Marine Worms

 

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There are hundreds of worm species found on Cornish beaches, almost all of which all belong to the animal class Polychaetes. A definite description of Polychaetes is almost impossible due to the number of diverse species. This successful class has produced a huge range of species enabling them to be found in every marine habitat. Each species has evolved and adapted to perfectly fit their specific environmental niche.

There are three main life strategies used by polychaetes; sessile, burrowing, or free moving. Sessile worms fix themselves to hard surfaces and remain attached for their lifespan such as in species of Spirorbis. There are sand burrowing worms like as the Lugworm Arenicola marina. Free moving the most mobile strategy that can include swimming such as the ragworm. The life strategy that a species exploits is reflected most of the other aspects of their life.

Polychaetes have bodies with distinct segments. The majority of the segments have a pair of paddle like flaps parapodia with tiny bristles chetae. The paropodia are used for movement and in some cases modified for respiration. The chetae or bristles are where the polychaetes get their common name, bristle worms.

Paropodia in free moving worms tend to be large as they are required for crawling on the sea bed or even for swimming. Those species that burrow and hence do not require parapods for crawling or swimming but instead burrowing, evolutionary constraints has kept them small. In many cases the parapods have been adapted for movement in the burrow or to produce a current into the burrow for respiration.

With the diverse range of species the methods of feeding will differ. Sessile species are fixed and have to wait for food to come to them. Then when it arrives there is required a method of collecting or catching it. A strategy used by the Sand Mason Lanice conchilega are tentacles which catch food particles which then pass them to their mouth. Other sessile species are filter feeders.

Burrowing worms such as lugworms are the marine equivalent of earthworms. They take in sand, as it the sand passes through the body any organic matter is digested in the gut. Free moving a common strategy with carnivores such as in the ragworm Nereis, which need mobility to search and catch their prey.

Reproductive strategies vary depending on the species. In most species the sexes are separate however there are a few that are hermaphrodite. The sexes can sometimes be easily told apart as in the case of the Ragworm Nereis diversicolor, where originally both sexes are brown, but when they reach breeding condition; the males change to green while the females are a much darker green.

Most species have a planktonic stage. The majority of polychaetes expel their eggs and sperm into the currents where fertilization takes place, the larva joining the rest of the plankton. After a period of determined by the species the larva will return to the sea bed. There are free moving species that improve their reproductive chances by swarming to breed such as Nereis virens.

In Cornwall worms vary in size from a couple of centimetres to over eighteen inches in the case of the king ragworms Nereis virens.

Worms have many predators hence they remain hidden and are not often seen, more common being traces of their existence such as their casts or egg cases.

 

Jelly marble size, worm egg cases possibly of a paddleworm.

 

Lugworm Casts

 

Calcareous tube of a tubeworm.

 

 

 

 

 

Egg Case

 

Worm Cast

 

Calcareous Worm Cast

 

 

 

 

 

Worm Species Found on Cornish Shores

 

 

 

  Lugworm Arenicola marina

  Keelworm Pomatoceros lamarki

  King Ragworm Nereis virens

  Keelworm Pomatoceros triqueter

  Ragworm Nereis diversicolor

  Spirorbis

  Sand Mason Lanice conchilega

  Honeycomb Worm Sabellaria alveolata

  Peacock Worm Sabella pavovina

 

 

 

 

Lugworm Arenicola marina   

Lugworms are a favourite of anglers, who dig them up in great numbers. The typical beach goer rarely sees them, but evidence of them is abundant.

They make their U shaped burrows leaving casts on the sand, seen at low tide.

Burrowing in this way makes them easy pickings for the bait digger, as if they dig between the feeding hole 1 and the cast 2, they are almost certain to capture the worm.

Casts tend to get larger and less numerous the further out goes down the shore. Young smaller worms group together higher up the shore.

 

Lugworm Burrow

Lugworm Cast.

