Steroid hormones, ectoparasites, and color: Sex, species, and seasonal differences in Sceloporus lizards

High-temperature stress will put the thermo-sensitive teleost yellow catfish (Tachysurus fulvidraco) in danger through reducing reproductivity

Recently, concerns for species that sex differentiation is influenced by temperature in the context of global warming have increased because disrupted operational sex ratios could threaten population maintenance. In contrast, little attention has been given to the reproductive ability of populations that experienced elevated temperatures. In this study, we demonstrated that high temperature (HT) would decrease population size via three different aspects of reproductive ability for the first time. We show that, in a thermo-sensitive teleost yellow catfish, a short period of HT (+3 °C) exposure during the critical period of sex differentiation leads to a different percentage of masculinization of XX genotypic females (1-23%) in wet-lab and natural water bodies. Combining the results of gonadal appearance, histology, sperm parameters, and fertilization rate, we found that XX pseudo-males induced by HT display significantly discounted fertility and reproductive performance compared to XY normal males. We demonstrate that the survival of the XY genotype is lower than XX genotype under environmental stress, including HT, hypoxia, and parasite infection, and the differential survival seems unrelated to male-biased sexual size dimorphism. The mathematical model predicts that the phenotypic female percent will be stabilized at 50% and the population will be sustainably maintained when masculinizing force is less than 0.5, while HT will put the population in danger when the masculinizing force exceeds 0.5. However, when we combine the real-world data of reproductive ability and mathematic model, our results suggest the population size decreases and the long-term survival of the studied species are threatened under the projected pace of increasing temperature. These findings will be useful for understanding the long-term effects of increasing temperature on sex ratio, reproduction and population maintenance in teleost.

Parasite-Mediated Mate Preferences in a Cooperatively Breeding Rodent

Females of many species discriminate among males when choosing a mate and this can bear indirect and direct benefits including the avoidance of parasite transmission from infested males. In rodents, this may be mediated by androgen hormones that affect the expression of urinary odors. Female choosiness may also vary with a female’s infestation status, with infested females being less choosy. In the current study we tested the preference of cooperatively breeding highveld mole-rat (Cryptomys hottentotus hottentotus) females for male urinary odors from healthy males and those naturally infested with a cestode (Mathevotaenia sp.). Thirty females (15 healthy, 15 infested) were allowed to explore a Y-maze with urine samples from healthy and infested males and the frequency of entering choice arms and chambers as well as the duration spend with each odor sample was recorded. Infestation status did neither affect male body mass, urinary testosterone, nor cortisol levels or the body condition of females. Although overall female activity was not affected by infestation status, infested females entered choice arms and chambers significantly less frequently than healthy females. Surprisingly, healthy females preferred odors from infested males while the opposite was true for infested females, independent of male hormone levels. As the study species lives in groups that tend to share the same infestation status, we suggest that highveld mole-rat females may exhibit a preference for unfamiliar odors, possibly as an indicator of genetic diversity, rather than discriminate between infestation status of males. Similar mechanisms may also play a role in other social species.

Information out of the blue: phenotypic correlates of abdominal color patches in Sceloporus lizards

Colorful ornaments are important visual signals for animal communication that can provide critical information about the quality of the signaler. In this study, we focused on different color characteristics of the abdominal patches of males of six lizard species from the genus Sceloporus. We addressed three main objectives. First, we examined if size, brightness, saturation, and conspicuousness of these ornaments are indicative of body size, condition, immune function, or levels of testosterone and corticosterone. Second, we evaluated if the distinct components of these abdominal patches (blue or green patches and black stripes) transmit similar information about the signaler, which would support the redundant signal hypothesis, or if these components are related to different phenotypic traits, which would support the multiple message hypothesis. Third, we compared the phenotypic correlates of these ornaments among our six species to understand the degree of conservatism in the signaling patterns or to find species-specific signals. Using data collected from males in natural conditions and a multi-model inference framework, we found that in most species the area of the patches and the brightness of the blue component are positively related to body size. Thus, these color characteristics are presumably indicative of the physical strength and competitive ability of males and these shared signals were likely inherited from a common ancestor. In half of the species, males in good body condition also exhibit relatively larger blue and black areas, suggesting that the expression of these ornaments is condition-dependent. Abdominal patches also provide information about immunocompetence of the males as indicated by different correlations between certain color characteristics and ectoparasite load, counts of heterophils, and the heterophil:lymphocyte ratio. Our findings reveal that area and brightness of the abdominal patches signal the size and body condition of males, whereas blue saturation and conspicuousness with respect to the surrounding substrate are indicative of immune condition, thus supporting the multiple message hypothesis. However, some of these correlations were not shared by all species and, hence, point to intriguing species-specific signals.

Influence of sex hormones on the immune response to leishmaniasis

The differences in morbidity and mortality patterns and life expectancy between the sexes are well established in different infectious and parasitic conditions, such as in leishmaniases, in which biological, genetic, sexual and hormonal variations can modulate the immune response indicating greater infectivity, prevalence and clinical severity in men. In this regard, in seeking the understanding of factors related to protection and susceptibility to infection, this review aimed to discuss the influence of sex hormones on the immune response to leishmaniases. In the literature, sex hormone variations promote differences in the innate, humoral and cell-mediated immune response, leading to greater susceptibility, mortality and complications in males. Epidemiological estimates confirm these results, showing a predominance of the disease, in its different clinical forms, in men and suggesting that sexual variations influence immunomodulatory mechanisms since the prevalence of cases comprises the post-puberty and adulthood period. In this perspective, the action of sex hormones has been investigated in different clinical models, highlighting the potential of testosterone in immunosuppression, given its association with greater susceptibility and poor control of parasite load and the induction of cell apoptosis and attenuation of pro-inflammatory signalling pathways. Therefore, hormonal variations influence the immune response among males and females against leishmaniases, in which androgens may present immunosuppressive potential, while steroids present immunomodulatory characteristics.