Chiridiella abyssalis is an aetideid calanoid copepod, known after both sexes (female 2.45-2.90 mm and male 2.70-2.30 mm in length). The species occurs in the central part of the Arctic Basin and in the north-western part of the Pacific Ocean, recorded from meso- to abyssopelagic.
Female. Total length 2.45-2.90 mm. Cephalothorax 3.2-4.0 times longer than abdomen. Anterior part of lateral skeleton structures of genital field wavy (lateral view). A1 24-segmented, may be equal to cephalothorax, reaches the end of genital segment. Ri A2 about two thirds of Re in length, external lobe of Ri2 A2 with 6, internal with 6-7 setae; coxo- and basipodite with 1 seta each. Ri2 Md with 3-4 setae. Mx1 gnathobase with 10 setae, second internal lobe absent, third with 3, Ri with 4, Re with 4, external lobe with 7-8 setae. Mx2 of "macrodactyla" type with 5 endites: first (proximal) with 1-2, second with 1 very small, weak, often badly visible seta, third endite with 1 long seta. Re P1 with 1 external terminal spine, external lobe of Ri not developed. Ri P2-P4 one-segmented, on P3-P4 there are visible traces of separation between Ri1 and Ri2 as a badly visible suture.
Male. Total length 2.70-3.00 mm. Cephalothorax (dorsal view) with small projection on the top anteriorly. Cephalothorax about 3 times longer than abdomen. Cephalon and Th1, as well as Th4-Th5 fused. A1 24-segmented, reaching the end of Abd2 (sometimes with aesthetascs). Ri2 A2 with 6 setae at external lobe and 6-7 setae on internal lobe. Ri1 A2 without setae; coxo- and basipodite with 1 seta each. Ri1 Md with 4 setae. Setation at Mx1 and Mx2, as well as of Mxp reduced. P1 with one-segmented rami, Re P1 with 1 external terminal spine. P2 with 3-segmented Re and incompletely 2-segmented Ri, P3-P4 with 2-segmented Ri and 3-segmented Re. P5 with one-segmented Ri and 3-segmented Re. P5 of simple structure. Left and right legs are nearly equal in length.
In the central part of the Arctic Basin in hauls with ranges: 200-750, 250-960, 740-1572 and 1100-4330 m, in the abyssopelagic of the Kurile-Kamchatka Trench area, also in total hauls (Markhaseva, 1996). More possible: meso- and upperbathypelagic species in Arctic Basin and abyssopelagic in the north-western part of the Pacific Ocean.
Pacific Ocean: the north-western part (Brodsky, 1950); the Kurile-Kamchatka Trench region and the Aleutian Trench (Markhaseva, 1996). The central part of Arctic Basin (Markhaseva, 1983a).
Type locality: North-western part of the Pacific Ocean (Brodsky, 1950).
23 females and 3 males from samples: 138, 176, 196, 460, 477, 483-485, 488, 490, 492-507, 510, 512-514, 517-520, 524, 548, 554, 558, 560, 563. See examined samples module.
Lectotype: Ch. abyssalis (female), N 39812; high latitude expedition of Arctic Scientific Institution, 25 July 1946; ice-breaker "Severny Polus"; depth of site 4600 m, stratum of sampling: 4000-0 m.
Male: former lectotype of Ch. reducta (male), Arctic Basin, 1946, drifting station "SP-2", stratum of catching 0-2000 m.