ISSN 10227954, Russian Journal of Genetics, 2015, Vol. 51, No. 10, pp. 1036–1039. © Pleiades Publishing, Inc., 2015.
Original Russian Text © L.D. Safronova, E.J. Krysanov, 2015, published in Genetika, 2015, Vol. 51, No. 10, pp. 1203–1206.
includes 64 valid fish
species . Members of this genus inhabit the fresh
water reservoirs of East Africa (from Ethiopia to the
Republic of South Africa), which dry up during the dry
season. Thus, these species possess a life cycle charac
terized by a short life span and the ability of spawn to
diapause. Some members of this genus with a short life
cycle (3–5 months) became a convenient model to
study the aging process. Moreover, some species
appeared to be quite convenient for use in toxicologi
cal tests, particularly for studying the genotoxicity of
some environmental factors.
To date, the karyotypes of 12 species of the genus
have been investigated . Significant
karyotype variability was observed within the genus. In
addition, the members of this genus differ from most
fish from other systematic groups by their uniquely low
number and comprehensively long chromosomes.
For example, 2
= 16 in
= 38 in
However, a detailed description of the karyotypes
of these species has not been performed to date. Mei
osis in members of this genus has been little studied.
Chromosomal sexual heteromorphism was detected in
only one species of genus
= 35, and in females 2
= 36. The authors
suggested that the sex in this species is determined by
a X1X2Y/X1X1X2X2 scheme .
To analyze meiotic chromosomes and the specifics
of their synapses in meiotic prophase I in two fish spe
= 16) and
= 18), we applied a karyotyp
ing method based on the analysis of synaptonemal
complexes by Dresser and Moses . This method is
widely applied at present to study meiosis in animals,
humans, plants, and fungi [3–6]. Whole mounts of
spread synaptonemal complexes (SC) of meiotic
chromosomes were obtained. The electron micro
scope makes it possible to investigate the chromo
somal synapsis process at early prophase I stages .
The number of SCs in a cell is equal to the haploid
number of chromosomes. Comparison of the relative
SC lengths of autosomal bivalents in spermatocytes
and the lengths of metaphase chromosomes allowed a
determination of the identity of SC morphometric
characteristics in spermatocytes with the length of
metaphase chromosomes in somatic cells [4–6].
A small number of studies have been devoted to the
investigation of meiosis in fish via the analysis of syn
aptonemal complexes [7–10].
In this report the SCs of two fish species of genus
that are characterized by a low chro
mosome number (2
= 16 in
) and do not have heteromorphic sex
chromosomes  are described.
Males from two fish species—
from members of the Nothobranchius Club (killi.ru),
and they were kept in the aquaria of the Severtsov
Institute of Ecology and Evolution, Russian Academy
Somatic chromosomes were prepared from pro
nephros cells of male fish after a preliminary injection
of 0.1% colchicine according to the method in 
with several modifications. The chromosomes were
stained with Gimsa solution and analyzed under a
Axioplan Karl Zeiss microscope.
Synaptonemal Complex of Two Fish Species
of the Genus
L. D. Safronova and E. J. Krysanov
Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, 119071 Russia
Received December 18, 2014; in final form, April 20, 2015
—The karyotype of males of two species of the genus
with the lowest diploid num
bers was investigated:
= 16) and
= 18). For the first
time, whole mounts of spread syneptonemal complexes (SC) of these species were obtained and investigated.
When the SC was painted with silver nitrate and immunostained with rabbit antibodies against the SCP3 pro
tein, eight and nine homomorphic SCs were detected in the nuclei of class I spermatocytes of
, respectively. The sex chromosomes were not identified.
: meiosis, synaptonemal complex, genus