Actinonema, Cobb, 1920

Chu, Mengdi, Hao, Yingdong & Huang, Mian, 2023, Two new species of Chromadorida (Nematoda) from the intertidal zone of the Yellow Sea, China, Journal of Natural History 57 (25 - 28), pp. 1364-1376 : 1369-1370

Key to species of the genus Actinonema including the new species and A. dolichurum

1. Head end with six cuticularised cones ........................................................................................ 2

– Head end without cuticularised cones ....................................................................................... 5

2. Cephalic setae 1 μm, tail long with more than 70% posterior flagellum............................ ........................................................................................... A. dolichurum Gagarin and Long, 2017

– Cephalic setae longer than 2 μm, tail comparatively short ................................................ 3

3. Dorsal tooth large, lateral differentiation without ′V̍ markings .............................................. ........................................................................................................... A. pachydermatum Cobb, 1920

– Dorsal tooth small, lateral differentiation with ′V̍ markings .............................................. 4 4. Body slender (a = 32–44), spicule absent .......... A. smolae Muthumbi and Vincx, 1998

– Body thick (a = 22–23), spicule present ................... ................... A. parvum Gagarin, 2015

5. Tail long with posterior flagellum longer than 70% of total tail length ....................... 6

– Tail comparatively short, without obvious posterior flagellum ........................................ 7

6. Males with extended cuticle in front of cloaca ...... A. longicaudatoides Gagarin, 2015

– Males without extended cuticle in front of cloaca ....................................................................... .............................................................................. A. longicaudatum ( Steiner 1918) Wieser 1954

7. Males with spicules ............................................................................................................................. 8

– Males without spicules .................................................................................................................... 11

8. Telamon absent .................................................................................................................................... 9

– Telamon present ................................................................................................................................ 10

9. Dorsal tooth small, spicules 20 μm with cephalic proximal end ............................................ ......................................................................................................................... A. fidatum Vitiello, 1970

– Dorsal tooth large, spicules 24–31 μm with tapered proximal end ...................................... ................................................................................................................................ A. grafi Jensen, 1991

10. Pharynx with double posterior bulbs .................................................. A. diplobulba sp. nov.

– Pharynx without double posterior bulbs ...................................... A. celtica Boucher, 1976

11. Only telamon present, gubernaculum absent, telamon falciform ......................................... ................................................................................................................... A. falciforme Shi et al. 2018

– Both telamon and gubernaculum present, telamon L-shaped with a broad mid part ...................................................................................... A. paraceltica Muthumbi and Vincx, 1998