Thalassematidae
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| Forbes & Goodsir , 1841 |
Thalassema is the name of a family of hedgehog worms (Echiura) that includes over 100 marine species in 7 genera worldwide.
features
The mostly green, reddish or brown hedgehog worms of the family Thalassematidae do not have rings of anal bristles on their rear end; they also lack a diaphragm behind the pharynx. The proboscis at the front end of the body is usually well developed, sometimes flattened at the tip, but never forked, and easily separates from the trunk. Most species of the Thalassematidae have 1 to 7 pairs of nephridia , but there can be 20 pairs in the genus Ikedosoma . The lips of the nephrostomata can be inconspicuous, leaf-like or elongated and rolled in spirals. The longitudinal muscles of the skin muscle tube are continuous in Thalassema , Anelassorhynchus and Arhynchite , while they are thickened in bands in Ochetostoma , Listriolobus , Lissomyema and Ikedosoma .
Distribution, habitat and way of life
The hedgehog worms of the Thalassematidae family are found in all three major oceans. They live in rather shallow waters in the intertidal zone and below. All species are detritus eaters, which ingest microscopic food particles from the substrate with the proboscis.
Life cycle
Males and females are the same size in the Thalassematidae family. The gametes are given outside via the nephridia, where fertilization takes place in the open sea water. Are developing free-floating, as zooplankton living Trochophora - larvae that sink down after a few weeks and ground-dwelling worms metamorphose .
Internal system
The family is currently divided into 7 genera:
- Anelassorhynchus Annandale, 1922
- Arhynchite Satô, 1937
- Ikedosoma Bock, 1942
- Lissomyema Fisher, 1946
- Listriolobus Fischer, 1926 (not Spengel, 1912!)
- Ochetostoma Rüppell & Leuckart, 1828
- Thalassema Pallas, 1774
literature
- Stanley J. Edmonds: Fauna of Australia, Volume 4A. Polychaetes & Allies. The Southern Synthesis 4. Commonwealth of Australia, 2000. Phylum Echiura. Pp. 19-21, Family Thalassematidae.
Web links
Individual evidence
- ^ Thalassematidae Forbes & Goodsir, 1841. WoRMS , 2018. Retrieved May 14, 2018.