Prevalencia de endoparásitos en roedores sinantrópicos (Rodentia: Muridae) en una localidad de La Habana, Cuba / Prevalence of endoparasites in synanthropic rodents (Rodentia: Muridae) in an area of Havana, Cuba

Introducción: los roedores sinantrópicos se encuentran estrechamente vinculados a las condiciones de vida del hombre. Algunos de sus endoparásitos juegan un papel importante en los ciclos de muchas enfermedades parasitarias, por lo que representan un riesgo para la salud pública. Objetivo: determinar la prevalencia de grupos y especies de endoparásitos en roedores sinantrópicos en una localidad de La Habana. Métodos: el estudio se realizó en la localidad Arroyo Arenas, municipio La Lisa, provincia La Habana, Cuba. En las capturas de roedores, se emplearon trampas de captura viva. Después de realizada la eutanasia y la necropsia, se tomaron muestras fecales de la última porción del intestino grueso y del recto. Las muestras se procesaron mediante diagnóstico coproparasitológico convencional. Resultados: se capturaron un total de 78 roedores identificados como Rattus rattus, Rattus norvegicus y Mus musculus. Se registraron 13 especies de parásitos, las de mayor prevalencia fueron los nematodos Nippostrongylus brasiliensis (33,3 por ciento) y Strongyloides ratti (23,1 por ciento), y el cestodo Hymenolepis diminuta (11,5 por ciento). Conclusiones: se reportan las especies de endoparásitos en los roedores sinantrópicos. Hymenolepis diminuta es la especie de mayor prevalencia entre las especies zoonóticas, lo que demuestra su circulación activa en el ambiente. Los resultados resaltan la importancia de estos roedores como vectores potenciales de las parasitosis intestinales(AU)

Introduction: the synanthropic rodents are closely associated with human living conditions. Some of their endoparasites play an important role in many cycles of parasitic diseases, thus representing a public health risk. Objectives: to determine the prevalence of groups and species of endoparasites in synanthropic rodents in an area of Havana. Methods: the research study was carried out in Arroyo Arenas, La Lisa municipality, Havana province, Cuba. Live traps were used to capture rodents. Stool samples of the last portion of the large intestine and rectum were taken after euthanasia and necropsy. The stool samples were processed by usual parasitological diagnostic techniques. Results: a total of 78 rodents identified as Rattus rattus,Rattus norvegicus and Mus musculus were captured. Thirteen species of endoparasites were recorded, being nematodes Nippostrongylus brasiliensis (33.3 percent) and Strongyloides ratti (23.1 percent), and tapeworm Hymenolepis diminuta (11.5 percent) the most prevalent. Conclusions: some species of endoparasites are reported in the synanthropic rodents. Hymenolepis diminuta was found to be the most prevalent among zoonotic species, which shows its active circulation in the environment. This type of research highlights the importance of these rodents as potential vectors for intestinal parasitic infections(AU)

Comparison between Oligoryzomys nigripes and O. flavescens by RAPD and genetic diversity in O. nigripes (Rodentia, Cricetidae) / Comparação entre Oligoryzomys nigripes e O. flavescens e diversidade genética em O. nigripes (Rodentia, Cricetidae) por RAPD

The genus of Oligoryzomys includes species of small size, morphologically similar, which may impede taxonomic identification, mainly between O. flavescens (Waterhouse, 1837) and O. nigripes (Olfers, 1818). The main objective of this work was to investigate whether the RAPD markers are capable of genetically differentiating the specimens O. nigripes and O. flavescens, coming from Rio Grande do Sul (RS) and Santa Catarina (SC) states, and also to estimate the genetic variability among populations of O. nigripes, with the Uruguay River as a geographical barrier. For this purpose, samples were collected in fragments of forests situated in the North of RS, at FLONA (Floresta Nacional de Passo Fundo) and in fragments from SC, close to the Uruguay River. The karyotyping of two samples for each species was carried out and compared using the RAPD technique together with non- karyotyped individuals. Samples of O. nigripes presented 2n = 62; NA = 82, with submetacentric arms on the largest chromosomes, while samples of O. flavescens showed 2n = 64; NA = 66, with the largest chromosomes presenting acrocentric morphology, making such a result the main difference between the species. The analysis was able to detect two distinct groups, being the first one with karyotyped O. flavescens and the second with karyotyped O. nigripes. Identification afforded 211 loci, among them 181 (85.78%) polymorphic. The Jaccard similarity coefficient was in the range of 0.45 to 0.87. The UPGMA and Main Coordinate Analysis techniques demonstrated the existence of heterogeneous genetics among populations, but did not separate them completely in terms of geographical standards, and they are not influenced by the Uruguay River, which did not act as an efficient barrier.

