Resistance of morphological and behavioral sexual traits of the palmate newt (Lissotriton helveticus) to bacterial lipopolysaccharide treatment

Abstract

Infectious diseases are considered as a significant factor in the global decline of amphibians. In some vertebrates, the assessment of the individual sexual traits can be useful for assessment of their health status and immunocompetence due to trade-off between them and investment in the immune system. Our aim here was to determine whether the trade-off between the expression of sexual morphological and behavioral traits and investment in the immune system is present in an urodele, the Palmate newt (Lissotriton helveticus). The groups of males were injected by solutions of proinflammatory agent, lipopolysaccharide (LPS) from Escherichia coli serotype O:55:B5, at dosages toxic to vertebrates (2 and 10 mg/kg of body mass) or by saline solution only (control groups). They were subsequently measured for variations in body condition and expression of both morphological (filament length, hind-foot-web, crest) and behavioral (courtship frequency) sexual traits. The injection of either LPS or saline solution did not cause any adverse effect on health in any male of all groups. No significant differences in any of the sexual traits were observed between two groups of males injected by LPS and control groups of males indicating the absence of a trade-off between immune response and expression of sexual traits. Our result suggests that measuring morphological or behavioral sexual traits may not be a useful method for monitoring emergence of infectious diseases in the palmate newt.