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Wolfenden, 1911

Short description:

Aetideopsis minor is an aetideid calanoid copepod known after female (total length 2.87-3.90 mm). The species is mostly meso-bathypelagic, bipolar.

Taxonomic description:

Female. Total length 2.87-3.90 mm. Cephalothorax 2.7 times longer than abdomen. Rostrum with divergent rami, degree of divergence varying in different specimens. Crest present, not clearly developed, situated at the level of A2. Points of Th5 corners slightly shorter the midlength, or extending beyond the middle of genital segment (dorsal view). A1 reaching Abd2. Re2 A2 with medial seta. Ri1 Md with 3, Ri2 Md with 10 setae (9 terminal and 1 posterior). Mxp protopodite without projection in the proximal part of joint. Ri P1 with well developed external lobe; spines at Re1-Re2 long, usually exceeding the base of next joint by one third of their length. Segmentation of Ri P2 may be incomplete, all other features of segmentation typical of the genus, sometimes on the anterior surface of Ri P2-P4 minute denticles are visible (Wolfenden, 1911).

Male unknown.

Remarks. A. minor was described briefly, without figures (Wolfenden , 1911). Later the species was redescribed (Vervoort, 1951; Park, 1978; Bradford, 1971b; Bradford and Jillett, 1980), and considered to be distributed in the Antarctic region, that is why nobody had compared A. minor Wolfenden with A. modesta (=Chiridius modestus With, 1915) from the North Atlantic. During my study of Aetideopsis specimens from the Arctic Ocean I have found that except A. rostrata in this region one more species occurs - A. minor , and species A. modesta (=Ch. modestus ) is its junior synonym. Features, earlier proposed as diagnostic (shape of rostrum, the degree of rostral rami divergence, length of Th5 points and length of external spines at Re3 P2) proved rather variable (even in specimens from the same sample), and should be considered intraspecific variability.

Vertical distribution:

In high latitudes of the Antarctic the species is found in epipelagial (0-100m) at the T 0.9°C, and 1.4-1.6°C (Vervoort, 1951), also in hauls taken with closing nets from meso-bathypelagial (Vervoort, 1957). In the northern hemisphere species is known from bathypelagial of the Greenland Sea: 1000-3000 and 2000-2800 m and mesopelagial of the central part of the Arctic Ocean (Markhaseva, 1996). Also found from series of total hauls from depths more than 1000 m.

Geographical distribution:

The central part of the Arctic Ocean, the Greenland Sea (Markhaseva, 1996), North Atlantic (not far south than 61°N) (With, 1915). Circumpolar in Antarctic (Wolfenden, 1911; Farran, 1929; Vervoort, 1951, 1957; Bradford, 1971b; Park, 1978): northernmost records 50°25' S (Markhaseva, 1996), 47°43' S (Vervoort, 1957) - this is probably endurence and in the Pacific sector the most northern finding - 58°58'S (Markhaseva, 1996), A. minor may be characterized as bipolar species.

Type locality: to the south of 60°S, in region of 85°W (Wolfenden, 1911).

Material examined:

20 females from samples 269, 302, 337, 338, 379, 405, 429, 434, 466, 467, 491, 511, 523, 542. See examined samples module.

Aetideopsis minor