Discriminating Males and Unpredictable Females: Males Bias Sperm Allocation in Favor of Virgin Females

When both sexes mate with multiple partners, theory predicts that males should adjust their investment in ejaculates in response to the risk and/or intensity of sperm competition. Here, we demonstrate that, in the harlequin beetle riding pseudoscorpion, Cordylochernes scorpioides, males use cues deposited on females by previous males to distinguish between virgin, once‐mated, and multiply‐mated females and adjust sperm allocation accordingly. Sperm number declined in direct proportion to the number of previous males, with virgin females receiving nearly three times more sperm than females exposed to three previous males. Given the lack of first‐male sperm precedence in C. scorpioides, this pattern is not consistent with current sperm competition models and appears best explained by a significant risk of wasting ejaculates on deceitful, mated females. In C. scorpioides, males transfer sperm indirectly to females via a stalked spermatophore deposited on the substrate. Mated females often feign sexual receptivity and cooperate throughout mating, only to reject the sperm packet produced by the male. While indirect sperm transfer facilitates a high level of female deceit and control, females of many species are able to influence the number and fate of sperm transferred during copulation and are likely to conceal their sexual unreceptivity to minimize male retaliation. If males cannot accurately assess female receptivity, increased risk of sperm rejection by mated females could outweigh the risk of sperm competition and favor greater sperm allocation to virgin females.     

Pair Swimming and Mutual Partner Guarding in Monogamous Butterflyfish (Pisces,Chaetodontidae): a Joint Advertisement for Territory

The ecology and social systems of Red Sea butterflyfish were studied along the Sinai coast. Distribution, population density and sociography indicate a preponderance of monogamy in all species, independent of reef zonation and seasonal or long-term changes of the reef environment. The social and mating systems are mutual monogamy; partners remain together for up to 6 years. Links between the monogamy and benthic habits of these fish are indicated by their feeding ecology and by a comparison with Indopacific plankton-feeding species, which usually occur in groups. Territories are defended pairwise. Pair partners nearly always remain within visual contact, but a species-typical distance apart. Pair swimming is independent of season or time of day. Experimental partner removals led to speedy replacement of mates. Possible causes of high partner permanency with little partner fidelity are discussed. In good habitats, single territorial adults do not occur. They would be unable to defend and maintain a territory over long periods. While cooperating in defence and maintenance of a territory, each individual can exploit the resources of the territory including availability of a mate. Pair swimming with mutual partner guarding is considered a joint territorial advertisement similar to duetting in birds; it minimizes agonistic interactions between territory holders. As butterflyfish have planktonic larvae without any broodcare, monogamy could not have evolved in response to broodcare activities as in many other vertebrate groups.     

Incubation Feeding and Nest Attentiveness in a Socially Monogamous Songbird: Role of Feather Colouration,Territory Quality and Ambient Environment

Parental investment and environmental conditions determine reproductive success in wild‐ranging animals. Parental effort during incubation, and consequently factors driving it, has profound consequences for reproductive success in birds. The female nutrition hypothesis states that high male feeding enables the incubating female to spend more time on eggs, which can lead to higher hatching success. Moreover, both male and female parental investment during incubation might be signalled by plumage colouration. To test these hypotheses, we investigated relationships between male and female incubation behaviour and carotenoid and melanin‐based plumage colouration, territory quality and ambient temperature in the Great Tit Parus major. We also studied the effect of female incubation behaviour on hatching success. Intensity of male incubation feeding increased with lower temperatures and was higher in territories with more food supply, but only in poor years with low overall food supply. Female nest attentiveness increased with lower temperatures. Plumage colouration did not predict incubation behaviour of either parent. Thus, incubation behaviour of both parents was related mainly to environmental conditions. Moreover, there was no relationship between male incubation feeding, female nest attentiveness and hatching success. Consequently, our data were not consistent with the female nutrition hypothesis.     

Systemic Non-Reproductive Effects of Sex Steroids in Adult Males and Females

Sex steroids are well known for their reproductive actions, however, their roles are not confined to reproduction only and they have been shown to exert wide ranging effects on systemic physiology. Further, the effects of the so-called male and female sex steroids are not limited to their respective genders but they are present in both sexes where they have a significant impact upon systemic functions, reproductive as well as non-reproductive. This work reviews the existing knowledge base and recent reports on the effects of sex steroids on non-reproductive physiology.     

Differential Flower Herbivory and Gall Formation on Males and Females of Neea psychotrioides, a Dioecious Tree

The goal of this study was to determine whether there exists intersexual differences in the degree of herbivore attack on a tropical, dioecious tree. Neea pychotrioides is a Costa Rican tree that experiences at least two types of attack on its reproductive structures: flower herbivory and gall formation on inflorescences. Although female trees were more common than males in the two study populations (overall sex ratio = 1.5 females/male), male flowers were more likely to be eaten by lepidopteran larvae. Similarly, inflorescence-borne, fly-induced galls were more frequent on males. Ten families of insects from three orders (Diptera, Hymenoptera, Lepidoptera) occupied the galls with varying levels of parasitism and hyperparasitism occurring within. Although the sexes were not significantly different in vegetative size, males had larger floral displays (more inflorescences and larger flowers) that may have acted as attractants to herbivores and gallmakers. The results are consistent with the hypothesis that flower damage and the energetic costs of producing galls exert a greater expense to males, ultimately resulting in death, and over time, a skewing of the sex ratio.     