O gênero Oligoryzomys inclui espécies de tamanho pequeno, morfologicamente semelhantes, com difícil identificação taxonômica, principalmente entre O. flavescens e O. nigripes. O objetivo principal deste trabalho foi investigar se os marcadores RAPD são capazes de diferenciar geneticamente as amostras de O. nigripes e O. flavescens, oriundas do Rio Grande do Sul (RS) e Santa Catarina (SC) e também para estimar o variabilidade genética entre populações de O. nigripes, tendo o rio Uruguai como uma barreira geográfica. Para este fim, as amostras foram coletadas em fragmentos florestais situados no Norte do RS, na FLONA (Floresta Nacional de Passo Fundo) e em fragmentos florestais de SC, próximos ao Rio Uruguai. O cariótipo de duas amostras de cada espécie foi realizado e comparado com a técnica RAPD em conjunto com indivíduos não cariotipados. As amostras de O. nigripes apresentaram 2n = 62, NA = 82, com braços submetacêntricos nos cromossomos maiores, enquanto que as amostras de O. flavescens mostraram 2n = 64, NA = 66, com os maiores cromossomos apresentando morfologia acrocêntrica, tornando tal resultado a principal diferença entre as espécies. As análises por RAPD foram capazes de detectar dois grupos distintos, sendo o primeiro com O.flavescens cariotipados e o segundo com O. nigripes cariotipados. Foram avaliados 211 loci, e entre eles 181 (85,78%) foram polimórficos. O coeficiente de similaridade de Jaccard variou de 0,45 a 0,87. A análise por UPGMA e análise de coordenadas principais demonstraram a existência de heterogeneidade genética entre as populações, mas não foi possível separá-las completamente em termos de padrões geográficos, e estas não são influenciadas pelo rio Uruguai, o qual não agiu como uma barreira eficiente.

Description of Karyotype of Kerodon acrobata, an endemic rodent in Brazilian Cerrado / Primeira descrição do cariótipo de Kerodon acrobata, um roedor endêmico do semiárido brasileiro

Kerodon acrobata is a caviidae rodent endemic from Brazilian Cerrado. It was described only in 1997 and the data about it is very scarce. The aim of this work was to characterize the karyotype of K. acrobata. Giemsa staining, nucleolar organizer region (NOR) banding, C-positive heterochromatin banding and DAPI fluorescence were used in N metaphases of a specimen collected in Asa Branca Farm, in Aurora do Tocantins municipality, Tocantins state, Brazil. K. acrobata showed the same diploid number, fundamental number and chromosome morphology as Kerodon rupestris. But its NOR location and heterochromatin distribution patterns indicated a unique cytogenetic profile when compared to its sister species, emphasizing the evolutionary uniqueness of this relatively new and unknown species. This record also extends the distribution of this species northward.

Kerodon acrobata é um roedor caviídeo endêmico do Cerrado brasileiro. A espécie foi descrita apenas em 1997, e as informações sobre ela são muito escassas. O objetivo deste trabalho foi caracterizar o cariótipo K. acrobata. Coloração em Giemsa, bandeamento da região organizadora do nucléolo, bandeamento da heterocromatina C-positiva e fluorescência DAPI foram utilizados em N metáfases de um espécime coletado na fazenda Asa Branca, na cidade de Aurora do Tocantins, estado do Tocantins, Brasil. K. acrobata apresentou o mesmo número diplóide, número fundamental e morfologia dos cromossomos de Kerodon rupestris. Mas a localização de sua NOR e os padrões de distribuição de heterocromatina indicam um perfil citogenético único quando comparado com sua espécie irmã, enfatizando a singularidade evolutiva desta espécie pouco conhecida. Este registro também estende a distribuição desta espécie em direção ao norte.

