Interaction of B chromosomes with A or B chromosomes in segregation in insects

Abstract

Additional or B chromosomes not belonging to the regular karyotype of a species are found in many animal and plant groups. They form a highly heterogeneous group with respect to their morphology and behaviour both in mitosis and meiosis. Achiasmatic mechanisms that ensure the segregation of a B chromosome from another B chromosome or from an A chromosome are reviewed. An achiasmatic mechanism characterized by the “distance pairing” of segregating univalents at metaphase I was found to be responsible for the preferential segregation of B chromosome univalents in Hemerobius marginatus L. (Neuroptera), and a mechanism characterized by the “touch and go pairing” of segregating univalents was responsible for the highly regular segregation of a B chromosome and the X chromosome in Rhinocola aceris (L.) (Psylloidea, Homoptera). The latter mechanism resulted in the integration of a B chromosome to the A chromosome set as a Y chromosome in a psyllid species Cacopsylla peregrina (Frst.). Furthermore, B chromosomes can disturb the regular segregation of the achiasmatic X and Y chromosomes resulting in the formation of X0/XY polymorphism in a population, which might precede the loss of the Y chromosome. The absence of observations on accurately functioning achiasmatic segregation mechanisms in grasshoppers (Orthoptera) was attributed to the X and B chromosomes, which re-orient one or several times during metaphase I. Apparently, these re-orientations mask any achiasmatic segregation mechanism that might operate during meiotic prophase in these insects.

Heteropicnotic chromatin and nucleolar activity in meiosis and spermiogenesis of Limnogonus aduncus (Heteroptera, Gerridae): a stained nucleolar organizing region that can serve as a model for studying chromosome behavior

“…In meiosis, which is achiasmatic or chiasmatic, the autosomes go through a pre-reductional division, while in the sex chromosomes division is post-reductional. The karyotype may include microchromosomes, B chromosomes or univalent chromosomes (Ueshima, 1979;Manna, 1984;Papeschi and Mola, 1990;González-Garcia et al, 1996;Grozeva and Nokkala, 1996;Suja et al, 2000;Nokkala and Nokkala, 2004). Nucleolar organizer regions (NORs) have been detected in a small number of species; in all cases their location was subterminal or median, occurring in a single pair of autosomes or in the sex chromosomes (Camacho et al, 1985;Fossey and Liebenberg, 1995;González-García et al, 1996;Papeschi and Bressa, 2002;Papeschi et al, 2003;Rebagliati et al, 2003).…”

New record of B-chromosome through meiosis in the Egyptian locust Anacridium aegyptium (Acrididae) with indication to its origin

“…Furthermore, Nokkala and Nokkala (2004) analyzed the behaviour of B-chromosomes through mitosis and meiosis and found that they were without segregation and chiasmatic mechanism.…”

“…The properties of accessory or B-chromosomes had been reviewed by Mu¨ntzing (1974). Nokkala and Nokkala (2004) declared that B-chromosomes are not belonging to the regular karyotype of any species of Acrididae. Martin et al (1996) found a decrease of mating involving males with B-chromosomes in the grasshopper Eyprepocnemis plorans.…”

“…Nokkala and Nokkala (2004) declared that B-chromosome behaviour in both mitosis and meiosis is without segregation and chiasmatic mechanism.…”

Cytogenetics of the true bug infraorder Cimicomorpha (Hemiptera, Heteroptera): a review

“…However the X and Y chromosomes in Heteroptera generally show little or no evidence of homology expected of a neo-XY system (Blackman 1995). Recently, a mechanism is revealed by which a heteropteran-like achiasmate Y-chromosome can evolve from a B-chromosome (supernumerary, or accessory, or extra chromosome; see below) (Nokkala et al 2003, Nokkala and Nokkala 2004, Carvalho et al 2009). …”