Cognition in Males and Females with Autism: Similarities and Differences

The male bias in autism spectrum conditions (ASC) has led to females with ASC being under-researched. This lack of attention to females could hide variability due to sex that may explain some of the heterogeneity within ASC. In this study we investigate four key cognitive domains (mentalizing and emotion perception, executive function, perceptual attention to detail, and motor function) in ASC, to test for similarities and differences between males and females with and without ASC (n = 128 adults; n = 32 per group). In the mentalizing and facial emotion perception domain, males and females with ASC showed similar deficits compared to neurotypical controls. However, in attention to detail and dexterity involving executive function, although males with ASC showed poorer performance relative to neurotypical males, females with ASC performed comparably to neurotypical females. We conclude that performance in the social-cognitive domain is equally impaired in male and female adults with ASC. However, in specific non-social cognitive domains, performance within ASC depends on sex. This suggests that in specific domains, cognitive profiles in ASC are modulated by sex.     

Physiological Comparison of Concentric and Eccentric Arm Cycling in Males and Females

Lower body eccentric exercise is well known to elicit high levels of muscular force with relatively low cardiovascular and metabolic strain. As a result, eccentric exercise has been successfully utilised as an adaptive stressor to improve lower body muscle function in populations ranging from the frail and debilitated, to highly-trained individuals. Here we investigate the metabolic, cardiorespiratory, and energy costs of upper body eccentric exercise in a healthy population. Seven men and seven women performed 4-min efforts of eccentric (ECC) or concentric (CON) arm cycling on a novel arm ergometer at workloads corresponding to 40, 60, and 80% of their peak workload as assessed in an incremental concentric trial. The heart rate, ventilation, cardiac output, respiratory exchange ratio, and blood lactate concentrations were all clearly greater in CON condition at all of the relative workloads (all p<0.003). Effect size calculations demonstrated that the magnitude of the differences in VO₂ and work economy between the ECC and CON exercise ranged from very large to extremely large; however, in no case did mechanical efficiency (η_MECH) differ between the conditions (all p>0.05). In contrast, delta efficiency (η_Δ), as previously defined by Coyle and colleagues in 1992, demonstrated a sex difference (men>women; p<0.05). Sex differences were also apparent in arteriovenous oxygen difference and heart rate during CON. Here, we reinforce the high-force, low cost attributes of eccentric exercise which can be generalised to the muscles of the upper body. Upper body eccentric exercise is likely to form a useful adjunct in debilitative, rehabilitative, and adaptive clinical exercise programs; however, reports of a shift towards an oxidative phenotype should be taken into consideration by power athletes. We suggest delta efficiency as a sensitive measure of efficiency that allowed the identification of sex differences.     

Males Prefer Small Females in a Dichotomous Choice Test in the Poeciliid Fish Heterandria formosa

Male choice is expected to evolve when females differ in quality, even if male investment in each mating is low. The family Poeciliidae is an example of fishes in which males show little parental investment as they only provide sperm. Up until now, a preference for large females has been found in all species studied. Here we show that unexpectedly, males of the least killifish (Heterandria formosa) prefer to interact with small instead of large females in a dichotomous male choice test, even though large females are more fecund. During a free‐swimming choice experiment, males did not discriminate between females based on their size. We suggest that this unique preference for small females, or the lack of preference for large females, results from strong first male sperm precedence in this species. Smaller females are younger and therefore more likely to be virgin, which probably makes them more profitable mates for males. When presented with a virgin and a mated female of similar size, males showed no preference for either type. This suggests that males do not use pheromone cues to assess female mating status but that they are likely to use female size as a proxy for it.     

Muscle Damage following Maximal Eccentric Knee Extensions in Males and Females

Aim

To investigate whether there is a sex difference in exercise induced muscle damage.

Materials and Method

Vastus Lateralis and patella tendon properties were measured in males and females using ultrasonography. During maximal voluntary eccentric knee extensions (12 reps x 6 sets), Vastus Lateralis fascicle lengthening and maximal voluntary eccentric knee extensions torque were recorded every 10° of knee joint angle (20–90°). Isometric torque, Creatine Kinase and muscle soreness were measured pre, post, 48, 96 and 168 hours post damage as markers of exercise induced muscle damage.

Results

Patella tendon stiffness and Vastus Lateralis fascicle lengthening were significantly higher in males compared to females (p<0.05). There was no sex difference in isometric torque loss and muscle soreness post exercise induced muscle damage (p>0.05). Creatine Kinase levels post exercise induced muscle damage were higher in males compared to females (p<0.05), and remained higher when maximal voluntary eccentric knee extension torque, relative to estimated quadriceps anatomical cross sectional area, was taken as a covariate (p<0.05).

