Passos Cristiano et al. / Comparative Cytogenetics eight(three): 22331 (2014)Figure 1. Mitotic karyotypes of Melitoma segmentaria. a Giemsa staining (female) b Cbanding (male). Bar=5m.tern as well as the nomenclature proposed by Imai (1991), the chromosomes may be classified into three distinct kinds: seven pseudoacrocentric pairs (AM) with 1 heterochromatic arm, seven pseudoacrocentric pairs with an interstitial heterochromatin (AMi), and a single totally heterochromatic metacentric pair (Mh) (see Fig. 1c). According to Imai (1991), pseudoacrocentric chromosomes are the result of a centric fission, followed by a considerable addition of heterochromatin in the telomere area, to be able to restore the stability in the chromosome. The totally heterochromatic metacentric pair could arise from the centric fusion of two heterochromatic acrocentric chromosomes (Ah). A fully heterochromatic metacentric chromosome is uncommon, and this morphological form is identified in some supernumerary and Ychromosomes (Imai 1991, Costa el al.Sodium triacetoxyborohydride uses 1992, Camacho et al. 2000, Lopes et al. 2008). All people analyzed, each females and males, possess this totally heterochromatic chromosome, which inCytogenetics of Melitoma segmentaria (Fabricius, 1804) (Hymenoptera, Apidae)…Figure 2. Female mitotic karyotypes of M. segmentaria stained with fluorochromes: a CMA3 b DAPI c CMA3/DAPI and d DAPI/CMA3. Arrows indicate totally heterochromatic metacentric chromosomes (Mh). Bar=5m.dicates that it is a part of the autosome complement, and therefore, it has not been treated as a supernumerary chromosome. The pattern of heterochromatin distribution in M. segmentaria is related to that observed in many of the studied Meliponini species (Rocha et al. 2003, Carvalho and Costa 2011, Miranda et al. 2013), where a lot of the chromosomes within the complement have a single heterochromatic arm. This seems to agree using the “minimum interaction hypothesis,” proposed by Imai et al. (1988), as the key mechanism of karyotype evolution in these bees.Benzyl (4-nitrophenyl) carbonate site In accordance with this hypothesis, one particular metacentric chromosome breaks apart at the centromere generating two acrocentric chromosomes.PMID:23618405 Therefore, due to the instability of those acrocentric chromosomes, the repetitive DNA begins an intandem development in the telomere region, major to chromosomes with a heterochromatic arm (see Imai et al. 1988), as observed right here in M. segmentaria. Having said that, this pattern is extremely distinct from that observed in the solitary bee Euglossa carolina (Linnaeus, 1758) (Fernandes et al. 2013), suggesting that alternative mechanisms of karyotype change may perhaps take place via the evolutionary diversification of those species. A lot more detailed karyotype studies are necessary to point out the trend inside the karyotype evolution of solitary bees.Maykon Passos Cristiano et al. / Comparative Cytogenetics eight(three): 22331 (2014)Figure three. Female mitotic chromosomes of M. segmentaria submitted to silvernitrate staining. Dark regions on the heterochromatin arms indicate silver staining. Bar=5m.Chromosome staining with all the fluorochromes CMA3 and DAPI (Fig. 2) shows that heterochromatin has an apparently homogeneous constitution. Even so, the fluorochrome CMA3 shows that the heterochromatin present inside the chromosomal arms of M. segmentaria is far more GCrich than ATrich. DAPI in M. segmentaria marked the centromeric and pericentromeric regions in the chromosomes, indicating that these regions are rich in AT base pairs. In Meliponini bees the heterochromatin is wealthy in AT base pairs (it i.