Autor: Leila M. Pessôa

Leila Maria Pessôa

Chromosomal differentiation in Kerodon rupestris (Rodentia: Caviidae) from the Brazilian semi-arid region

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Kerodon rupestris (Wied, 1820) is the most specialized species among caviid rodents and is endemic to the extensive rocky outcrops in the semi-arid region in Brazil. Herein we describe different karyotypes for K. rupestris, based on samples collected in Itapajé, Ceará (CE), Iraquara in Bahia (BA), and Botumirim in Minas Gerais (MG). Our samples included northern, center and southern populations in the range of the species distribution. The results were compared with a karyotype from Pernambuco previously described for the species. The diploid number (2n = 52) was constant among the analyzed population samples, but the fundamental number (FN) varied from 92 in Itapajé (CE) and Iraquara (BA), to 94 in Botumirim (MG). Pericentric inversions affecting one small pair of acrocentric chromosomes may explain this variation. C-bands showed that constitutive heterochromatin was distributed in the pericentromeric region of all chromosomes, constant for all examined populations. NOR sites were found in chromosomes pairs 10 and 11, constant for all populations. X chromosome was entirely heterochromatic, with greater heterochromatin concentration in interstitial and distal parts of the arms. Y chromosome was completely heterochromatic. Differences in chromosomal composition in Botumirim sample are congruent with the results of previous studies about cranial variability: Botumirim had the largest cranial size and was discriminated from other population samples in the multivariate character space. Since Botumirim is only 100 km away from the type locality, it is proposed—in congruence with previously published results—that the FN for the species is polytypic (94/92).

Diferenciação cromossômica em Kerodon rupestris (Rodentia: Caviidae) da região semiárida brasileira. Kerodon rupestris (Wied, 1820) é a espécie mais especialista entre os roedores caviídeos endêmica dos afloramentos rochosos da região semiárida do Brasil, a Caatinga. No presente trabalho foram descritos diferentes cariótipos para K. rupestris, baseado em amostras coletadas em Itapajé, Ceará (CE), Iraquara na Bahia (BA) e Botumirim em Minas Gerais (MG). As amostras incluem populações do norte, centro e sul da distribuição da espécie. Os resultados foram comparados com um cariótipo de Pernambuco, previamente descrito para a espécie. O número diploide (2n = 52) foi constante para as populações analisadas, mas o número fundamental (FN) variou de 92 em Itapajé (CE) e Iraquara (BA), para 94 em Botumirim (MG). Inversões pericêntricas afetando um pequeno par de cromossomos acrocêntricos podem explicar essa variação. Bandas C mostraram que a heterocromatina constitutiva estava distribuída na região pericentromérica de todos os cromossomos, constante para todas as amostras estudadas. Sítios de NOR foram encontrados nos pares de cromossomos 10 e 11, também constantes para todas as populações. O cromossomo X é inteiramente heterocromático, com grande concentração de heterocromatina nas porções intersticial e distal dos braços. Diferenças na composição cromossômica nas amostras de Botumirim são congruentes com os resultados prévios sobre a variabilidade cranial: os indivíduos de Botumirim apresentaram tamanho cranial maior do que os de outras populações no espaço de caractereres multivariados. Uma vez que Botumirim está a apenas 100 km de distância da localidade-tipo, propõe-se —de acordo com os resultados publicados previamente— que o FN para a espécie seja classificado como politípico (94/92).

The karyotype of Noctilio albiventris (Chiroptera, Noctilionidae) from the northern Pantanal of Brazil and its taxonomic implications

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The complete karyotype of Noctilio albiventris cabrerai is described on the basis of specimens from the northern Pantanal region of central Brazil. The G-banded karyotype comprises a diploid number (2n) of 34, an autosomal fundamental number (FNa) of 62, and respectively submetacentric and acrocentric X and Y chromosomes. Active nucleolar organizer regions (NORs) were located in pair 12. C-banding showed constitutive heterochromatin in the pericentromeric regions of all autosomes and in the X chromosome. Differences were found with respect to specimens from Honduras, referable to N. a. minor, which had a pair of autosomes with totally heterochromatic short arms, and from Colombia, referable to N. a. affinis, which had a metacentric X chromosome.

El cariotipo de Noctilio albiventris (Chiroptera, Noctilionidae) del norte del Pantanal brasileño y sus implicancias taxonómicas. Se describe el cariotipo completo de Noctilio albiventris cabrerai en base a especímenes del norte del Pantanal, Brasil. El cariotipo en bandeo G presentó un número diploide (2n) de 34, un número fundamental autosómico (FNa) de 62, el cromosoma X submetacéntrico y el Y acrocéntrico. Las regiones organizadoras del nucléolo (RONs) activas se ubican en el par 12. El bandeo C reveló bloques de heterocromatina constitutiva en las regiones pericentroméricas de todos los autosomas y en el cromosoma X. Se resumen las diferencias con respecto a cariotipos asignables a N. a. minor (Honduras), con un par cromosómico de brazos cortos totalmente heterocromático, y a N. a. affinis (Colombia), con un cromosoma X metacéntrico.

