Virus-like particles from the poison glands of the parasitic wasp Biosteres longicaudatus (Hymenoptera: Braconidae)

Abstract

Two virus-like particles occur in the venom apparatus (poison glands) associated with the ovaries of the parasitic wasp Biosteres longicaudatus (Hymenoptera: Braconidae). The venom apparatus consists of accessory gland filaments (tubules) (AGFs) and a short, carrot-shaped, muscular sac, Dufour's gland. Rod-shaped particles measuring 250–300 nm long and 60–70 nm wide with convex ends occur in 100% of the cells examined along the middle third of the AGFs. These particles are associated with an electron-dense crystalline matrix within a stroma surrounded by vesicles. Similar particles are present in vacuoles in 76–90% of the epidermal cells in the pharate pupal host, Anastrepha suspensa (Diptera: Tephritidae), after parasitization by B. longicaudatus. The second type of particle is spherical and has an outer membrane with a beaded surface. It is about 250 nm in diameter and has an electron-dense biconcave central core with two lateral bodies, and resembles entomopoxviruses. Such particles occur within a stroma in 80–90% of the cells along the proximal third of the AGF, and within its lumen, to which the cells are connected by a short, cuticle-lined duct. These AGF cells are morphologically distinct from those containing the rod-shaped particles. The "mature" spherical particles accumulate in the Dufour's gland, which empties into the median oviduct, and are injected into the host by the wasp during oviposition. Similar particles are present in 63–80% of the hemocytes of parasitized hosts.