Immune challenge reduces reproductive output and growth in a lizard

1. A fundamental assumption in evolutionary immunology is that the immune system is costly to develop, maintain or activate. 2. Two plausible costs of activation of the immune system are decreased resources for growth and reproductive investment. However, few studies have estimated direct effects of an immune challenge, in particular in ectotherm vertebrates. We studied the consequences of an immune challenge in reproductive female dragons, Ctenophorus fordi, and in their offspring by exposing lizards to bacterial lipopolysaccharides (LPS). 3. The immune challenge led to decreased reproductive investment in terms of egg mass, but with no effect on probability of future reproduction. 4. Maternal immune challenge did not influence the response of their offspring to the same challenge. However, juveniles that were induced to mount an immune response had a higher thermal preference and showed reduced growth, but the magnitude of the growth effect was dependent on the date of oviposition, indicating maternal effects on offspring immunity. 5. Our results suggest that costs of immune activation may be important in shaping growth and reproductive strategies in ectotherms. © 2006 The Authors