Gaetanus brevispinus (Sars G. O. 1900)

A common midwater copepod of the Arctic

Anterior body and digestive track strongly red colored; Posterior corners of prosome (body) with moderate spine; Urosome (tail) ~ 1/3 prosome; Antennae equal to or longer than total length; Mouth parts and antennae typcial of a predator

Cosmopolitan in deep waters, but most common in polar waters; In the Arctic, range from near surface to 1500m, with peak depth between 100 and 750m; In mid-latitudes generally much deeper, down to 3000 m

Predatory on other zooplankton, primarily other copepods

In the Arctic, females spawn 2-6 large eggs, likely only once per season; Life expectancy unknown, potentially 2-3 years

Front part of the body has a bright red color

Central Arctic Basin, North Atlantic, Sea of Japan, Se of Okhotsk, Bering Sea, North-Western Pacific

Oceanic, bathypelagic species. In the Pacific occurs at depths less than 200m, in the Arctic can be found at the surface

Females:
Body plump and does not narrow towards the bottom, top of the head flattened. Rostrum widens at the base has a deep crevice on the top. Head fused with the thorax, 2 last segments separate. Spines on the last thoracic segment short, thin and face straight backward. A1 reach the back edge of the second abdominal segment, the endopodite of A2 is shorter than the outer branch by 0.25 of its length. Exopodite of P1 three-segmented, endopodite of P2 two-segmented. Mxp2 has a lateral plate. The basipodite of P4 carries 20-24 narrow, long spines. Abdomen 3.5 times shorter than the cephalothorax. The genital segment is equal in length to the next 3 segments combined, the back side of all abdominal segments carry small serrations.

Males:
Smaller and more slender than the female. A1 reach the first third of the second abdominal segment. Rostrum does not widen as much at the base. The spines on the last thoracic segment have the same structure as in females, but they are not separated from the segment. The left endopodite of P5 relatively short, it is equal in length to 2/3 of the first segment of the exopodite of the same branch.

Broadcast spawners (release eggs freely into the water), usually 2-6 eggs per spawning event. Eggs possess 2 membranes with a perivitelline space between them.

Females: 3.60-4.90 mm
Males: 2.08-4.00 mm

Opprotunistic omnivores; studies suggest that diet is primarily carnivorous

meso-bathypelagic, hadopelagic