Ultrastructural observations of the testicular epithelium and spermatozoa of Pseudochordodes bedriagae (Gordiida, Nematomorpha)

Abstract

Two questions are of interest concerning the male reproductive system in Gordiida: (1) is the epithelium surrounding the testis continuous or discontinuous and (2) is the type of spermatozoon as described at the transmission electron-microscopical level for the two species of Gordius typical for all Gordiida? An examination of the South American species Pseudochordodes bedriagae has allowed us to add new information to this poorly studied phylum. Testicular tubes are large, filled with spermatozoa, and surrounded by a continuous epithelium. The epithelial cells that line the posterior testes occasionally overlap, and their cytoplasm is narrow and contains dense granules, abundant endoplasmic reticulum, and vesicles. The plasma membrane possesses microvilli with many filaments. This epithelium rests on a basement membrane. The spermatozoa in P. bedriagae resemble the known spermatozoa of two Gordius species but differ in presenting a uniform halo layer of less dense chromatin that surrounds the dense chromatin in the nucleus. The finding that a similar type of spermatozoa occurs in both genera (Pseudochordodes and Gordius) makes it likely that it is present in all other Gordiida and is therefore an autapomorphy of the Gordiida.