Fluctuating asymmetry in an ornamental trait in the cave weta, Pleioplectron simplex Hutton (Orthoptera: Rhaphidophoridae): No role for parasites

Abstract

Using digitised pictures of the pronotum, we investigated the influence of nematomorph and mermithid parasites on the expression (intensity and fluctuating asymmetry) of cuticular ornamentation in the cave weta, Pleioplectron simplex. Because P simplex is nocturnal, this ornamentation is probably not subject to strong directional or stabilising selection. Based on measurements of brightness, we found no significant difference in the amount of pigmented area between unparasitised and parasitised males or females. Parasitised individuals were not significantly more asymmetrical than unparasitised ones. This result was not due to measurement error. Among parasitised wetas, brightness and the fluctuating asymmetry were not related to the length of the parasite, even when the size of the host was taken into account. These results are discussed in relation to current ideas concerning the influence of parasites on fluctuating asymmetry of traits in the host.