Estructura genética de un grupo de capibaras, Hydrochoerus hydrochaeris (Rodentia: Hydrocheridae) en los Llanos orientales colombianos

Genetic structure of a group of capybaras, Hydrochoerus hydrochaeris (Rodentia: Hydrocheridae) in the Colombian Eastern Llanos. The capybaras are the biggest rodents in the world but, however, there are not extensive population genetics studies on them. In the current work, we studied the genetic structure of a troop of 31 capybaras (Hydrochoerus hydrochaeris) sampled in Hato Corozal, Casanare Department at the Colombian Eastern Llanos, by means of five microsatellite markers. The gene diversity was 0.61 and the average allele number was 5.2, which is a medium-low level for markers of this nature. Out five markers employed, three were in Hardy-Weinberg equilibrium meanwhile one showed a significant homozygote excess and other presented a significant heterozygote excess. There were not significant genetic differences between males and females inside this troop. The application of different procedures to determine possible historical demographic changes (population expansions or bottlenecks) clearly showed that the population analyzed crossed over a very narrow recent bottleneck. The illegal hunt is the possibly cause of this strong genetic bottleneck. Rev. Biol. Trop. 59 (4): 1777-1793. Epub 2011 December 01.

Los capibaras son los roedores más grandes del mundo, sin embargo, no se han realizado estudios genético poblacionales exhaustivos con ellos. En el presente trabajo se analizó la estructura genética de una manada de 31 capibaras (Hydrochoerus hydrochaeris) muestreada en Hato Corozal, Departamento de Casanare en los Llanos Orientales de Colombia, mediante cinco marcadores microsatelitales. La diversidad genética se determinó en 0.61 y un número promedio de alelos de 5.2, lo cual se puede considerar medio-bajo para este tipo de marcadores. De los cinco marcadores empleados, tres mostraron proporciones genotípicas en concordancia con lo esperado en equilibrio Hardy-Weinberg, mientras que un marcador mostró un exceso significativo de homocigotos y otro un exceso significativo de heterocigotos. No se encontraron diferencias significativas para esos cinco marcadores entre machos y hembras de la manada muestreada. La aplicación de diferentes procedimientos para detectar posibles cambios demográficos históricos (expansiones poblacionales o cuellos de botella) mostró claramente que la población analizada ha pasado por un cuello de botella extremadamente fuerte en épocas recientes. La limitada variabilidad genética encontrada y la fuerte evidencia de que la manada estudiada ha pasado por un cuello de botella reciente es probablemente el resultado de la cacería ilegal.

Description of the karyotype of Rhagomys rufescens Thomas, 1886 (Rodentia, Sigmodontinae) from Southern Brazil Atlantic forest

Rhagomys rufescens (Rodentia: Sigmodontinae) is an endemic species of the Atlantic forest from Southern and Southeastern Brazil. Some authors consider Rhagomys as part of the tribe Thomasomyini; but its phylogenetic relationships remain unclear. Chromosomal studies on eight specimens of Rhagomys rufescens revealed a diploid number of 2n = 36 and a number of autosome arms FN = 50. GTG, CBG and Ag-NOR banding and CMA3/DAPI staining were performed on metaphase chromosomes. Eight biarmed and nine acrocentric pairs were found in the karyotype of this species. The X and Y chromosomes were both acrocentric. Most of the autosomes and the sex chromosomes showed positive C-bands in the pericentromeric region. The X chromosome showed an additional heterochromatic block in the proximal region of the long arm. Nucleolus organizer regions (NORs) were located in the pericentromeric region of three biarmed autosomes (pairs 4, 6 and 8) and in the telomeric region of the short arm of three acrocentrics (pairs 10, 12 and 17). CMA3/DAPI staining produced fluorescent signals in many autosomes, especially in pairs 4, 6, and 8. This study presents cytogenetic data of Rhagomys rufescens for the first time.

