Sars, 1905
Short Description:
Pseudeuchaeta brevicauda is an aetideid calanoid copepod known after both sexes (female 4.80-6.58 mm and male 5.90 mm in length) from the Atlantic, Indian and Pacific oceans and Antarctic, of mostly bathypelagic.
Taxonomic description:
Female. Total length 4.80-6.58 mm. Cephalothorax 3.4-3.9 times longer than abdomen. Rostrum like rounded plate. Cephalon and Th1 incompletely fused (Park (1978) mentioned complete separation between cephalon and Th1). Th5 posterior corners triangular with rounded, or sometimes slightly prolonged top (Tanaka and Omori, 1970b). Genital segment nearly as long as 2 following segments, it is widest in the first third of its length. A1 reaching the anterior border of Th5, or to the end of cephalothorax. A2 rami equal in length, sometimes Ri slightly longer. A2 coxopodite and basipodite usually with 1 seta, Tanaka and Omori (1970b) recorded 2 setae on basipodite, after Sewell (1947) and Markhaseva (1996) this seta absent. Re1 and Re2 A2 with 2 setae each (according to Sars (1924) with 1 seta). Md palp base and Ri1 Md with 1 seta each, Ri2 Md with 8-9 setae (according to Sars (1925) with 7 setae). Mx1 with 13 setae on gnathobase, 4 on the second and 3 on third internal lobes, protopodite near the Ri base with 5 setae (Bradford and Jillett (1980), Park (1978), Tanaka and Omori (1970b) mentioned 4 setae), Ri with 13-14 sclerotized setae, Re with 11 setae (Sewell (1947) noted 10); external lobe with 8 setae. Mx2 typical of the genus. Digital appendage on Mxp protopodite shorter than the longest seta in distal group. P1 lacking external spine on Re1. Swimming legs typical of the genus. Length of spine on Re2 P1 varying. Sometimes it reaches the midlength of following segment, sometimes nearly its end (Tanaka and Omori, 1970b; Park, 1978; Bradford and Jillett, 1980).
Male. (Description after Tanaka and Omori (1970b)). Total length 5.90 mm. Cephalothorax 3.8 times longer than abdomen. Cephalon and Th1 separated, Th4 and Th5 fused. Rostrum as cone. A1 reaching the end of Th3. Ri A2 slightly longer than Re A2; Re2 A2 with small projection on proximal border; seta on basipodite small; Ri2 with 6 setae on external lobe. Ri2 Md with 9 setae, gnathobase strongly reduced. Mx1 with 11 setae on Re, 8 setae on Ri and 4 setae on protopodite near the Ri base, 1 seta on third internal lobe, second internal lobe lacking seta, gnathobase with 1 small seta. Mx2 well developed; first-sixth endites with 2, 3, 3, 3, 3 and 1 setae respectively, Ri with 5 setae. Protopodite and Ri1 Mxp nearly equal in length, digital appendage present in distal part of protopodite. P1 with 3-segmented Re and one-segmented Ri, Re1 P1 lacking external spine, Re2 P1 with long spine, reaching the base of Re3 external spine. Swimming legs as in females. Re P2 terminal spine with about 50 spinules. Re3 P5 with many spinules along internal border; Ri elongated, swelled in the midlength of the segment. Right leg with 3-segmented Re, Re1 and Re3 with external small spine, Re3 prolonged into saber like projection. Left Re3 P5 without 2 spinules, but supplied with short tooth terminally and with row of minute spinules along internal margin.
Vertical distribution:
In hauls mostly in bathypelagic (Vervoort, 1957; Grice and Hulsemann, 1967), rarely outside this vertical zone. Also found in total hauls from depths more than 7000 m. Very probable bathypelagic species.
Geographical distribution:
Atlantic Ocean: widespread in the Northern Hemisphere: up to the North till 62°N (Jespersen, 1934), to the South down to the Gulf of Guinea (Vervoort, 1963), to the South from equator was not found in the Atlantic Ocean. In the Indian ocean recorded in the western (Grice and Hulsemann, 1967) and eastern (Markhaseva, 1996) parts in the Arabian Sea (Sewell, 1947). In the Pacific Ocean found: in the north-western part: the Izu region, in the Marianas and Kurile-Kamchatka trenches area (Tanaka and Omori, 1970; Markhaseva, 1996), in the south-eastern (Bjornberg, 1973; Markhaseva, 1996) and south-western parts near New Zealand (Bradford and Jillett, 1980), to the South to 59°08'S (Park, 1978). In high latitudes of Antarctic recorded to the South to 60°S (Vervoort, 1957; Markhaseva, 1996).
Type locality: The north-eastern part of the Atlantic Ocean (Sars, 1905).
Material examined:
5 females from samples 48, 140, 201, 381, 398, 399, 447. See examined samples module.