C-banding and DNA content in three species of Belostoma (Heteroptera) with large differences in chromosome size and number

Abstract

C-banding was carried out on Belostoma elegans (2n = 26 + X1X2Y ) (o'), B. micantulum (2n = 14 + XY) (~) and B. oxyurum (2n = 6 + XY) (o') (Belostomatidae, Heteroptera). The C-bands always have a telomeric localization and no interstitial bands were detected. An inverse relationship between chromosome size and chromosome number exists, and besides, an inverse relationship between chromosome size and the size of the Cbands was observed. The DNA content was determined in all three species. B. elegans has a C content of 1.55 + 0.06 pg, B. micantulum has 0.88 + 0.04 pg and B. oxyurum had 0.53 + 0.04 pg.Considering the male meiotic characteristics, the chromosome complement and the results of C-banding and DNA content, the karyotype of B. oxyurum probably originated through autosomal fusions. The karyotype of B. micantulum and B. elegans could have originated through autosomal fusions or fragmentations respectively; with the information available up to now it is not possible to discard any of the two pathways.

Sex chromosome differentiation in Belostoma (Insecta: Heteroptera: Belostomatidae)

“…The X chromosome corresponds to a medium-sized chromosome, and the Y, to small-sized chromosome. This karyotypic organization has been observed in other species of the genus, such as B. micantulum (Stål, 1860) (Papeschi, 1988), B. plebejum (Stål, 1860) (Papeschi, 1994), and B. orbiculatum Estévez andPolhemus, 2001 (Papeschi, 1996).…”

“…The cytogenetic data show that most species have males with chromosome numbers ranging from 2n = 4 in Lethocerus sp. (Chickering, 1927(Chickering, , 1932 to 2n = 29 in some species of Belostoma (Papeschi and Bidau, 1985;Papeschi, 1988Papeschi, , 1991. Nevertheless, analyzed species showed holokinetic chromosomes, a characteristic common to all species of heteropterans (Papeschi and Bressa, 2006).…”

C-banded Karyotype of Psyllid Species Aphalara calthae (L.) (Psylloidea, Homoptera, Insecta).

“…An unexpectedly large amount of constitutive heterochromatin was discovered in permanently thelytokous aphid species of the tribe Tramini (Lachnidae) (Blackman 1980). All other known exceptions involve specialized chromosomes (X-and Y-chromosomes, B-chromosomes and also m-chromosomes in bugs) or specialized chromosome sites (NORs), which in some species of aphids and bugs contain considerable amounts of constitutive heterochromatin (Blackman 1976, Camacho et al 1985, Kuznetsova and Maryarnska-Nadachowska 1993, Papeschi 1988, 1991. This is the first study in psyllids with regard to constitutive heterochromatin.…”

Exophenotypic effects of chromosomal change: the case of Leptysma argentina (Orthoptera)

“…The effect on segment s1 is more enigmatic; it is known that increased DNA contents are usually correlated with increased body size, both in plants and insects (Papeschi, 1988;Poggio & Naranjo, 1990), but in this case the effect of the segment on body size was only identifiable in the populations here analysed, not in others. In any case, this is the first indication of an exophenotypic effect of a supernumerary segment and, added to its presence in all populations of L. argentina so far studied (Bidau & Hasson, 1984), the nonrandomness of its distribution (Colombo, 1993b), its effects on recombination (Colombo, 1992), its gametic phase disequilibrium with fusion 3/6 (Colombo, 1993c) and now its effects on body size (this study), suggests that this segment may well not be adaptively neutral for natural populations of this species.…”