Hidden heterochromatin: characterization in the Rodentia species Cricetus cricetus, Peromyscus eremicus (Cricetidae) and Praomys tullbergi (Muridae)

The use of in situ restriction endonuclease (RE) (which cleaves DNA at specific sequences) digestion has proven to be a useful technique in improving the dissection of constitutive heterochromatin (CH), and in the understanding of the CH evolution in different genomes. In the present work we describe in detail the CH of the three Rodentia species, Cricetus cricetus, Peromyscus eremicus (family Cricetidae) and Praomys tullbergi (family Muridae) using a panel of seven REs followed by C-banding. Comparison of the amount, distribution and molecular nature of C-positive heterochromatin revealed molecular heterogeneity in the heterochromatin of the three species. The large number of subclasses of CH identified in Praomys tullbergi chromosomes indicated that the karyotype of this species is the more derived when compared with the other two genomes analyzed, probably originated by a great number of complex chromosomal rearrangements. The high level of sequence heterogeneity identified in the CH of the three genomes suggests the coexistence of different satellite DNA families, or variants of these families in these genomes.

Familial osteopetrosis in Agouti paca: report of nine cases / Osteopetrose familiar em Agouti paca: relato de nove casos

Nine cases of familial osteopetrosis were studied in Agouti paca rodents maintained in captivity. Animals were distributed in three groups depending on the severity of their skeletal lesions. Based upon clinical, radiological, and microscopic findings, it was concluded that one animal had level I lesions, three animals had level II lesions, and five animals had level III osteopetrosis and osteonecrosis. Throughout the entire axial and appendicular skeleton, there was an increased amount of both trabecular and cortical bone tissue. All analyzed bones showed thickened cortex and reduced medullary canals. Bone trabeculae were thick and confluent. Cortex showed a narrowing of Haversian canals. Numerous cementing lines resulted in typical mosaic patterns. Osteocytes were pycnotic. Osteonecrosis was characterized by the disappearance of osteocytes and bone matrix decomposition.

Descreveram-se nove casos de osteopetrose familiar em Agouti paca mantidas em cativeiro. Os animais foram distribuídos em três grupos de acordo com a gravidade das lesões do esqueleto. Com base nos exames clínico, radiológico e microscópico, foi concluído que um animal apresentou lesões de nível I, três animais tiveram lesões de nível II e cinco animais tiveram osteopetrose de nível III. Por todo o esqueleto axial e apendicular, a quantidade de osso trabecular e osteônico estava aumentada. Todos os ossos analisados mostraram córtex espesso e canais medulares reduzidos. As trabéculas ósseas eram espessas e confluentes. No córtex, verificou-se um estreitamento de canais de Havers. Numerosas linhas de cimentação resultaram em um padrão de mosaico típico. Osteócitos estavam picnóticos e a osteonecrose foi caracterizada pela morte dos osteócitos, com desintegração da matriz óssea.

The conservation status of the tuco-tucos, genus Ctenomys (Rodentia: Ctenomyidae), in southern Brazil

The goal of conservation biology should be related to the preservation of species and also to the evolutionary and ecological processes that were responsible to form them and that are still acting. We review the conservation status of the species of tuco-tuco (Ctenomys torquatus, C. lami, C. minutus, and C. flamarioni) from southern Brazil, and relate these data to the geological history of a particular area in that region, the Coastal Plain of the States of Rio Grande do Sul and Santa Catarina. The implications of the data on these species from the Southeastern Brazil are also discussed in relation to the evolution and risk of extinction of these subterranean rodents.

O objetivo da biologia da conservação deve estar relacionado com a preservação das espécies e também com os processos evolutivos e ecológicos que foram responsáveis por sua formação e que continuam ocorrendo. Este trabalho revisa o status de conservação das espécies de tuco-tuco (Ctenomys torquatus, C. lami, C. minutus e C. flamarioni) do sul do Brasil, assim como a relação entre estas informações e a história geológica de uma região de especial importância, a planície costeira dos Estados do Rio Grande do Sul e Santa Catarina. São também discutidas as implicações do conhecimento acumulado sobre as espécies de tuco-tuco no sul do Brasil em relação aos aspectos evolutivos e a ameaça de extinção que estas espécies de roedores subterrâneos sofrem.

