Pogonophora muscle anomaly claimed

Geoff Read g.read at niwa.co.nz
Thu Sep 26 22:17:11 EST 2002


Matsuno, A. ; Sasayama, Y. 2002: A comparative study of body wall 
structures of a pogonophore and an annelid from a phylogenetic viewpoint. 
Zoological Science (Tokyo) 19: 695-701.  

Abstract: "Pogonophores are tube worms that live in reducing deep-sea 
waters where sunlight does not penetrate. They are highly adapted for their 
special habitat in lacking guts and possessing endosymbiotic 
chemosynthetic bacteria. Because of these peculiar characteristics, it is not 
yet clear whether they should be classified as annelids or not. Electron- 
microscopic observations of sections of a Japanese pogonophore 
(Oligobrachia mashikoi) show that the body wall has circular and longitudinal 
muscular systems. These muscular systems, however, differ from the 
annelid (Branchiura sowerbyi) in these ways: (1) The outer circular muscle 
of the pogonophore was constructed of smooth muscle cells. In contrast, 
that of the annelid was composed of obliquely-striated muscle cells, even 
though the cells were small and bore undeveloped characteristics. (2) The 
inner longitudinal muscle of the pogonophore was constructed of 
undeveloped obliquely-striated muscle cells, whereas that of the annelid was 
composed of well-developed ones. These observations suggest that this 
pogonophore can not be classified as an annelid, although many previous 
studies have placed pogonophores in that phylum." 

--
  Geoff Read <g.read at niwa.co.nz>
  http://www.annelida.net/


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