Esterly, 1906
Short Description:
Gaetanus brevicornis is an aetideid calanoid copepod known after both sexes (female 3.70-4.98 mm and male 4.25 mm in length) from the Atlantic, Indian and Pacific oceans, mainly upper mesopelagic.
Taxonomic Description:
Female. Total length 3.70-4.98 mm. Cephalothorax 3.4-4.0 times longer than abdomen. Frontal spine present, not large, strongly curved to rostrum. Spines on Th5 posterior corners situated in the middle of posterior border of Th5 (lateral view), they are abruptly curved to the back side of specimen (lateral view), divergent (dorsal view). A1 longer than body by 2-3 segments. Re1 A2 lacking setae, Re2 A2 with 2 setae. Md palp base with 2 setae, Ri1 Md with 1, Ri2 Md with 9 terminal setae. Second internal Mx1 lobe with 4 setae, Ri with 14 setae. Lateral plate on Mxp protopodite present, with a deep excavation, elongated towards the distal part of the segment. Re P1 indistinctly 3-segmented, Re P1 lacking spine, 2 following segments with external spines. Ri P2 2-segmented. P4 coxopodite with about 20 spines.
Male. Description of G. brevicornis male (Wilson, 1950; Bradford and Jillett, 1980) are very brief. Total length 4.25 mm. Frontal spine more powerful than in females. Spines on Th5 posterior corners shorter and weaker than in females. Right P5 slightly longer, than left.
Vertical distribution:
The species was found in hauls 160-500 m from the tropical part of the Pacific Ocean (Markhaseva, 1996) also in total hauls from depths 300-7000 m.
Geographical distribution:
The northernmost locality in the Atlantic Ocean: region of 32°N in the Sargasso Sea (Deevey and Brooks, 1977). Also found in the Gulf of Mexico, the Gulf of Guinea, tropical Atlantic (Wolfenden, 1911; Vervoort, 1963; Park, 1975b); in the Arabian Sea and the Bay of Bengal (Sewell, 1929, 1947), also in the region of 12°S in the Indian Ocean (Markhaseva, 1996), recorded in the region of the Malay Archipelago (A. Scott, 1909); in the Pacific Ocean found in the north-western part (Tanaka, Omori, 1970a); in the region of the Marianas Trench (Markhaseva, 1996), the north-eastern (Esterly, 1906; Markhaseva, 1996), south-western (Bradford and Jillett, 1980; Markhaseva, 1996) and south-eastern (Markhaseva, 1996) parts of Ocean.
Type locality: off the San Diego region (Esterly, 1906).
Material examined:
9 females from samples: 201, 204, 386, 401, 444, 449. See examined samples module.