A Single, Abdominal Ganglion in <I>Anastrepha suspensa</I> (Diptera: Tephritidae) and Its Innervation of the Female Sperm Storage Organs

Abstract

The association between the ventral nervous system and the sperm storage organs in Anastrepha suspensa Loew was examined to elucidate possible mechanisms that may influence sperm transport in the female reproductive tract. Such mechanisms are of importance with respect to the sexual conflict over paternity. A single, abdominal ganglion is present under the first abdominal sternite of A. suspensa. The ganglion is ovoid (L = 280 ± 18 μm ±SD, W = 230 ± 15 μm ±SD) and has a large nerve fiber extending anteriorly to the thoracico-abdominal ganglion and a large, branched nerve fiber extending posteriorly to the reproductive system. The presence of an abdominal ganglion is atypical for the Cyclorrapha flies and its position in the abdomen is atypical for the Insecta. The ganglion’s position suggests that in some taxa the evolutionary trend toward fewer abdominal ganglia has occurred with the concomitant displacement of caudal ganglia to more anterior positions in the abdomen. Nerves extending from this ganglion synapse with muscle fibers at the base of the spermathecae and the surface of the unicellular gland cells surrounding the spermathecal capsule. When stained with HRP Ab, synaptic boutons are also visible along the length of the spermathecal ducts in association with the longitudinal muscle fibers and on the muscle fibers surrounding the ventral receptacle. These findings suggest that females have the potential to affect sperm transport in their reproductive tract.