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Fine structure of the digestive tubules of Meretrix
Pal, S.G.; Ghosh, B.; Modak, S. (1990). Fine structure of the digestive tubules of Meretrix, in: Morton, B. (Ed.) The Bivalvia: Proceedings of a Memorial Symposium in honour of Sir Charles Maurice Yonge (1899-1986) at the 9th International Malacological Congress, 1986, Edinburgh, Scotland, UK. pp. 167-175
In: Morton, B. (Ed.) (1990). The Bivalvia: Proceedings of a Memorial Symposium in honour of Sir Charles Maurice Yonge (1899-1986) at the 9th International Malacological Congress, 1986, Edinburgh, Scotland, UK. Hong Kong University Press: Hong Kong. ISBN 962-209-273-X. 355 pp., more

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    VLIZ: Proceedings [7763]

Keyword
    Marine

Authors  Top 
  • Pal, S.G.
  • Ghosh, B.
  • Modak, S.

Abstract
    The fine structure of the digestive tubules of Meretrix meretrix has been studied by conventional transmission electron microscopy (CTEM). There are three types or phases of epithelial cells lining the tubules: (a) centrally placed flagellated basiphilic cells numbering about 5 in the crypts; (b) a few non-flagellated basiphilic cells and (c) numerous vacuolated digestive cells. The non-flagellated basiphil cells have a large, basally situated and uneven nucleus with a prominent nucleolus, extensive RER profiles, Golgi apparatus and numerous mitochondria and secretory droplets. The early secretory droplets originate in the cavities of the RER and the membrane-bound secretory granules lie close to the Golgi apparatus. Besides these, there occur lipid droplets, lysosome-like bodies, multi vesicular bodies and autophagic vesicles. Conversely, the digestive cells are characterised by a large basal nucleus, numerous phagosomes and residual bodies and several apically situated smooth-surfaced vesicles, vermiform bodies and micropinocytotic channels and numerous mitochondria. The Golgi apparatus is not extensive. There are a few lipid-like bodies towards the base of the digestive cells. Some of the phagosomes possess small lipid droplets and a granular matrix. The apical cytoplasm of the digestive cells of Meretrix infrequently demonstrates the presence of tonofilament- like elements which run along the axis of the cells. Laterally the plasma membranes of both the digestive and basiphil cells show the usual surface specializations, i.e. desmosomes, septate desmosomes and tight junctions. The presence of smooth muscles is noted behind the basement membrane of the tubules. The significance of these results is discussed in the light of current knowledge of digestion in the Bivalvia.

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