First insights into the morphological development of tarsal claws in terrestrial oribatid mites

Mites occupy a wide range of ecological niches and are good models to investigate correlations of morphological structures and ecology in arthropods. Here we compare tarsal claw shape of three terrestrial oribatid mite species with different ecological backgrounds. By means of geometric morphometrics we describe shape, size and development of the tarsal claw of the monodactyl mite species Lamellovertex caelatus and Platynothrus peltifer, and the tridactyl Melanozetes meridianus. After analysis of juvenile and adult mites we can distinguish the euryoecious P. peltifer and the alpine M. meridianus with similar claw curvatures from the saxicolous L. caelatus with considerably less curved claws. The claw height of P. peltifer, on the other hand, is remarkably higher than in the other two species. Despite these differences, no correlation between claw characteristics and environmental factors can be inferred. During the development of the mites, claw curvature and shape remain constant from protonymph to adult and claw size increases direct proportionally with body growth in all studied species. Neither the monodactyl nor the tridactyl species show any specific changes in claw characteristics.