Cytogenetics of three parthenogenetic Psocid species (Psocoptera, Psocomorpha)

Abstract

A novel method was applied to study chromosomes and their behavior in female meiosis in three parthenogenetic psocid species (Psocoptera). Two of these species Valenzuela flavidus (Steph.), Caeciliusidae and Peripsocus subfasciatus (Rambur), Peripsocidae displayed a triploid chromosome number 3x=27 while the third species Trichadenotecnum majus (Kolbe) was diploid (2n=18). In all species meiosis consisted of only a single, mitosis‐like maturation division, i.e. meiosis was of apomictic type. Models for the formation of polyploid parthenogenetic forms are discussed.

The variability of the chromosome numbers in Psocomorpha (Insecta, Psocoptera)

“…Trichadenotecnum sexpunctautum has 2n = 17 (16 + X). In the large genus Trichadenotecnum three further bisexual and one facultatively parthenogentic species T. majus have been previously karyotyped (WONG and THORNTON 1966;ZEFA et al 1996;NOKKALA and GOLUB 2002). Bisexual species were found to have 2n = 17 (16 + X) in males and the parthenogenetic females of T. majus 2n = 18 (16 + XX), that is in fact the same pattern.…”

“…Their karyotype is triploid, expressed by 2n = 3x = 27 (24 + XXX). It includes the modal number 2n = 18 (16 + XX) and one more added haploid set n = 9 (8 + X) (NOKKALA and GOLUB 2002).…”

“…By now, 66 species (about 2% of world psocopteran fauna) of 38 genera, 20 families and all three suborders have been karyotyped (ZEFA et al 1996;GOLUB and NOKKALA 2001;NOKKALA and GOLUB 2002, for other references see GOL-UB 1999). The overwhelming majority of karyotyped species (57), genera (32) and families (15) fall in the largest and most advanced psocopteran suborder Psocomorpha.…”

Chromosome numbers in eight species of Palaearctic Psocoptera (Insecta)

“…The same chromosome complement is characteristic of 72 bisexual and diploid parthenogenetic species of Psocoptera. For triploid parthenogenetic species the chromosome number 3n = 27 was reported (Nokkala, Golub, 2002, 2006, which number comprises 18 chromosomes of the diploid complement and one additional haploid chromosomal set. Thus, our new results confi rm the high stability of chromosome numbers in Psocoptera (Wong, Thornton, 1966;Mesa et al, 1991;Golub, 1999).…”

“…Chromosome systems of Psocoptera are still not adequately explored, although some papers concerning psocopteran karyotypes have been published recently (Nokkala, Golub, 2002, 2006Golub, 2004). Like the other Paraneoptera, the species of Psocoptera have holocentric chromosomes.…”