Comparative studies of acarine limb regeneration, apolysis, and ecdysis

Abstract

A comparative study of acarine limb regenerative capacity, apolysis, and ecdysis was based on nine species representing the five major suborders of Acari. An autotomy plane was lacking in all. The ixodid completely regenerated limbs (regardless of site of amputation) after one apolysis. The argasid required two apolyses to completely regenerate amputated limbs. The uropodid regenerated a maximum of two distorted segments bevond the site of amputation. In the gamasid, the site of amputation generally formed the terminal end of the limb in the next instar. Regardless of the number of apolyses or site of amputation, the astigmatid and cryptostigmatids possessed limbs in subsequent instars which displayed segmental reduction · and/or distortion proximal to the site of amputation. Over 90 per cent of the prostigmatids died following amputation of any part of a leg. Following amputation the haemolymph coagulated quickly and a good clot formed in the ixodid, gamasid, uropodid, and astigmatid. The clot was diffused in the cryptostigmatids. Coagulation was very slow in the argasid, but a clot eventually formed. Coagulation did not occur in the prostigmatid, and a clot was never observed. The limbs of the gamasid, argasid, uropodid, prostigmatid, and both cryptostigmatids apolysed in place. The pharate form of the gamasid, uropodid, and argasid was mobile. The pharate form of the prostigmatid and both cryptostigmatids is immobile, but withdrew the newly formed limbs from the old leg hulls prior to ecdysis. The ixodid and astigmatid had an extended inactive stage in each instar during which the limb regressed to the coxal region and the pharate limb grew into the ventral exuvial space. At ecdysis the cuticle split anteriorly in the gamasid, argasid, ixodid, and uropodid, while the cuticle split posteriorly in the astigmatid and both superior cryptostigmatids. The cuticle split in the prostigmatid around the middle of the mite.