Post squirrel worm

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Post squirrel worm
Lime tubes of Spirorbis spirorbis on Tang, Mull, Scotland.

Lime tubes of Spirorbis spirorbis on Tang, Mull, Scotland.

Systematics
Trunk : Annelids (Annelida)
Class : Polychaete (Polychaeta)
Order : Serpulida
Family : Serpulidae
Genre : Spirorbis
Type : Post squirrel worm
Scientific name
Spirorbis spirorbis
( Linnaeus , 1758)

The Posthörnchen worm ( Spirorbis spirorbis ) is a marine annelid from the family of Serpulidae within the class of polychaete (Polychaeta), which in the northern Atlantic Ocean is widespread and MM in its about 3 large, reminiscent of the house of a horn snail burrow on various brown algae ( Seaweed ) lives.

features

Spirorbis spirorbis has a left-wound, greenish body up to 6.5 mm long, brown on the belly, with around 35 segments , 3 of which form the thorax, and a tentacle crown made up of around 9 main tentacles, the tips of which are not much longer than the adjacent side branches . Unlike the larva, the adult animal has no eyes. The thorax is slightly wider than the short abdomen.

The asymmetrical collar forms a large flap on the dorsal convex edge. The first bristle-bearing segment, on which there are no ventral tori , has a single thin and smooth capillary- shaped bristle and two collar bristles on the notopodia . The kneeled collar bristles are covered with a group of large teeth below the knee and small teeth subdistally. The remaining two bristle-bearing segments of the thorax have capillary-shaped bristles, the third also have apomatus-like bristles. Two pairs of the ventral tori have hook-shaped bristles with 4 rows of teeth. The bristles on the neuropodia of the abdomen are strongly kneeled and roughly toothed in the distal section. As on the thorax, the tori have hook-shaped bristles.

Residential tube

The approximately 3 mm large, left-handed, but similar to a ramshorn snail, lying almost in one plane, shiny living tube of Spirorbis spirorbis has a small flange peripherally with which it is anchored to the substrate. The living tube is closed with a crooked, concave operculum with a flat claw on the lower edge.

distribution and habitat

Spirorbis spirorbis is distributed in the Arctic , the northern Atlantic Ocean with the coasts of Ireland , Great Britain and Norway , the English Channel , the entire North Sea and the Skagerrak .

habitat

Spirorbis spirorbis lives in its living tube mainly on various types of brown algae , especially Fucus and here in particular Fucus serratus - often in a very large number of individuals on a plant - but also on Fucus vesiculosus , species of Laminaria and Himanthalia (including Himanthalia elongata ) and occasionally on rocks in the intertidal zone and in shallow sea water.

Development cycle

Spirorbis spirorbis is a hermaphrodite in which two individuals fertilize each other's eggs in the respective living tube. In South Wales pairing April to November will take place - this is possible every 2 weeks - and the neap a Eischnur is fastened with 20 to 35 eggs inside of the tube wall. Both sex partners hatch their young in their apartment tube. The larvae leave the mother at an advanced stage of development and spend a maximum of a few hours as free-swimming zooplankton before they settle on the substrate - often on the same brown algae as the mother -, deposit a burrow and metamorphose into small bristle worms .

Food and protection from enemies

Spirorbis spirorbis is a filter feeder that catches food particles ( phytoplankton and detritus ) with its tentacles and transports them to the mouth with the cilia sitting on them. One of the tentacles is slightly larger than the others and serves to close the living tube with the saucer-like operculum and thus protect the animal from predators and - at low water - from dehydration.

literature

  • Gesa Hartmann-Schröder (1996): Annelida, Borstenwürmer, Polychaeta. Tierwelt Deutschlands 58, pp. 1–648, here p. 541, Spirorbis .
  • John D. Fish, Susan Fish: A Student's Guide to the Seashore . Cambridge University Press, Cambridge 2011. 540 pages. Spirorbis spirorbis (Linnaeus) , p. 179f.

Web links

Commons : Spirorbis spirorbis  - collection of images, videos and audio files