Vervoort, 1949
Short description:
Aetideus arcuatus is an aetideid calanoid copepod known after both sexes (female 1.43-1.78 mm and male 1.22 mm in total length). Most likely mesopelagic species distributed in the Atlantic and Pacific Oceans.
Taxonomic description:
Female. Total length 1.43-1.78 mm. Cephalothorax 2.8-2.9 times longer than abdomen. Rostrum with widely spaced rami, without crest. Rostral excavation with width depth ratio - 1.4, but apparently this feature varies. Th5 posterior corners rounded. Length of A1 variable: they may reach posterior border of genital segment up to the end of caudal rami. Ri Mx1 with 12-13 setae. There are 10 setae at Ri2 Md (Park(1970 )noted 9 setae). Ri1 Mxp by one fourth of its length longer than protopodite. There are few little spinules at P4 coxopodite near the base of internal seta. Re3 P2-P4 terminal spines with 15-17 teeth. Ri P2 incompletely 2-segmented.
Male. (Description after Roe (1975) with modifications). Total length 1.22 mm. Caudal rami are 3 times longer than wide. Th5 posterior corners rounded. A1 20-segmented and reaching posterior border of Abd2. Oral appendages in comparison with that in female reduced. Ri P2 incompletely 2-segmented. There are no spinules near the base of P4 coxopodite. Second-fourth P5 segments with width length ratio - 1:(3.75), 1:(6.4) and 1:(6.2).
Vertical distribution:
Most likely mesopelagic species, found in hauls 690-790 and 505-1000 m in the north part of Atlantic and the Caribbean Sea (Park, 1970; Roe, 1975), also in total tows from other regions.
Geographical distribution:
The Malay Archipelago (Vervoort, 1949); the north-eastern and tropical parts of Atlantic (Roe, 1975; Brenning 1983, 1985; Markhaseva, 1996), the Caribbean Sea; in the Pacific Ocean: the south-eastern part (54-49°S 119-120°W) (Park, 1970; 1978); the north-western part (Markhaseva, 1996), the north-eastern part (27°N 115°W) (Bradford, 1971a).
Type locality: the Malay Archipelago (Vervoort, 1949).
Material examined:
3 females from samples 2, 3, 571. See examined samples module.