Comportamiento de cepas argentinas del virus de la Coriomeningitis Linfocitaria en roedores / Behavior of Argentine lymphocytic choriomeningitis virus strains in rodents

La actividad del virus LCM fue informada en Argentina a comienzos de la década del 70 y sólo han sido aisladas cinco cepas a partir del roedor Mus domesticus y dos de humanos. El objetivo de este trabajo consistió en investigar características biológicas de las cepas argentinas de virus LCM para compararlas entre sí y respecto a las cepas históricas WE y Armstrong. En células L 929 se obtuvieron placas bajo agarosa tanto con las cepas humanas como con las cepas de ratón, pero en células Vero sólo se obtuvieron placas con las cepas humanas. No se observó ninguna característica morfométrica de las placas que distinguiera nítidamente a las cepas históricas de las cepas argentinas, ni se observaron diferencias que se relacionen con las especies de origen de las cepas. Las cepas históricas y las cepas argentinas no fueron letales para ratón recién nacido (rrn) generando una infección persistente, según se comprobó al inocular ratones recién nacidos (rrn) por vía intracerebral con cepas de virus LCM y detectarse virus en los cerebros cosechados a diferentes días post inoculación. La única excepción fue la cepa Cba An 13065 que resultó virulenta para rrn ya que con sólo 0.026 UFP se logró 1 DL50. Todas las cepas resultaron letales en ratón adulto (rad), siendo las cepas de ratón más virulentas que las cepas de humanos. Estos resultados permitieron evidenciar el diferente comportamiento en cultivos celulares de las cepas de ratón con respecto a las cepas humanas, e identificar marcadores de virulencia mediante la respuesta a la inoculación por vía intracerebral del rad y del rrn.

The activity of LCM virus was first reported in Argentina at the beginning of the seventies and only five strains have been isolated from rodents Mus domesticus and two from humans. The objective of this paper was to find differential biological characteristics of Argentine strains of LCM virus comparing them in relation to the historical strains WE and Armstrong. Regarding the results obtained in tissue culture, when L 929 cells were used, plaque forming units (PFU) were obtained with human and mouse strains, whilst on Vero cells only human strains developed PFU. Differentials characteristics of historical and Argentine strain's plates were not found, neither differences related to the strain's origin. Neither historical nor Argentine strains were lethal to new-born mice giving a persistent infection, that was demonstrated when we inoculated new-born mouse by intracranial route with different strains of LCM virus and virus was isolated from brains harvested at different days post inoculation. The only exception was Cba An 13065 strain that exhibited virulence in new-born mice, only with 0.026 PFU was obtained 1 DL50. All the strains resulted lethal to adult mice. The mouse strains were more virulent than human strains, being Cba An 13065 the most virulent. These results demonstrate a different behavior in tissue culture between human and mouse strains and allow the identification of virulence markers by intracranial inoculation into new-born or adult mice.

Karyotype composition of some rodents and marsupials from Chapada Diamantina (Bahia, Brasil)

The Chapada Diamantina (CD) is located in Bahia State, between 11-14° S and 41-43° W, being part of the Serra do Espinhaço. The occurrence of different habitats and transition areas permits an interesting mammal fauna composition, with species from different biomes living in sympatry. Species of Didelphimorphia and Rodentia are important members of mammal communities in almost all different habitats, and morphological and cytogenetic characters are important for a correct identification of most of these species. In this work 258 specimens of small mammals from the orders Didelphimorphia (six genera and six species) and Rodentia (two families, five Sigmodontinae tribes, nine genera and 11 species) were collected during the whole field work (44 nights with traps). Chromosome preparations were obtained from 145 specimens from the species: Marmosops incanus, Gracilinanus microtarsus, Monodelphis domestica, Akodon aff. cursor, Necromys lasiurus, Cerradomys sp., Oligoryzomys fornesi, O. nigripes, O. rupestris, Calomys expulsus, Rhipidomys macrurus, Wiedomys pyrrhorhinus and Thrichomys inermis. Didelphis albiventris, Micoureus demerarae, Thylamys karymii and Nectomys sp. were identified by morphological characters. Most analyzed specimens do not show karyotype variation. However, numerical chromosomic variation was found in two individuals of Akodon aff. cursor (2n = 15) and in one individual of Cerradomys sp. (2n = 51). Structural variation in karyotype was observed in seven individuals of Cerradomys sp., showing one additional pair of metacentric chromosomes.

