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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