The pattern of heterochromatin distribution in M. segmentaria is similar to that observed in most of the studied Meliponini species (Rocha et al. 2003, Carvalho and Costa 2011, Miranda et al. 2013), where most of the chromosomes in the complement have a single heterochromatic arm. This seems to agree with the “minimum interaction hypothesis,” proposed by Imai et al. (1988), as the main mechanism of karyotype evolution
in these bees. According to this hypothesis, one metacentric chromosome breaks apart at the centromere producing two acrocentric chromosomes. Therefore, due to the instability of these acrocentric chromosomes, the repetitive DNA starts an in-tandem growth at the telomere region, leading to chromosomes with a heterochromatic arm (see Imai et al. 1988), as observed here in M. segmentaria. However, this pattern is very different from that observed in the solitary bee Euglossa carolina (Linnaeus, 1758) (Fernandes
et al. 2013), suggesting that alternative mechanisms of karyotype change may occur through the evolutionary diversification of these species. More detailed karyotype studies are needed to point out the trend in the karyotype evolution of solitary bees.
Figure 2. Female mitotic karyotypes of M. segmentaria stained with fluorochromes: a CMA3 b DAPI c CMA3/DAPI and d DAPI/CMA3. Arrows indicate entirely heterochromatic metacentric chromosomes (Mh). Bar=5μm.
The pattern of heterochromatin distribution in M. segmentaria is similar to that observed in most of the studied Meliponini species (Rocha et al. 2003, Carvalho and Costa 2011, Miranda et al. 2013), where most of the chromosomes in the complement have a single heterochromatic arm. This seems to agree with the “minimum interaction hypothesis,” proposed by Imai et al. (1988), as the main mechanism of karyotype evolutionin these bees. According to this hypothesis, one metacentric chromosome breaks apart at the centromere producing two acrocentric chromosomes. Therefore, due to the instability of these acrocentric chromosomes, the repetitive DNA starts an in-tandem growth at the telomere region, leading to chromosomes with a heterochromatic arm (see Imai et al. 1988), as observed here in M. segmentaria. However, this pattern is very different from that observed in the solitary bee Euglossa carolina (Linnaeus, 1758) (Fernandeset al. 2013), suggesting that alternative mechanisms of karyotype change may occur through the evolutionary diversification of these species. More detailed karyotype studies are needed to point out the trend in the karyotype evolution of solitary bees.Figure 2. Female mitotic karyotypes of M. segmentaria stained with fluorochromes: a CMA3 b DAPI c CMA3/DAPI and d DAPI/CMA3. Arrows indicate entirely heterochromatic metacentric chromosomes (Mh). Bar=5μm.
การแปล กรุณารอสักครู่..
