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Giesbrecht, 1888

Short Description:

Undeuchaeta major is an aetideid calanoid copepod known after both sexes (female 4.15-5.50 mm and male 3.90-4.92 mm in length) from the Atlantic, Pacific and Indian oceans, also in the Ross Sea, mainly meso-bathypelagic.

Taxonomic Description:

Female. Total length 4.15-5.50 mm. Cephalothorax about 4 times longer than abdomen. Crest present. Th5 posterior corners slightly asymmetrical, prolonged into lobes of about the same length. They are of triangular configuration. Genital segment asymmetrical, similar to that of U. incisa , there is also a small projection on the right (dorsal view). On the right of the genital field the spine is present, well visible when looking laterally. A1 23-segmented, reaching the end of Abd2. Re1 A2 with 1 small seta. Oral parts and P1-P4 typical of the genus. P4 coxopodite with spinules (Tanaka, 1957b; Bradford and Jillett, 1980), examined specimens devoid of such spinules.

Male. Total length 3.90-4.92 mm (or 6.00 mm (Esterly, 1911; Farran, 1929; Vervoort, 1952)). Cephalothorax about 3 times longer than abdomen. Cephalon with crest. It is slightly lower than in females. Segmentation of cephalothorax as in female. Th5 posterior corners rounded. A1 reaching the end of Abd2. Oral parts in comparison with female reduced. P1-P4 as in female. P5 structure typical of the genus; length of left Re2 in 1.5 (or less) more than width.

Vertical distribution:

Deep-water species, sometimes occurs in surface layers (mostly during night time (Vervoort, 1957)). Recorded in total hauls from meso- and bathypelagic.

Geographical distribution:

Widespread in the Atlantic Ocean: the most northern finding 63°N (Jespersen, 1940), the most southern about 52°S (Hardy and Gunther, 1935); frequently recorded in the Indian Ocean (Wolfenden, 1911; Grice and Hulsemann, 1967), in the Arabian Sea and the Bay of Bengal (Sewell, 1947). Widespread in the Pacific Ocean: the most northern finding in the Sea of Okhotsk (Markhaseva, 1996), the most southern is the Ross Sea (Farran, 1929).

Type locality: 20°N 173°E (Giesbrecht, 1888).

Material examined:

12 females and 4 males from samples : 201, 202, 391, 400, 401, 573. See examined samples module.

Undeuchaeta major