Submitted to: Arthropod Structure and Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2002
Publication Date: 7/15/2003
Citation: ZACARO, A.A., PORTER, S.D. FEMALE REPRODUCTIVE SYSTEM OF THE DECAPITATING FLY PSEUDACTEON WASMANNI SCHMITZ (DIPTERA: PHORIDAE). ARTHROPOD STRUCTURE AND DEVELOPMENT. 2003. v. 31. p. 329-337. Interpretive Summary: Pseudacteon wasmanni is a South American decapitating fly that parasitizes fire ant workers. Information about the biology of Pseudacteon decapitating flies is important because they are being reared and released as potential self-sustaining biocontrol agents for imported fire ants in the United States. Researchers from Sao Paulo State University at Rio Claro, Brazil and the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Florida used light microscopy and scanning electron microscopy to analyze the female reproductive system. All flies analyzed by light microscopy showed mature eggs inside the ovaries. The lack of nurse cells in all specimens suggested that egg formation occurs during the pupal stage. The total number of eggs found ranged from 31 to 280 with an average of 143. The egg has a torpedo shape (about 0.130 by 0.020 mm) with a pointed end. The micropyle where the sperm enters appears to be in a depression at the other end. A hypodermic like ovipositor is extended from the hard external ovipositor during egg laying. The existence of a muscular bulb associated with the end of the oviduct suggests that the egg is injected into the ant's body by a strong contraction of the bulb which probably is stimulated by bending of several stout hairs on the underside of the abdomen. During egg laying, the abdomen telescopes out along a large fold between the upper 6th and 7th segments in such a way that the external ovipositor is rotated ventrally into a slightly anterior orientation in preparation for injecting the egg.
Technical Abstract: Pseudacteon wasmanni is a South American decapitating fly that parasitizes workers of Solenopsis fire ants. We used light microscopy (historesin serial-sectioning stained with Haematoxylin/Eosin) and scanning electron microscopy to show and analyze internal and whole external views of the female reproductive system. All specimens analyzed (n=9) by light microscopy showed post-vitellogenic oocytes inside the ovaries. The lack of typical follicles (oocyte-nurse cell complexes) in all specimens suggests that oogenesis occurs during the pupal stage. The total number of eggs found ranged from 31 to 280 (X = 142 ñ 73, SD). The egg has a slugform or torpedo shape (about 130 by 20 m) with a pointed apex at the posterior pole as defined by the fly; the micropyle appears to be in a depression or invagination at the anterior pole. An acute hypodermic-like ovipositor is evaginated from the hard sclerotized external genitalia during egg laying. The existence of a muscular bulb associated with the end of the common oviduct suggests that the egg is injected into the ant's body by a strong contraction of the bulb which probably is stimulated by bending of several ventral sensilla. During contraction, the abdomen extends out along a large fold between the 6th and 7th tergites in such a way that the sclerotized genitalia is rotated ventrally into a slightly anterior orientation in preparation for oviposition.