A Chapada Diamantina (CD) está localizada no estado da Bahia entre as coordenadas 11°-14° S e 41°-43° W, fazendo parte da Serra do Espinhaço. A ocorrência de diferentes hábitats e áreas de transição levam a uma composição da mastofauna interessante, podendo ser encontradas espécies de diferentes biomas convivendo em simpatria. As espécies das ordens Didelphimorphia e Rodentia compreendem membros importantes nas comunidades de mamíferos, praticamente em todos os diferentes habitats, e as características morfológicas e citogenéticas são importantes para a correta identificação da maioria das espécies. Neste trabalho, 258 espécimes de pequenos mamíferos das ordens Didelphimorphia (seis gêneros e seis espécies) e Rodentia (duas famílias, cinco tribos Sigmodontinae, nove gêneros e onze espécies) foram coletados durante todo o trabalho de campo (44 noites de armadilhamento). As preparações cromossômicas foram obtidas em 145 indivíduos dentre as seguintes espécies: Marmosops incanus, Gracilinanus microtarsus, Monodelphis domestica, Akodon aff. cursor, Necromys lasiurus, Cerradomys sp., Oligoryzomys fornesi, O. nigripes, O. rupestris, Calomys expulsus, Rhipidomys macrurus, Wiedomys pyrrhorhinus e Thrichomys inermis. Didelphis albiventris, Micoureus demerarae, Thylamys karymii e Nectomys sp. foram identificadas por análises morfológicas. A maioria dos indivíduos coletados não apresentou variação cariotípica. Porém, variação cromossômica numérica foi encontrada em dois espécimes de Akodon aff. cursor (2n = 15) e em um indivíduo de Cerradomys sp. (2n = 51). Foi também observada variação estrutural no cariótipo de sete indivíduos de Cerradomys sp., mostrando um par a mais de cromossomos metacêntricos.

Analysis of the nucleolar cycle in the seminiferous epithelium of rodents

The nucleolus is a subcompartment of the nucleus and the site of ribosome biogenesis. During the mitotic and meiotic cell cycles, a disorganization and later reorganization of the nucleolar material occur, an event called nucleologenesis. In the spermatogenesis of mammals and other vertebrates, there is evidence of the disorganization of the nucleolus at the end of meiosis I, which supplies material for the cytoplasmic formation of an organelle called the “chromatoid body” (CB). The CB is a structure characteristic of spermatogenic cells and seems to be responsible for RNA metabolism in these cells and for some events of spermiogenesis, such as the formation of the acrosome, cellular communication between spermatids, and the formation of the spermatozoon middle piece and tail. The aim of this paper was to obtain information about the cytochemical and ultrastructural nature of the nucleolar cycle and the distribution of cytoplasmic RNAs in the seminiferous tubule cells of Rattus novergiucus, Mus musculus and Meriones unguiculatus. The testis was fixed in Bouin and Karnovsky solutions for conventional histological analysis and for cytochemical study that included: periodic acid-Schiff, hematoxylin-eosin, Feulgen reaction, silver-ion impregnation, Gomori’s reticulin stain, toluidine blue, modified method of critical electrolyte concentration, and basic and acid fast green. The blocks of testis fixed in glutaraldehyde were used for ultrastructural analysis by transmission electron microscopy. Ultrathin sections were double-stained with uranyl acetate and lead citrate. All the techniques used provided information on the origin and function of the CB in the spermatogenic cells. Therefore, considering the persistence of the RNA and nucleolar ribonucleoproteins during spermatogenesis of Rattus novergicus, Mus musculus and Meriones unguiculatus, our findings corroborate the statement that these molecular complexes are very important in the spermiogenesis phases...

