Peristomium

The peristomium , also peristom ( ancient Greek περί perí "around (around)" and στόμα stóma "mouth") is the second body section of the annelid worms (Annelida) following the prostomium , on which the mouth is located.

Many Vielborstern (Polychaeta) the Peristomium bears paired or numerous tentacles - palps or fleshy cirrus clouds , while any existing antennas always sit at Prostomium and not on Peristomium. If there is an evertable pharynx , it is located in the peristomium, but in the everted state it can fill up to 20 segments.

In some multi- bristles , the peristomium - as in the Eunicidae and Dorvilleidae - is designed as one or two complete rings that separate the prostomium from the first bristle-bearing segment (the first Chaetiger) or a bristle-free segment in between. The Peristomium and Prostomium are at different groups of polychaete as the Maldanidae and Paraonidae merged and following the cephalization as clearly recognizable head set off from the rest of the body. In the Sabellidae and Serpulidae , however, the ring of the peristomium is fused with the tentacle crown and is therefore no longer recognizable as a separate structure. In the Terebellidae and Trichobranchidae , the peristomium is reduced to lips around the mouth, in particular to a "roof of the mouth".

The peristomium is created in the polychaetes by fusing the mouth region with mostly 2 adjoining segments of the larva. The counting of the peristomium as a separate segment is not uniform. With multiple bristles, the peristomium or at least the anterior part of the peristomium counts as part of the presegmental region, and usually it is not the numbers of the segments as a whole, but the numbers of the bristle-bearing segments (chaetiger) that are given. With few bristles , however, it is common to count the peristomium as the first segment.

literature

Stanley J. Edmonds: Fauna of Australia, Volume 4A. Polychaetes & Allies. The Southern Synthesis 4. Commonwealth of Australia, 2000. Class Polychaeta. Pp. 15-19, Head and Head Structures.
Kristian Fauchald (1977): The polychaete worms, definitions and keys to the orders, families and genera. Natural History Museum of Los Angeles County. Los Angeles, CA (USA), Science Series. 28, pp. 1 - 188, here Peristomium , pp. 2f.

Web links

Polychaeta . In: Lexicon of Biology , online edition, 1999.
Peristome . In: Lexicon of Biology , online edition, 1999.

Individual evidence

↑ PL Chan: Marine Errant Polychaetes in Hong Kong - Introduction, Polychaetes City University of Hong Kong, Department of Biology and Chemistry.
^ PS Verma, BP Pandey: ISC Biology Book I for Class XI. S. Chand Publishing, Ram Nagar (New Delhi) 1991. p. 302, in section Pheretima posthuma - The Indian Earthworm , pp. 300-320.

[1] PL Chan: Marine Errant Polychaetes in Hong Kong - Introduction, Polychaetes City University of Hong Kong, Department of Biology and Chemistry.

[2] PS Verma, BP Pandey: ISC Biology Book I for Class XI. S. Chand Publishing, Ram Nagar (New Delhi) 1991. p. 302, in section Pheretima posthuma - The Indian Earthworm , pp. 300-320.