Astylus variegatus (Coleoptera, Melyridae): Cytogenetic study of a population exposed to agrochemical products

Abstract

In this work we describe the cytogenetic analyses performed in specimens of Astylus variegatus (Germar, 1824) collected in two localities: one area of natural vegetation and one of agricultural crops, where agrochemical products were used. Astylus variegatus had karyotypes with 2n(male) = 16+Xy p and 2n (female) = 16+XX p , with exclusively metacentric chromosomes. Pachytene spermatocytes showed synapsed autosomal bivalents and non-associated sex chromosomes. In diplotene, the autosomal bivalents exhibited one or two terminal chiasmata and the Xy p had a typical parachute configuration. In meiotic cells of some specimens, an extra chromosome, interpreted as a B chromosome, was observed. C-banding showed constitutive heterochromatin in the pericentromeric region of all chromosomes, with the exception of the y p . Silver nitrate staining revealed one nucleolus organizer region (NOR) on the terminal region of the short arm of the second autosome pair. Silver staining of meiotic cells confirmed the NOR pattern detected in mitotic cells and revealed an argentophilous material on the Xy p . A cytogenetic comparison between the two populations of A. variegatus showed a statistically significant divergence (χ 2 = 117.10; df = 1) in the number of aneuploid cells and a higher frequency of B chromosome in the population exposed to agrochemicals.

Cytogenetic analysis of Astylus antis (Perty, 1830) (Coleoptera, Melyridae): Karyotype, heterochromatin and location of ribosomal genes

“…In this species, the nucleolus organizer region (NOR) is located in autosome pair 2 (Schneider et al , 2007a). …”

“…The 12 species of Cleridae, distributed among five genera ( Enoclerus , Priocera , Thanasimus , Trichodes and Necrobia ), exhibit karyotype uniformity, i.e. , 2n = 18, the basal sex determination system for Coleoptera, Xyp, and meta/submetacentric morphology for all chromosomes ( Smith, 1953 ; Virkki, 1963 ; Smith and Virkki, 1978 ; Yadav and Dange, 1989 ; Schneider et al , 2007a ). However, the four species belonging to the family Melyridae display differences both in their chromosome number and their sex determination system ( Smith and Virkki, 1978 ).…”

“…However, the four species belonging to the family Melyridae display differences both in their chromosome number and their sex determination system ( Smith and Virkki, 1978 ). Chromosome morphology was only described for A. variegates , in which all chromosomes are metacentric ( Schneider et al , 2007a ).…”

Chromosomal characteristics and karyotype evolution of Oxyopidae spiders (Araneae, Entelegynae)

“…In contrast, the high number of chiasmata per bivalent was verified in all large-sized bivalents of O. salticus. Similarly to this latter species, the presence of more than one chiasma per bivalent was also observed in some beetles whose diploid complement seems to have evolved by fusions (Schneider et al, 2007). According to John (1990) the number of chiasma per bivalent is partially dependent on the chromosome size.…”

First cytogenetic information on four checkered beetles (Coleoptera, Cleridae)

“…Although the Cleroidea have a large representative and wide distribution area, only 18 species (13 Cleridae, 5 Melyridae) of the superfamily have been cytogenetically studied so far. The 13 species of Cleridae in five genera (Enoclerus Gahan, 1910, Priocera Kirby, 1818, Thanasimus Latreille, 1806, Trichodes Herbst, 1792, and Necrobia Olivier, 1795) display monotypic chromosome number as "2n = 18", the basic sex chromosome system for Coleoptera as Xy p , and metacentric/submetacentric morphology for all chromosomes (Smith and Virkki 1978;Schneider et al 2007;Mendes-Neto et al 2010).…”