Morphological adaptation for precopulatory guarding in astigmatic mites (Acari: Acaridida)

Abstract

Abstract Precopulatory guarding of female tritonymph is common in feather mites, Proctophyllodes stylifer and P. picae (Proctophyllodidae), and is assumed to be present in psoroptid skin parasites, Psoroptes cuniculi and P. natalensis (Psoroptidae). Partners are fixed together through the male adanal suckers cooperating with unique protrusions of the female tritonymph dorsal cuticle. Scanning electron microscopical investigations indicate that the adanal suckers have a conspicuous, cylindrical shape with a piston-like bottom. At the periphery of the sucker, a delicate and flexible cuticle forms a large collar. This structure of the adanal suckers matches a pair of finger-like protrusions (docking papillae) on the dorsal, highly plicated surface of the female tritonymph. The papillae and the suckers probably form a ball and socket-type junction during coupling. The peripheral cuticular collar is considered to be a functional adaptation for a better sealing of the sucker on the rough dorsum of the tritonymph and, later, on the dorsum of the female. Precopulatory and the presence of docking papillae in tritonymphs are related to the male and female sexual strategies, respectively, resulting from supposedly strong shortening in the receptivity of newly moulted females.