Variaciones nucleotídicas de dos grupos de tepezcuintles, Agouti paca (Rodentia: Agoutidae), en cautiverio provenientes de dos localidades de Yucatán, México / Nucleotidic variations of two captive groups of tepezcuintle, Agouti paca (Rodentia: Agoutidae), from two sites in Yucatan, Mexico

The objective of this work was to estimate the nucleotidic variation between two groups of tepezcuintles (Agouti paca) from the states of Campeche and Quintana Roo, Mexico and within members of each group. Blood samples were collected from eleven A. paca kept in captivity. DNA from leukocytic cells was used for Ramdom Amplification of DNA Polimorphism (RAPD). The primers three 5'-d(GTAGACCCGT)- 3' and six 5'-d(CCCGTCAGCA)- 3' were selected from de Amersham kit (Ready.To.Go. RAPD Analysis Beads, Amersham Pharmacia Biotech), because they produced an adequate number of bands. The electrophoretic pattern of bands obtained was analyzed using software for phylogenetic analysis based on the UPGMA method, to estimate the units of nucleotidic variation. The phylogenetic tree obtained with primer three reveals a dicotomic grouping between the animals from both states in the Yucatan Peninsula showing a divergent value of 1.983 nucleotides per hundred. Animals from Quintana Roo show a grouping with primer six; an additional grouping was observed with animals from Campeche. Nucleotidic variation between both groups was 2.118 nucleotides per hundred. The nucleotidic variation for the two primers within the groups from both states, showed fluctuating values from 0.46 to 1.68 nucleotides per hundred, which indicates that nucleotidic variation between the two groups of animals is around two nucleotides per hundred and, within the groups, less than 1.7 nucleotides per hundred.

Estimamos las variaciones nucleotídicas entre dos grupos de tepezcuintles (Agouti paca) provenientes de los estados de Campeche y Quintana Roo, México y, dentro de cada grupo. Se colectaron muestras sanguíneas de once A. paca mantenidos en cautiverio. El ADN de leucocitos se utilizó para efectuar la amplificación aleatoria de polimorfismos de ADN (RAPD). Se seleccionaron los iniciadores número tres 5’ -d(GTAGACCCGT)-3’ y seis 5’ -d(CCCGTCAGCA)-3’ del estuche (Ready.To.Go. RAPD Analysis Beads, Amersham Pharmacia Biotech), porque produjeron un adecuado número de bandas. Los patrones electroforéticos de bandas fueron procesados con el software para análisis filogenético basado en el método de UPGMA para estimar la variación nucleotídica. El árbol filogenético obtenido con el iniciador tres reveló una agrupación dicotómica entre los animales de ambos estados de la Península de Yucatán, con un valor de divergencia de 1.983 nucleótidos de cada cien. Los animales de Quintana Roo mostraron un agrupamiento con el iniciador seis y, otro grupo más con animales procedentes de Campeche. La variación nucleotídica entre estos dos grupos fue de 2.118 nucleótidos por cada cien. Las variaciones nucleotídicas dentro de los grupos procedentes de ambos estados, para los dos iniciadores, mostraron valores que fluctuaron entre 0.46 y 1.68 nucleótidos de cada cien, lo cual indica que la variación nucleotídica entre los dos grupos de animales es alrededor de dos nucleótidos por cada cien y, dentro de grupos es menor a 1.7 nucleótidos por cada cien.

Phylogenetic relationships and karyotype evolution in the sigmodontine rodent Akodon (2n = 10 and 2n = 16) from Brazil

Comparison of G-bands from 2n = 10 and 2n = 16 karyotypes of Akodon revealed tandem fusions, pericentric inversions and Robertsonian rearrangement in autosomes and addition/deletion of constitutive heterochromatin in sex chromosomes. Cytochrome-b sequences indicate that the 2n = 10 karyotype is a new species and show it to be a sister taxon of the 2n = 14, 2n = 15 and 2n = 16 karyotypes. Indeed, this group shows a particular evolutionary situation in which a unique taxonomic unit based on morphological data can be detected, but, karyologically, it can be separated into two groups (2n = 14-15-16 and 2n = 10). Cytochrome-b sequences show a finer resolution, indicating that these four karyotypes represent three molecular entities (2n = 14-15, 2n = 16 and 2n = 10) that may be derived from a common ancestor with a 2n = 16 karyotype.

