Morphology and Ultrastructure of the Female Reproductive Apparatus of an Asexual Strain of the Endoparasitoid Meteorus pulchricornis (Wesmael) (Hymenoptera, Braconidae)

Abstract

Meteorus pulchricornis (Wesmael) is a solitary endoparasitoid of lepidopteran pests and a good candidate for the control of Spodoptera frugiperda. To elucidate the structure of the female reproductive apparatus, which may play a role in facilitating successful parasitism, we presented the description of the morphology and ultrastructure of the whole female reproductive system in a thelytokous strain of M. pulchricornis. Its reproductive system includes a pair of ovaries without specialized ovarian tissues, a branched venom gland, a venom reservoir, and a single Dufour gland. Each ovariole contains follicles and oocytes at different stages of maturation. A fibrous layer, possibly an egg surface protector, coats the surface of mature eggs. The venom gland consists of secretory units (including secretory cells and ducts) with abundant mitochondria, vesicles and end apparatuses in the cytoplasm, and a lumen. The venom reservoir is comprised of a muscular sheath, epidermal cells with few end apparatuses and mitochondria, and a large lumen. Furthermore, venosomes are produced by secretory cells and delivered into the lumen via the ducts. As a result, myriad venosomes are observed in the venom gland filaments and the venom reservoir, suggesting that they may function as a parasitic factor and have important roles in effective parasitism.