Corresponding author: Valentina G. Kuznetsova (

Academic editor: Pavel Štys

The Cimicomorpha is one of the largest and highly diversified infraorders of the

The

The cytogenetics of the

Since Ueshima’s publication a large body of new cytogenetic data on the

The

Autosome numbers’ range in

Distribution of sex chromosome systems in _{n} - the number of X-chromosomes exceeds 5.

Holokinetic chromosomes (sometimes designated as holocentric) occur in certain scattered groups of plants and animals, being particularly widespread in insects, including the

Despite an important role of chromosomal change in the evolution and diversification of many groups of organisms (

Chromosome numbers have been published for approximately 465 species (180 genera) of cimicomorphan true bugs, including many of the higher taxonomic categories within the infraorder (

However, the commonest chromosome number needs not to be plesiomorphic in a taxon. A good example comes from the family

Considering the lack of a centromere, holokinetic chromosomes exhibit a very limited number of characters that can be used as markers. That is why, in spite of recent progress in developing of different staining techniques, chromosomal rearrangements not changing the number of chromosomes, such as inversions and reciprocal translocations, have been very rarely reported in the

The term “m-chromosomes” has been introduced by

In Ueshima’s review (

The currently available data suggest that the presence or absence of m-chromosomes represents a quite stable character at higher taxonomic levels in the

Genetic sex determination is predominant in insects and is often accompanied by the presence of a heteromorphic chromosome pair in one sex. The true bugs share male heterogamety with the great majority of other insects. Within the _{n}0, X_{n}Y, and XY_{n}) as well as rare neo-XY systems do occur (

The question as to whether the common ancestor of all

On the other hand, (

The most basal heteropteran infraorders are considered to be _{1}Y_{2 }(_{1}Y_{2} species (

The existence of Y-chromosome in the

In the

Compared to other _{1}X_{2}Y) to 15 (X_{1}X_{2}Y+13 extra Xs) in different populations while sometimes between males of a population and even between different cells of a male (

B-chromosomes, also known as supernumerary, accessory, or extra chromosomes, are dispensable elements which do not recombine with other chromosomes (the A-chromosomes) of the standard complement and follow their own evolutionary pathway (

It is common knowledge that in meiosis, chiasmata (the points of genetic crossing-over) are formed uniting homologous chromosomes together until their separation in the reductional division. However in some animal groups chiasma formation is replaced by other, achiasmate means. When meiosis is achiasmate, at early prophase I one can see the conventional sequence of leptotene, zygotene and pachytene stages. However, no chiasmata are formed and hence no diplotene or diakinesis stages can be recognized. Typically, achiasmate meiosis is restricted to the heterogametic sex of a species. In most heteropteran males, autosomal bivalents are chiasmate whereas sex chromosomes have no chiasmata, however in a number of families male meiosis is completely achiasmate (

Multiple origins of achiasmate meiosis in

The multiple origin of achiasmate meiosis is well in accordance with the observations on the divergence in its cytological properties. The most common type of achiasmate meiosis is the so-called

In the

Additionally, in the

In general, during the first division of meiosis the chromosomes reduce in number (reductional division), whereas during the second division the chromatids separate (equational division), and this pattern is named “pre-reduction” (

In most

Another characteristic feature is the configuration of metaphase I and metaphase II plates, which pattern seems to show species-specific variation in the

For technical reasons, most research on heteropteran chromosomes has used males and as a consequence, there is very little evidence on meiosis in females.

One of the mirid species,

In general, cytogenetic studies of the

In the last few decades, the ability to identify chromosomes has been markedly improved by the development of molecular cytogenetic technologies such as fluorescence

A potential ﬁeld of interest concerns the molecular composition of telomeres, which is totally unknown in the true bugs. Telomeres are terminal regions of chromosomes that protect chromosomes from destruction and stabilize their structure (_{n}, is the commonest and most likely an ancestral telomeric motif of Insecta that supports their origin from a common ancestor. _{n} telomeric sequence is absent as evidenced by FISH and/or Southern and/or dot-blot hybridization with a TTAGG probe (_{n} motif was suggested to be lost in the early evolution of the true bugs being secondarily replaced by another motif or an alternative telomerase-independent mechanism of telomere maintenance (_{n} and (TTGGGG)_{n}, nematode (TTAGGC)_{n}, shrimp (TAACC)_{n}, vertebrate (TTAGGG)_{n}, and plant (TTTAGGG)_{n}, yielded likewise negative results (

