Giesbrecht, 1888
Short description:
Euchirella venusta is an aetideid calanoid copepod known after both sexes (female 4.25-4.88 mm and male 3.57-4.16 mm in length) from the Pacific and Indian Oceans, mainly epipelagic.
Taxonomic Description:
Female. Total length 4.25-4.88 mm. (Description after Bradford and Jillett (1980) with modifications). Cephalothorax nearly 4 times longer than abdomen. Crest absent. Rostrum well developed. Posterior Th5 corners rounded (lateral and dorsal view). Genital segment asymmetrical, probably its shape variable. A1 reaching the midlength of abdomen, Tanaka and Omori (1969a) mentioned that A1 exceeds caudal rami. Coxo- and basipodite, as well as Ri1 A2 with 1 seta each; Ri2 A2 with 5 setae on external and 4 on internal lobe. Md palp base and Ri1 Md without setae; Ri2 Md with 9 setae. Mx1 gnathobase with 3 setae on posterior surface, second and third internal lobes with 4 and 2(?) setae respectively, protopodite near Ri base with 3 setae (2 long and 1 short), Ri with 4, Re with 11 and external lobe with 6 setae. Ri1 Mxp with 2 small smooth projections in the distal part of the segment externally; all other features in structure of Mxp and Mx2 typical of the genus. First external spine on Re1 P1 reaching the middle of the second external spine. P4 coxopodite with 2 spines.
Male. (Description after Tanaka and Omori (1969a) with modifications). Total length 3.57-4.16 mm. Cephalothorax about 3.4 times longer than abdomen. Crest absent. Rostrum weak. Ri2 A2 with 6 setae on external and 7 on internal lobes. First-third internal lobes of Mx1 strongly reduced, external lobe with 5 setae, Re with 11 setae, Re1 with 2 very small spines. Left P5 basipodite reaching the distal border of right coxopodite. Left Re P5 weak, its distal end exceeding the third projection of right Re P5.
Remarks. The species is very close to E. speciosa Grice and Hulsemann, 1968. Some authors consider that E. tanseii is an aberrant form of E. venusta (Tanaka and Omori, 1969a; Von Vaupel Klein, 1984).
Vertical distribution:
The species was basically found from epipelagic (Vervoort, 1949; Grice, 1962; Bradford and Jillett, 1980; Von Vaupel Klein, 1984), also in total hauls from 300-1500 m.
Geographical distribution:
In the Pacific and Indian Oceans: the species was found mostly in tropical and subtropical parts (Grice, 1962; Grice and Hulsemann, 1967: Sewell, 1947), in the north-western part of the Pacific Ocean recorded from the Izu region (Tanaka and Omori, 1969a), noted in the south-western part of the Pacific Ocean (Bradford and Jillett, 1980).
Type locality: the tropical part of the Pacific Ocean (Giesbrecht, 1888).
Material examined:
1 female from sample 403. See examined samples module.