Identification of a long-standing colony of Proechimys at the Instituto Evandro Chagas, Pará, Brazil, based on cytogenetic information / Identificação de uma colonia de longo prazo de Proechimys no Instituto Evandro Chagas, Pará, Brasil, com base em informações citogenéticas

The taxonomic classification of the genus Proechimys is complex because many of its species are morphologically similar but chromosomally different, with diploid (2n) values ranging from 14 to 62. The "Seção de Criação e Produção de Animais de Laboratório do Instituto Evandro Chagas" (The Division for Breeding and Production of Laboratory Animals, Instituto Evandro Chagas, Brazil) maintains a Proechimys colony for biomedical research. The colony members have been classified as P. guyannensis, which reportedly has 2n=40 and a fundamental number (FN) = 54. However, using karyotype analysis to aid in their taxonomic classification, we instead observed that a sample of the animals in this colony have 2n = 30 and FN = 56, with a medium-sized submetacentric X chromosome and a small acrocentric Y chromosome. Constitutive heterochromatin was distributed as follows: in the pericentromeric regions of chromosomes 6, 7, 9, 10, 11, 12, 13, 14 and X; on the distal short arms of chromosomes 3, 6, 10 and X; on the distal long arm of chromosome 12; on the long arm of the Y chromosome; and distally on both arms of chromosomes 7, 9 and 11. The nucleolar organizer regions (NORs) are located on the long arm of chromosome 9. This karyotype is consistent with that described previously for P. roberti, but not P. guyannensis, thus demonstrating the importance of using karyotyping for the taxonomic identification of Proechimys.

A classificação taxonómica do gênero Proechimys é complexa porque muitas de suas espécies são morfologicamente semelhantes, porém diferentes cromossomicamente, com números de diploide (2n) que variam entre 14 e 62. A Seção de Criação e Produção de Animais de Laboratório do Instituto Evandro Chagas mantém uma colónia de Proechimys para pesquisa biomédica. Os membros da colónia foram classificados como P. guyannensis, que possui 2n = 40 e um número fundamental (NF) = 54. No entanto, ao utilizar a análise do cariótipo para auxiliar em sua classificação taxonómica, observamos que uma amostra dos animais desta colónia possuem 2n = 30 e NF = 56, com um cromossomo X submetacêntrico de tamanho médio e um cromossomo Y acrocêntrico pequeno. A heterocromatina constitutiva foi distribuída da seguinte forma: nas regiões pericentromérica dos cromossomos 6, 7, 9, 10, 11, 12, 13, 14 e X; na porção distal dos braços curtos dos cromossomos 3, 6, 10 e X; na porção distal do braço longo do cromossomo 12; no braço longo do cromossomo Y; e nas porções distais de ambos os braços dos cromossomos 7, 9 e 11. As regiões organizadoras nucleolares (NORs) localizam-se no braço longo do cromossomo 9. Este cariótipo é consistente com o descrito anteriormente para P. roberti, não para P. guyannensis, o que demonstra a importância do uso de cariotipagem para a identificação taxonómica de Proechimys.

Cytogenetic studies in fishes of the genera Hassar, Platydoras and Opsodoras (Doradidae, Siluriformes) from Jarí and Xingú Rivers, Brazil

We studied the karyotypes of Hassar cf. orestis and an undescribed Hassar species from the Jarí River and Opsodoras ternetzi, H. orestis and Platydoras cf. costatus from the Xingú River, all with 2n = 58. Constitutive heterochromatin is located in the centromere in most metacentric pairs; in some chromosomes this banding is not present, or it is located on the whole chromosome arm or in the distal regions. The NOR is located on a single biarmed pair at a distal region of the short arm in H. cf. orestis, H. orestis and P. cf. costatus at a distal region of the long arm in O. ternetzi and at a proximal region of the long arm in the Hassar species. In all species (except for Hassar sp.) the CMA3 analysis revealed a rich G-C region coincident with the NOR. Probably inversions occurred in the NOR chromosome during the chromosomal differentiation of the Doradidae species here described.

Comparative cytogenetic analysis in the species Uroderma magnirostrum and U. bilobatum (cytotype 2n = 42) (Phyllostomidae, Stenodermatinae) in the Brazilian Amazon

The genus Uroderma includes two species: U. magnirostrum and U. bilobatum. These species are characterized by their high degree of karyotypic evolution, diverging from most other species of the subfamily Stenodermatinae, which have a lower degree of chromosomic evolution. The present study reports the first banding patterns of U. magnirostrum (G-, C-banding and Ag-NOR) and U. bilobatum (C-banding and Ag-NOR). The chromosomic data in conventional staining of U. magnirostrum (2n = 36, NF = 62) and U. bilobatum (cytotype 2n = 42, NF = 50) are equivalent to that described in the literature. When compared, chromosomal homeologies are found in both karyotypes, as well as differences, confirming that karyotypic evolution in the Uroderma genus is intense. Fission, fusion, inversion or translocation events are required to explain the karyotypic evolution of this genus. The comparison of karyotype, described here, to one of the species of the genus Artibeus (2n = 30/31), suggests that some chromosomic forms are apomorphic and shared between the two species of Uroderma. This confirms the monophyly of the genus, and that U. magnirostrum presents a more primitive karyotype when compared to U. bilobatum.

The karyotype of Callicebus moloch moloch (Cebidae, primates)

No presente trabalho é estudado o cariótipo de Callicebus moloch moloch (Cebidae, Primates). Foram analisados 22 animais, provenientes de Tucuruí, Pará, Brasil. O número diplóide é de 48 cromossomos. É apresentado o padräo de bandeamento G. As bandas C säo centroméricas, havendo ainda bandas teloméricas. Pelo menos três pares de cromossomos acrocêntricos säo organizadores nucleolares, estando a NOR localizada na extremidade distal do braço longo