Bradynema rigidum

{{short description|Species of roundworm}}

{{Speciesbox

|taxon=Bradynema rigidum

| authority = (Von Siebold, 1836)

| synonyms = Filaria rigidum Von Siebold, 1836

| synonyms_ref =

}}

Bradynema rigidum is a parasitic species of nematode in the Allantonematidae family.{{Cite book|last=Doncaster|first=L.|url=https://books.google.com/books?id=KbOwBgAAQBAJ&dq=Bradynema+rigidum&pg=PA168|title=The Determination of Sex|date=2015-03-12|publisher=Cambridge University Press|isbn=978-1-107-49284-4|pages=122|language=en}} The species has been classified as androdioecious.{{Cite journal|last=Weeks|first=Stephen C.|date=2012|title=The Role of Androdioecy and Gynodioecy in Mediating Evolutionary Transitions Between Dioecy and Hermaphroditism in the Animalia|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1558-5646.2012.01714.x|journal=Evolution|language=en|volume=66|issue=12|pages=3670–3686|doi=10.1111/j.1558-5646.2012.01714.x|pmid=23206127|s2cid=3198554|issn=1558-5646|url-access=subscription}} The parasite will live freely in its host; groupings of 2–3 to up to twenty may occur together.{{Cite book|url=https://books.google.com/books?id=WOoVAAAAYAAJ&dq=who+discovered+%22Bradynema+rigidum%22&pg=PA633|title=Journal of the Royal Microscopical Society|date=1893|publisher=Royal Microscopical Society.|language=en}}

In this species it was found that blastomeres in the 4 cell stage might be in 2 possible arrangements.{{Cite book|last1=Giese|first1=Arthur C.|url=https://books.google.com/books?id=2q3SBAAAQBAJ&dq=Bradynema+rigidum&pg=PA467|title=Acoelomate and Pseudocoelomate Metazoans|last2=Pearse|first2=John S.|date=2013-09-17|publisher=Elsevier|isbn=978-1-4832-6055-6|pages=442|language=en}}

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.{{Cite book|last1=Killy|first1=Walther|url=https://books.google.com/books?id=0-hrRQvGV7sC&dq=Bradynema+rigidum&pg=PA585|title=Schmidt - Theyer|last2=Vierhaus|first2=Rudolf|date=2011-11-30|publisher=Walter de Gruyter|isbn=978-3-11-096629-9|pages=585|language=en}}

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.{{Cite book|last=Nickle|first=William R.|url=https://books.google.com/books?id=kkMPEAAAQBAJ&dq=Bradynema+rigidum&pg=PT1400|title=Manual of Agricultural Nematology|date=2020-12-17|publisher=CRC Press|isbn=978-1-000-14771-1|language=en}} All adults are hermaphrodites. It has been suggested that males develop ovaries and become hermaphrodites while the females degenerate.{{Cite book|last=Doncaster|first=L.|url=https://books.google.com/books?id=KbOwBgAAQBAJ&dq=Bradynema+rigidum&pg=PA168|title=The Determination of Sex|date=2015-03-12|publisher=Cambridge University Press|isbn=978-1-107-49284-4|pages=123|language=en}}