[New marine parasitic nematode, Abos bathycola, from priapulids and the position of the fam. Marimermithidae in the class Nematoda].

A new genus and species of the marine parasitic nematode Abos bathycola gen. et sp. n. are described. The diagnosis of the new order Marimermithida with one family Marimermithidae Rubtzov et Platonova including 6 genera of marine parasitic nematodes is given. The new order resembles the order Mermithida in its extraintestinal feeding but differs from it in the following characters. The mouth, oesophagus, rectum and anus are reduced or absent. The mid-gut is transformed into trophosome, without lumen as a rule. If the lumen is present, no food is traced in the trophosome. The location of rudiments of oesophagus, chords, undeveloped trophosome, rudiments of rectum, if present, is consecutive. Stichosome is absent in contrast to the order Mermithida, in which it is well developed and is located in parallel with trophosome. Nematodes of the new genus are parasites of marine invertebrates unlike mermithids which are parasitic in land and freshwater arthrpods and sometimes in mollusks.