Eubostrichus topiarius sp. n., a new free-living, marine species of Stilbonematinae (Nematoda : Desmodoridae) from a shallow subtidal sand bottom

Eubostrichus topiarius sp. n. is a new species of the small subfamily Stilbonematinae, whose members are obligatorily associated with ectosymbiotic bacteria. It is recorded from the Bay of Vestar (northern Adriatic Sea) where it inhabits the interstitial space of a moderately sorted, coarse subtidal sand. The new species is much larger than, and of different proportions from the previously described species. The unispiral amphid is comparatively small and close to the anterior end; the cephalic region shows circles of 6 inner and 6 outer labial sensillae; the 4 cephalic sensillae are elongated; the anterior circle of 8 subcephalic setae inserts at the posterior margin of the amphid; the females are larger than the males showing up to 7 eggs in their uterus. This is a contribution to a revision of a very interesting genus to which a number of inadequately described specimens have been assigned.