Cytological Markers
Cytological Markers
In the present study, differences in cytogenetic features with respect to
chromosome number and size, meiotic behavior of chromosomes, constitutive
heterochromatin organization, sequence specificity of heterochromatic regions and
nucleolar behavior during meiosis have been described for two species of
Cletomorpha, Anhomoeus and Acanthocoris each, three species of Cletus and
Anoplocnemis each and four species of Homoeocerus.
Two species of Cletomorpha can be differentiated on the basis of diploid
chromosome complement, chromosome size, meiotic behavior and banding pattern.
C. hastata has 2n=22=18A+2m+X1X20 and C. raja has 2n=20=16A+2m+ X1X20. C.
hastata has 3 large autosomal bivalents while C. raja has 1 extremely large autosomal
bivalent. In C. hastata, all bivalents show single chiasma each while in C. raja, the
extremely large autosomal bivalent shows two terminal chiasmata. Fused X1X2 body
is C-positive and DAPI bright at diffuse stage in C. hastata while in C. raja, it is Cnegative and dull to both DAPI and CMA3 (Table: 11).
Three species of Cletus, Cletus pallescens, Cletus punctiger and Cletus sp.
show same chromosome complement of 2n=18=14A+2m+ X1X20. At diffuse stage, in
C. pallescens, fused X1X2 body is C-negative and dull to both DAPI and CMA3 while
in Cletus punctiger and Cletus sp., it is C-positive, DAPI bright and CMA3 dull. The
latter two species are differentiable only on the basis of number of nucleoli (Table:
12).
Three species of Anoplocnemis, Anoplocnemis phasiana, Anoplocnemis
compressa and Anoplocnemis binotata show the same chromosome complement of
2n=15=14A+X0. X chromosome is completely C-positive in A. compressa,
completely C-negative in A. binotata and shows a terminal C-band in A. phasiana. X
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Cytological Markers
is DAPI bright and CMA3 dull in A. compressa and DAPI and CMA3 dull in A.
binotata. A. compressa shows 4 nucleoli while A. phasiana shows single nucleolus at
diffuse stage (Table: 13).
Two species of Acanthocoris viz., Acanthocoris anticus and Acanthocoris sp.
have similar chromosome complement of 2n=24=22A+X1X20. In Acanthocoris
anticus, all autosomal bivalents show single chiasma each while in Acanthocoris sp.,
two to three autosomal bivalents are seen with two chiasmata each while the rest show
single chiasma per bivalent. Metaphase I arrangement pattern in two species of
Acanthocoris is different. In A. anticus, all autosomal bivalents form a ring with mpseudobivalent lying in the center and X1X2 lying outside the ring while in
Acanthocoris sp., 1 or 2 autosomal bivalents lie within the ring formed by rest of the
bivalents and sex chromosomes lie outside the ring (Table: 14).
Four species of Homoeocerus (H. signatus, H. borealis, H. lacertorsus and H.
macula) show the same chromosome complement of 2n=21=18A=2m=X0. In H.
signatus, 1 pair of autosomes is distinctly large while in H. borealis and H. macula, 2
pairs of autosomes are distinctly large and in H. lacertorsus, 3 pairs of autosomes are
distinctly large. Microchromosomes are unusually large in H. macula as compared to
H. borealis, H. signatus and H. lacertorsus. X chromosome is the largest element of
the complement in H. lacertorsus while it is almost equal to the medium sized
autosomes in H. signatus, H. borealis and H. macula. C-banding pattern and base
specificity is different in all the species of Homoeocerus (Table: 15).
Two species of Anhomoeus viz., Anhomoeus anticus and Anhomoeus sp. have
similar chromosome complement of 2n=21=18A+2m+X. In A. nepalensis, one
autosome pair is distinctly large while in A. sulcatus, all the autosomes show gradual
gradation (Table: 16).
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Cytological Markers
Prionolomia sp. has been seen to be unique in showing two heavy terminal Cheterochromatin blocks in the largest autosomal bivalent while rest of the complement
is completely C-negative.
Such differences have been used as cytogenetic markers to distinguish
individual chromosomes and to differentiate related species with similar chromosome
complements in earlier studies. Perez et al. (1997) used a C-band block in one of the
autosomes in Triatoma infestans (Reduviidae) to analyze the behavior of this
chromosome during meiosis. Grozeva and Nokkala (2001) distinguished some
Tingidae species possessing same chromosome number (2n=12A+XY/X0) based on
the C-banding pattern of chromosomes. Similarly, Rebagliati et al. (2003) described
differences between two species of Edessa (Pentatomidae) with a similar chromosome
complement of 2n=12A+XY based on chiasma frequency, metaphase I arrangement
of chromosomes, fluorescent signals and nucleolar behavior. Angus et al. (2004)
provided cytogenetical markers on the basis of characteristic C-banding pattern of
four long autosomes and the X-chromosome in three species of the genus Notonecta
(Notonectidae) having same diploid number (2n=22A+XY) and similar chromosome
sizes. Lanzone and Souza (2006b) compared the karyotypes of three species of
Antiteuchus (Pentatomidae) with similar chromosome complement (2n=12A+XY)
and recorded differences in size and location of C-bands, fluorescent signals and
nature of nucleolar organizer regions. Similarly, Kaur et al. (2010) reported
differences in the C-banding pattern of chromosomes in two species of Dieuches
(Lygaeidae) having similar chromosome complement (2n=8A+2m+XY) and
suggested certain cytogenetical markers for species differentiation. Karylogical
differences have also been identified in seven species of Belostoma by Papeschi
(1988, 1991), two species of Nabis by Grozeva et al. (2004) and five species of
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Cytological Markers
Corixa by Waller and Angus (2005). Similarly, Grozeva and Simov (2008) provided
certain cytological features of two species of Cremnocephalus (Miridae) which could
serve as cytological markers for species identification.
