Cleve, 1904
Short description:
Aetideus giesbrechti is an aetideid calanoid copepod known after both sexes (female 1.80-2.20 mm and male 1.52-1.60 mm). Species was found mostly in upper 500 m in the tropical and subtropical parts of World Ocean.
Taxonomic description:
Female. Total length 1.80-2.20 mm. Cephalothorax 4-4.7 times longer than abdomen. Body surface with well visible chitinous thickenings all over the body. Copepods strongly chitinized. Rostrum very strong with well visible rostral rami (ventral view) arising from wide undivided base. There are two rounded protrusions between rami. Width of excavation is 1.7 times more than depth. Crest present, low, clearly visible (looking dorsally and laterally). Th5 posterior corners extended into wing-like lobes ending by points, reaching posterior border of Abd2. Ventral and dorsal parts of spermatheca connected by considerably narrowed duct. A1 as long as body. Oral appendages typical of the genus.
Male. (Description after Park (1974) with modifications). Total length 1.52-1.60 mm. Cephalothorax 3.4 times longer than abdomen. Th5 posterior corners considerably shorter than in females, points reaching posterior border of genital segment (Abd1). Length of caudal rami 2.27-2.37 times more than width. A1 reaching posterior border of Abd3. Oral appendages as in A. acutus. Ri P2 exceeding border between Re2-Re3. Re3 terminal spine longer than its segment, bearing 24 teeth. Second - fourth P5 segments with width length ratio: 1:(3.35-4.00), 1:(6.00-6.25) and 1:(5.00-6.65) respectively.
Remarks: Size of A. giesbrechti males is close to that of A. mexicanus. The species differs in higher anterior part of cephalon, comparatively shorter Abd segments and longer Ri2 P2.
Vertical distribution:
The species is recorded from the upper 500 m, from hauls 200-350 m (Vervoort, 1957); 0-100 m (Farran, 1929); 250-500 m, 0-88 m (Bradford, 1971a).
Geographical distribution:
The species is widespread in tropical and subtropical waters in all oceans. In the Atlantic Ocean the most northern locality - the region of the Faroe Islands, the most southern 30°S (Wolfenden, 1911). Recorded in the Mediterranean, the Caribbean and the Red Seas (Rose, 1937), in the Gulf of Mexico (Park, 1970, 1974). In the Pacific Ocean: discovered in the north-western part from Japanese waters (Tanaka, 1957a; Markhaseva, 1996); in equatorial part (Grice, 1962); and to 40 S to the south (Farran, 1929); in the Indian Ocean (Vervoort, 1957), from Malay Archipelago (A. Scott, 1909).
Type locality: the sea West of South Africa (Cleve, 1904).
Material examined:
11 females from samples 202, 211, 410, 412, 413, 416, 420, 421. See examined samples module.