Hesionura elongata (Southern 1914)

Small bristle worm measuring up to 20 mm long. The head is clearly longer than wide with two pairs of antennae. The first segment is merged with the head; the second segment features 4 long tentacular cirri. The ventral cirri are longer than the parapodia.

This species is also reported in the Bahamas. Generally found between 0 - 50 m in fine sand to gravel.

In both periods Hesionura elongata was mainly observed in the open sea zone. In the area of the Flemish Banks and the Zeeland Banks the species mainly lives on the tops of the sandbanks. Further off the coast specimens are also found in the gullies between the banks. In comparison to the 1994-2001 period H. elongata had a high frequency of occurrence outside the near-coastal zone in the 1976-1986 period. This is probably mainly due to the difference in sampling technique: in the 1994-2001 period samples were sieved alive, as a result of which small bristle worms such as H. elongata had the opportunity to actively slip through the meshes of the sieve. In both periods a maximum density of 1,200 to 1,600 ind./m2 was reached.

Hesionura elongata typically occurs in coarse-grained sediments: the maximum relative occurrence (> 30%) is observed in the coarsest sediments on the Belgian part of the North Sea (median grain size 600-650 µm). The mud content of the sediments is 20% maximally: the optimum is reached in sediments with a mud content ranging between 0 and 10%.