Conclusion

Based on isometric torque loss, there is no sex difference in exercise induced muscle damage. The higher Creatine Kinase in males could not be explained by differences in maximal voluntary eccentric knee extension torque, Vastus Lateralis fascicle lengthening and patella tendon stiffness. Further research is required to understand the significant sex differences in Creatine Kinase levels following exercise induced muscle damage.     

Sexual Imprinting in Zebra-finch Females: Do Females Develop a Preference for Males that Look Like Their Father?

Recently, it has been proposed that through sexual imprinting on their parents, young birds learn to discriminate between males and females. Support for this suggestion was given by a study on zebra-finch males Taniopygia guttata, which showed that males of this species develop a strong sexual preference for mother-like females over father-like females. The present study investigates whether zebra-finch females also develop a sexual preference for mates resembling the opposite-sex parent. The females used had been raised either by normal pairs, by white pairs or by pairs of both morphs. The preferences were tested by confronting these females with normal and white males, both in simultaneous two-stimulus tests and successive one-stimulus tests. In contrast to males, females raised by a pair of mixed-morph parents did not show a preference for mating partners of the opposite-sex-parent's morph. Instead, they showed a preference for males of the mother's plumage type. It is suggested that the difference in which sexual imprinting proceeds in males and females may be related to the different role each sex plays in the pair formation.     

Males of a Strongly Polygynous Species Consume More Poisonous Food than Females

We present evidence of a possible case of self-medication in a lekking bird, the great bustard Otis tarda. Great bustards consumed blister beetles (Meloidae), in spite of the fact that they contain cantharidin, a highly toxic compound that is lethal in moderate doses. In addition to anthelminthic properties, cantharidin was effective against gastrointestinal bacteria that cause sexually-transmitted diseases. Although both sexes consumed blister beetles during the mating season, only males selected them among all available insects, and ingested more and larger beetles than females. The male-biased consumption suggests that males could use cantharidin to reduce their parasite load and increase their sexual attractiveness. This plausibly explains the intense cloaca display males perform to approaching females, and the meticulous inspection females conduct of the male''s cloaca, a behaviour only observed in this and another similar species of the bustard family. A white, clean cloaca with no infection symptoms (e.g., diarrhoea) is an honest signal of both, resistance to cantharidin and absence of parasites, and represents a reliable indicator of the male quality to the extremely choosy females. Our results do not definitely prove, but certainly strongly suggest that cantharidin, obtained by consumption of blister beetles, acts in great bustards as an oral anti-microbial and pathogen-limiting compound, and that males ingest these poisonous insects to increase their mating success, pointing out that self-medication might have been overlooked as a sexually-selected mechanism enhancing male fitness.     

Cyfluthrin and Deltamethrin Induce Changes in the Fat Body Composition of Tenebrio molitor Larvae,Males and Females

The purpose of present study was to analyze the chemical composition of the fat body of insects (Tenebrio molitor) and its eventual variation after the application of insecticides. Using the GC/MS technique, the fat body composition of larvae, males and females was analyzed. The insects were stressed with selected insecticides containing cyfluthrin (Cyflok 50EW) and deltamethrin (K‐othrine) recommended for this species of insect by insecticides producers and farmers. The effect of these two chemicals on the chemical compounds patterns from fat body of insects was compared. Possible differences in the fat body composition between developmental stages and the sex of insects were also compared. Possible identified compounds included amino acids, carboxylic acids, alcohols, sterols, glycerol and urea. Our results show that the composition of lipids was different depending on the stage of development, the insecticide used and the elapsed time since its application.     

Bourgeois Males of the Peacock Blenny,Salaria pavo,Discriminate Female Mimics from Females?

In a Portuguese population of Salaria pavo, two types of reproductively active males occur: large bourgeois males that defend nests and have fully developed secondary sex characters (SSC) and small sneaker males that mimic the females’ morphology and behaviour to approach nests and parasitize fertilizations. These two alternative reproductive tactics are sequential, as sneakers develop into bourgeois males. We investigated whether bourgeois males were able to discriminate between sneakers and females of different sizes. In a laboratory experiment bourgeois males were sequentially presented with a female and a sneaker matched for size. Complementary field observations were conducted on the interactions between females and sneakers with bourgeois males. If bourgeois males discriminated females from sneakers, we predicted that they should direct more aggressive behaviours towards sneakers and more courtship acts towards females. In general, bourgeois males courted and attacked small females and sneakers equally. However, large sneakers were courted less and attacked more than large females. Larger sneakers, beginning to develop SSC, were attacked more and courted less by the bourgeois male than smaller sneakers, and larger females were attacked less and courted more than smaller females. These results strongly suggest that only small female‐mimicking males were able to deceive bourgeois males. In S. pavo, if the sneakers’ fertilization success correlates with their female‐mimicking ability, a fitness decrease with an increasing body size can be predicted.