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lugworm
The lugworm or sandworm, ''Arenicola marina'', is a large marine worm of the phylum Annelida. Its coiled castings are a familiar sight on a beach at low tide but the animal itself is rarely seen except by those who, from curiosity or to use as fishing bait, dig the worm out of the sand.
When fully grown, the lugworm of the coasts of Europe is up to long and in diameter. Other species on the North American coast range from . The body is like that of an earthworm: ringed or segmented. Its head end, which is blackish-red and bears no tentacles or bristles, passes into a fatter middle part which is red. This in turn passes into a thinner yellowish-red tail end. The middle part has bristles along its sides and also pairs of feathery gills. There is a well-developed system of blood vessels with red blood rich in the oxygen-carrying pigment, haemoglobin.〔(Marine Species Identification Portal )〕
== Life in a burrow ==
A lugworm lives in a U-shaped burrow in sand. The U is made of an L-shaped gallery lined with mucus, from the toe of which a vertical unlined shaft runs up to the surface. This is a head shaft. At the surface the head shaft is marked by a small saucer-shaped depression. The tail shaft, from it, is marked by a highly coiled cast of sand. The lugworm lies in this burrow with its head at the base of the head shaft, swallowing sand from time to time. This makes the column of sand drop slightly, so there is a periodic sinking of the sand in the saucer-shaped depression. When it first digs its burrow the lugworm softens the sand in its head shaft by pushing its head up into it with a piston action. After that the sand is kept loose by a current of water driven through the burrow from the hind end by the waves of contraction passing along the worm's body. It weighs . Lugworms also have groups of hair on the outside of their bodies that act as external gills. These can rapidly increase its uptake of oxygen.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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