Chromosome numbers in eight species of Palaearctic Psocoptera (Insecta)

Karyotypes of eight Psocoptera species are reported for the fi rst time. In Valenzuela 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.

Chromosome systems of Psocoptera are still not adequately explored, although some papers concerning psocopteran karyotypes have been published recently (Nokkala, Golub, 2002, 2006;Golub, 2004).Like the other Paraneoptera, the species of Psocoptera have holocentric chromosomes.So far, chromosome numbers have been established for 82 species from 48 genera and 21 families of Pso-coptera.The majority of species (72) belong to the most advanced suborder Psocomorpha.
The present study reports data on the karyotypes of 8 species from 8 genera and 6 families of Psocomorpha.The data on Neopsocopsis Badonnel, 1936, Hemineura Tetens, 1891and Kolbia Bertkau, 1882 are the fi rst ones for these genera.For 6 species data on numbers of seminal follicles are also given.

MATERIAL AND METHODS
The material studied is listed in Table 1.For karyological studies, the specimens were fi xed in a mixture of 96% ethanol and glacial acetic acid (3:1).Testes were dissected out of the abdomens and squashed on slides in a drop of 45% acetic acid.The prepara-tions were made permanent by a dry ice technique (Conger, Fairchild, 1953).After cover slips were removed, slides were dehydrated in fresh 3:1, air-dried and stained by Feulgen-Giemsa procedure (Grozeva, Nokkala, 1996).Slides were treated in 1N HCl at room temperature for 20 min, hydrolysed in 1N HCl at 60 o C for 7 min, stained with Schiff's reagent for 30 min, rinsed in distilled water and then, rinsed in Sorensen's phosphate buffer, pH 6.8.Finally, slides were stained with 5% Giemsa solution for 30 min.After staining, slides were rinsed briefl y with distilled water, air dried, and mounted in Entellan.
Each testis contains three seminal follicles arranged in consecutive order on seminal duct.In MI, 8 autosomal bivalents and the X chromosome have been revealed (Fig. 1).The bivalents gradually decrease in size; the X chromosome is the smallest element of set.In the majority of cells, the X chromosome is situated at the periphery of the metaphase plate.The formula of the male diploid karyotype has
In MI, 8 bivalents have been revealed (Fig. 2).In the majority of cells, one of the bivalents is clearly heteromorphic and could be considered the sex chromosome bivalent (Fig. 3).Apparently, the X chromosome is fused with an autosome resulting in a neo-XY sex chromosome system.The formula of the male diploid karyotype has been determined as 2n = 16 (14 + neo-XY).
Each testis contains one large seminal follicle.In MI, 8 autosomal bivalents and the X chromosome have been revealed (Fig. 4).The bivalents gradually decrease in size; the X chromosome is the smallest element of the set.The formula of the male diploid karyotype has been determined as 2n = 17 (16 + X0).
Each testis contains one large seminal follicle.In MI, 8 autosomal bivalents and the X chromosome have been revealed (Fig. 5).The bivalents gradually decrease in size; X chromosome is the smallest element of the set.In the majority of cells, the X chromosome is situated at the periphery of the metaphase plate.In MII homologues segregate regularly and chromosomal plates with 8 and 9 univalent chromosomes respectively, have been observed (Fig. 6).The formula of the male diploid karyotype has been determined as 2n = 17 (16 + X0).
In MI, 6 autosomal bivalents and the X chromosome have been revealed (Fig. 7).One of the bivalents is nearly twice as large as any other.The X chromosome is close in size to smallest half-bivalents.In the majority of cells, the X chromosome is situated at the periphery of the metaphase plate.The formula of the male diploid karyotype has been determined as 2n = 13 (12 + X0).A female mitotic metaphase (Fig. 8) displays 12 chromosomes with one large chromosomal pair.Sex chromosomes are not distinguished.
Each testis contains three seminal follicles arranged in consecutive order on seminal duct.In MI, 8 autosomal bivalents and the X chromosome have been revealed (Fig. 9).The bivalents gradually decrease in size; the X chromosome is close in size to the middle-sized half-bivalents.In the majority of cells, the X chromosome is situated at the periphery of the metaphase plate.The formula of the male diploid karyotype has been determined as 2n = 17 (16 + X0).
Each testis contains three seminal follicles which are terminally brought together on seminal duct.In MI, 8 autosomal bivalents and the X chromosome have been revealed (Fig. 10).The bivalents gradually decrease in size; the X chromosome is close in size to the middlesized half-bivalents.The formula of the male diploid karyotype has been determined as 2n = 17 (16 + X0).Neopsocopsis hitricornis (Reuter, 1893): 2n = 14 + XX/X0.
Each testis contains three seminal follicles which are terminally brought together on seminal duct.In MI, 7 autosomal bivalents and the X chromosome have been revealed (Fig. 11).One of the bivalents is noticeably larger then others.The X chromosome is close in size to the middle-sized half-bivalents.In the majority of cells, X chromosome is situated at the periphery of the metaphase plate.The formula of male diploid karyotype has been determined as 2n = 15 (14 + X0).
Neopsocopsis hitricornis (Psocidae) was shown to have 2n = 14 + XX/X0.These are the fi rst karyological data on the genus as a whole.In the family Psocidae 26 species have been karyologically studied so far, among them three species also display 2n = 14 + XX/ X0 (Table 2).
Kolbia quisquiliarum (Amphipsocidae) has 2n = 14 + neo-XY/XX, and these are the fi rst karyological data on the genus as a whole.Previously, the neo-XY-mechanism of sex determination has been found in Amphipsocus japonicus Enderlein, 1906 (Amphipsocidae) (Golub, Nokkala, 2001).Although this derivative sex-determining mechanism has never been reported for any other families, karyological data are still inadequate to consider this mechanism as characteristic of the family Amphipsocidae.
two species of the suborder display 2n = 17 in males, whereas all other studied species have the higher chromosome numbers: 2n = 19, 21 and 29 in males.Karyological data on Troctomorha are presently extremely scanty.In four so far studied species of the suborder 2n = 14 + XX/X0 and 2n = 16 + XX/X0 have been found (Table 2).

Table 1 .
Material used for chromosomal analysis.