Peristomium

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The peristomium is the first true body segment in an annelid worm's body in the anterior end. It is directly behind the prostomium and contains the mouth, tentacular cirri, and sometimes feeding palps, which may instead occur on the prostomium. If an eversible pharynx is present, it is contained in this segment as well, and can fill up to 20 segments when inverted, depending on the species.

Annelid Phylum of segmented worms

The annelids, also known as the ringed worms or segmented worms, are a large phylum, with over 22,000 extant species including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecologies – some in marine environments as distinct as tidal zones and hydrothermal vents, others in fresh water, and yet others in moist terrestrial environments.

The prostomium is the first body segment in an annelid worm's body in the anterior end. It is in front of the mouth, being usually a small shelf- or lip-like extension over the dorsal side of the mouth.

The prostomium and peristomium can be variously fused, either completely distinct, or comprising a joint structure of a peristomial ring and a tentacular crown. [1]

See also

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References

  1. Beesley, Pamela; Graham J. B. Ross; Christopher J. Glasby (2000). Polychaetes & Allies: The Southern Synthesis. Fauna of Australia. Vol. 4A Polychaeta, Myzostomida, Pogonophora, Echiura, Sipuncula. Melbourne, Australia: CSIRO Publishing. pp. 11–12. ISBN   0-643-06571-7.