The structure of the proboscis musculature in <Emphasis Type="Italic">Baseodiscus delineatus</Emphasis> (Delle Chiaje, 1825) (Heteronemertea) and the comparative analysis of the proboscis musculature in heteronemerteans |
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Authors: | T Yu Magarlamov A V Chernyshev |
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Institution: | 1.Zhirmunsky Institute of Marine Biology,Vladivostok,Russia;2.Far Eastern Federal University,Vladivostok,Russia |
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Abstract: | The proboscis musculature was studied in the nemertean Baseodiscus delineatus using confocal laser scanning and electron transmission microscopy. Three muscle layers were differentiated in the proboscis
wall: the outer-longitudinal, the diagonal, and the inner-circular layer. The endothelium consists of two cell types: apical
supportive cells with rudimentary cilia and subapical myocytes making up the inner-circular musculature of the proboscis.
The supportive cells have thin processes attached to the basal extracellular matrix and their perikarya are spread over the
apical surfaces of myocytes. The endothelium of B. delineatus is characterized by a folded basal layer of the extracellular matrix and by different heights of myocyte processes, giving
an impression that the inner-circular musculature is multilayered. Comparative analysis shows that the diagonal musculature
of Baseodiscus is not homologous to that of other heteronemerteans. An assumption is made that the inner-circular muscles have endothelial
origin in all heteronemerteans. |
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