Chromosome numbers and sex chromosome systems in

24+XY | ||||

28+X0 | ||||

32+XY | ||||

18+XY | ||||

14+XY | ||||

26+2m+XY | ||||

20+X_{1}X_{2}X_{3}X_{4}X_{5}Y (1) |
||||

n=16 (1) | ||||

22+XY | ||||

22+X_{1}X_{2}X_{3}Y |
||||

24+X_{1}X_{2}X_{3}Y |
||||

24+X_{1}X_{2}Y |
||||

24+X_{1}X_{2}Y |
||||

24+X_{1}X_{2}Y |
||||

24+X_{1}X_{2}X_{3}Y |
||||

22+XY | ||||

24+X_{1}X_{2}Y |
||||

10+XY (1) | ||||

10+XY | ||||

12+XY | ||||

24+X_{1}X_{2}X_{3}Y |
||||

24+X_{1}X_{2}X_{3}Y |
||||

24+X_{1}X_{2}Y |
||||

24+X_{1}X_{2}X_{3}Y (5) 20+X_{1}X_{2}X_{3}X_{4}X_{5}Y (1) |
||||

24+X_{1}X_{2}X_{3}Y |
||||

24+X_{1}X_{2}X_{3}Y |
||||

24+XY | ||||

24+XY | ||||

20+XY | ||||

20+XY (1) 20+X_{1}X_{2}Y (2) |
||||

20+X_{1}X_{2}Y |
||||

26+XY | ||||

26+XY | ||||

26+XY | ||||

24+X_{1}X_{2}X_{3}X_{4}Y |
||||

20+XY (1) 26+XY (1) | ||||

24+XY | ||||

20+X_{1}X_{2}Y (4) 20+X_{1}X_{2}X_{3}Y (1) 22+X_{1}X_{2}X_{3}Y (2) |
||||

20+X_{1}X_{2}X_{3}X_{4}Y |
||||

22+XY (1) 22+X_{1}X_{2}Y (1) |
||||

20+X_{1}X_{2}X_{3}X_{4}Y |
||||

20+X_{1}X_{2}Y |
||||

20+XY | ||||

20+X_{1}X_{2}Y |
||||

20+X_{1}X_{2}Y |
||||

18+X_{1}X_{2}Y (1) 20+X_{1}X_{2}Y (7) |
||||

18+X_{1}X_{2}Y (1) |
||||

20+XY (1) | ||||

20+XY | ||||

18+X_{1}X_{2}Y (1) 20+XY (25) 20+X_{1}X_{2}Y (21) 20+X_{1}X_{2}X_{3}Y (2) |
||||

20+X_{1}X_{2}Y |
||||

22+X_{1}X_{2}Y |
||||

12+XY | ||||

12+XY | ||||

22+XY | ||||

32+XY | ||||

32+XY | ||||

32+XX (♀♀) | ||||

36+XY (1) 40+XY (1) 44+XY(1) 44+X_{1}X_{2}Y (1) 46+XY (8) 46+2m+X_{1}X_{2}X_{3}Y (1) 46+X_{1}X_{2}Y (1) 46+X_{1}X_{2}X_{3}Y (1) |
||||

