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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 959

M. Laval-Peuto and F. Rassoulzadegan; Autofluorescence of marine planktonic oligotrichina and other ciliates. Hydrobiologia 159:99-110, 1988

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Planktonic ciliates, principally from the suborders Oligotrichina and Tintinnina, were examined by epifluorescence microscopy. This allowed (1) to check is isolated symbiotic plastids demonstrated by TEM in some species could keep and show an important autofluorescence, (2) to count and identify the species presenting this characteristic, and (3) to determine their proportion compared with the other strictly heterotrophic planktonic ciliates. An average of 40.6% of the Oligotrichina species, collected during the fall and winter, displayed a strong autofluorescence. This indicated chlorophyll contents, in a good state of activity, which most often masked the digestive vacuoles shown by TEM. It seems that the maintenance of plastids, or of symbiotic algae, is common in this sub-order. These autofluorescent ciliates are probably all mixotrophic. We suggest to call them 'plastidic ciliates', and to consider their role in marine primary production. Discussion deals with the origin and the role of autofluorescent pigments in the Oligotrichina, compared with the other planktonic ciliates. The interest and the limits of the methods employed up to now, or to be used in this field, are analysed. Finally the evolutionary and ecological significance of such a development of symbiosis among planktonic ciliates is discussed.