Bradynema rigidum
Bradynema rigidum is a parasitic species of nematode in the Allantonematidae family. The species has been classified as androdioecious. The parasite will live freely in its host; groupings of 2–3 to up to twenty may occur together. In this species it was found that blastomeres in the 4 cell stage might be in 2 possible arrangements. The species was originally discovered by Philipp Franz von Siebold in the 19th century. Otto zur Strassen received a doctorate in 1892 for writing his dissertation about the nematode. The larva development was first described by Wülker. In this species male larva develop into adults after 8 days, while the females develop into adults after 7 or 10 days. All adults are hermaphrodites. It has been suggested that males develop ovaries and become hermaphrodites while the females degenerate. References 

Tylenchida
Nematodes
Taxa named by Philipp Franz von Siebold
Animals described in 1836