Giesbrecht, 1895
Short Description:
Gaetanus pungens is an aetideid calanoid copepod known after both sexes (female 2.65-3.20 mm and male 2.28 mm in length) from the Pacific and Indian oceans, meso-bathypelagic.
Taxonomic Description:
Female. Total length 2.65-3.20 mm. Cephalothorax slightly more than 3 times longer than abdomen. Spines on Th5 posterior corners exceeding the midlength of genital segment and covering about three fifth of its length. The species is very close to G. tenuispinus , only more slender. Structure of oral parts and swimming legs identical to those in G. tenuispinus , with the only difference: Md palp base with 1 (not 2) setae (Park, 1978; Markhaseva, 1996).
Male. (Description after Tanaka and Omori (1970a) with modifications). Total length 2.28 mm. Cephalothorax 3.3 times longer than abdomen. Spines on Th5 posterior corners covering about first third of Abd1. A1 exceeding the posterior border of Abd4. Re A2 slightly longer than Ri. Re2 A2 with 2 setae. Md palp base with 1, Ri2 Md with 9 terminal setae. Mx1 with 11 setae on Ri, first-third Mx1 internal lobes reduced, Ri with 10 setae.
Remarks. The first description of this species is very brief (Giesbrecht, 1895), containing the useful data on body size and figures of Re P1 2-segmented and Ri P2 one-segmented. Wolfenden (1911: 114) suggested the identity of this species G. tenuispinus (Sars, 1900). Later on the base of this conclusion the species was synonymized with G. tenuispinus (Bradford and Jillett, 1980). However this decision is premature, because Park (1978: 131) found the feature well distinguishing these species: presence of 1 seta on Md palp base in G. pungens and of 2 setae in G. tenuispinus. It may be added that the shape of genital segment (dorsal view) is also useful: the genital segment is narrower in its anterior part in G. pungens than in G. tenuispinus.
Vertical distribution:
The species is known from total hauls from 500-2000 m.
Geographical distribution:
The north-western and north-eastern parts of the Pacific Ocean (Giesbrecht, 1895; Tanaka and Omori, 1970a), the Malay Archipelago (Vervoort, 1949), the New Zealand region (Bradford and Jillett, 1980) to 61°N. The north-eastern part of the Indian Ocean (Markhaseva, 1996).
Type locality: 35°N 125°W (Giesbrecht, 1895).
Material examined:
2 females from samples 415, 418. See examined samples module.