Epsilonema Steiner 1927

Genus Epsilonema Steiner, 1927

Diagnosis (after Gourbault & Decraemer, 1996): Epsilonematinae. Body ɛ-shaped, with widest regions at level of pharynx and reproductive system. Ambulatory setae slender, almost straight or bent, arranged in four to five longitudinal rows in anterior half of posterior body region; pre- and postvulvar in females but postvulvar ambulatory setae fewer in number or missing at all. Supporting setae present. Rostrum with eight subcephalic setae in most species (six and 16 setae also possible). Amphideal fovea spiral, cryptospiral or almost circular with possible sexual dimorphism in shape.

Type species: Epsilonema cygnoides (Metschnikoff, 1867) Gerlach & Riemann, 1973.

Discussion. The first epsilonematid nematode was described by Metschnikoff (1867) as Rhabdogaster cygnoides. Steiner (1927) replaced the name Rhabdogaster with Epsilonema because of homonymy of the former and established the new family Epsilonematidae. Later, Steiner (1931) published a large work on epsilonematid nematodes from Antarctic and Subantarctic seas where he diagnosed 125 new species, eight new varieties and six new genera based on 134 specimens. That study was criticized by Lorenzen (1973), who recognised only three valid species among Steiner’s decriptions, namely Archepsilonema celidotum Steiner, 1931, Bathyepsilonema drygalskii Steiner, 1931 and Epsilonema cyrtum Steiner, 1931. Decraemer (1991) re-examined Epsilonema specimens of the Steiner’s collection and identified there E. cyrtum Steiner, 1931, formerly declared valid by Lorenzen. She also re-described and re-established E. docidocricum (Steiner, 1931) as valid. Gourbault & Decraemer (1996) reviewed the composition of Epsilonematidae and listed 23 valid species of Epsilonema.