Morphometrics and cytogenetics of Gracilinanus agilis and Cryptonanus spp. (Didelphimorphia: Didelphidae) from central and northeastern Brazil

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Species of the didelphid genera Gracilinanus and Cryptonanus are morphologically and cytogenetically very similar. Several qualitative characters, some of which exhibit intraspecific polymorphisms, have been used to distinguish these genera, but more data are needed to characterize them better. Samples of G. agilis and Cryptonanus spp. from nine localities in central and northeastern Brazil were analyzed. Multivariate analyses of craniodental measurements and descriptive statistics of external body measurements indicate that G. agilis is conspicuously larger than Cryptonanus spp., and that general size is the main factor distinguishing these forms. Size differences can be combined with qualitative characters making the differentiation between G. agilis and Cryptonanus spp. easier. Cytogenetic analyses, including the first description of C-bands and Ag-NORs of G. agilis, revealed that the karyotypes of G. agilis and Cryptonanus sp. from Barão de Melgaço, Mato Grosso, are very similar, except for the fourth autosomal pair and the X chromosome.

Morfometría y citogenética de Gracilinanus agilis y Cryptonanus spp. (Didelphimorphia: Didelphidae) del centro y nordeste del Brasil. Los didélfidos Gracilinanus y Cryptonanus poseen una morfología y citogenética muy semejantes. Estos géneros han sido diferenciados por caracteres polimórficos cualitativos, pero más datos son necesarios para caracterizarlos mejor. Fueron analizadas muestras de G. agilis y Cryptonanus spp. de nueve localidades de centro y nordeste de Brasil. Los análisis multivariados de las medidas craneodentarias y las estadísticas descriptivas de las medidas corporales externas indican que G. agilis es claramente mayor que Cryptonanus spp. y que el tamaño general es el principal factor para distinguir esas formas. La variación en tamaño puede ser asociada a los caracteres cualitativos para facilitar la diferenciación entre G. agilis y Cryptonanus spp. Los análisis citogenéticos, incluyendo la primera descripción del bandeo C y las Ag-NORs de G. agilis, revelaron que los cariotipos de G. agilis y Cryptonanus sp. de Barão de Melgaço, Mato Grosso, son muy semejantes, excepto por el cuarto par de autosomas y el cromosoma X.

The first description of the karyotype of Dasyprocta azarae Lichtenstein, 1823 (Rodentia, Dasyproctidae) from Brazil

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The karyotype of Dasyprocta azarae has not been described previously. In this article we describe the karyotype of D. azarae from Northern Pantanal, Mato Grosso, Central Brazil. D. azarae has a diploid number 2n = 64 and a number of autosomal arms NA = 122. The 2n and NA are the same as those reported for other Brazilian species of Dasyprocta, but differ in chromosome morphology. Differences in the sex chromosomes were also found. The Y chromosome is acrocentric whereas in other Dasyprocta species is metacentric or submetacentric. The C-banding pattern coincides with that described for other species, except for pair six, having two bands of heterochromatin. The NOR patterns revealed intraindividual variation, with 1 to 6 NOR chromosomes. In the other species of Dasyprocta the NOR is present in only 1 pair. Although few data about morphological variation is available and restricted to color pattern, the small chromosomal differences observed among species of Dasyprocta are however, capable to differentiate taxa of the genus.

Primera descripción del cariotipo de Dasyprocta azarae Lichtenstein, 1823 (Rodentia, Dasyproctidae) de Brasil. En este artículo se describe por primera vez el cariotipo de D. azarae procedente del norte del Pantanal, Mato Grosso, Brasil. La especie posee un número diploide 2n = 64 y un número de brazos autosómicos NA = 122. Los resultados para 2n y NA son los mismos que los encontrados para otras especies brasileñas de Dasyprocta, pero difieren en la morfología cromosómica. También fueron identificadas diferencias en los cromosomas sexuales. El cromosoma Y es acrocéntrico en esta, mientras que en otras especies del género es metacéntrico o submetacéntrico. El patrón de bandas C es igual al descrito para otras especies, con la excepción del par seis, que presenta dos bandas de heterocromatina. Los patrones NOR demuestran variación interespecífica, con uno a seis cromosomas marcados con NORs. En otras especies de Dasyprocta el NOR está presente en apenas un par. Aunque hay poca información disponible sobre variación morfológica, restringida al patrón de color, las pequeñas diferencias cromosómicas entre especies de Dasyprocta son, sin embargo, capaces de diferenciar taxas del género.