Karyotypic description of the stingless bee Meliponaquinquefasciata Lepeletier, 1836 (Hymenoptera, Meliponini) with emphasis on the presence of B chromosomes.

Stingless bees are distributed widely in the tropics, where they are major pollinators of several plant species. In this study, the karyotype of Meliponaquinquefasciata Lepeletier, 1836 was analysed, with emphasis on the presence of B chromosomes. Post-defecating larvae were analysed using Giemsa staining, the C-banding technique, sequential staining with fluorochromes, and FISH. The chromosome number ranged from 2n = 18 to 22 (females) and from n = 9 to 13 (males) due to the presence of 0-4 B chromosomes. This result demonstrates that M.quinquefasciata has the same chromosomal number as other Melipona Illiger, 1806 species. Considering the A complement, heterochromatin was located only in the pericentromeric region of pair 1. Staining with chromomycin A3 (CMA3) and labelling with rDNA probe, indicated that this region corresponded to the nucleolus organising region. The B chromosomes of M.quinquefasciata could be found in individuals from different localities, they were completely heterochromatic (C-banding) and uniformly stained by 4',6-diamidino-2-phenylindole (DAPI). Variations in the number of B chromosomes were detected between cells of the same individual, between individuals of the same colony, and between colonies from different localities.

Mitotic activity of the brain ganglia in different subphases of the last larval instar of Melipona quadrifasciata lepeletier (Hymenoptera, apidae, meliponini) / Atividade mitótica do gânglio cerebral em diferentes fases do último instar larval de melipona quadrifasciata (hymenoptera, apidae, meliponini) / MITOTIC ACTIVITY OF THE BRAIN GANGLIA IN DIFFERENT SUBPHASES OF THE LAST LARVAL INSTAR OF MELIPONA QUADRIFASCIATA LEPELETIER (HYMENOPTERA, APIDAE, MELIPONINI)

In recent years, the number of cytogenetic studies on Melipona species has increased considerably. However, most cytogenetic techniques used for these studies require preparations with a great number of metaphase cells for reliable analysis of the karyotypes. The present study seeks to evaluate which subphase of the last larval instar of Melipona quadrifasciata Lepeletier provides the greatest number of metaphases, which is here considered a direct measure of mitotic activity. A total of 25 defecating larvae were selected based on the quantity of feces in their intestines, so as to maintain five larvae in each of the five different developmental subphases. The brain ganglia of each larva were extracted and used for cytogenetic preparation. The number of metaphase mitotic cells per preparation was counted. An analysis of variance (ANOVA) model, with Tukey's post hoc tests, was conducted. It was observed that larvae in the second subphase, defined here as the subphase in which feces were visible below the segment VII, provided the greatest number of metaphases. Therefore, it is the most appropriate developmental subphase for cytogenetic preparations of brain glanglia in M. quadrifasciata and possibly in other Melipona species.

Estudos citogenéticos envolvendo o gênero Melipona vêm aumentando nos últimos anos. Entretanto, a utilização de várias técnicas para o estudo do cariótipo exigem preparações com um grande número de células em metáfase para uma análise confiável das características citogenéticas das espécies. O presente estudo teve como principal objetivo avaliar, para Melipona quadrifasciata, o instar do desenvolvimento larval mais adequado para estudos citogenéticos, no que se refere à atividade mitótica. Foram selecionadas 25 larvas defecantes divididas em cinco subfases de acordo com a quantidade restante de fezes no intestino. Os gânglios cerebrais das larvas foram extraídos e utilizados para a obtenção dos cromossomos mitóticos metafásicos. O número de metáfases por lâmina foi contabilizado para cada indivíduo e os dados submetidos à análise de variância (ANOVA) e ao teste de TUKEY. Foi observado que larvas da segunda subfase, definidas aqui como a subfase na qual as fezes se encontram na altura do VII segmento apresentaram o maior número de metáfases. Logo, esta é a subfase mais indicada para obtenção de grande número de metáfases em células do gânglio cerebral de Melipona quadrifasciata e, possivelmente, para outras espécies do gênero Melipona.

Karyotypic description of the stingless bee Oxytrigona cf. flaveola (Hymenoptera, Apidae, Meliponina) of a colony from Tangará da Serra, Mato Grosso State, Brazil.

