Pselionema Cobb, 1933

Leduc, Daniel, 2024, Four new free-living marine nematode species (Plectida: Ceramonematidae) and two new species records (Desmodorida: Desmodorinae) from Rangitāhua / Kermadec Islands, Aotearoa / New Zealand, European Journal of Taxonomy 970, pp. 138-174 : 160-163

Pselionema Cobb, 1933

Pselionema Cobb, 1933: 33 .

Pselionemoides Haspeslagh, 1973: 335 .

Type species

Pselionema annulatum (Filipjev, 1922) Cobb, 1933 .

Diagnosis (from Tchesunov & Mijutina 2002 and Holovachov 2014)

Cuticle consists of 70–210 annules. Annules usually thick and broad, zygapophyses usually distinct. Labial region not separated by constriction. Outer labial sensilla papillose, cephalic sensilla setose. Amphidial aperture loop-shaped, elongate.

Remarks

A key to species of Pselionema was provided by Tchesunov & Miljutina (2002). The latter authors included P. rigidum Chitwood, 1936 as a valid species; however, this species was synonymised with P. beauforti Chitwood, 1936 by Hopper (1973). An additional species was subsequently described by Holovachov et al. (2008a).

List of valid species of Pselionema Cobb, 1933

P. annulatum (Filipjev, 1922) Cobb, 1933

P. beauforti Chitwood, 1936

P. concinnum Tchesunov & Miljutina, 2002

P. deconincki Vitiello & Haspeslagh, 1972

P. detriticola Vitiello, 1974

P. dissimile Vitiello, 1974

P. huakita sp. nov.

P. longissimum Gerlach, 1953

P. minutum Vitiello & Haspeslagh, 1972

P. mirabile Tchesunov & Miljutina, 2002

P. ornatum (Timm, 1961) Hopper, 1973

P. parasimplex Vitiello, 1971

P. psednum Holovachov, Tandingan De Ley, Mundo-Ocampo, Baldwin, Rocha-Olivares & De Ley, 2008

P. richardi De Coninck, 1942

P. simile De Coninck, 1942

P. simplex De Coninck, 1942

Key to species of Pselionema Cobb, 1933 (updated from Tchesunov & Miljutina 2002)

1. Body with about 200 annules ........................................................................................................... 2

– Body with about 160 or less body annules ....................................................................................... 4

2. Body annules narrow (2–4 µm), body slender, ratio of a ≥ 70 ......................................................... 3

– Body annules broad (8–11 µm), body stouter, ratio of a about 40 ..................................................... ........................................................................................... P. mirabile Tchesunov & Miljutina, 2002

3. Body length 1444–1747 µm, 252–292 body annules, cephalic setae 13–17 µm, spicules 25 µm long .................................................................................................................................. P. psednum Holovachov, Tandingan De Ley, Mundo-Ocampo, Baldwin, Rocha-Olivares & De Ley, 2008

– Body length 1032 µm, 203 body annules, cephalic setae 7 µm, spicules 17 µm long ....................... .................................................................................................................... P. dissimile Vitiello, 1974

4. Body length> 400 µm ...................................................................................................................... 5

– Body length <400 µm, ratio of a = 20–30 ........................ P. minutum Vitiello & Haspeslagh, 1972

5. Body length about 1000 µm or more ................................................................................................ 6

– Body length <900 µm ...................................................................................................................... 9

6. Body relatively stout (ratio of a = 50–65) ........................................................................................ 7

– Body slender (ratio of a> 70) ........................................................................................................... 8

7. Cephalic setae 7–8 µm, cephalic capsule length 25–31 µm, amphid length 12–14 µm, 17–20 body annules in tail region ............................................................................... P. simile De Coninck, 1942

– Cephalic setae 10–15 µm, cephalic capsule length 38–43 µm, amphid length 16–18 µm, 24–30 body annules in tail region ............................................................................................. P. huakita sp. nov.

8. Gubernaculum present ....................................................................... P. longissimum Gerlach, 1953

– Gubernaculum absent .................................................. P. concinnum Tchesunov & Miljutina, 2002

9. Zygapophyses distinct .................................................................................................................... 10

– Zygapophyses indistinct ..................................................... P. ornatum (Timm, 1961) Hopper, 1973

10. Cephalic capsule with pores ............................................................................................................11

– Cephalic capsule without pores … .................................................................................................... 2

11. Spicules about 30 µm long .............................................. P. annulatum (Filipjev, 1922) Cobb, 1933

– Spicules about 20 µm long ...................................................................... P. detriticola Vitiello, 1974

12. Less than 130 body annules, body length 500–700 µm .................................................................. 13

– About 150 body annules or more, body length about 580 µm, ratio of c = 8, amphid about 12 µm long ...................................................................................................... P. richardi De Coninck, 1942

13. Body very short, about 500 µm long .............................................................................................. 14

– Body longer, 600–700 µm long ...................................................................................................... 15

14. About 70 body annules cephalic setae 5–7 µm long ........................... P. simplex De Coninck, 1942

– About 120 body annules, cephalic setae about 3 µm long ................................................................. ......................................................................................... P. deconincki Vitiello & Haspeslagh, 1972

15. Cephalic setae about 4 µm long, ventral pore on 19 th body annule, spicules about 20 µm long ........ .............................................................................................................. P. parasimplex Vitiello, 1971

– Cephalic setae about 8 µm long, ventral pore on 13 th body annule, spicules about 30 µm long ........ ............................................................................................................... P. beauforti Chitwood, 1936