Marine Species Identification Portal : Evadne nordmanni

Lovén, 1836

Description
Female in lateral view oval (North Sea form) or triangular (Baltic form). Brood pouch narrowing posteriorly, pointed or more or less rounded, with a short spine (mucro) [E.nordmanni-f ]. Head small compared to body, anteriorly rounded regularly, near the antennulae faintly convex. Compound eye large, but by far not occupying the forehead. Antennulae very small, fused at the base; pointed in lateral view, rounded distally and bearing 3-4 sensory papillae. Legs rather short, the first leg not elongated. Exopodite of leg 1 long and narrow, with two long distal setae. Endopodite of leg 1 consisting of three segments, the first segment long, with four setae; the second and third segments with one or two long curved setae respectively. Propodites of legs 2-3 having a well developed maxillary extension [me] that bears a small and a large distal tooth [E.spinifera-app]. Distal segment of endopodites of leg 2-3 with four setae. Exopodite of leg 3 with only one setae. Leg 4 very short, not well segmented, with four small distal bristles; the exopodite bears one seta. The postabdomen is very short and bifurcated; the caudal peduncle is rudimentary. Up to 7-8 embryos in the brood pouch (North Sea specimens).
Male carapace triangular in lateral view, separated from the head with a dorsal depression [E.nordmanni-m]. Compared to the female, the head and eyes are larger, and the lower edge is curved more sharply. The distal segment of the endopodite of leg 1 has a strong, inwardly curved hook [h] [E.spinifera-app ]. The copulatory organ is cylindrical, distally with longitudinal grooves.
Colour, grey to bright yellow, occasionally brownish or bright blue-green; very transparent.

Ecology
E. nordmanni is a neritic, eurytherm and euryhaline species, and prefers coastal waters. Oceanic occurrence during summer, as a sign of coastal currents. Salinity range 1.33-37.75 ä; temperature range 1-25°C.

Size
Female 0.53-1.5 mm; male ca. 1 mm (including the posterior spine on the carapace).

Depth range
Surface.

Distribution in the North Sea
Northern North Sea, Wadden Sea, Skagerrak, also Kattegat and Baltic. Present in the pelagic during the whole year, but in low densities during the winter.

World distribution
World-wide, including subpolar waters; but preferring temperate waters. Regarding the NE Atlantic: all European coasts, north as Iceland, North Cape, Barentsz Sea and Kara sea; Mediterranean, Black Sea.

[After Flößner, 1972]

Evadne nordmanni