© 2013 The Japan Mendel Society Cytologia 78(4): 411–415 Cytogenetical Studies of Four Species in Subfamily Peiratinae from North India (Heteroptera: Reduviidae) Rajdeep Kaur, and Harbhajan Kaur* Department of Zoology and Environmental Sciences, Punjabi University, Patiala-147 002, Punjab, India Received March 15, 2013; accepted October 7, 2013 Summary The diploid chromosome number and male meiosis in Ectomocoris atrox, E. tibialis, E. melanopterus, and Peirates bicolor (Heteroptera: Reduviidae: Peiratinae) have been described. Three species of Ectomocoris have 2n=23=20A+X1X2Y, while Peirates bicolor has 2n=23=20A+X1X2Y. One pair of autosomes is distinctly large in all the species of Ectomocoris, while Peirates bicolor possesses three pairs of large bivalents suggesting autosomal fusion. In Peirates bicolor with XY mechanism, X is larger than the X components of E. atrox, E. tibialis, and E. melanopterus with X1X2Y mechanism, indicating fragmentation of X to be the mode of origin of X multiplicity. In the presently studied four species, the general course of meiosis is typical of Reduviidae. Sex chromo- somes remain condensed and distantly placed during the diffuse stage. Single terminal chiasma per bivalent is seen in all except Ectomocoris atrox. At metaphase I, chromosomes arrange in a regular pattern in all the species, which is strikingly different from the typical random arrangement pattern previously reported in Reduviidae. Key words Autosome, X multiplicity, Diffuse stage, Metaphase I, Metaphase II. Peiratinae is one of the most important predaceous subfamilies of Reduviidae distributed worldwide with 32 genera and over 300 described species (Maldonado 1990). From India, 39 spe- cies belonging to nine genera have been taxonomically described in which Ectomocoris dominates with 21 species, followed by Peirates with five species. Peiratinae distinguishes itself with unique ecological, morphological, and behavioral attributes, and exhibits affinities with its close subfamily Reduviinae and distances itself from subfamilies like Harpactorinae and Stenopodainae (Ambrose 2006, Ambrose et al. 2007). Peiratines are known to be active predators and are used in biocontrol programmes. Populations of Ectomocoris are known to predate on pest Dysdercus cingulatus popu- lations in highly infested crops of Gossypium hirsutum (Ambrose 1999, Schaefer and Panizzi 2000). Cytogenetic data on Peiratinae pertains to only 11 species belonging to five genera, which include 10 species belonging to four genera from India and only one species from Japan. The modal diploid number of autosomes of Peiratinae is 20, and both simple and multiple sex chro- mosome systems are prevalent (Jande 1959a, b, Ueshima 1979, Manna and Deb-Mallik 1981). In the present study, cytogenetic data of three species has been added, the sex mechanism of one species has been modified, and cytoevolutionary trends have been discussed in light of the new data. Materials and methods Adult specimens of Ectomocoris atrox (Stal), Ectomocoris tibialis Distant, Ectomocoris * Corresponding author, e-mail: [email protected] DOI: 10.1508/cytologia.78.411 412 R. Kaur, and H. Kaur Cytologia 78(4) melanopterus Distant, and Peirates bicolor Distant were collected from Uttrakhand and Himachal Pradesh (North India) using a light trap. Live males were dissected to take out the gonads and were fixed in Carnoy’s mixture (absolute alcohol : acetic acid, 3 : 1). Chromosome preparations were made using an air-drying method. About four-week-old slides were stained in Carbol Fuchsin and differentiated in N-butanol, dried at room temperature, and finally mounted in DPX for microscopic examination (Carr and Walker 1961). Images were captured under a Nikon Optiphot microscope with a Nikon DXM 1200 C digital camera. Results and discussion Three species, viz., Ectomocoris atrox, Ectomocoris tibialis, and Ectomocoris melanopterus, show a diploid chromosome number of 23 (20A+X1X2Y) as also observed in Ectomocoris cordiger and Ectomocoris ochropterus by Jande (1959a). One unidentified species (Ectomocoris sp.), how- ever, possesses a diploid number of 22 (20A+XY) as observed by Manna and Deb-Mallick (1981). Therefore, out of the six species of Ectomocoris studied so far, five possess 2n=23 (20A+X1X2Y). In Peirates bicolor, cytologically described for the first time, the diploid chromosome number is 18 (16A+XY) as also found in Peirates sp. by Satapathy et al. (1990). However, 2n was found to be 22 (20A+XY) in Peirates sanctus and 26 (24A+XY) in Peirates sp. by Manna and Deb-Mallick (1981) (Table 1). The data on the six species of Ectomocoris studied so far clearly depicts that the autosomal number of 20 is constant in this genus. However, in Peirates, it is inconsistent, showing autosome numbers of 16, 20, and 24 among its four species. The overall data on 14 species of Peiratinae studied so far (including the present three new species) shows 20 to be the dominant autosomal number (nine species), followed by 24 (two spe- cies), 16 (two species), and 26 (one