Structure of the female reproductive system and oogenetic mode in a schizomid, Schizomus sawadai (Arachnida, Schizomida)

The structure of the adult female reproductive system was examined in a schizomid, Schizomus sawadai. The system consists of a single median ovary, a pair of lateral oviducts, and 4 single common oviduct with a pair of triplets of small seminal receptacles and a simple slit-like genital pore. Smaller previtellogenic oocytes less than 40 gm in diameter are found sparsely scattered in the dorsal ovarian wall among the ovarian epithelial cells, while two size groups of advanced oocytes, larger previtellogenic and vitellogenic, protrude from the lateral and ventral ovarian walls, respectively, accompanied by short cellular stalks. Neither nurse cells nor follicle cells are present around all the oocytes. Oogonia are not found in the adult ovary, indicating the lack of a continued supply of oocytes. The ovarian lumen is connected with the lumens of the lateral and common oviducts, and then with the genital pore. Modes of oogenesis, ovulation, and oviposition, deduced from the structural features of the female reproductive system of S. sawadai, are compared with those in some other arachnids, merostomes and pycnogonids.