A light and electron microscopical study of the spermathecae and ventral receptacle of Anastrepha suspensa (Diptera: Tephritidae) and implications in female influence of sperm storage.

Female insects with multiple sperm storage organs may potentially influence patterns of paternity by differential storage of sperm from competing males. The Caribbean Fruit Fly, Anastrepha suspensa, stores sperm differentially with respect to its three spermathecae. To understand the mechanisms and processes responsible for patterns of sperm storage and use in A. suspensa, details of the fine structure of female sperm storage organs were resolved by UV-light microscopy, confocal microscopy, tissue sectioning, and scanning and transmission electron microscopy. Structures not previously described for this species include a ventral receptacle for sperm storage and osmoregulation, a conical-shaped valve at the junction between the spermathecal capsules and their ducts, laminar and granular secretions, secretions from the signum, hemocytes surrounding the spermathecae, and spermathecae with sclerotized, hollow projections that terminate in single glandular cells. The independent organization of sperm storage organs, spermathecal ducts, associated musculature, gland cells, and innervation offer possible mechanisms by which sperm movement may be influenced by females. The implications of these structures for insemination and fertilization events are discussed.