Three new free-living nematode species (Monhysterida) from the Arctic abyss, with revision of the genus Eleutherolaimus Filipjev, 1922 (Linhomoeidae)

摘要

Three new nematode species of the order Monhysterida were found in the Molloy Deep (Fram Strait, Arctic Ocean) at a depth over .5000 m Sphaemlaimus micropapillatus sp. n. (Sphaerolaimidae) is characterised by the position of the amphids at the level of the gymnostom or stegostom; arched spicules of moderate length, with elongate, handle-like manubria and without a prominent gubernacular apophysis and three to five preanal supplementary papillae, Sphaemlaimus micropapillatus sp. n. differs from the related species S. glaphyrus Vitiello, 1971 and S. profundus Vitiello, 1971 by length of the body, subcephalic setae and spicules. Males of Daptonema curvispicula sp. n. (Xyalidae) possess strongly curved spicules, while females are distinguished by an oblique muscular vagina and absence of any spermatheca. Daptonema curvispicula sp n also differs from all related species in morphometry. Eleutherolaimus minutus sp. n. (Linhomoeidae) is the smallest species of the genus and is distinguished by a set of features such as short cephalic setae, position of the amphids well posterior to the buccal cavity and position of the ventral pore just posterior to the nerve ring. Eleutherolaimus minutus sp. n. differs from related species E. stenosoma de Man, 1907 by having a smaller body and organs and the position of ventral pore posterior to the nerve ring. A taxonomic review of the genus Eleutherolaimus Filipjev, 1922 is provided, Eumorpholaimus Schulz, 1932 is considered to be a junior synonym of Eleutherolaimus Filipjev, 1922. The genus Eleutherolaimus includes fourteen valid species. Eleven species are qualified as species inquirendae, mainly because of inadequate type material lacking adult stages and/or incomplete descriptions. A pictorial key for the identification of valid Eleutherolaimus species is presented.