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

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 Dysponetuspygmaeus (Chrysopetalidae) with confocal laser scanning microscopy showed that circular muscles...

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Bibliographic Details
Published in:Acta zoologica (Stockholm) 2002-01, Vol.83 (1), p.81-85
Main Authors: Tzetlin, Alexander B, Zhadan, Anna, Ivanov, Ilia, Müller, Monika C. M, Purschke, Günter
Format: Article
Language:English
Subjects:
Annelida
body wall
Chrysopetalidae
circular muscles
Dysponetus pygmaeus
evolution
longitudinal muscles
Marine
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Summary: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 Dysponetuspygmaeus (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:0001-7272
1463-6395
DOI:10.1046/j.1463-6395.2002.00104.x