A simple version of the immunocompetence handicap hypothesizes that through condition-dependence, the size of the sexual trait may be positively related to immune function at the population level. In the present study, we investigated the relationship between sexual advertisement and immune function in a natural population of male wolf spiders, Hygrolycosa rubrofasciata (Araneae: Lycosidae). Ma...

Secondary sexual traits (SST) are usually thought to have evolved as honest signals of individual quality during mate choice. Honesty of SST is guaranteed by the cost of producing/maintaining them. In males, the expression of many SST is testosterone-dependent. The immunocompetence handicap hypothesis has been proposed as a possible mechanism ensuring honesty of SST on the basis that testostero...

Vitamin A is the generic name given to a group of fat-soluble compounds including retinol (the alcohol form), retinyl esters, retinaldehyde and retinol acid. Deficiency, first recognized in 1912, can damage the epithelial cells lining the respiratory tract. It can also affect immunocompetence, the reproductive function, growth and vision. The dose of vitamin A for neonates is 5,000 IU given int...

The immunocompetence handicap hypothesis (ICHH) provides a functional explanation for how sexual ornaments can provide honest signals of male quality. A key aspect of this hypothesis is that testosterone (T) has a bimodal effect: a higher T level enhances the expression of ornaments (increasing mating success and, ultimately, fitness); however, at the same time, it suppresses immune function. T...