Comparative study of the female reproductive system within the Tylenchomorpha (Nematoda: Tylenchina)

The cellular gonoduct structure of 97 species belonging to the Tylenchomorpha and of eight species belonging to outgroups were studied, this to explore diagnostic applications of gonoduct characteristics and their use to assess phylogenetic relationships within the Tylenchomorpha. The morphology of the spermatheca has been shown to have particular value as a taxonomic character, while the cellular arrangement of oviduct and uterus seems to be a reliable phylogenetic marker. The gonoduct of the studied tylenchs (without Criconematoidea) displays important similarities: the oviduct consists of two rows of three to seven cells; the spermatheca comprises 10 to 20 cells and the uterus cells are arranged in three or four rows. The spermatheca of Meloidogyne is formed by a variable number of thick, lobe-like cells making it distinctive from any other known nematode genus. Ultrastructural data substantiate that the Meloidogyne spermatheca and oviduct are exceedingly complex structures and that their function is broader than a simple conduit for oocytes and receptacle for sperm. In the Criconematoidea, cells of the uterus-spermatheca complex are not arranged in distinct rows and a lumen is present. The gonoduct structures of the Aphelenchidae and Aphelenchoididae are remarkably distinct from each other and from the remaining Tylenchomorpha, this does not preclude the polyphyly of the Aphelenchoidea as suggested by molecular data