F-ACTIN AND TUBULIN DURING SPERMATOGENESIS IN GAMASID MITES (ACARI, PARASITINA)

F-actin and tubulin behaviour was investigated using fluorescence prob es and electron microscopy in the course of spermatogenesis in two gam asid mites, Porrhostaspis lunulata Muller (Parasitidae) and Pergamasus truatellus Athias-Henriot (Pergamasidae). In spermatogonia and primar y spermatocytes of both species, the proteins were localized mainly in the intercellular bridges and, in lesser quantities, in the cytoplasm . Overall, actin was present along the plasmalemmal contact sites of t he gonial cells. At the beginning of spermatid elongation, actin could be detected in two regions: in peri-nuclear cytoplasm and under the p lasmalemma. Subplasmalemmal actin, visible as threads running along ac rosome-adhering protrusions of the nuclear envelope, is supposedly loc ated within the electron-dense material filling the subacrosomal gap. Tubulin was found on both sides of each actin thread; its location was consistent with two sets of microtubules adhering to the inner acroso mal membrane. Their involvement in acrosome shaping is suggested. As s permatid elongation terminated, the previous pattern of proteins disap peared. In Pergamasus, however, actin emerged briefly near the centrif ugal ends of spermatids (granular bodies zone). In spermatocyte-contai ning cysts, actin and tubulin fluorescence (more pronounced in Porrhos taspis) was associated with intercellular junctions between the cyst c ells. In both species, diffuse actin fluorescence was also detected in the cytoplasm of cyst cells assembling elongated spermatids; the reac tion was intensified at the end of the elongation process, when the cy toplasm of cyst cells aggregated around the centripetal ends of sperma tids.