ABSTRACT
Tetragonisca angustula and Tetragonisca fiebrigi have recently been listed as valid species. This study aimed to cytogenetically investigate both species, emphasizing the new registry of B chromosomes in the tribe Meliponini. We analyzed colonies of T. angustula and T. fiebrigi collected at Tangará da Serra, Mato Grosso, Brazil, through conventional Giemsa staining, C-banding, and base-specific fluorochrome staining (CMA3/DAPI). T. angustula showed 2n = 34 chromosomes in females and n = 17 in males, with karyotype formula 2K = 34A M. T. fiebrigi showed numeric variation, with chromosome number varying from 2n = 34 to 2n = 36 in females and from n = 17 to n=18in males, with karyotype formula 2K = 32A M+2A Mc and 2K = 32A M+2A Mc + 1 or 2 B-chromosomes. The B chromosomes are heterochromatic. In T. fiebrigi, the CMA3/DAPI staining revealed four chromosomes with a CMA3 positive band. All individuals from the same colony showed the same number of B chromosomes. T. angustula and T. fiebrigi showed karyotype divergence, principally due to the presence of B chromosomes, which are found only in T. fiebrigi. Our data corroborate the status of valid species for both T. angustula and T. fiebrigi, as recently proposed.
ABSTRACT
Four colonies of the stingless bee Partamona cupira (Hymenoptera: Apidae) were cytogenetically analyzed using conventional staining and the fluorochromes CMA3 e DAPI. The females have 2n = 34 chromosomes (2K=32
+2
). Some females, however, presented an additional large B acrocentric chromosome, to a total of 2n = 35. Chromosome B and the chromosomal pairs 2, 9 and 10 showed CMA3+ bands, indicating an excess of CG base-pairs. A clear association was verified between the P. helleri B chromosome SCAR marker and the presence of a B chromosome in P. cupira. The data obtained suggests that B chromosomes in P. helleri and P. cupira share a common origin.
ABSTRACT
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.
Subject(s)
Animals , Bees/genetics , Cytogenetic Analysis , Brazil , Chromosomes , Fluorescent Dyes , KaryotypingABSTRACT
The stingless bees Melipona rufiventris and M. mondury were analyzed cytogenetically by conventional staining with Giemsa, C-banding and sequential staining with the fluorochromes CMA3/DA/DAPI. Both species presented 2n = 18 and n = 9, except for one colony of M. rufiventris, in which some individuals had 2n = 19 due to the presence of a B chromosome. After Giemsa staining and C-banding the chromosomes appeared very condensed and presented a high heterochromatic content, making it difficult to localize the centromere and therefore to visualize the chromosomes morphology. The constitutive heterochromatin was located in interstitial chromosome regions covering most of the chromosomes extension and consisted mainly of AT, as shown by DAPI staining. The euchromatin was restricted to the chromosome extremities and was GC-rich, as evidenced by CMA3 staining. The B chromosome was CMA3-negative and DAPI-positive, a heterochromatic constitution similar to that of the A genome chromosomes.
Subject(s)
Animals , Bees/genetics , Chromosome Banding , Fluorescent DyesABSTRACT
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.
Subject(s)
Animals , Bees , Chromatin , Cytogenetics , Heterochromatin , KaryotypingABSTRACT
The karyotypes of Neotropical Pseudomyrmecinae were analyzed for the first time. Seven species belongingto the Pseudomyrmex genus from four Brazilian localities had their chromosome number and morphologystudied. Six of the nine species groups of Pseudomyrmex were sampled. Chromosome numbers rangedfrom 2n=24 to 2n=70, characterized in acrocentrics and metacentrics. Our cytogenetic studies indicatethat, as in other ants, karyoptype evolution in Pseudomyrmex may have evolved increasing chromosomenumber and diversifying chromosome morphology, minimizing genetics risks for deleterious mutationsthrough centric fission and pericentric inversion. Such a karyotypic diversity is also recognized in otherants subfamilies, especially Myrmeciinae, Ponerinae and Myrmicinae. These first cytogenetic studies in thegenus Pseudomyrmex should contribute with other data to the evolutionary history of the Pseudomyrmecinaesubfamily.
Subject(s)
Animals , Ants , Cytogenetics , Ants/cytology , Brazil , Fauna , Genetic VariationABSTRACT
The stingless bees of the Partamona genus have been studied taxonomically, ecologically and behaviourally, but cytogenetic studies are still rare. The objective of this study was to obtain cytogenetic data to contribute to Partamona peckolti species characterization. Heterochromatin was localized in all chromosome pericentromeric regions but some blocks could be visualized on some large chromosomes arms. A large heterozygous DA-CMA(3)-positive band was observed on one large chromosome arm, but was completely absent when C banding was applied before fluorochrome staining, with only one small positive band being visualized. Sequential DA-CMA(3)-NOR staining of interphase nuclei provided coincident positive responses. This suggests that DA-CMA(3)-positive bands of P. peckolti correspond to nucleolar organizer regions, as previously confirmed for another Partamona species by FISH
Subject(s)
Bees , Chromosome Banding , Cytogenetics , Fluorescent Dyes , KaryotypingABSTRACT
Cytogenetic analysis based on the distribution of C-bands showed two groups of karyotypes in a Trypoxylon nitidum population from the Rio Doce Park, State of Minas Gerais, Brazil. One of these groups, that was identical to a previously described karyotype (n = 15; 2n = 30), had a stable chromosome number and was rich in acrocentric chromosomes, whereas the other had a variable chromosome number (n = 12 to 14; 2n = 25 to 28) and was rich in pseudo-acrocentric chromosomes. We propose a hypothesis explaining the dynamics of the modifications which occurred in the karyotype of this species, based on the minimum interaction theory of Imai et al. (1986, 1988, 1994) and on the chromosome rearrangements and heteromorphisms observed by us