Marine Species Identification Portal : Nyctiphanes couchi

(Bell, 1853)

Description
Eye round, large, and tends to remain black under preservation [N.couchi eye & rostrum ]. The ratio of the eye diameter and the carapace length is about 0.22.
Peduncle of the first antenna [N.couchi peduncle 1st ant ]: the dorsal surface of the first segment carries a backward-directed pointed leaflet on the upper distal margin; triangular in dorsal view. In the male, the leaflet is inclined more closely to the horizontal stalk of the segment than in the female. The second segment of the peduncle has a multi-toothed, keel-like expansion resembling a chicken's comb but varying in shape, arising from the anterior margin; the marginal teeth on the expansion may be absent on large specimens >16 mm. In the male the third segment is convex on its outer side and concave on its inner side from which a row of 3 strong plumose setae are directed forward.
Rostrum absent; the frontal plate is short, and forms an obtuse triangle with raised margins [N.couchi eye & rostrum ].
Carapace without lateral denticles [N.couchi-m-drawing ].
Thoracic leg 8 is rudimentary; leg 7 with endopodites consisting of only two segments. Legs 1-6 (endopods) are similarly developed. Exopods present on legs 1-7 in males, and on legs 1-5 in females. In the female, paired eggs sacs are secreted adhering to the two posterior thoracic endopods (sixth and seventh).
Abdomen: the sixth segment has a small mid-dorsal posterior spine [N.couchi-m-drawing ].
Petasma with a spine-shaped process, but proximal and terminal processes are lacking. The curved lateral process and the median lobe are about the same length, both extending well short of the tip of the inner lobe [N.couchi petasma].
Reproduction: matures sexually at about 12 mm length, breeding at age of one year during spring and summer. May breed a second time at two years of age. Female carries ca. 50 eggs attached to the thoracic legs. (After Mauchline, 1984).

Size
Adults are 12-17 mm.

Larval stages
N.couchi-A
N.couchi-B
N.couchi-C
N.couchi-D
N.couchi-E

Ecology
N. couchi is a neritic species extending along the coasts of W Europe providing a food source for numerous fishes and decapods. It is believed to feed both in the water column and on the bottom where detritus is consumed (Hickling, 1925).

Depth range
A shelf species that has been observed foraging on the bottom at depths of 200 m in the daytime, then surfacing at night.

Distribution in the North Sea
All North Sea; it is the only euphausiid common in the S North Sea (Hamond, 1971).

World distribution
N. couchi is a neritic species, occurring in the NE Atlantic extending from 65°N along Norway southward to the British Isles, North Sea, Bay of Biscay, NW Africa, W Mediterranean, but also the Adriatic and Aegean Seas.

[After Brinton et al., 1999]

Nyctiphanes couchi