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Cytological Markers
Table 11. Differences in cytogenetic features of 2 species of Cletomorpha
Taxa
Cletomorpha
raja
Cletomorpha
hastata
Chromosome
complement
(2n)
20=16A+2m+X1X20
22=18A+2m+X1X20
Chromosome size
Meiotic behavior
C- banding
Sequence specific staining
Diplotene/Diakinesis
Diffuse stage
Diffuse stage
1 extremely large
autosomal bivalent
Extremely large autosomal
bivalent shows two
terminal chiasmata.
Fused X1X2 body is Cve
Fused X1X2 body is DAPICMA3 dull.
3 large autosomal
bivalents
All autosomal bivalents
show single chiasma each
Fused X1X2 body is
C+ve.
Fused X1X2 body is DAPI
bright and CMA3 dull.
Table 12. Differences in cytogenetic features of 3 species of Cletus
Taxa
Chromosome
complement
(2n)
C- banding
Sequence specific staining
Diffuse stage
Diffuse stage
Silver staining
Cletus
pallescens
18=14A+2m+X1X20
Fused X1X2 body is C- ve
Fused X1X2 body is DAPI-CMA3
dull.
Cletus
punctiger
18=14A+2m+X1X20
Fused X1X2 body is C+ ve
Fused X1X2 body is DAPI bright
and CMA3 dull.
Nuclei with one big and two small
nucleoli
Cletus
borealis
18=14A+2m+X1X20
Fused X1X2 body is C+ ve
Fused X1X2 body is DAPI bright
and CMA3 dull.
Nuclei with only one big nucleolus
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Cytological Markers
Table 13. Differences in cytogenetic features of 3 species of Anoplocnemis
Taxa
Chromosome
complement
(2n)
C- banding
Sequence specific
staining
Diplotene
Diplotene
Anoplocnemis
compressa
15=14A+X0
X is completely C+ve
X is DAPI bright and
CMA3 dull
Anoplocnemis
phasiana
Anoplocnemis binotata
15=14A+X0
X shows a terminal C band
15=14A+X0
X is completely C-ve
Silver banding
Diffuse stage
Four nucleoli
One nucleolus
X is both DAPI-CMA3
dull
Table 14. Differences in cytogenetic features of 4 species of Homoeocerus
Taxa
Homoeocerus
signatus
Homoeocerus
borealis
Chromosome
complement
(2n)
21=18A+2m+X0
21=18A+2m+X0
Chromosome size
C- banding
Diplotene
One pair of autosomes is distinctly large. X is equivalent to
small sized autosomes
Two pairs of autosomes are distinctly. X is equal to small
sized autosomes.
Homoeocerus
lacertorsus
21=18A+2m+X0
Three autosomes are distinctly large. X is the longest element
of the complement
Homoeocerus
macula
21=18A+2m+X0
Two autosomes are distinctly large. Microchromosomes
unusually large. X is equal to small sized autosomes.
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Autosomal bivalents show terminal C bands.
Microchromosomes are C-ve
Three autosomal bivalents show terminal and
interstitial C bands, five bivalents show terminal
bands, one bivalent shows thin C bands.
Microchromosomes are C-ve.
Six autosomal bivalents show thick C-bands while
three show thin C-bands. Microchromosomes are Cve.
All autosomes show C bands at one or both terminal
ends. Microchromosomes are C+ve.
Cytological Markers
Table 15. Differences in cytogenetic features of 2 species of Acanthocoris
Taxa
Diplotene/Diakinesis
Metaphase I
Acanthocoris anticus
Chromosome
complement
(2n)
24=22A+X1X20
Each autosomal bivalent shows single chiasma
which may be terminal, sub-terminal or
interstitial
Acanthocoris sp.
24=22A+X1X20
Two to three autosomal bivalents show two
chiasmata while the rest show single chiasma
each which may be terminal or sub-terminal
Two types of chromosome
arrangements are observed. In one, all
the autosomal bivalents form a ring and
X1 and X2 lie outside the ring while in
the other, one or two autosomal
bivalents lie within the ring.
Autosomal bivalents form a ring, X1
and X2 lie outside the ring
Table 16. Differences in cytogenetic features of 2 species of Anhomoeus
Taxa
Chromosome size
Anhomoeus nepalensis
Chromosome
complement
(2n)
21=18A+2m+X0
Anhomoeus sulcatus
21=18A+2m+X0
One autosomal pair is distinctly
large.
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Autosomes show gradual gradation
in size,