PROGRESS IN PROTOZOOLOGY

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possess flagella. Bacterial symbionts occurring in dinoflagellates were
studied by autoradiographic techniques and by fluorescent microscopy
by S. Franca and E. S. S i 1 v a. These workers concluded that the
symbionts gained entrance into the dinoflagellates early in its life cycle.
Viral Symbionts
J. T e r a s and L. K e s a studied protozoan-viral interactions using
Tetrahymena pyriformis, myxovirus and picornaviruses. Previous studies
showed that whereas Tetrahymena served as host for picorna-viruses,
myxovirus was rapidly inactivated by the protozoan. However,
previous exposure of Tetrahymena to myxovirus rendered the protozoan
incapable of harboring picornavirus, thus establishing for the first time,
viral interference in a protozoan-virus system. In studies of the interaction
of Giardia duodenalis and picornaviruses in vitro, G. Takhonia,
J. Teras and L. K e s a found that the picornaviruses were
not only taken up by the protozoans but were capable of exerting a cytopathogenic
effect on new-born white mice even after several passages
of the infected protozoan in virus-free medium. Further, the virus could
be re-isolated from the protozoans even after several subcultures in
virus-free medium. These results suggested that the cytopathic effects
of the virus remained unchanged as a consequence of protracted residence
in the protozoan host. S. Perez-Prieto, M. A. Jareno
and A. Garcia Cancedo studied the uptake of vaccinia virus in
ciliates. In experiments carried out at 25°C, extracellular viruses disappeared
progressively, although low levels of viral activity remained for
some time. In similar experiments with Onycchodromus acuminatus,
viral liters decreased to non-detectable levels. Future experiments were
planned with T. pyriformis strains adapted to 37°C.
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