© Comparative Cytogenetics, 2009 . Vol. 3, No. 1, P. 33-41. ISSN 1993-0771 (Print), ISSN 1993-078X (Online) Chromosome numbers in eight species of Palaearctic Psocoptera (Insecta) N.V. Golub1, S. Nokkala2 1Zoological Institute, Russian Academy of Sciences, Universitetskaya nab. 1, St. Pe- tersburg 199034, Russia. 2Laboratory of Genetics, Department of Biology, University of Turku, FIN-20014, Turku, Finland. E-mails: [email protected], 2seppo.nokkala@utu.fi Abstract. Karyotypes of eight Psocoptera species are reported for the fi rst time. In Va- lenzuela oyamai (Enderlein, 1906) (Caeciliusidae), Peripsocus golubae Lienhard, 2006 (Peripsocidae), Trichopsocus dalii (McLachlan, 1867) (Trichopsocidae), Hemineura dispar Tetens, 1891 (Elipsocidae), and Amphigerontia contaminata (Stephens, 1836) (Psocidae) 2n = 16 + XX/X0. In Elipsocus moebiusi Tetens, 1891 (Elipsocidae) 2n = 12 + XX/X0. Neopsocopsis hitricornis (Reuter, 1893) (Psocidae) has 2n = 14 + XX/ X0, and Kolbia quisquiliarum Bertkau, 1883 (Amphipsocidae) has 2n = 14 + neo-XY/ XX. In addition, three seminal follicles per testis have been established in V. oyamai, H. dispar, A. contaminata, and N. hitricornis and one follicle in P. golubae and T. dalii. All the data available on psocopteran karyotypes are tabulated and shortly reviewed. Key words: Psocoptera, karyotype, chromosome number, chromosomal mechanism of sex determination. INTRODUCTION coptera. The majority of species (72) belong Psocoptera are a hemimetabolous insect to the most advanced suborder Psocomorpha. order, belonging with the orders Phithiraptera, The present study reports data on the Thysanoptera, Heteroptera, and Homoptera to karyotypes of 8 species from 8 genera and 6 the Cohort Paraneoptera. Within Psocoptera families of Psocomorpha. The data on Neop- three suborders, Trogiomorpha, Troctomor- socopsis Badonnel, 1936, Hemineura Tetens, pha, and Psocomorpha, have been accepted 1891 and Kolbia Bertkau, 1882 are the fi rst (Lienhard, 1998; Lienhard, Smithers, 2002). ones for these genera. For 6 species data on Chromosome systems of Psocoptera are numbers of seminal follicles are also given. still not adequately explored, although some papers concerning psocopteran karyotypes MATERIAL AND METHODS have been published recently (Nokkala, Gol- The material studied is listed in Table 1. ub, 2002, 2006; Golub, 2004). Like the other For karyological studies, the specimens Paraneoptera, the species of Psocoptera have were fi xed in a mixture of 96% ethanol and holocentric chromosomes. So far, chromo- glacial acetic acid (3:1). Testes were dissected some numbers have been established for 82 out of the abdomens and squashed on slides species from 48 genera and 21 families of Pso- in a drop of 45% acetic acid. The prepara- http://pensoftonline.net/compcytogen doi: 10.3897/compcytogen.v3i1.6 34 N.V. Golub, S. Nokkala tions were made permanent by a dry ice tech- RESULTS nique (Conger, Fairchild, 1953). After cover slips were removed, slides were dehydrated Family Caeciliusidae in fresh 3:1, air-dried and stained by Feulgen- Valenzuela oyamai (Enderlein, 1906): 2n = Giemsa procedure (Grozeva, Nokkala, 1996). 16 + XX/X0. Slides were treated in 1N HCl at room tem- Each testis contains three seminal follicles perature for 20 min, hydrolysed in 1N HCl at arranged in consecutive order on seminal duct. 60o C for 7 min, stained with Schiff’s reagent In MI, 8 autosomal bivalents and the X chro- for 30 min, rinsed in distilled water and then, mosome have been revealed (Fig. 1). The bi- rinsed in Sorensen’s phosphate buffer, pH 6.8. valents gradually decrease in size; the X chro- Finally, slides were stained with 5% Giemsa mosome is the smallest element of set. In the solution for 30 min. After staining, slides were majority of cells, the X chromosome is situ- rinsed briefl y with distilled water, air dried, ated at the periphery of the metaphase plate. and mounted in Entellan. The formula of the male diploid karyotype has Table 1. Material used for chromosomal analysis. Species Locality, year of collection, number of specimens studied, feeding plants Valenzuela oyamai (Enderlein, 1906) Russia, Irkutsk Prov., Bolshie Koty, 2007, 12, undet. herbs (Caeciliusidae) Kolbia quisquiliarum Bertkau, 1883 Russia. Voronezh Prov., Hopersky State Reserve, 2005, 2, (Amphipsocidae) Calamagrostis epigeios Peripsocus golubae Lienhard, 2006 Russia, Krasnodar Terr.,12 km N Adler, 2004, 2W, Buxus sp. (Peripsocidae) Trichopsocus dalii (McLachlan, 1867) Russia, Krasnodar Terr.,12 km N Adler, 2004, 5W, undet. herbs (Trichopsocidae) Elipsocus moebiusi Tetens, 1891 Finland, Kustavi, 2003. 4, deciduous trees (Elipsocidae) Finland, Katanpää, 2003. 