Sars, 1862
Description
Female with a hemispherical brood pouch. The head is large, slightly bended downwards; the dorsal edge is almost straight or slightly curved. The eyes are large and hemispherical. The antennulae [a1] are very small and unable to move, situated on a common protuberance and are fused partially with this protuberance and the lower side of the head; the antennulae bear at the end four sensory papillae [P.leuckartii-f]. The antennae are very large; both branches (= endopod and exopod) with six hairy setae [P.leuckartii-app ]. Legs 1-3 with five segments; leg 4 is shorter and has only three segments. Leg 1 with a short and narrow exopodite bearing a firm seta. Leg 1 with a long endopodite; the first (= basal) segment bears 6-7 setae, of which the distal one is very long; the second and third segment are short, both with two large, stout setae with short hairs. Leg 4 with an exopodite bearing two setae, one very long, the other short. The post-abdomen is sharply pointed, straight or slightly S-curved, with a few fine lateral spines. Postabdominal setae about twice in length as the caudal peduncle on which they are situated.
Male about the same size as female but more straightened in lateral view and the head somewhat larger [P.leuckartii-m ]. The endopodite of leg 1 with second segment bearing only one, long seta; the last segment with a convex protuberance bearing a hook [P.leuckartii-app ]. Postabdomen directed more backwards than in female. Copulatory organ weakly pointed.
Colour bright grey-yellow, very transparent (unpreserved specimens).
Ecology
P. leuckartii is a neritic species, found mostly at temperatures from 10 to 17 °C, but is able to survive near-freezing conditions. The salinity range is 6-35 ä (optimal at 23-25 ä). Occurs in the North Sea from spring to autumn.
Size
Both sexes about 1 mm long.
Depth range
Surface.
Distribution in the North Sea
All North Sea, including the shallow inshore waters (e.g. Waddenzee). Also Skagerrak, Kattegat and Baltic.
World distribution
North Atlantic, north as Barents Sea, Iceland, South Greenland; North Sea and Baltic Sea; North Pacific. Marginal occurrence in the W Mediterranean, the Black Sea and the South Atlantic.
[After Flößner, 1972]