by allthegearnoidea Fri Jul 03, 2009 7:41 am
| Ragworm
Nereis diversicolor
Ragworms are abundant in estuaries and muddy shorelines, where they live in burrows in the substrate.
 Life span
They can live for 1-3 years depending on how fast they reach maturity and spawn.
Statistics
Adults may reach 6-12cm (2-4in) in length and consist of between 90-120 segments.
Physical Description
Ragworms have long, flattened bodies, consisting of many segments each with a pair of parapods, or swimming legs. These parapods are covered with bristles called chaete and are used for crawling and swimming. At the head end, they have a toothed proboscis, four eyes, and two pairs of antennae.
They are variable in colour, typically appearing reddish brown but turning quite green during the spawning season.
Distribution
They are common throughout north-west Europe, along Atlantic coasts to the Mediterranean.
Habitat
Abundant in estuaries and sandy or muddy beaches. They inhabit U- or J-shaped burrows in the sand that may stretch for around 20cm (8 inches) depth.
Diet
The ragworm is both an omnivorous scavenger and efficient predator. When scavenging, it feeds on mud, detritus, phytoplankton and plankton. It is also a active predator, rapidly shooting out its powerful jaws to catch other soft-bodied invertebrates. This species also feeds on phytoplankton by spinning a net at the top of the burrow. By undulating it's body within its burrow it causes a water current which carries phytoplankton into the sticky net. After a while it consumes the net and the particles, then spins another.
Behaviour
The feeding behaviour of the ragworm depends on phytoplankton densities. When densities are high, it uses its net to catch prey. When densities are low, it scavenges or actively hunts prey.
Ragworms are tuned to the lunar phase, reproducing in synchrony at distinct times in the moon phase (e.g. new or full moon, depending on the locality).
Reproduction
Spawning is triggered by a rise in temperature during spring. Females brood eggs within their bodies. As the eggs develop, the female's body becomes brittle and ultimately ruptures, releasing the eggs into the burrow. Males are drawn to the burrow by pheromones and discharge their sperm around the burrow entrance. The female draws this sperm down into the burrow using water currents where they fertilise the eggs. After spawning, both males and female ragworms die.
Conservation status
Rag worms are very abundant. They are important prey for wading birds and are the main prey of at least 15 different bird species. They are also used by anglers as bait for fishing. They are not considered to be threatened.
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