2W, 3, deciduous trees Finland, Ruissalo, 2003, 3W, 1, deciduous trees Russia. Voronezh Prov., Hopersky State Reserve, 2005, 1W, 1, Quercus sp. Hemineura dispar Tetens, 1891 Finland, vicinity of Turku, 2003, 11, deciduous trees (Elipsocidae) Amphigerontia contaminata (Stephens, Finland, vicinity of Turku, 1999, 4, dead coniferous branches 1836) (Psocidae) Neopsocopsis hitricornis (Reuter, 1893) Russia, republic of Altai, 40 km SE Chamal, 2006, 6W, undet. (Psocidae) coniferous Comp. Cytogenet., 2009 3(1) Chromosome numbers in eight species of Palaearctic Psocoptera 35 been determined as 2n = 17 (16 + X0). Family Elipsocidae Elipsocus moebiusi Tetens, 1891: 2n = 12 Family Amphipsocidae + XX/X0. Kolbia quisquiliarum Bertkau, 1883: 2n = In MI, 6 autosomal bivalents and the X 14 + neo-XY/XX. chromosome have been revealed (Fig. 7). In MI, 8 bivalents have been revealed (Fig. One of the bivalents is nearly twice as large 2). In the majority of cells, one of the biva- as any other. The X chromosome is close in lents is clearly heteromorphic and could be size to smallest half-bivalents. In the majority considered the sex chromosome bivalent (Fig. of cells, the X chromosome is situated at the 3). Apparently, the X chromosome is fused periphery of the metaphase plate. The formula with an autosome resulting in a neo-XY sex of the male diploid karyotype has been deter- chromosome system. The formula of the male mined as 2n = 13 (12 + X0). A female mitotic diploid karyotype has been determined as 2n = metaphase (Fig. 8) displays 12 chromosomes 16 (14 + neo-XY). with one large chromosomal pair. Sex chro- Family Peripsocidae mosomes are not distinguished. Peripsocus golubae Lienhard, 2006: 2n = Hemineura dispar Tetens, 1891: 2n = 16 16 + XX/X0. + XX/X0. Each testis contains one large seminal fol- Each testis contains three seminal follicles licle. In MI, 8 autosomal bivalents and the arranged in consecutive order on seminal duct. X chromosome have been revealed (Fig. 4). In MI, 8 autosomal bivalents and the X chro- The bivalents gradually decrease in size; the mosome have been revealed (Fig. 9). The bi- X chromosome is the smallest element of the valents gradually decrease in size; the X chro- set. The formula of the male diploid karyotype mosome is close in size to the middle-sized has been determined as 2n = 17 (16 + X0). half-bivalents. In the majority of cells, the X chromosome is situated at the periphery of the Family Trichopsocidae metaphase plate. The formula of the male dip- Trichopsocus dalii (McLachlan, 1867): 2n loid karyotype has been determined as 2n = 17 = 16 + XX/X0. (16 + X0). Each testis contains one large seminal fol- licle. In MI, 8 autosomal bivalents and the X Family Psocidae chromosome have been revealed (Fig. 5). The Amphigerontia contaminata (Stephens, bivalents gradually decrease in size; X chro- 1836): 2n = 16 + XX/X0. mosome is the smallest element of the set. Each testis contains three seminal follicles In the majority of cells, the X chromosome which are terminally brought together on sem- is situated at the periphery of the metaphase inal duct. In MI, 8 autosomal bivalents and the plate. In MII homologues segregate regularly X chromosome have been revealed (Fig. 10). and chromosomal plates with 8 and 9 univa- The bivalents gradually decrease in size; the lent chromosomes respectively, have been ob- X chromosome is close in size to the middle- served (Fig. 6). The formula of the male dip- sized half-bivalents. The formula of the male loid karyotype has been determined as 2n = 17 diploid karyotype has been determined as (16 + X0). 2n = 17 (16 + X0). Comp. Cytogenet., 2009 3(1) 36 N.V. Golub, S. Nokkala Figs 1-11. Chromosome complements of Psocomorpha. 1 - Valenzuela oyamai. Male meiotic metaphase I showing 8 autosomal bivalents and univalent X chromosome. 2-3 - Kolbia quisquiliarum. Male meiotic metaphase I showing 8 bivalents. One of the bivalents is clearly heteromorphic (better represented in Fig. 3). 4 - Peripsocus golubae. Male meiotic metaphase I showing 8 autosomal bivalents and univalent X chromosome. 5-6 - Trichop- socus dalii; 5 - Male meiotic metaphase I showing 8 autosomal bivalents and univalent X chromosome; 6 - Male meiotic metaphases II showing 8 (autosomes only) and 9 (autosomes + X chromosome) elements. 7-8 - Elipsocus moebiusi; 7 - Male meiotic metaphase I showing 6 autosomal bivalents and univalent X chromosome; 8 - Female mitotic metaphase showing 12 chromosomes. 9 - Hemineura dispar. Male meiotic metaphase I showing 8 auto- somal bivalents and univalent X chromosome. 10 - Amphigerontia contaminate. Male meiotic metaphase I show- ing 8 autosomal bivalents and univalent X chromosome. 11 - Neopsocopsis hitricornis. Male meiotic metaphase I showing 7 autosomal bivalents and univalent X chromosome. Sex chromosomes are indicated by arrowheads. Bar = 10 μm. Comp. Cytogenet., 2009 3(1) Chromosome numbers in eight species of Palaearctic Psocoptera 37 Neopsocopsis hitricornis (Reuter, 1893): by 2n = 16 + XX/X0 (Table 2). 2n = 14 + XX/X0. Neopsocopsis hitricornis (Psocidae) was Each testis contains three seminal follicles shown to have 2n = 14 + XX/X0. These are which are terminally brought together on sem- the fi rst karyological data on the genus as a inal duct. In MI, 7 autosomal bivalents and the whole. In the family Psocidae 26 species have X chromosome have been revealed (Fig. 11). been karyologically studied so far, among One of the bivalents is noticeably larger then them three species also display 2n = 14 + XX/ others. The X chromosome is close in size to X0 (Table 2).