An endosymbiotic Chlorella-bearing ciliate: Platyophrya chlorelligera Kawakami 1989

The morphology of an endosymbiotic Chlorella-bearing ciliate, Platyophrya chlorelligera Kawakami, 1989, isolated in a suburb of Hiroshima and cultivated in a culture medium constituted of mineral salts, was investigated by means of protargol staining, scanning and transmission electron microscopy. Trypsin treatment was found to be highly effective for observation of resting cysts by transmission electron microscope as it prevents the occurrence of perforations and increases contrast in cell organelles in sections. The ciliate differs from its congeners, especially with respect to the number of somatic kineties and adorai organelles. The vegetative ciliate is 58 × 24 μm on average in size in vivo, and is slender reniform and dorso-ventrally flattened. The somatic kineties are 19–24 in number and run longitudinally, spiralling in a clockwise direction. A slit-like to ellipsoid oral aperture of about 7 μm in length is situated on the left of the apical end of the body. There are 7–8 adorai organelles which are arranged in a line on the left side of the oral aperture. Two rows of closely arranged pairs of ciliated kinetosomes surround the left side of the adorai organelles. A spherical macronucleus is located in the posterior half of the body together with a lenticular micronucleus which is enclosed in the perinuclear space of the macronucleus. The ciliate multiplies by binary division while swimming freely. The endosymbiotic Chlorella remains in the cytoplasm of the ciliate during the entire life cycle of the ciliate which consists of vegetative, division, encystment, resting cyst and excystment stages. In recognition of the intimate association between the ciliate and the endosymbiotic Chlorella, the ciliate has been named P. chlorelligera.