Studies on oogenesis and oviposition in the brown spider Loxosceles intermedia (Araneae: Sicariidae).

Abstract

Loxosceles intermedia is a poisonous spider that has a wide distribution in southern Brazil, and constitutes a public health problem. In this study, the ovaries of mature females were examined by light and electron microscopy, and by histochemistry. Oocytes at all stages of development were observed in the same area of the mature ovarian wall, surrounded by a basement membrane and a proteic band. They were supported by a group of pedicular cells, which may function as follicular cells. No follicular cell was seen around the oocyte. Mature oocytes pass through the ovarian epithelial wall and are released into the ovarian lumen, covered by a vitelline membrane. The basement membrane and proteic band remain in the ovarian wall. On its way out, the oocyte is coated by proteins that will form the chorion. The presence of different coats throughout oogenesis, and at the time of egg release, is correlated with conditions that indicate fertilization occurs in the uterus lumen during oviposition.