Pseudochirella pacifica is an aetideid calanoid copepod known after both sexes (female 7.00-7.60 mm and male about 6 mm in length) from boreal-tropical zones of the World Ocean, mainly bathy-abyssopelagic.
Female. Total length 7.00-7.60 mm. Cephalothorax about 4 times longer than abdomen. Th5 posterior corners rounded, right one covered with hairs distally. Genital segment asymmetrical with significant projection on the right densely covered with hairs (dorsal view). Abd1-3 covered with hairs. A1 reaching the midlength of abdomen. Re1 A2 supplied with 1 very small seta, Re2 A2 with the distal seta only, Ri1 A2 with 1 seta, Ri1 Md with 2, Ri2 Md with 9 long terminal setae and 1 posterior seta. Mx1, Mx2, Mxp typical of the genus. Separation of Re1 and Re2 P1 incomplete, Ri P2 incomplete. P4 coxopodite with 9-10 spines.
Male. Total length about 6 mm. Cephalothorax about 3 times longer than abdomen. Th5 posterior corners with small spines. Left Re2 P5 with 1 tooth in the distal part of segment.
Bathy-abyssopelagic species. In the region of the Kurile-Kamchatka Trench was often found in stratum 2000-3000 m, however found also in hauls between 1000-2000 m, 3000-4000 and 4000-5000 m (Markhaseva, 1996).
Most probably species may be characterized as tropical-boreal. It is often found in the north-western part of the Pacific Ocean: in the Sea Okhotsk, the region of the Kurile-Kamchatka Trench, once recorded from the region of Marianas Trench (Markhaseva, 1996).
Type locality: the north-western part of the Pacific Ocean, Kamchatka, 90 miles to the south-east off Cape Shipunsky (Brodsky, 1950).
23 females and 6 males from samples: 1, 19, 21, 66, 69, 73, 81, 83, 95, 96, 121-123, 140, 161, 175, 181, 201. See examined samples module.
Lectotype: 1 male, N 39810; 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. Kept in the Zoological Institute, Russian Academy of Sciences, St. Petersburg.