 

 

 

Lugworms are the marine equivalent of the earthworms. They take in sand which as it goes through the body, any organic matter is digested in the gut. To keep the burrows clear, lugworms are required to reverse up the burrow to the surface to defecate the sand, and so form the cast. This is the time of greatest danger as the worm is just below the surface, and more accessible to birds. Usually only their tail suffers but the lugworm survives. The sight of the cast being formed is not an uncommon sight as the process continues even when uncovered by the tide.

 

Ragworms Nereis

Ragworms are a great favourite of anglers, and are by far the most common worm bait available in shops. This is primarily due to the fact that they will easily survive a few days storage, unlike their rivals the lugworm. They are very distinctive worms with strong jaws. Ragworm do burrow but are also good swimmers. They are predators hunting their prey on the surface.

 

King Ragworm Nereis virens

This can be a large worm reaching easily over fifteen inches. The larger the worm the stronger and larger the jaws, and care is required when handled as they can give a ferocious bite. King Ragworm are mainly green, but their paddles may have a pinkish purple band.

 

Ragworm Nereis diversicolor

Very similar in form to the king ragworm but are smaller, reaching a length of five inches. The colour varies from orange to pink, a distinctive feature being the dorsal blood vessel that runs along the length of its body. Ragworms will readily tolerate brackish environments and can be found in estuaries.

 

Tube Worms

A non scientific grouping of marine worms and is done for convenience. These sessile worms secrete tubes, this can be mucus lined with particles of sand and shell adhered to it such as the Sand Mason Lanice conchilega, or calcium carbonate as in the case of the Keelworm Pomatoceros lamarki.

 

Sand Mason Lanice conchilega

The sand mason makes a tube of up to twelve inches long that incorporates sand grains and shell fragments. Only the last few inches of the tube protrudes from the sand. It is very common on sandy beaches. The top portion has sandy tentacle like structures.

It has white to pinkish coloured tentacles that are only extended when covered by water which are quickly retracted if disturbed. These tentacles catch food and pass it to their mouth; or used to pick up sand to fix to their tube.

 

Sand Masons Lanice conchilega, uncovered at low tide.

 

 

 

Peacock Worm Sabella pavovina

Like the sand mason, the peacock worm makes a tube of up to twelve inches, but it do not possess sandy tentacle like structures. The tentacles are a light brown with a banding of a darker brown, or violet through to black.

 

Keelworm Pomatoceros lamarki

 

The worm makes a white solid calcareous tube which varies in length and bends in random twists. The tube is adhered to rocks. The tube has two ridges (one on each side) running down the length of it. The worm extends its feathery head through the head of the tube to feed on plankton.

Keelworm Pomatoceros triqueter

This worm is similar to the Keelworm Pomatoceros lamarki but can be distinguished by the single top ridge running down the length of the tube. The worm's feathery head is red and white.

 

Keelworm Pomatoceros lamarki

 

 

 

Spirorbis

Spirorbis spirorbis is a very common coiled tube worm, but due to its small size of an eighth of an inch, is often overlooked.

 

Magnified shot of Spirorbis spirorbis

 

 

 

They are normally found on brown seaweeds principally fucoids. The tube coils clockwise.

Spirorbis spirillum is a rarer species of coiled tube worm. It is similar to spirorbis spirorbis, but its tube coils anti-clockwise.

 

Honeycomb Worm Sabellaria alveolata

The honeycomb worm makes sandy tubes which when in large numbers produce a distinctive honey comb colonies. These honey comb colonies structures made of sand particles can be seen among rocks forming a “reef” of over a foot in depth. Each opening is a tube that contains one of these worms. The worms when covered by the tide will poke out their tentacled head.

 

 

 

Colony of Honeycomb Worm Sabellaria alveolata photographed in Devon

 

Close up of Colony of Honeycomb Worm Sabellaria alveolata photographed in Devon

 

 

 

Colony of Honeycomb Worms

 

Close up of Colony of Honeycomb Worms

 

 

 

 

 

 

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