Sars, 1905
Short Description:
Gaetanus robustus is an aetideid calanoid copepod known after both sexes (female 7.50-9.20 mm and male 7.00 mm in length) from the Atlantic, Pacific and Indian oceans, of meso-, and bathy-abyssopelagic.
Taxonomic Description:
Female. Total length 7.50-9.20 mm. Cephalothorax about 4.5 times longer than abdomen. Spines on Th5 posterior corners robust, slightly curved to the back side of specimen (lateral view), situated in the ventral part of posterior Th5 border and reaching the midlength of genital segment, or even slightly longer (lateral view). A1 reaching the end of caudal rami, or are slightly shorter. Re1 A2 with 1, Re2 A2 with 3 setae. Md palp base with 2, Ri1 Md with 2, Ri2 Md with 9 terminal and 2 short posterior setae. Second Mx1 internal lobe with 5 setae, Ri with 14-15 setae. Mxp protopodite with lateral plate. Re P1 3-segmented, bears external spine on each segment; first and second internal spines not reaching the base of following one. Ri P2 2-segmented. P4 coxopodite with more than 30 spines.
Male. Total length 7.00 mm. Frontal spine absent. Posterior Th5 corners with poorly visible spines. Re3 P5 left bilobated, not stylet-like, about 2.5 times shorter than Re2.
Vertical distribution:
The species was found in the Kurile-Kamchatka Trench area in hauls from bathy- and upper abyssopelagic, also in other regions from hauls from meso- and bathypelagic.
Geographical distribution:
The species was found to the North to 62°N (Jespersen, 1934), in the Northern Atlantic, the southernmost locality 31°N (Sars, 1925), recorded in the southern part of Atlantic (Wolfenden, 1911), in the Indian Ocean between 12°S and 37°S (Grice and Hulsemann, 1967), in the Pacific Ocean in the north-western part from the Kamchatka to the Izu region (Tanaka and Omori, 1970a; Markhaseva, 1996) in the south-eastern part between 30°and 40°S (Grice and Hulsemann, 1968; Bjornberg, 1973).
Type locality: the Azores Islands region (Sars, 1905).
Material examined:
10 females from samples 7, 18, 47, 73, 94, 134-137, 161, 457, 468, 474. See examined samples module.