Four larger plates occur across the root of each arm with the outer pair having a comb-like edge, with 20 to 30 fine papillae in each.

[1][5] It is a common species with 20 to 50 individuals occurring per square metre in some years in the North Sea.

[1] In the Clyde sea fishery for scampi (Nephrops norvegicus) in Scotland, the unwanted invertebrates that get caught up in the trawl include O. ophiura, as well as the starfish Asterias rubens.

A study undertaken to discover the survival rate of these animals when discarded and returned to the water found that uninjured A. rubens had a mortality rate of 4%, whereas virtually all the O. ophiura died within 14 days, even when they were returned to the sea immediately after being caught.

[8] Another study examined the rate at which the discarded invertebrates sank to the bottom and their ultimate fates.

On the sea bed, a succession of benthic scavengers thrived on their remains with crangonid shrimps and crabs such as Carcinus maenas and Liocarcinus depurator being prominent.