Giesbrecht, 1888
Short Description:
Gaetanus miles is an aetideid calanoid copepod known after both sexes (female 3.40-3.80 mm and male about 3 mm in length) from the Atlantic, Pacific and Indian oceans, of epi-mesopelagic. Female with A1 twice as long as body.
Taxonomic Description:
Female. Total length 3.40-3.80 mm. Cephalothorax more than 4 times longer than abdomen. Frontal spine present, less than in G. pileatus and G. secundus and slightly curved to rostrum. Spines on posterior Th5 corners straight, arranged in the middle of posterior Th5 corner (lateral view) reaching the midlength of genital segment (dorsal view). A1 twice as long as body. Re1 A2 without setae, Re2 A2 with 1 distal seta. Md palp base with 1? seta, Ri1 Md with 1, Ri2 Md with 9 terminal setae. Second internal Mx1 lobe with 4 setae, Ri Mx1 with 14 setae. Mxp protopodite with lateral plate, usually strongly cut, its shape variable. P1 with indistinctly 3-segmented Re supplied with 2 external spines, the first spine exceeding the midlength of Re3 P1. Ri P2 2-segmented.
Male. Total length about 3 mm. Cephalothorax about 3 times longer than abdomen. Frontal spine absent. Spines on Th5 posterior corners were not seen. A1 shorter than body, reaching the last abdominal segment. Re1-Re2 A2 lacking setae. Md palp base with 1, Ri2 Md with 9 terminal setae, Ri Mx1 with 7, Re with 11 setae. Mxp protopodite without lateral plate, with 2 setae distally. P1 indistinctly 3-segmented, first 2 segments of Re without external spines. P2 with 2-segmented Ri. Re3 P5 left stylet-like, not bilobated.
Vertical distribution:
The species is one of Gaetanus species regularly found in surface waters (Vervoort, 1963; Bjornberg, 1973; Park, 1975b; Bradford and Jillett, 1980). In original material species was found in hauls from epi- and mesopelagic and also recorded from total hauls from depths 500-3000 m.
Geographical distribution:
Due to mixing of this species with G. secundus Esterly, 1911 it is difficult to give exact range of species distributional area. G. miles is distributed in the Atlantic, Indian and Pacific oceans from temperate to tropical waters. In the Atlantic Ocean species is known to about 61°N (With, 1915), in the Baffin Bay found in the region of 74°N (Jespersen, 1934), to the South from Equator recorded in this ocean only once (Wolfenden, 1911); found in the Arabian Sea and the Bay of Bengal (Sewell, 1929, 1947), also in tropical waters of the Indian Ocean (Markhaseva, 1996); in the Pacific Ocean the northernmost finding of species: region of 35°N (Giesbrecht, 1892), the southernmost 32°S (Markhaseva, 1996).
Type locality: the north-eastern part of the Pacific Ocean (Giesbrecht, 1888).
Material examined:
13 females and 1 male from samples: 204, 205, 207, 403, 444, 446. See examined samples module.