Onchnesoma
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| Onchnesoma | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Annelida |
| Class: | Sipuncula |
| Order: | Golfingiida |
| Family: | Phascolionidae |
| Genus: | Onchnesoma Koren & Danielssen, 1875 |
| Species | |
|
4 (see text) | |
Onchnesoma is one of the two genera that constitute the family Phascolionidae of Phylum Sipuncula, described by Koren and Danielssen established in 1873 as the type species to Onchnesoma steenstrupii.[1][2][3][4][5]
The species of this genus are usually small in size (with a trunk of less than 1 cm in length). The introverted is much longer than the trunk. The body wall muscle layers presents continuous. The disc may present oral tentacles (usually less than 10 and about 8 mm. in length) arranged around the mouth, but those tentacles can be reduced in size or completely absent. The retractor muscle system is a highly modified introverted form fused to form a muscle retractor. The anus is located in the distal half of introverted. Gallbladder contractile is rarely observed and if present is without villi. They have a single nephridium.[3][5][6][7]
