Females choose gentle, but not healthy or macho males in Campbell dwarf hamsters (Phodopus campbelli Thomas 1905)

Androgen-dependent male sexual traits (STs) as well as immunocompetence are theoretically assumed to be key indicators of a male's quality for the mate-choosing female. We studied mate choice by sexually motivated (SM) females of Campbell's dwarf hamsters. Females chose between 2 tethered male siblings that differed in expression of STs. Males were unrelated to the female and able to contact and copulate with her. In both males, we measured sex-related morphology of body mass, mid-ventral specific skin gland, ano-genital distance, and external testicular diameter. We also estimated levels of blood testosterone and cortisol, specific T- and B-cell immune responses to antigens, as well as aggressive and sexual dominance in sibling males through additional encounter experiments with another SM female (male sibs could freely compete for the female). We found that SM females chose a partner among 2 male sibs and spent over 80% of their time on average with the preferred male compared with the non-preferred one. Her choice was not associated with the first visit of the chosen male, with a higher expression of sex-related traits, higher levels of blood testosterone, or with aggressive dominance. The choice was not associated with the intensity of T-cell immune response to phitohemagglutinin (PHA). Instead there was a tendency for a negative relationship with the expression of STs and B-cell response to the antigen challenge. The only character that unambiguously influenced female choice was the non-aggressive male to female grooming during sexual contact. There was no difference in breeding success between preferred and non-preferred males paired with virgin females.

Body height and immune efficacy: testing body stature as a signal of biological quality

According to the good genes hypothesis and energy allocation theory, human adult body height may reflect biological quality. An important aspect of this quality is immune system functioning (ISF). The aim of this study was to evaluate the relationship between ISF and body height in healthy people. The ISF was determined by several important innate (total complement and lysozyme activity, neutrophil function) and adaptive immune parameters (lymphocytes, IgA and IgG, and response to the flu vaccine). Overall, 96 males and 97 females were subjected to flu vaccination, and of these, 35 males and 34 females were subjected to tetanus. Blood samples were collected before and four weeks after vaccination. Immunomodulatory factors, participant's age, body fat, and free testosterone levels, were controlled. There was no association between body height and all analysed immune parameters for both sexes. That might suggest that in Western society, a women's preference for taller men is not related to 'good genes for immune competence'. We propose the novel Immunity Priority Hypothesis that explains the lack of relationship between adult body stature and ISF. This hypothesis, however, does not contradict the signalling role of a man's body height as a morphological marker of biological quality.

Negative relationships between cellular immune response, Mhc class II heterozygosity and secondary sexual trait in the montane water vole

Heterogeneities in immune responsiveness may affect key epidemiological parameters and the dynamics of pathogens. The roles of immunogenetics in these variations remain poorly explored. We analysed the influence of Major histocompatibility complex (Mhc) genes and epigamic traits on the response to phytohaemagglutinin in males from cyclic populations of the montane water vole (Arvicola scherman). Besides, we tested the relevance of lateral scent glands as honest signals of male quality. Our results did not corroborate neither the hypotheses of genome-wide heterozygosity-fitness correlation nor the Mhc heterozygote advantage. We found a negative relationship between Mhc hetetozygosity and response to phytohaemagglutinin, mediated by a specific Mhc homozygous genotype. Our results therefore support the hypothesis of the Arte-Dqa-05 homozygous genotype being a ‘good’ Mhc variant in terms of immunogenetic quality. The development of the scent glands seems to be an honest signal for mate choice as it is negatively correlated with helminth load. The ‘good gene’ hypothesis was not validated as Arte-Dqa-05 homozygous males did not exhibit larger glands. Besides, the negative relationship observed between the size of these glands and the response to phytohaemagglutinin, mainly for Mhc homozygotes, corroborates the immunocompetence handicap hypothesis. The Mhc variants associated with larger glands remain yet to be determined.