26+XY | ||||

16+XY (1) 18+XY (1) | ||||

24+XY (1) 24+X_{1}X_{2}X_{3}Y (1) 26+XY (1) |
||||

32+XY | ||||

26+XY | ||||

32+XY (11) 34+XY (1) 30+2m+XY (2) | ||||

32+XY | ||||

32+XY (1) 34+XY (1) | ||||

20+XY (1) 22+XY (2) 24+XY (1) 26+XY (1) | ||||

12+2m+XO | ||||

30+XY | ||||

2n=28 | ||||

26+X_{1}X_{2}0 |
||||

32+XY | ||||

32+XY | ||||

32+XY | ||||

30+2m+XY | ||||

32+XY | ||||

32+XY (1) | ||||

30+XY | ||||

32+XY | ||||

12+XY | ||||

30+XY | ||||

32+XY | ||||

32+XY (1) | ||||

28+2m+XY (1) | ||||

30+XY | ||||

32+XY | ||||

30+XY | ||||

32+XY | ||||

32+XY | ||||

32+XY | ||||

32+XY | ||||

32+XY (10) | ||||

32+XY | ||||

32+XY (4) | ||||

n=19? | ||||

30+2m+X0 | ||||

32+XY | ||||

30+XY | ||||

32+XY | ||||

30+XY | ||||

32+XY | ||||

12+2m+X0 | ||||

30+XY | ||||

22+XY | ||||

32+XY | ||||

32+XY (8) 30+XY (1) | ||||

32+XY | ||||

32+XY | ||||

30+XY | ||||

30+XY (1) 32+XY (1) | ||||

40+XY (1) | ||||

30+XY | ||||

32+XY | ||||

2n=32-34 | ||||

32+XY | ||||

32+XY | ||||

32+XY | ||||

22+XY | ||||

18+XY (1) 22+XY (3) | ||||

21+ X_{1}X_{2}Y |
||||

32+XY (1) | Grozeva and Simov 2011 | |||

32+XY | ||||

34+X_{1}X_{2}Y |
||||

28+XY | ||||

32+XY | ||||

24+XY | ||||

38+XY | ||||

78+XY | ||||

20+XY (1) | ||||

26+XY | ||||

28+XY | ||||

22+XY (2) 24+XY (1) 26+XY (2) 28+XY (1) | ||||

24+XY | ||||

26+XY | ||||

22+XY | ||||

28+XY | ||||

24+XY | ||||

24+XY | ||||

30+XY | ||||

30+XY | ||||

30+XY | ||||

30+XY | ||||

30+XY | ||||

30+XY | ||||

26+XY (1) 28+XY (1) | ||||

30+XY | ||||

30+XY | ||||

32+XY | Grozeva, 2003 | |||

24+XY (1) 2n=4 (1)** | ||||

30+XY | ||||

32+XY | ||||

30+XY | ||||

30+XY | ||||

32+XY | ||||

30+XY | ||||

30+X0 | ||||

26+XY (1) 28+XY (3) | ||||

30+X0 (1) 30+XY (4) 32+XY (1) | ||||

32+XY (1) | ||||

28+XY | ||||

30+XY | ||||

32+XY | ||||

30+XY | ||||

28+XY (3) 30+XY (4) | ||||

2n=8** | ||||

12+X0 (2) | ||||

10+XY | ||||

12+X0 | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

12+XY | ||||

10+XY | ||||

36+XY | ||||

16+XY | ||||

38+XY | ||||

32-36+XY (1) | ||||

32+XY (1) | ||||

30+XY | ||||

16+XY | ||||

16+XY | ||||

16+XY (6) | ||||

16+XY | ||||

18+XY | ||||

32+XY | ||||

16+XY | ||||

32+XY | ||||

16+XY | ||||

16+XY | ||||

16+XY | ||||

16+XY | ||||

16+XY | ||||

26+XY | ||||

26+XY | ||||

28+XY | ||||

22+XY | ||||

30+XY | ||||

22+X_{1}X_{2}Y |
||||

8+XY | ||||

8+XY 10+XY | ||||

36+X_{1}X_{2}Y |
||||

22+XY | ||||

8+XY | ||||

22+XY (1) 36+X_{1}X_{2}Y (1) |
||||

22+XY (1) 24+XY (1) 28+XY (1) 26+X_{1}X_{2}Y (3) 28+X_{1}X_{2}Y (6) 28+X_{1}X_{2}X_{3}Y (6) 28+X_{1}X_{2}X_{3}X_{4}Y (1) |
||||

28+X_{1}X_{2}Y |
||||

36+X_{1}X_{2}Y (4) 36+X_{1}X_{2} X_{3}Y (2) 36+4-9XY (2) |
||||

32+XY | ||||

10+XY | ||||

28+X_{1}X_{2}Y |
||||

38+X_{1}X_{2}X_{3}Y (1) 38+XY (1) 40+XY (1) |
||||

8+XY | ||||

28+X_{1}X_{2}Y |
||||

28+X_{1}X_{2}Y |
||||

22+XY | ||||

22+XY | ||||

26+XY | ||||

28+XY | ||||

4+XY (1) 10+XY (1) | ||||

6+XY |

* In the paper, only the number of chromosomes (2n/n) is provided, then, the karyotype formula for the species is deduced here from 2n/n, ** But see the text

This study was supported financially by the Russian Foundation for Basic Research (grant 11-04-00734) and programs of the Presidium of the Russian Academy of Sciences “Gene Pools and Genetic Diversity” and “Origin of the Biosphere and Evolution of Geo-biological Systems” (for VK) and by National Scientific Fund of Bulgarian Ministry of Education, Youth and Science (TK-B-1601 and DO-02-259/08) (for SG), by Russian Academy of Sciences and Bulgarian Academy of Sciences. We express our thanks to Nikolay Simov (NMNH, Sofia) for the valuable advices and help to verify the taxonomic status and latin names of different taxa in Table. We are obliged to anonymous reviewers and particularly to the editor for useful comments on the earlier versions of the manuscript.

_{n}repeat in seven species of true bugs (Hemiptera: Heteroptera).