1062-3604/05/3601- © 2005 Pleiades Publishing, Inc.
Russian Journal of Developmental Biology, Vol. 36, No. 1, 2005, pp. 34–42. Translated from Ontogenez, Vol. 36, No. 1, 2005, pp. 41–50.
Original Russian Text Copyright © 2005 by Dudkina, Kiseleva.
Intracellular symbionts of many insects and nema-
, are usually found in the host repro-
ductive tissues (Hertig, 1936; Werren, 1995; Bandi
, 1998; Stouthamer
, 1999). The interest to
these bacteria is related to their capacity of affecting the
host reproductive functions. The presence of endosym-
bionts could lead to cytoplasmic incompatibility, par-
thenogenesis, and feminization (O’Neill and Karr,
1990; McGraw and O’Neill, 1999; Stouthammer
1999). Cytoplasmic incompatibility is a unique form of
male sterility described in many insects containing
. It is expressed when the males infected
with bacteria are mated with noninfected females,
which leads to embryonic mortality (Hoffmann
1986). A spermatozoon penetrated in the egg but no
complete embryo was formed, since mitotic divisions
of the nuclei were disturbed at the in the initial stage of
development (Lassy and Karr, 1996). However, when
infected females were mated with noninfected males,
normal progeny was obtained. It is not yet clear how the
bacteria affect embryogenesis in the former case. It was
proposed that this phenomenon could be induced by
incomplete decompactization of paternal chromosome
during fusion of pronuclei after fertilization (Lassy and
Karr, 1996). It was already shown using ﬂuorescence
were found in great amounts in
the embryos and cells of ovaries and testes of
, but bacteria were not found in the
mature spermatozoa (Binnington and Hoffman, 1989).
This allowed a suggestion that endosymbionts exerted
a certain inﬂuence on the maturation of spermatozoa.
Studies of the mechanisms underlying symbiont-
host interactions during spermato- and embryogenesis
have been mostly carried out using light microscopy.
No comparative analysis of the organization and distri-
bution of endosymbionts in various cells of the testes
was conducted at the ultrastructural level and their pos-
sible inﬂuence on the formation of spermatozoa was
practically not studied.
This work was aimed at studying the ﬁne structure
and distribution of endosymbiotic bacteria
in cells at different stages of spermatogenesis in a line
strongly infected by these bacteria.
Electron microscopy studies combined with morpho-
metric analysis demonstrated the dynamics of distribu-
tion of the bacteria in different cells of the testes and
showed their highest concentration at the stage of sper-
matid elongation, when compactization of sperm chro-
matin takes place.
MATERIALS AND METHODS
lines and conditions of their
The line of
strongly infected with
was obtained from the collection of Prof.
T. Karr, University of Chicago, USA. The line Canton-
Structural Organization and Distribution of the Symbiotic
N. V. Dudkina
and E. V. Kiseleva
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences,
pr. Akademika Lavrent’eva 10, Novosibirsk, 630090 Russia
Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090 Russia
Received September 19, 2003; in ﬁnal form, July 29, 2004
—Electron microscopy and morphometric analysis have shown that the symbiotic bacteria
occur the testis cells
during spermatogenesis and are absent in mature spermatids. Bacteria did not
affect the structural organization of testis cells, which have a typical morphology during morphogenesis. Bac-
teria were distributed along the meiotic spindle microtubules near the mitochondria. They increased in number
in spermatids at the stage of elongation. Endosymbionts aggregated at the spermatid distal end and contained
many vacuoles but were absent at the spermatid proximal end near the nuclei. It was shown for the ﬁrst time
that the diameter of spermatids in a strongly infected line was two of three times that in a noninfected line. We
hypothesize that the increase in the number of endosymbionts during spermatid elongation can affect the chro-
matin condensation in the spermatozoon.
Wolbachia, Drosophila simulans
, endosymbionts, spermatogenesis, electron microscopy.