species) (Table 1). The basic autosomal number for this sub- family is 20 as represented in the majority of the species, and the rest appear to have originated as a result of fusions and fragmentations (Poggio et al. 2007). This is evidenced in the present study on the basis of the size of the autosomes. In Ectomocoris atrox, Ectomocoris tibialis, and Ectomocoris melanopterus with 10 pairs of autosomes, one pair of autosomes is distinctly large whereas in Peirates bicolor with eight pairs of autosomes, three pairs are large suggesting autosomal fusion. In the species of Pieratinae having 24 and 26 autosomes (Jande 1959a, b, Manna and Deb-Mallick Table 1. Chromosome complements of species of Peiratinae studied so far (including four species of the present work). Sr. Diploid Chromosomal Taxa References No. number (♂) complement 1. Anrdrochus pictus Stal 22 20A+XY Jande (1959b) 2. Ectomocoris atrox (Stal) 22 20A+XY Jande (1959a), 23 20A+X1X2Y Present work 3. Ectomocoris tibialis Distant 23 20A+X1X2Y Present work 4. Ectomocoris melanopterus Distant 23 20A+X1X2Y Present work 5. Ectomocoris cordiger Stal 23 20A+X1X2Y Jande (1959a) 6. Ectomocoris ochropterus Stal 23 20A+X1X2Y Jande (1959a) 7. Ectomocoris sp. 22 20A+XY Manna and Deb Mallick (1981) 8. Peirates bicolor Distant 18 16A+XY Present work 9. Peirates sanctus Lethierry 22 20A+XY Manna and Deb Mallick (1981) 10. Peirates sp. 26 24A+XY Manna and Deb Mallick (1981) 11. Peirates sp. 18 16A+XY Satapathy et al. (1990) 12. Rasahus thoracicus Stal 23 20A+X1X2Y Ueshima (1979) 13. Sirthenia flavipes (Stal) 26 24A+XY Manna and Deb Mallick (1981) 14. Sirthenia sp. 28 26A+XY Jande (1959b) 2013 Cytogenetic Study of Subfamily Peiratinae from North India 413 Fig. 1. Pie diagram showing the percent age of sex mechanisms in Peiratinae. 1981), autosome size has not been discussed nor the photographs given (only lists of chromosome complements were given), so it is not possible to comprehend the basis of increase in autosome number. Sex mechanism All the species of Ectomocoris (Ectomocoris atrox, E. tibialis, and E. melanopterus) have an X1X2Y sex mechanism, whereas Peirates bicolor has an XY sex mechanism. Jande (1959a) reported an XY sex mechanism (no photograph) in Ectomocoris atrox. The specimens of our study clearly depict three sex bodies during the diffuse stage and during the entire course of meiosis. The specimens have been identified by Prof. K. Sahayaraj, an expert in Reduviidae taxonomy. In the absence of any photograph given by Jande, it is impossible to confirm whether the different results are due to genetic polymorphism or due to misidentification of the specimens. Both simple and multiple sex mechanisms have been reported in the subfamily Peiratinae with XY (57.15%) having an edge over the XnY (42.85%) mechanism (Fig. 1). Poggio et al. (2007) em- phasized that during karyotype evolution, Peiratinae maintains the ancestral sex chromosome sys- tem XY in some genera, while in other genera, the original X is fragmented to give rise to XnY. The data on the four species added by the present study supports this contention. It is clear that the genus Peirates retains the ancestral sex chromosome system XY, while the genus Ectomocoris shows X multiplicity (excepting one unidentified species). Further, in Peirates bicolor with an XY mechanism, X is large in size, while in Ectomocoris atrox, E. tibialis, and E. melanopterus with X1X2Y, the X components are smaller in size, indicating fragmentation of X to be the mode of ori- gin of X multiplicity. Meiosis In all the species (Ectomocoris atrox, E. tibialis, E. melanopterus, and Peirates bicolor), condensed sex chromosomes do not fuse or associate but lie closely against the decondensed autosomes during the diffuse stage (Fig. 2a, e, h, l). As prophase I progresses from diplotene to diakinesis, sex chromosomes start dispersing from each other. All the autosomal bivalents in Ectomocoris tibialis, E. melanopterus, and Peirates bicolor each show single chiasma (Fig. 2i, m), whereas in Ectomocoris atrox, the distinctly large autosomal bivalent shows two chiasmata (Fig. 2b). In Reduviidae, most of the species fail to show any definite pattern at metaphase I. So far, only two species of Harpactorinae (Cosmoclopius nigroannulatus and Cosmoclopius poecilius) are recorded to show a regular arrangement by which autosomes form a ring and sex chromosomes lie within the ring (Manna 1951, 1962, Banerjee 1958, Ueshima 1979, Poggio et al. 2007). However, during the present study, this regular arrangement has been observed in all four species of 414 R. Kaur, and H. Kaur Cytologia 78(4) Fig. 2a–d. Ectomocoris atrox. a. diffuse stage; b. diplotene stage; c. metaphase I; d. metaphase II. e–g. Ectomocoris tibialis. e. diffuse stage; f. metaphase I; g. metaphase II. h–k. Ectomocoris melanopterus. h. diffuse stage; i. diplotene stage; j. metaphase I; k. metaphase II. l–o. Peirates bicolor. l. diffuse stage; m. diplotene stage; n. metaphase I; o. metaphase II. Arrows represent Y chromosomes, arrowhead represents X chromosomes.