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G.O. Sars, 1883

Description
Eye bilobed and large; the upper lobe is almost as wide as the lower lobe [N.megalops eye & rostrum ].
Peduncle of first antenna without lappets or protuberances, but the distal part of the first segment is higher than the second segment [N.megalops ped 1st ].
Rostrum prominent and acute in females, but short or absent in males. In females it is usually long, slender, and downward curving [N.megalops rostrum N.megalops-rostr-ph ].
Carapace without lateral denticles on the margin in adults, but a pair of denticles are present in immature specimens.
Thoracic leg 2 is greatly elongated, naked, with apical bristles on the terminal segment and the distal end of the preceding segment [N.megalops thoracic leg ]. The penultimate segment (propodus) of the first thoracic leg has six setae in a row along its inner side and seven on or near its posterior margin.
Abdomen without dorsal spines or keels [N.megalops-drawing ].
Petasma with spine-shaped process that is is less than half the length of the terminal process and reaches to the angular bend in the terminal process. The terminal process has its basal part directed somewhat outwards, and then the process bends abruptly. The distal part of the terminal process is longer and more slender than the basal part and is flatly curved, with the concave outer margin serrated; there are about 44 dentate serrations on the outer margin. The proximal process is shorter than the terminal, with its distal part slender, straight and finely serrate along the outer margin reaching about the middle of the serrate margin of the terminal process [N.megalops petasma ].
Reproduction: sexually mature at a length of >17 mm, breeding at an age of one year, in spring and early summer. A part of the population may survive to breed a second time at an age of two years. The female carries the eggs.

Length
Adults are 22-26 mm.

Larval stages
N.megalops-A
N.megalops-B
N.megalops-C
N.megalops-D

Ecology
N. megalops is a food source for fishes.

Depth range
Occurs at 300-500 m depth during the day, but may migrate vertically to 100-300 m at night (Mauchline, 1984).

Distribution in the North Sea
N. megalops is unlikely to occur in the shallow North Sea. The species is known from the northern entrance (S. Hay, pers. com.).

World distribution
Warm-temperate belts of the N (10-60°N) and S (35-50°S) Atlantic Ocean, Indian and S Pacific Oceans; present in the Mediterranean Sea. In the N Atlantic N. megalops occasionally is are carried to the NE, as far as the North Cape at 71°N (Mauchline, 1984).

Remark
N. megalops has been found infected with the trematode Distomum filiferum and with cysts of apostome Ciliata.

[After Brinton et al., 1999]

Nematoscelis megalops