Armored Bristleworm

The bristle worm Scoloplos armiger is a thin, flat, segmented worm with short 'feet'. Just like the lugworm, it eats sand. It makes horizontal tunnels in the mudflat bottom. Its body consists of 200 segments. Like many marine animals, eggs are laid in the spring and fertilized in synchronization with a spring tide.

The sexes are separate. No breeding is observed below water temperatures of 5 °C. Breeding occurs in early spring and is synchronized with spring tides. There also exist reports of a second breeding period. In some habitats the larvae probably have a benthic development and in other places a short planktonic stage. S. armiger is a fast growing species, breeding for the first time in its second year and living for about four years. S. armiger builds a burrow system in the upper 10-15 cm of the sediment and crawls through the top layer as well. lt does not roam on the sediment surface. S. armiger is relatively tolerant to low winter temperatures. This species shows a distinct and identifiable food preference for organic detritus (Hartmann-Schröder, 1971; Wolff, 1973; Curtis, 1977; Kirkegaard, 1978; Beukerna, 1979; Fish & Fish, 1989; Bosselmann, 1991).

Bristle worm measuring up to 120 mm long. The head part is pointed without any visible appendages. The rest of the body consists of numerous segments and can be subdivided into two regions; the central region (segment 12-22) is flattened whereas the posterior region is long and semicylindrical. Gills are present from segment 9 onwards. Colour: orange to deep red.

Arctic; Labrador to Massachusetts; Bering Sea to California; Central America; north Japan Sea

S. armiger occurs in almost the entire area, except for the central part of the Oyster Ground. The polychaete is also abundant in the Wadden Sea and in almost the whole Delta area.

Scoloplos armiger is a widely spread species that was only found scarcely in the eastern coastal zone (1994-2001 period). In the same period the species was mainly distributed near the western coastal zone, the Flemish and Zeeland Banks, where the species reached a very high distribution frequency. The distribution frequency on the Zeeland Banks was remarkably lower. High densities were recorded in both periods: up to 5,000 ind./m2 (1994-2001 period).

Found from the intertidal zone to 2013 m depth; prefers sea grass beds and sand, mud and gravel substrates.

The species inhabits a wide range of sediment types, ranging from coarse to fine sand. In the study area it prefers substrates composed of fine sand. S. armiger is also known to occur in anoxic sediments and in sea grass beds (Hartmann-Schröder, 1971; Wolff, 1973; Hayward & Ryland, 1990).

Scoloplos armiger is found in all sediment types but prefers sediments with a median grain size of 200 to 350 µm that are enriched with mud (mud content up to 40%). The relative occurrence of the species in such sediments exceeds 50%.

The species superficially resembles a Scolelepis. The head is pointed sharply, smooth and lacks antenna or palps. The body is thin, fragile and reaches a maximum length of 80 mm with more than 200 segments. Parapodia in the front region have simple, short lobes. Those in tail region are more complex with more prominent lobes and dorsal gills. Gills are present on the dorsal surface from about the 12th segment onward. The colour is bright orange-pink or red, with the main blood vessels clearly visible (Hartmann-Schröder, 1971; Fish & Fish, 1989; Hayward & Ryland, 1990).