Sexual size dimorphism and functional morphology of legs of Loxosceles laeta (Nicolet, 1849)

Abstract

Alometric relationships among morphological characters provide evidence of the evolutionary forces that act on a particular trait. Spiders that live on the ground are less dimorphic than orb web spiders, which have been attributed to their different reproductive and foraging strategies. It has been proposed that long legs with respecto to the body size in males, yields an optimization of locomotion costs. The aim of this study was to characterize the variability of the length of legs in the Chilean recluse spider Loxosceles laeta and to compare the alometric relationships of the locomotor legs in males and females. Both sexes showed negative alometric relationships between the length of the legs and the lengtgh of the cephalotorax, ie spiders of large body size have proportionally shorter legs than that of small body size, which may be explained by bio mechanic causes. The males showed longer legs than females both in absolute and relative terms. That means that males have a higher locomotor efficiency than females. The relative small body size is related to a low transportation cost, which associated with long legs is the expected morphology for the more active and mobile males in this species.