Acartia longiremis (Lilljeborg, 1853)
Very transparent copepod with a light blue tint
Female: the presence of long and sharp spines on the corners of the 5th thoracic segment. Long and slender apical chaetae on P5.
Male: structure of P5 very similar to that of A. clausi, but armature is less developed and and the penultimate segment lacks a sharp denticulate edge.
Female: Body elongate, slender. No rostrum. Corners of 5th thoracic segment rounded, but each one carries a relatively long and sharp spine on the back side of the body. Genital segment is slightly swollen and carries a set of tiny spines on the back edge. The second segment carries very thin and sharp spines on the back edge. Anal segment is more than two times shorter than the previous one and carries no armature. Caudal rami slightly asymmetrical, the left ramus is larger than the right (rarely reversed). Apical chaeta of P5 lacks setae, is long and narrow, slightly curved, and slightly longer than the pubescent chaeta.
Male: The armature of the last thoracic segment and abdomen identical to that of females. Abdomen contains 5 segments - the second is the longest, the fourth is very short. Right A1 is geniculate. P5 has modified structure: second and third segments of the right leg have dull protrusions facing the inner side, the protrusion on the third segment is armed with a small spine. The fourth segment is elongate and curved. The penultimate segment on the left leg is smooth. The last segment is armed with a spine and a finger-shaped outgrowth that is the same length as the spine.
Ecology and Distribution
Very common species, found in all of northern Atlantic and Pacific and in northern seas, Arctic basin
Neritic species, characteristic for upper layers; estuarine, coastal
Occuring in large numbers in coastal zones, this species can compose a significant part of the diet of fish larvae and planktivirous fish