Do skin pockets of lizards reduce the deleterious effects of ectoparasites? An experimental study with Psammodromus algirus

Abstract

Many species of lizards have skin invaginations that contain ectoparasites. These structures could concentrate ectoparasites and reduce their harmful effects, but experimental evidence supporting this hypothesis is largely lacking. We report here the first experimental test of this hypothesis which we conducted with the lacertid lizard Psammodromus algirus, a species that has a nuchal pocket on each side of the neck and is a regular intermediate host of the tick Ixodes ricinus. We manipulated circulating testosterone levels of males to increase tick infestation and blocked pockets to prevent tick attachment. When ticks had free access to pockets, ticks were attached mainly in pockets when tick load was low, but they were present in similar proportions in ears, pockets, and axillae in heavily parasited males. When tick pockets were blocked, infestation rates were comparable to those of unblocked lizards, but ticks were concentrated on the ears and in the axillae. The experimental group, with blocked pockets, was seen over a shorter period and in a smaller patch of habitat. This suggests that survival and home range were reduced. These data indicate that concentration of ticks in pockets may be beneficial for P. algirus and support the functional value of these structures.