The aim was to broaden knowledge on the cytogenetics of the subtribe Meliponina, by furnishing cytogenetic data as a contribution to the characterization of bees from the genus Oxytrigona. Individuals of the species Oxytrigona cf. flaveola, members of a colony from Tangará da Serra, Mato Grosso State, Brazil, were studied. The chromosome number was 2n = 34, distributed among four chromosomal morphologies, with the karyotype formula 8m+8sm+16st+2t. Size heteromorphism in the first metacentric pair, subsequently confirmed by sequential staining with fluorochrome (DA/DAPI/CMA(3) ), was apparent in all the examined individuals The nucleolar organizing regions (NORs) are possibly located in this metacentric chromosome pair. These data will contribute towards a better understanding of the genus Oxytrigona. Given that species in this group are threatened, the importance of their preservation and conservation can be shown in a sensible, concise fashion through studies such as this.

Karyotypic description of the stingless bee Oxytrigona cf. flaveola (Hymenoptera, Apidae, Meliponina) of a colony from Tangará da Serra, Mato Grosso State, Brazil

The aim was to broaden knowledge on the cytogenetics of the subtribe Meliponina, by furnishing cytogenetic data as a contribution to the characterization of bees from the genus Oxytrigona. Individuals of the species Oxytrigona cf. flaveola, members of a colony from Tangará da Serra, Mato Grosso State, Brazil, were studied. The chromosome number was 2n = 34, distributed among four chromosomal morphologies, with the karyotype formula 8m+8sm+16st+2t. Size heteromorphism in the first metacentric pair, subsequently confirmed by sequential staining with fluorochrome (DA/DAPI/CMA3), was apparent in all the examined individuals The nucleolar organizing regions (NORs) are possibly located in this metacentric chromosome pair. These data will contribute towards a better understanding of the genus Oxytrigona. Given that species in this group are threatened, the importance of their preservation and conservation can be shown in a sensible, concise fashion through studies such as this.

Melípona: seis décadas de citogenética / Melípona: six decade of cytogenetic

São 59 anos de estudos citogenéticos no gênero Melipona e esse artigo é uma revisão dessa história, que vai desde trabalhos com apenas a determinação do número cromossômico até os trabalhos de citogenética molecular. Os principais focos do artigo são: o número e morfologia dos cromossomos, conteúdo heterocromático e a natureza da cromatina. Fundamentadas nesses dados são feitas inferências sobre a evolução cariotípica do gênero.

They are 59 years of cytogenetics study in Melipona genus and this paper has a review about this history, going to the works only with the chromosome number determination, up to molecular cytogenetic. The mainly focuses of this paper are: chromosome number and morphology, heterochromatin content and the chromatin nature. With base of this data they are realized inferences about the karyotype evolution of this genus.

DNA characterization and karyotypic evolution in the bee genus Melipona (Hymenoptera, Meliponini).

We analyzed patterns of heterochromatic bands in the Neotropical stingless bee genus Melipona (Hymenoptera, Meliponini). Group I species (Melipona bicolor bicolor, Melipona quadrifasciata, Melipona asilvae, Melipona marginata, Melipona subnitida) were characterized by low heterochromatic content. Group II species (Melipona capixaba, Melipona compressipes, Melipona crinita, Melipona seminigra fuscopilosa e Melipona scutellaris) had high heterochromatic content. All species had 2n = 18 and n = 9. In species of Group I heterochromatin was pericentromeric and located on the short arm of acrocentric chromosomes, while in Group II species heterochromatin was distributed along most of the chromosome length. The most effective sequential staining was quinacrine mustard (QM)/distamycin (DA)/chromomycin A3(CMA3)/4-6-diamidino-2-phenylindole (DAPI). Heterochromatic and euchromatic bands varied extensively within Group I. In Group II species euchromatin was restricted to the chromosome tips and it was uniformly GC+. Patterns of restriction enzymes (EcoRI, DraI, HindIII) showed that heterochromatin was heterogeneous. In all species the first pair of homologues was of unequal size and showed heteromorphism of a GC+ pericentromeric heterochromatin. In M. asilvae (Group I) this pair bore NOR and in M. compressipes (Group II) it hybridized with a rDNA FISH probe. As for Group I species the second pair was AT+ in M. subnitida and neutral for AT and GC in the remaining species of this group. Outgroup comparison indicates that high levels of heterochromatin represent a derived condition within Melipona. The pattern of karyotypic evolution sets Melipona in an isolated position within the Meliponini.