Aetideopsis rostrata Sars G. O. 1903

A1 longer than cephalothorax. Rostral filaments long, widely separated at the base.

Arctic Basin, Norwegian Sea, Greenland Sea, North Sea, Northern Atlantic, Sea of Okhotsk, mid-Atlantic, Malay Archipelago

Oceanic, bathypelagic species, occurs at depths greater than 500m. In Arctic Basin found at depths of 400-2000m, in west Greenland water at 600-3000m. In the Pacific at 1000-4000m.

Female: Head widened in middle; not fused with thorax, has a somewhat triangular shape. Boundary between 4th and 5th thorcic segments sometimes visible only at edges of carapace. Protrusions (spines) at the end of the last segment of the thorax reach the middle of the genital segment and are placed toward the back of the body. Abdomen 3.5 times shorter that the cephalothorax. Integuments finely granulated. Rostrum stout, bifurcate and strongly divergent. A1 (24-segmented) extends to distal margin of 2nd or 3rd urosomal somite. Exopodite of A2 longer than endopodite by 1/6 its length. Apical spines of thoracic appendages have long serrations with well pronounced intervals between them. The outer spine on the first segment of P1 reaches the middle of the next spine.

Male: Head and 1st thoracic segment fused, 4th and 5th partially fused (the line of fusion faintly visible in dorsal view). Thoracic segments finely granulated. Proportional lengths of urosomites and furca 12:31:25:18:2:12 = 100. Anal segment concealed beneath the previous segment. A1 reaches back to distal margin of 2nd thoracic segment. P5 biramous and asymmetrical; right leg longer than left, exopod with first two segments fused, 3rd segment with a long a slightly curved terminal spine, endopod 1-segmented and reduced in size; left leg exopod 3-segmented.

Females: 3.01-4.60 mm
Males: 3.13-4.20 mm

Opprotunistic omnivores; mainly feed phytoplankton and/or phytodetritus, but may also consume microzooplankton and copepod juveniles