, and there was no sex specific pattern in allometric slopes. Unexpectedly, we found no predictor for reproductive success as indicated by copulation duration, cannibalism, and leg loss.

Copulation of Ixodes ricinus males and females on the host and its potential impact on pathogen transmission.

INTRODUCTION AND OBJECTIVE: The common tick Ixodes ricinus is one of Europe's most important vectors of tick-borne diseases. The increased risk of attacks by this tick suggests the need for identification of factors contributing to the transmission of tick-borne pathogens, and the routes of pathogen circulation in nature. MATERIAL AND METHODS: Polymerase chain reaction was used to investigate the prevalence of four pathogens, i.e. Borrelia burgdorferi s.l. (Bb), Anaplasma phagocytophilum (Ap), Babesia spp. (Bs), and Bartonella spp. (Ba) in I. ricinus females and males mating on dogs in south-central Poland. RESULTS: The study revealed the presence of three pathogens: Bb, Ap, and Bs in 9.4%, 5.4%, and 5.4% of all I. ricinus adults in copula, respectively. Co-infection with two pathogens was detected in one tick specimen. Borrelia burgdorferi spirochetes were isolated in two females and two males in copula, but the sexual transfer of the spirochetes between these specimens could not be clearly confirmed. CONCLUSIONS: By increasing the feeding dynamics in females, the copulation of I. ricinus males with females attached to the host's skin may stimulate pathogen replication in tick tissues and migration from the gut to the salivary glands. Further investigations of the I. ricinus copulation on the host on female feeding and pathogen transmission may contribute to the elucidation of the eco-epidemiology of tick-borne diseases transmitted by this tick species.

Mating without intromission in a bat.

Copulatory behaviours stand as cornerstones of sexual selection, yet they remain mysterious in many species. Because of their nocturnal and elusive lifestyle, the copulatory behaviours of bats have been mostly overlooked1. Several aspects of bat reproduction differ from other mammals (e.g. prolonged sperm storage2, delayed development3). Here, we show that in serotine bats (Eptesicus serotinus) the penis is used as a 'copulatory arm' rather than an intromittent organ, revealing a novel copulatory behaviour in mammals.

The effect of cigarette smoke extract exposure on the size and sexual behaviour of Drosophila melanogaster.

Drosophila melanogaster is a widely used animal model in human diseases and to date it has not been applied to the study of the impact of tobacco use on human sexual function. Hence, this report examines the effects of different concentrations of cigarette smoke extract (CSE) exposure on the size and sexual behavior of D. melanogaster. Wild-type flies were held in vials containing CSE-infused culture media at concentrations of 10%, 25%, and 50% for three days, and their offspring were reared under the same conditions before measuring their body size and mating behavior. CSE exposure during development reduced the tibia length and body mass of emerging adult flies and prolonged the time required for successful courtship copulation success, while courtship behaviors (wing extension, tapping, abdomen bending, attempted copulation) remained largely unchanged. Our findings indicate that CSE exposure negatively affects the development of flies and their subsequent reproductive success. Future experiments should investigate the CSE effect on male female fertility.

Social opportunities and mate preference improve breeding success in Caribbean iguanas.

Conservation breeding of West Indian rock iguanas (Cyclura) has met with limited success historically. Many facilities witness high levels of aggression and mate incompatibility resulting in failed breeding introductions which often require animals to be separated. This may be due, in part, to lack of knowledge of how mate familiarity and preference affect reproductive outcomes in these species. We investigated whether social exposure during the pre-breeding season influenced copulation success, egg production, and breeding behaviors. Additionally, we examined whether mate preference, as determined by pre-mating dichotomous choice tests, increased these reproductive outcomes. Female rock iguanas that were socialized with males prior to breeding opportunities copulated with familiar males for longer periods of time than females that were not socialized. Socialization opportunities did not alter male reproductive success measurements or breeding behavior. Female rock iguanas introduced for mating to their preferred partners had a higher probability of successful copulations, higher average number of copulations, and less resting behavior during introductions than females mated to non-preferred males. Male mate preference had no effect on reproductive success measurements during mating introductions. These results indicate that socializing animals and providing mate choice opportunities increase breeding success of rock iguanas under managed care.

The cranial apparatus glands of the canthariphilous Pyrochroa coccinea (Coleoptera: Pyrochroidae: Pyrochroinae), and their implications in sexual behaviour.

