# Peristomium

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Peristomium
> Markdown URL: https://mediated.wiki/source/Peristomium.md
> Source: https://en.wikipedia.org/wiki/Peristomium
> Source revision: 1225723906
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Body segment of an annelid worm containing the mouth and sometimes feeding palps

The **peristomium** is the first true body segment in an [annelid](/source/Annelid) worm's body in the anterior end. It is directly behind the [prostomium](/source/Prostomium) and contains the mouth, [tentacular cirri](https://en.wikipedia.org/w/index.php?title=Cirrus_(Polychaeta)&action=edit&redlink=1), and sometimes feeding palps, which may instead occur on the [prostomium](/source/Prostomium). If an eversible [pharynx](/source/Pharynx#Invertebrates) is present, it is contained in this segment as well, and can fill up to 20 segments when inverted, depending on the species.

The [prostomium](/source/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

- [Prostomium](/source/Prostomium)

- [Pygidium](/source/Pygidium)

## References

1. **[^](#cite_ref-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](/source/ISBN_(identifier)) [0-643-06571-7](https://en.wikipedia.org/wiki/Special:BookSources/0-643-06571-7).

---
Adapted from the Wikipedia article [Peristomium](https://en.wikipedia.org/wiki/Peristomium) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Peristomium?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.