Spinning worm
| Spinning worm | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Phascolion strombus | ||||||||||||
| ( Montagu , 1804) |
The gyro splashworm ( Phascolion strombus ) is a small to medium-sized species of the splashworm (Sipuncula) from the family Phascolionidae that lives in empty mollusc shells in temperate and tropical seas around the world.
features
The body of Phascolion strombus, which is very variable in shape and size and adapted to the dwelling, is grayish, almost always yellowish in color in the rear section and becomes up to 5 cm long.
Tentacles are located around the mouth on the mouth disk located at the very front, which form a single ring with 8 to 16 tentacles in small, young animals under 2.5 cm in size, but with increasing age and size more tentacles grow in a radial direction, so that adults have about 40 to 50 tentacles in multiple rings. The introvert, the retractable trunk at the front, is studded with irregularly distributed simple thorn-like hooks. On the entire surface of the body, papillae of various sizes sit closest to the base of the introvert and the anterior portion of the trunk, where they are largest and broadly conical in shape. In the middle of the trunk are chitinous, brown-colored adhesive papillae of different, often horse-hoofed shapes. The animal has only one, the right nephridium , the exit of which is behind the protruding anus on the front part of the trunk. The longitudinal muscles of the skin muscle tube run continuously and are not combined in bundles.
Inside, two retraction muscles of unequal size attach to the rear end of the trunk. The back muscle has a broad, undivided base, while the abdominal muscle has two roots that attach to each side of the abdominal nerve. The intestine has a series of longitudinal loops and is held in place by numerous muscles; its middle section is usually slightly wound in a double spiral and has no spindle muscle. The contractile blood vessel is often the same size as the esophagus on which it runs. A rectal appendix is present. The nephridium is attached over much of its length.
Distribution, habitat and way of life
The gyro splashworm is widespread and can be found in southern Chile and the Red Sea as well as in the entire Atlantic Ocean, from shallow water below the intertidal zone to a depth of more than 3000 m on sandy and muddy surfaces. Phascolion strombus lives in empty mollusc shells, especially of elephant teeth ( scotchips ) or marine snails such as aporrhais and turritella , but sometimes also free in the sediment. The opening of the bowl is closed with sediment, but a small hole remains in the middle through which the worm stretches its proboscis outwards.
nutrition
Phascolion strombus feeds on detritus and microorganisms, which it grazes on the sandy substrate with its tentacles at the tip of the proboscis.
Life cycle
Phascolion strombus is sexually separated with males and females of equal size. The gametes are released into the sea water, where fertilization takes place. Are developing free-floating, as zooplankton living larvae that sink after a week-long pelagic phase and crawling worms metamorphose .
Commensals and parasites
In the mollusc shells inhabited by Phascolion strombus , the clam Montacuta phascolionis often lives as a commensal . The splash worm is attacked by the small parasitic snail Ondina diaphana , which sucks its body fluids with its trunk.
literature
- Johannes Fischer (1913): The Sipunculoideen of the North and Baltic Seas taking into account the shapes of the North Atlantic area. Inaugural dissertation to obtain a doctorate from the high philosophical faculty of the Royal Christian Albrechts University in Kiel, pp. 17 / 101-19 / 103: Phascolion strombi Montagu.
- JD Fish, S. Fish: A Student's Guide to the Seashore. Cambridge University Press, Cambridge 2011. pp. 378f.
Web links
- MJ de Kluijver et al .: Phascolion strombus (Montagu, 1804). Marine Species Identification Portal