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Ragworm (Nereis spp)
Ragworm

There are several important ragworm species, the most spectacular being the large and colourful Nereis virens - The King Ragworm:

A very large and impressive worm usually about 30cm in length but certain populations can reach almost a metre in length; notably in the Menai Straits in North Wales. The worm can be distinguished from other Nereids by its general size and the frilly appearance afforded to it by leaf shaped structures on the parapods called lappets. The worm is usually an iridescent green-blue in colour on the body with the lappets being orange. The head end is well formed and has many conspicuous features such as 2 pairs of eyes. 4 pairs of antennae and an eversible proboscis containing a very impressive pincer like jaw. Th e King Ragworm lives in a network of of burrows which can be up to 40cm deep usually in mud or muddy gravel. It can tolerate salinities down to around 17 0 / 00 Here it searches for its food such as other worms but it is claimed to be omnivorous.

Nereis virens

Breeding takes place in the spring but has been recorded as early as late February. When the worms breed the males leave their burrows and swarm at the surface at high tide. The males swimming with an eel like motion whils releasing sperm. This is known as the epitoke stage. At the same time the non-epitokous females release eggs from the surface of their burrows. The worms are mature after about 2-3 years, they breed once and then die.

Close-up of the head of the King Ragworm

Close-up of the head of the King Ragworm

Perhaps the most common species and one associated with lower salinities is Hediste diversicolor - the Harbour or Estuary Ragworm

Hediste diversicolor is a small ragworm often found inhabiting the soft mud and sand of harbours estuaries and beaches where it can survive in salinities down to 1%. It can easily be identified by conspicuous red dorsal blood vessel. The worm inhabits a vertically orientated burrow and can reach huge densities in the upper reaches of estuaries where conditions are unsuitable for other species. It is an omnivore of the highest order being able to feed in a variety of ways. It can filter feed by spinning a mucus "web" inside its burrow which catches particulate food such as phytoplankton from water drawn in from outside. The web is then ingested along with any catches. It can deposit feed by taking gulps of the sediment surface outside of its burrow. It can act as an herbivore feeding on algae or it can predate small invertebrates such as amphipods. Breeding takes place in the spring on spring tides when males crawl around on the sediment releasing sperm which is caught by the females using their proboscis. This species forms an important part of the diet of many estuarine birds and fishes.

dead Neried but with the pharynx everted

A side view of a dead Neried but with the pharynx everted so that the teeth contained down inside the gut can be seen. These chitinous teeth are used to grip the prey and pulled into the gut.


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