MITOSIS IN THE FREE-LIVING FLAGELLATE BODO SALTANS STRAIN PS+ (KINETOPLASTIDEA, BODONIDA)
M. N. Malysheva,1 M. S. Karpova,2 A. O. Frolov 1
1 Zoological Institute RAS, St. Petersburg, and 2 Chair of Cytology, St. Petersburg
State University;
e-mail: frolal@online.ru
The mitosis in the free-living flagellate Bodo saltans Ps+ with prokaryotic cytobionts in perinuclear space
has been studied. The nuclear division in B. saltans Ps+ occurs by closed mitosis type without condensation of
chromosomes. Two spatially separated mitotic spindles begin to form consistently at the initial stages of nuclear
division. The spindle including about 20 microtubules appears first and later the second spindle with half the
number of microtubules comes at the angle of 30-40°. Both spindles rest their ends against the inner nuclear
membrane and form 4 distinct poles. The microtubules of the first spindle are associated with 4 pairs of kinetochores,
the microtubules of the second one are associated with 2 pairs of kinetochores. The divergence of the kinetochores
towards the poles occurs independently in each spindle. The equatorial phase is not revealed in
B. saltans Ps+. The poles of both spindles unite in pairs at the elongation phase of mitosis and form the integrated
bipolar structure. At this stage of the nuclear division, the kinetochores reach the poles of subspindles and
become indistinguishable. Then the nucleus takes the shape of a dumbbell. The inner nuclear membranes of just
formed nuclei have layers of condensed chromatin characteristic of the interphase nuclei of kinetoplastidea. The
daughter nuclei separate at the phase of reorganization. There are 1-2 prokaryotic endocytobionts in the perinuclear
space of the interphase nuclei in B. saltans Ps+. The symbionts multiply during mitosis and their number
reaches more than 20 specimens par nucleus.
Key words: Kinetoplastidea, Bodonida, Bodo saltans, ultrastructure, nucleus, mitosis, prokaryotic cytobionts
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