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

Abstract

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.

Claw shape variation in oribatid mites of the genera Carabodes and Caleremaeus: exploring the interplay of habitat, ecology and phylogenetics

“…It is possible that this narrow niche has resulted in the strongly deviating claw shape of this species, their claws are relatively large for the small body size and show a moderate curvature. We observed a similar phenomenon for Lamellovertex caelatus in a former study ( Kerschbaumer & Pfingstl, 2023 ), where the claw shape of this saxicolous species living only in dry mosses and lichens is significantly less curved than in more euryoecious species. In birds, lesser curved claws are significant for ground dwelling species ( Birn-Jeffery et al, 2012 ) and in lizards, species occurring on sandy soils usually show lower curved claws ( Tulli et al, 2009 ).…”

Multiple factors influence claw characteristics in oribatid mites (Acari)

“…The strong evolutionary pressure in this extreme environment even has led to the loss of a phylogenetic signal in the claws of intertidal oribatid mites 25 . However, recent initial studies on claws of a few typical terrestrial oribatid mite species 26 , 27 indicated that habitat specificity and lifestyle also have an impact on claw morphology in the terrestrial environment, but this correlation is apparently weaker than in intertidal oribatid mites which are subject to strong external forces. Moreover, a phylogenetic signal in the shape of claws could be quantified at least in one group of these terrestrial oribatid mites 27 .…”