Esterly, 1911
Short Description:
Euchirella truncata is an aetideid calanoid copepod known after both sexes (female 5.20-6.80 mm and male 4.50-5.60 mm in length) from the Atlantic and Pacific oceans and the Arabian Sea and the Malay Archipelago, mainly epi- and mesopelagic.
Taxonomic Description:
Female. Total length 5.20-6.80 mm. Cephalothorax about 3.8-5.0 times longer than abdomen. Crest absent. Rostrum comparatively not big. Genital segment asymmetrical, both sides with small "ear-like" projection in the anterior part of segment (dorsal view) and with large projection on the left reaching the posterior border of segment (lateral view), oval-rounded with "dotted structure". Length of genital segment nearly equal to width. A1 reaching caudal rami. Ri A2 slightly shorter than half Re length; coxopodite, basipodite and Ri1 A2 with 1 seta each, Ri2 A2 with 7 setae on each lobe (after Von Vaupel Klein (1984) internal lobe with 1 more seta). Md palp base and Ri1 Md without setae, Ri2 Md with 9 setae. Mx1 gnathobase with 3 setae on posterior surface, second internal lobe with 4, third with 3 setae, protopodite near Ri base with 2 small and 1 long setae; Ri with 4 long and 1 short thin seta, Re with 11, external lobe with 8 setae. Mx1 and Mxp typical of the genus. First external spine on Re1 P1 short, hardly reaching the base of the second external spine, P2-P4 typical of the genus. P4 coxopodite with 1 long spine.
Male. (Description after Tanaka and Omori (1969a), Park (1975c) with modifications). Total length 4.50-5.60 mm. Cephalothorax about 4 times longer than abdomen. Crest absent. Rostrum longer than in females. A1 reaching the end of caudal rami. Ri A2 1.4 times shorter than Re, Ri2 A2 external lobe with 6, internal lobe with 7 setae. Ri Mx1 with 11 setae, its external lobe with 6 setae. External spines on Re1 P1 reduced. Re1 P5 left reaching the distal end of right basipodite, Re3 with 2 large tooth-like projections in the distal part.
Vertical distribution:
The species was found in hauls from epipelagic (Vervoort, 1949; Von Vaupel Klein, 1984), mesopelagic (Tanaka and Omori, 1969a) and total hauls from depths 300-3000 m.
Geographical distribution:
Recorded in the North and South Atlantic (Wolfenden, 1911; With, 1915; Sars, 1925), the Arabian Sea; in the region of the Malay Archipelago (Sewell, 1947; Vervoort, 1949; Von Vaupel Klein, 1984), in the Pacific Ocean: in the south-western and south-eastern parts (Tanaka and Omori, 1969a; Bradford and Jillett, 1980; Markhaseva, 1996); in the north-western part (Tanaka and Omori, 1969a), the northern part (Park, 1968) and the north-eastern part (Esterly, 1911).
Type locality: San Diego region (Esterly, 1911).
Material examined:
3 females from sample 573. See examined samples module.