Onepunema, Leduc, Daniel & Verschelde, Dominick, 2013

Leduc, Daniel & Verschelde, Dominick, 2013, One new genus and two new free-living nematode species (Desmodorida, Desmodoridae) from the continental margin of New Zealand, Southwest Pacific Ocean, Zootaxa 3609 (3), pp. 274-290 : 277

Genus Onepunema gen. n.

Diagnosis. Body cylindrical with blunt head region. Thick, annulated cuticle, with annuli extending from posterior edge of amphideal aperture to near the tail tip. Though longitudinal rows of pores are distinct, somatic setae are unclear or hardly distinguishable in the pharyngeal region, and totally absent along the rest of the body except for the tail region where there can be a few pairs of pre-, para-, and/or postcloacal somatic setae. Striated head capsule separated into labial and main head regions. Six outer labial setae located close to four cephalic setae at junction of labial and main head regions. Cryptocircular amphideal fovea surrounded by fine striation in outer cuticle, giving the false impression of the presence of an amphideal plate; circular amphideal aperture. Buccal cavity small, teeth inconspicuous, presumably absent. Slender pharynx with conspicuous rounded terminal bulb, not partitioned.

Males with two opposed, outstretched testes. Short, arcuate spicules and complex arcuate gubernaculum, which can show a broad median part (cuneus) and lateral crurae. Four or five pre-cloacal supplements present. Females with vulva situated slightly anterior to middle of body. Short conical tail with spinneret.

Etymology. The genus name is derived from the Maori word onep ū (= sand) and Greek word nema (= thread; gender neutral).

Remark. Onepunema gen. n. shows characters of both Desmodorinae (thick cuticle, presence of head capsule) and Spiriniinae (small buccal cavity with inconspicuous teeth). Whilst head capsules are never found in species of Spiriniinae , some species of Desmodorinae possess buccal cavities with small or inconspicuous teeth, such as Zalonema myrianae Verschelde & Vincx, 1996 and Echinodesmodora moensi Verschelde & Vincx, 1996 , and large teeth are found in some genera within the Spiriniinae , such as in Chromaspirina and Metachromadora . Because the size of the teeth varies considerably within each subfamily, we assign Onepunema gen. n. to the subfamily Desmodorinae based on the presence of a head capsule.

Differential diagnosis. Onepunema n. gen. can be differentiated from all other genera of the family Desmodoridae by the presence of a striated head capsule, and the presence of two outstretched testes. The latter trait is unique within the entire superfamily Desmodoroidea, the holophyly of which was established based on a yellowish to brownish colour of the body in glycerine preparations, and the presence of only one anterior testis (Lorenzen 1981).

Onepunema gen n. resembles Metadesmodora (Desmodorinae) in the presence of a small buccal cavity without distinct teeth, but differs from the latter in the absence of a cuticularised amphideal plate and in the presence of a slender pharynx with conspicuous rounded terminal bulb. Onepunema gen. n. is similar to Zalonema (Desmodorinae) in the presence of a relatively narrow head capsule (vs broad head capsule in genera such as Desmodora ), but differs from the latter in amphideal fovea shape (cryptocircular vs multispiral), absence of somatic setae (present in Zalonema ), and indistinct teeth (small to large teeth in Zalonema ). Onepunema gen. n. resembles Spirinia and Chromaspirina (Spiriniinae) in the general shape of the head region, small size of buccal cavity, as well as structure of pharynx and spicules, but can be distinguished from them by the absence of distinct teeth in the buccal cavity and absence of somatic setae along the body. Onepunema gen. n. is also similar to Spirodesma in general body shape, thick cuticle, slender pharynx with conspicuous rounded terminal bulb, shape of amphideal fovea, and structure of the spicules. Onepunema gen. n. differs from the latter in the presence of head capsule (absent in Spirodesma ), and buccal cavity without teeth (three equal teeth in Spirodesma ).

Type species. Onepunema enigmaticum gen. et sp. n.