''Poecilochaetus serpens'' is a species of marine polychaete worm in the family

Poecilochaetidae Poecilochaetidae is a family of marine worms within the Polychaeta. It is a monotypic family containing the single genus '' Poecilochaetus''. Members of this family are benthic The benthic zone is the ecological region at the lowest level of a ...

. It is a

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

worm that burrows into soft sediment.

Taxonomy and habitat

The British marine biologist

Edgar Johnson Allen Edgar Johnson Allen (6 April 1866 – 7 December 1942) was a British marine biologist. He was elected a Fellow of the Royal Society in 1914 and won the Gold Medal of the Linnean Society in 1926 and the Royal Society's Darwin Medal in 1936. A ...

first described this worm in 1904, giving it the name ''Poecilochaetus serpens''. It was originally found buried in the sand of a beach near

Plymouth Plymouth () is a port city and unitary authority in South West England. It is located on the south coast of Devon, approximately south-west of Exeter and south-west of London. It is bordered by Cornwall to the west and south-west. Plymouth ...

, England, at extreme low water of a spring tide; the shore here consists of patches of ''

Zostera ''Zostera'' is a small genus of widely distributed seagrasses, commonly called marine eelgrass, or simply seagrass or eelgrass, and also known as seaweed by some fishermen and recreational boaters including yachtsmen. The genus ''Zostera'' con ...

'' seagrass separated by patches of bare sand, and the worm was only ever found in the bare sand areas, nor was it ever found in other habitats near Plymouth. The specific name was chosen because when they were swimming, both the worm and its planktonic larva were continually wriggling.

Description

This segmented worm is long and slender. For example, a worm with 110 segments was in length and in width, exclusive of appendages. The prostomium (head) has a single tentacle ventrally. Behind the head are two long palps which can be extended forward, or coiled loosely, and which may be half the length of the body. The peristomium (first segment) bears the mouth and four simple eyes, and it and the next five segments are large, with parapodia (branched outgrowths) and smooth chaetae (bristles) projecting forward, and

cirri Giovanni Battista Cirri (1 October 1724 – 11 June 1808) was an Italian cellist and composer in the 18th century. Biography Cirri was born in Forlì in the Emilia-Romagna Region of Italy. He had his first musical training with his brother ...

(thread-like structures) projecting backwards. The next seven segments have spiny chaetae, and the remainder of the segments from segment 17 onwards bear chaetae that are large, feather-like bristles. The first 15 segments of this worm are translucent but appear bright red or purplish-red, depending on the degree of oxygenation of the blood; the remaining segments appear dark green or black, because of pigments in the gut cells.

Ecology

''Poecilochaetus serpens'' forms a U–shaped burrow in sand, the tube being lined by particles of clay or mud cemented with mucus; digging is performed by the head using the parapodial cirri attached to the first segment and associated long bristles. A water current is drawn through the tube by undulations of the body and fan-like movements of the parapodia and bristles. The worm can turn around in its tube, and then the current direction is reversed. The worm probably feeds on plankton and organic particles removed from the water current, and

diatom A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...

s have been found in its gut.

References

{{Taxonbar, from=Q3612318 Canalipalpata Animals described in 1904 Taxa named by Edgar Johnson Allen