Population structure and genetic variability of mainland and insular populations of the Neotropical water rat, Nectomys squamipes (Rodentia, Sigmodontinae)

Seven microsatellite loci were used to investigate the genetic variability and structure of six mainland and two island populations of the Neotropical water rat Nectomys squamipes, a South American semi-aquatic rodent species with a wide distribution. High levels of variability were found within mainland populations while island populations were less variable but the more differentiated in respect to allele number and frequency. The time of biological divergence between mainland and island populations coincided with geological data. A significant geographic structure was found in mainland populations (q = 0.099; r = 0.086) although the degree of differentiation was relatively low in respect to the distance between surveyed localities (24 to 740 km). Genetic and geographic distances were not positively correlated as previously found with random amplified polymorphic DNA (RAPD) markers. Significant but low genetic differentiation in the mainland and lack of isolation by distance can be explained by large population size and/or recent population expansion. Additionally, the agreement between the age of geologic events (sea level fluctuations) and divergence times for insular populations points to a good reference for molecular clock calibration to associate recent environmental changes and the distribution pattern of small mammals in the Brazilian Atlantic Forest

Nine karyomorphs for spiny rats of the genus Proechimys (Echimyidae, Rodentia) from North and Central Brazil

Spiny rats of the genus Proechimys are morphologically diverse, widely distributed and have diploid numbers ranging from 2n = 14-16 to 2n = 62. In this paper we present cytogenetical data and brief comments on morphological and biogeographical issues related to spiny rats. In our sample of 42 spiny rats collected from 12 Brazilian Amazonian tropical rainforest and the Cerrado (Brazilian savanna) sites we detected nine karyological entities: four different karyomorphs with 2n = 30, three with 2n = 28, one with 2n = 15 and one with 2n = 44. Based on qualitative morphological characters these karyomorphs can be allocated to five species within the goeldii, guyannensis and longicaudatus species groups

Maintenance and breeding of Thrichomys (Trouessart, 1880) (Rodentia: Echimyidae) in captivity

South American histricognath rodents Thrichomys apereoides laurentius and Thrichomys pachyurus are natural hosts of Trypanosoma cruzi, agent of Chagas disease. We established breeding colonies of these species to serve as experimental models in various parasitological studies. Both species of Thrichomys have all the requirements necessary to become excellent laboratory models: they can be easily maintained in the standard laboratory conditions and breed throughout the year and they do not have any special dietary demands and can be fed by standard food pellets designed for laboratory mice. Both species produce precocious offspring that have their eyes and ears open, teeth erupted, fur well developed, and can eat solid food in the first week of life. T. a. laurentius has larger litter sizes and lower body masses at birth and weaning than T. pachyurus. Moreover, females of T. a. laurentius reach puberty earlier and with lower body mass than T. pachyurus.

Small mammals of Chapada dos Veadeiros National Park (Cerrado of Central Brazil): ecologic, karyologic, and taxonomic considerations

Este trabalho é baseado em um levantamento sobre pequenos mamíferos realizado no Parque Nacional da Chapada dos Veadeiros, localizado nas montanhas do Planalto Central Goiano, no Cerrado do Brasil Central. Foram coletadas 227 espécimes, representando 6 espécies de marsupiais e 13 de roedores. Considerações taxonômicas, cariológicas e ecológicas são apresentadas e discutidas. Nossos dados refletem a heterogeneidade da fauna em relação à altitude e à vegetação do Cerrado, sendo apenas 8 das 19 espécies coletadas comuns às altitudes elevadas e baixas. A composição da fauna de pequenos mamíferos do parque está influenciada pela predominância de formações florestais nas altitudes baixas e de cerrado rupestre nas altitudes elevadas. A presença de espécies endêmicas e uma ainda não descrita demonstram que o Cerrado apresenta uma fauna endêmica associada, sendo pouco entendida a diversidade de seus pequenos mamíferos.

Frequencies of chromosomal aberrations in rodents of the Rimac Valley-Perú

The present study analyzes the frequency of chromosomal aberrations found in rodents living in a polluted area near the Rimac river (Casapalca, minery zone) at 120 Km of Lima, compared to that observed in a non-polluted area in the Department of Lima, Perú. The species analyzed were: Phyllotis andium, P. darwini and Akodon boliviensis. The rodents were captured alive and bone marrow was processed the same day of capture to obtain metaphases. The results showed significant differences (p < 0.05) in the frequency of chromosomal aberrations in the rodents of the exposed area (2.46 percent of cells) vs those of the control area (0.82 percent of cells). These results are consistent with the hypothesis that heavy metals and pesticides present in the Rimac river may increment the frequency of chromosomal aberrations in rodents living near that river