Tubulanus polymorphus
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| Tubulanus polymorphus | |
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Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Nemertea |
| Class: | Palaeonemertea |
| Order: | Tubulaniformes |
| Family: | Tubulanidae |
| Genus: | Tubulanus |
| Species: | T. polymorphus |
| Binomial name | |
| Tubulanus polymorphus Renier, 1804[1] | |
| Synonyms | |
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Tubulanus polymorphus is a species of ribbon worm in the phylum Nemertea. It is found in the northern Atlantic Ocean and the northern Pacific Ocean. It occurs on the lower shore down to about 50 m (160 ft), on sand or gravel, under stones and among seaweed.
Like other ribbon worms, T. polymorphus is not divided into segments but is soft, smooth and contractile. It is up to 50 cm (20 in) long but just 5 mm (0.2 in) wide, with a rounded head slightly broader than the body. There is a proboscis pore and a mouth on the underside of the head but there are no eye-spots or cephalic slits.[2] Fresh specimens are a dark reddish-brown or orangeish-brown. Specimens preserved in alcohol lose their colour but exhibit a transverse dark band. This has a clear cut anterior margin but a posterior margin that fades gradually. A pair of sensory organs is located at the sides near the posterior margin of this band.[3] This worm can be distinguished from other similar species by the absence of whitish bands or stripes on the body or white patches on the head,[2] as well as by certain muscle fibres crossing over muscle layers in the dorsal part of the body wall, but not in the ventral part.[4]