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Phylogenetic relationship between Sipunculids and Annelid

Submitted by Mousumi Sepai, Last Modified on 2019-11-19

Sipunculids Annelid

Features Sipunculids Annelid
1. External segmentation In Sipunculids species there are no External segmentation Most of an annelid's body consists of segments, that are partially identical, having the same sets of internal organs and external chaetae and in some species appendages.
2. Repetition of internal organs The internal organs of sipunculids are not repeated like annelid The internal organ of the Annelid are repeated.
3. Septa between segmentation Septa between segments are seen in most sipunculid species. There are no septa between two segment in any species.
4. Cuticle materiel Sipunculids have a body wall somewhat similar to that of annelids in that it consists of a non-ciliated epidermis overlaid by a cuticle an outer layer of cuticular and an inner layer of longitudinal musculature Annelid's cuticle are made of collagen fibres usually in layers that spiral in alternating directions so that the fibres cross each other.
5. Moulting Sipunculid doesn't have any moulting of their any body part structure. Annelids moult their jaws, and leeches moult their skin.
6. Body Cavity Coelom is the main body cavity of the sipunculids In sipunculids there are two coelom main and proboscis. Coelom is the main body cavity of the annelid, but this is reduced or missing in many leeches and some small poly-chaetae
7. Circulatory system Circulatory system open outflow, return via branched vein. Circulatory systems are closed in most species.

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