Survey of cuticular structures on leg IV of cosmetid harvestmen (Opiliones: Laniatores: Gonyleptoidea)

Abstract

The legs of laniatorean harvestmen feature a considerable diversity of setae, glandular openings, sensory structures, and tubercles. In this study, we compared the morphology of cuticular structures occurring on leg IV of 12 species of cosmetid harvestmen and six species of other gonyleptoidean harvestmen representing the families Agoristenidae, Gonyleptidae (three subfamilies), and Stygnidae. Our results indicate that there is considerable interspecific variation in rough pit glands and the tarsal perforated organ among cosmetid and gonyleptoidean harvestmen. We also found interspecific variation in the relative size, number, distribution, and morphology of the tubercles on the femur, patella and tibia. We observed relatively little interspecific variation in the morphology of sensilla chaetica, trichomes, spines, single pores, tarsal aggregated pores, and slit sensilla. Additional studies of the ultrastructure of cuticular structures, especially rough pit glands, are needed to assess their functional significance. Future systematic revisions of cosmetid taxa may also benefit from the inclusion of characters based upon interspecific variation in the microanatomical structures of the legs.