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Koeller and Littlepage, 1976

Short description:

Azygokeras columbiae is an aetideid calanoid copepod of monotypic genus known after both sexes (female 2.58-2.87 mm and male 2.08-2.10 mm in length). The male of this genus is unique for Aetideidae in the presence of a right geniculate A1. The species recorded for British Columbia from an hyperbenthic locality.

Taxonomic description:

Female. (Description after Koeller and Littlepage (1976) with modification). Total length 2.58-2.87 mm. Cephalothorax about 3.5 times longer than abdomen. Cephalon and Th1 fused, Th4-Th5 separated. Rostrum and crest absent. Th5 posterior corners elongated into points not separated from Th5, covering the first third of genital segment. Th5 and Abd1 symmetrical. Abd-Abd3 covered with little denticles along posterior border. A1 24-segmented, bearing numerous setae, annulated in its distal part. Re and Ri A2 equal in length; coxopodite unique in setation among Aetideidae - with 2 setae (instead of 1 in other genera); basipodite with 2 setae; Ri1 A2 with 2 setae in distal part of segment, Ri2 with 14 setae (8 at internal and 6 at external lobe); Re1 A2 lacking setae, Re2 A2 with 3 setae, Re3-Re6 A2 supplied with 1 seta each, Re7 A2 with 3 terminal setae. Md palp base with 3 setae, Ri1 Md with 2, Ri2 Md with 9 terminal and 1 posterior setae; Re Md typical of Aetideidae, Re is more than 1.5 times longer than Ri. Mx1 gnathobase with 9 claw-like terminal (2 of which thinner) and 2 small setae on the posterior surface of segment, surface of that supplied with minute spinules; second and third internal lobes with 4 setae each, protopodite near the Ri base with 5 setae ; Ri with 15, Re with 11 setae external lobe bearing 7 setea. Mx2 typical of Aetideidae. Protopodite Mxp strong, twice as long as wide, with groups of 1 (proximal), 3 medial and 3 distal setae; Ri1 Mxp with 3 setea removed from medial part of segment to distal. P1 with 3-segmented Re and one-segmented Ri, Re segments with external spine each, nearly reaching the base of the next spine. Segmentation of P3-P4 typical of Aetideidae - rami 3-segmented. Posterior surfaces of Ri P2-P4 with minute spinules. P2 and P3 with groups of spinules on posterior anterior surfaces, also externally at coxopodite and on posterior surface of basipodite near the insertion of Re.

Male. (Description after Koeller and Littllepage (1976) with modifications). Total length 2.08 - 2.10 mm. Cephalothorax about 3 times longer than abdomen. Rostrum and crest absent. Segmentation of cephalothorax as in female, Th5 more reduced, but posterior corner of Th5 of triangular shape, reaching about posterior border of Abd1. Left A1 22-segmented, right 21-segmented, nearly all segments supplied with aesthetascs. Right A1 geniculated, last 6 segments in comparison with another segments enlarged, these segments curled in circle, and their setae transformed into robust spines. A2 similar to that in female, but Ri1 A2 without setae, setae at Re1 and Re2 A2 reduced. Md without gnathobase, base of mandibular palp lacking setae, Ri1 with 1, Ri2 Md with 9 setae. Mx1 and Mx2 rudimentary in comparison with that in female. Mxp slender than in female, protopodite lacking setae, Ri1 Mxp with 1 medial seta, P1 similar to that in female, at external border of basipodite with long thin spinules, P2-P4 as in female. P5 biramous, Ri -one-segmented, Re 3-segmented, legs of simple structure.

Vertical distribution:

Probably hyperbenthic species (Koeller and Littlepage, 1976), usually found in the near bottom layers (hauls made to the depths 400-650 m) and never was found above 300m.

Geographical distribution:

British Columbia (Koeller and Littlepage, 1976).

Type locality: 50°27' N 125°04' W (Koeller and Littlepage, 1976).

Material examined:

Species absent in collections of the Zoological Institute, St. Petersburg.

Azygokeras columbiae