Nereis pelagica is a very common species in Norway. It is found in both shallow and deep waters, among algae and mussels in the littoral zone and sublittoral waters, and on sediments in deeper waters.
- Biology, ecology and behaviour
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Up to 20 cm long, but usually between 5–12 cm.
This is one of the largest nereidids in Norway. They have a variable darkly coloured dorsal side, which is brownish-greenish. It has tentacular cirri reaching to about chaetiger 4, with two ligules in the upper part of the parapodia, and the characteristic four large conical paragnaths in a cross in Area VI on the eversible pharynx.
This species can be confused with the similar Nereis zonata, which can be found in the same habitat. Nereis pelagica can be distinguished from N. zonata by the four large conical paragnaths in Area VI on the pharynx, while N. zonata has six small conical paragnaths. In the anteriormost chaetigers the parapodial ligules are rounded in N. pelagica, while they are pointed in N. zonata.
Nereis pelagia is similar to Hediste diversicolor in general appearance at first sight. The latter species has three ligules and one lobe in the dorsal part of the parapodia, while there are two ligules in N. pelagica. Large simple chaetae (usually 1–3) among the other chaetae are present in the posterior parapodia in H. diversicolor, and usually visible under high magnification in a stereo microscope. These chaetae are lacking in N. pelagica.
Biology, ecology and behaviour
This species is active in its habitat searching for prey, which is other benthic invertebrates. It swarms during spring, normally March–April, and has pelagic larvae.
The species lives among pebbles and gravel with algae and build loose see-through tubes attached to sediment or shells.
Bakken T. Nereis pelagica Linnaeus, 1758. www.artsdatabanken.no/Pages/313085. Downloaded <year-month-day>.