Euchonicola linearis, Boxshall & O’Reilly & Sikorski & Summerfield, 2019

Boxshall, Geoff A., O’Reilly, Myles, Sikorski, Andrey & Summerfield, Rebecca, 2019, Mesoparasitic copepods (Copepoda: Cyclopoida) associated with polychaete worms in European seas, Zootaxa 4579 (1), pp. 1-69 : 55

Euchonicola linearis gen. et sp. nov.

Type material: Holotype ♀ from Chone sp., Fish 2010, Stn 2-5 (71.79853°N, 21.16865°E), depth 320 m, 23 May 2010; collected by A. Sikorski; NHMUK Reg. No. 2015.3009 . Paratype ♀ from Chone sp., FFH 3958, Stn B 3A (65.92825°N, 12.25177°E), depth 105 m, 23 March 2007; collected by A. Sikorski; NHMUK Reg. No. 2015.3010 .

Differential diagnosis. Adult female attached to host via short oral stalk connecting ectosoma with discoid, embedded endosoma ( Fig. 23A ). Total length of cylindrical ectosoma 465 to 530 µm, with trunk about 2 times longer than wide (390 µm by 190 µm, respectively); retaining apparent traces of subdivision along body in some specimens ( Fig. 23C ), and with distinct abdomen ( Fig. 23B ). Stalk located anteriorly on ectosoma, with paired antennules and subchelate antennae positioned close to base of stalk. Antennules lobate, unarmed. Antennae comprising broad basal segment with swollen inner margin, and strongly recurved, claw-like apical subchela: tip of subchela opposing rounded swelling on myxal margin of basal segment when adducted. Ectosoma bearing paired, unarmed, rounded genital lappets posteriorly, marking genital openings ( Fig. 23C ). Paired cement glands visible posteriorly in trunk ( Fig. 23A, C ), extending over half length of trunk. Abdomen distinct, unsegmented, about 2 times longer than wide; bearing posteriorly-directed caudal rami and with median anal slit ( Fig. 23B ). Caudal rami parallel; each ramus with slight proximal swelling and narrower distal part; rami unarmed. Egg sacs unknown.

Etymology. The name of the new species refers to the posterior orientation of the caudal rami, which are held parallel with the longitudinal axis of the body.

Remarks. This species is very similar to the type species E. caudatus gen. et sp. nov. but can be distinguished by its relatively large ectosoma, 465 to 530 µm in length, compared to 406 to 443 µm in E. caudatus gen. et sp. nov. The form of the caudal rami also differs: in E. linearis gen. et sp. nov. the rami have a slight proximal swelling and are directed posteriorly whereas in E. caudatus gen. et sp. nov. they are markedly bipartite and directed laterally. The validity of these characters as specific level discriminants should be tested as more material becomes available.

This species is only known from females found on unidentified specimens of the sabellid genus Chone Krøyer, 1856 , collected at depths of 105 to 320 m off the coast of northern Norway.

Figures

FIGURE 23. Euchonicola linearis gen. et sp. nov. female. A, damaged female attached to setiger 10 of host; B, detail showing abdomen of same specimen; C, trunk and abdomen of female attached to setiger 12 of host. Scale bars: A–C, 100 µm.