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Vervoort, 1949

Short Description:

Euchirella formosa is an aetideid calanoid copepod known after both sexes (female 4.80-5.50 mm and male 4.75-5.20 mm) from the Pacific and Indian oceans in epipelagic.

Taxonomic Description:

Female. Total length 4.80-5.50 mm. Cephalothorax 4.0-5.0 times longer than abdomen. Crest absent. Rostrum well developed. Th5 posterior corners rounded (lateral view), of slightly rectangular shape (dorsal view). Genital segment slightly asymmetrical with 2 (dorsal view) and 3 (lateral view) swellings on the left and 1 on the right. A1 reaching the end of genital segment. Ri A2 about a fourth of Re A2 length, Ri2 A2 with 5 setae on external and 4 setae on internal lobe; coxopodite, basipodite and Ri1 A2 with 1 seta each. Mx1 gnathobase with 3 setae on posterior surface, second and third lobes with 4 and 2 setae respectively; protopodite near Ri base with 3 setae (1 robust long and 2 small, thin setae), Ri with 4 setae, Re with 11, and external lobe with 8 setae. Md palp base and Ri1 Md without setae, Ri2 Md with 9 setae. Mx2 and Mxp typical of the genus. First external spine on Re P1 reaching the middle of following spine. P2-P4 typical of the genus, terminal spines on Re with 23-24 denticles. P4 coxopodite with 2 spines.

Male. (Description after Tanaka and Omori (1969a) with modifications). Total length 4.75-5.20 mm. Cephalothorax 4 times longer than abdomen. Cephalon differs from that of female by low crest with lens in its anterior part. Abd 2-3 supplied with minute denticles along posterior border. A1 reaching the end of Abd2. External Ri2 A2 lobe with 5, internal with 5 long setae and 1 short. Mx1 with strongly reduced first-third internal lobes, external lobe with 6, Re with 10 setae, Ri and protopodite near Ri base with 5 setae together. Re1 A2 with only 1 small spine. Left P5 basipodite exceeding right protopodite, left Re1 P5 not reaching proximal border of right Ri. Re1 of right P5 with 4 swellings on internal margin.

Remarks. E. formosa close to E. orientalis Sewell, 1929. Some authors (Tanaka and Omori, 1969a; Von Vaupel Klein, 1972, 1980) considered these species to be synonymous. Von Vaupel Klein in his recent work (1984: 50) noted, that E. orientalis Sewell, 1929 (non Tanaka and Omori, 1969a), though doubtful species, but should be considered for the present as self-dependent.

Vertical distribution:

The species was found in epipelagial (Vervoort, 1949; Von Vaupel Klein, 1984; Bradford and Jillett, 1980), known also from total hauls.

Geographical distribution:

The species was found in the western part of the Indian Ocean up to 29°S (Grice and Hulsemann, 1967), known from the region of the Malay Archipelago (Vervoort, 1949; Von Vaupel Klein, 1984), from the north-western part of the Pacific Ocean (Brodsky, 1962; Tanaka, 1957b; Tanaka and Omori, 1969a), in the tropical Pacific (Von Vaupel Klein, 1984), from the region of the Kurile-Kamchatka Trench (Markhaseva, 1996), in the south-western (Bradford and Jillett, 1980) and south-eastern (Grice and Hulsemann, 1968; Markhaseva, 1996) parts of the Pacific Ocean.

Type locality: 10°49'S 123°59'E (Vervoort, 1949).

Material examined:

1 female from sample 169. See examined samples module.

Euchirella formosa