Some Pyrochroidae species are known as "canthariphilous" for their attraction to cantharidin (CTD), a toxic terpene with anti-predatory effects, produced in nature by only two beetle families (Meloidae and Oedemeridae). It has been demonstrated that males of Neopyrochroa flabellata ingesting CTD are positively selected by females. Indeed, the compound is re-emitted from a glandular cranial apparatus as secretions that are licked up by females during courtship behaviour, inducing copulation. Herein, we provide the first description of the glands associated to the cranial apparatus of male Pyrochroinae using the European species Pyrochroa coccinea as a model. Morphological analyses show that the cranial apparatus consists of a concave pit lined with short setae retaining secretions emitted through numerous glandular pores. Ultrastructural investigations reveal the presence of two different class 3 glands (Gl.A and Gl.B), intermixed at the level of the pit but exhibiting distinct features. Gl.A are mainly characterised by short conducting canals, rounded nuclei and electrondense vesicles while Gl.B are characterised by long conducting canals, irregular nuclei, vesicles containing a particulate substance and a multifolded plasma membrane. Observations of sexual behaviour are also reported for P. coccinea and compared to N. flabellata, confirming the involvement of cranial apparatus secretions in courtship behaviour.

Sexual behavior and drive: Is it all in your brain?

Male mating behavior involves a series of behaviors aimed to recognize, approach and mate with a female. A new study in mice reveals an elaborated neural circuit that drives both sexual recognition, sexual reward, and copulatory behavior.

Multiple mechanisms for inbreeding avoidance used simultaneously in a wild ape.

Mating with close kin can have considerable negative fitness consequences, which are expected to result in selective pressure for inbreeding avoidance mechanisms, such as dispersal, mate choice and post-copulatory biases. Captive studies have suggested that inbreeding avoidance through mate choice is far less widespread than expected and may be absent where other mechanisms already limit inbreeding. However, few studies have examined multiple mechanisms of inbreeding avoidance simultaneously, particularly in the wild. We use 13 years of detailed dispersal, copulation and paternity data from mountain gorillas to examine inbreeding avoidance. We find that partial dispersal of both sexes results in high kinship in multimale groups, but that copulations between close kin occur 40% less than expected. We find strong kin discrimination in mate choice, with significant avoidance of maternal kin but more limited avoidance of paternal kin. We find no evidence for post-copulatory inbreeding avoidance. Our analyses support familiarity-based mechanisms of kin identification and age-based avoidance that limits mating between fathers and daughters in their natal group. Our findings demonstrate that multiple complementary mechanisms for inbreeding avoidance can evolve in a single species and suggest that inbreeding avoidance through mate choice may enable more flexible dispersal systems to evolve.

Copulatory courtship, body temperature and infection in Tenebrio molitor.

Ectothermic animals can raise their body temperature under varying circumstances. Two such situations occur during sexual activity (as metabolic rate rises during copulatory movements) and during infection (to control pathogens more effectively). We have investigated these two situations using Tenebrio molitor males. We recorded the copulatory courtship behavior of sick (= infected with Metharizium robertsii fungus) vs healthy males and its link with body temperature. We predicted a positive relation between copulatory courtship (measured as antennal and leg contact behavior) and body temperature, especially in sick males. We found that the intensity of contacts correlated with increased body temperature in sick males. Previous studies in this species indicated that partner females laid fewer eggs after mating with sick males above a certain male body temperature threshold. Thus, our present findings suggest that females may detect male infection via intensity of antennal-mediated courtship, body temperature or their combination. If this is the case, females may assess male cues directly related to health status such as body temperature.

Mating behavior of Pseudococcus calceolariae and Pseudococcus longispinus (Hemiptera: Pseudococcidae): are asexual reproduction and hybridization possible?

The study of insect reproduction is important from both basic and applied perspectives, particularly in mealybugs (Hemiptera: Pseudococcidae), because of the diversity of reproduction modes and also because they are important agricultural pests. Sex pheromone control strategies are currently being developed for many species. Pseudococcus calceolariae (Maskell) and Pseudococcus longispinus (Targioni Tozzetti) are closely related species that often coexist in the same host plant. In this study, mating behavior, the possible occurrence of asexual reproduction, and hybridization between them were investigated. We confirmed that both species did not show asexual reproduction and required the presence of a male to reproduce. When couples of the same species were put together, males had a highly stereotyped mating behavior, and females showed an active role in mating success by accepting or rejecting males with abdominal movements. In hybridization trials, no progeny was obtained for any of the interspecific combinations. Moreover, in interspecific pairs, males mainly moved randomly in the arena without direct contact with females and females showed no willingness to mate, escape, or not move in the presence of the male. Therefore, courtship and copulation success in both species were directly related to the specificity of the mating pair and, there was no evidence of hybridization. This information is useful for the understanding of reproduction in this family and supports the development of management techniques based on sex pheromones to disrupt reproduction or to monitor these mealybug species populations.