On the absence of circular muscle elements in the body wall of Dysponetus pygmaeus (Chrysopetalidae, `Polychaeta', Annelida)

Autor(en): Tzetlin, AB
Zhadan, A
Ivanov, I
Muller, MCM
Purschke, G 
Stichwörter: Anatomy & Morphology; Annelida; body wall; Chrysopetalidae; circular muscles; evolution; longitudinal muscles; Zoology
Erscheinungsdatum: 2002
Herausgeber: BLACKWELL PUBLISHING LTD
Journal: ACTA ZOOLOGICA
Volumen: 83
Ausgabe: 1
Startseite: 81
Seitenende: 85
Zusammenfassung: 
The annelid body wall generally comprises an outer layer of circular muscle fibres and an inner layer of longitudinal muscle fibres as well as parapodial and chaetal muscles. An investigation of Dysponetus pygmaeus (Chrysopetalidae) with confocal laser scanning microscopy showed that circular muscles are entirely absent. Further studies indicate that this feature is characteristic for all Chrysopetalidae. A scrutiny of the literature showed a similar situation in many other polychaetes. This lack of circular muscle fibres may either be due to convergence or represent a plesiomorphic character. Since circular muscles are very likely important for burrowing forms but not necessary for animals which proceed by movements of their parapodial appendages or cilia, this problem is also related to the question of whether the ancestral polychaete was epi- or endobenthic.
ISSN: 00017272
DOI: 10.1046/j.1463-6395.2002.00104.x

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