Meeting Abstract
Parasites and hosts form strongly interactive ecological bonds. Parasites extract matter and energy from their hosts and impose fitness costs on reproduction and survival. Previous reports on diverse species indicate that males are often more susceptible than females to ectoparasitism and that testosterone (T) may cause this sex bias. Furthermore, ectoparasitism among individuals typically varies substantially, suggesting that some individuals may consistently be more heavily parasitized than others. Thus, selection pressures imposed by ectoparasites may be sex-biased, and stronger on some individuals than others. We investigated seasonality, sex/age-specificity, and individual consistency of chigger mite loads (Eutrombicula alfreddugesi) on eastern fence lizards (Sceloporus undulatus) in the New Jersey pine barrens. Regardless of sex and age, mite loads exhibited seasonal variation associated with mean monthly temperature. Mite load increased in all age/sex classes from early June to mid-July, but the rank-order of mite loads was highly consistent among individual lizards. Mites were rare in the environment and on lizards during the breeding season, and adult males were not more heavily parasitized than females at this time. Mite loads were higher on yearlings than adults, higher on post-breeding adult females than males in early summer (when T is low in adult males), and higher on yearling males than females in mid- to late summer (when T is high in yearling males). These results suggest that costs and selection imposed by mites may differ systematically among individuals as well as between age/sex classes. The results only partially support the hypothesis that T causes male-biased mite-parasitism of lizards.
