Identificação das espécies brasileiras de Akodon (Rodentia: Cricetidae: Sigmodontinae) através da microestrutura dos pelos / Identification of the brazilian species of Akodon (Rodentia: Cricetidae: Sigmodontinae) through the microstructure of the hair

No Brasil há 10 espécies de Akodon Meyen, 1833 e a maioria apresenta algum grau de sobreposição geográfica havendo inclusive registros de simpatia. A identificação das espécies é difícil e pode ser feita pela análise da estrutura morfológica de pelos. Assim, para a identificação da microestrutura de pelos de nove espécies brasileiras de Akodon, foram utilizados pelos-guardas primários de amostras de coleções zoológicas. Foi adotado o método de análise das escamas cuticulares e da medula. O padrão de cutícula para todas as espécies foi folidáceo estreito. Já para a medula foram reconhecidos três padrões básicos como multisseriada alveolar, multisseriada listrada e misto de alveolar e listrada. Akodon cursor é a única espécie com predomínio de quatro fileiras sendo que exemplares 2n = 14 e 2n = 15 apresentam medula alveolar e o 2n = 16, medula listrada e células longilíneas. Para Akodon paranaensis e A. lindberghi a medula se alterna entre três e quatro fileiras. As demais espécies apresentam três fileiras. Akodon mystax apresenta um maior espaçamento entre as células. Akodon reigi possui o setor intermediário com fileiras ovaladas e bem ligadas e Akodon toba tem as células da fileira central variando com uma e duas células alveolares pequenas. No padrão listrado, Akodon montensis apresenta espaço intercelular mais estreito em relação à espessura da célula. No padrão misto, Akodon azarae apresenta células com contorno evidente, já Akodon serrensis as células apresentam formato irregular. Assim, o uso da microestrutura dos pelos como ferramenta para a identificação das espécies de Akodon mostrou-se perfeitamente viável.

There are 10 species of Akodon Meyen, 1833 in Brazil and most have some degree of geographic overlap, even with records of sympatry between some species. The identification of the species is difficult and can be performed by the analysis of the morphological structure of hair. Thus, in order to identify the microstructure of the nine Brazilian species of Akodon, guard-hairs samples from zoological collections were used. We adopted the method of analysis of the cuticle scales and medulla. The cuticle pattern for all species was narrow leaf shaped. For the medulla three basic patterns have been recognized: alveolar multiseriate, multiseriate striped and a mixture of alveolar and striped. Akodon cursor is the only species which has a predominance of four layers of cells, the specimens 2n = 14 and 2n = 15 have an alveolar medulla and the specimen 2n = 16, has a striped medulla and elongated cells. For Akodon paranaensis and A. lindberghi the medulla alternates between three and four layers. The others species have three layers. Akodon mystax, have a larger spaces between the cells. Akodon reigi shows an intermediary sector with layers of oval and well connected cells and for Akodon toba, the cells of the central layer are found in one or two small alveolar layers. In the striped pattern, Akodon montensis have narrow intercellular space in regard to the thickness of the cell. In a mixed pattern, Akodon azarae presents cells with clear outline, and Akodon serrensis show cells with irregular shape. Thus, the use of the microstructure of hairs as a tool for identification of the species of Akodon proved to be practicable.

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.

Evaluation of genetic variability in the collared peccary Pecari tajacu and the white-lipped peccary Tayassu pecari by microsatellite markers

In this study, the microsatellite technique was used to evaluate the genetic variability in populations of collared and white-lipped peccaries kept in captivity. Six primers developed for domestic pigs were used and amplified in both species. They revealed the presence of five polymorphic loci and one monomorphic locus. The polymorphic loci included 4 of the 16 alleles in collared peccaries, and 3 of the 10 alleles in the white-lipped peccaries. Polymorphic information content (PIC) in both species and all the loci was highly informative. The probability of paternity exclusion (PEC), if one of the parents is known, was almost as high in white-lipped peccaries (95.53 percent) as in the collared (99,48 percent). The Fst values for collared (0.042) and white-lipped (0.1387) peccaries showed that both populations are not structured. The Fis values for all loci, except ACTG2 in white-lipped peccaries (-0.0275) and in both species (0.1985 to 0.9284 in collared peccaries and 0.3621 to 0.4754 in the white-lipped), revealed a high level of homozygosis, probably caused by inbreeding. Data on heterologous amplification and genetic variability in collared and white-lipped peccaries are presented for the first time.

Unexpected chromosomal alterations in Tayassu tajacu (Artiodactyla: Tayassuidae) in captivity

Os animais silvestres têm sido utilizados como bioindicadores quando o ambiente é exposto a estressores químicos. Em geral, os agentes químicos podem induzir às alterações cromossômicas dos tipos falhas e quebras. Tayassu tajacu, é uma espécie aparentada dos porcos verdadeiro e apresenta uma grande estabilidade cariotípica. As únicas alterações descritas são em relação a forma do cromossomo X. Foram observadas falhas e quebras cromossômicas durante as análise citogenética. Estas alterações foram detectadas em cromossomos autossômicos. Levantamentos realizados na literatura associados as dados observados nos exemplares estudados, indicam um vermífugo, a base de ivermectina, como o possível causador dessas alterações cromossômicas.

Interrelationship between ectoparasites and wild rodents from Tijucas do Sul, State of Paraná, Brazil

Sixteen species of ectoparasites were collected from 50 wild rodents from August 1990 to August 1991, in an area of Araucaria augustifolia forest, in the municility of Tijucas do Sul, State of Paraná, Brazil. Ectoparasites infested 98 per cent of the rodents, with the highest indices of infestation found in the dry-cool season. Species that occurred in single or multiple infestations were recorded. Ectoparasites/host associations were significant (p<0.01) for Gigantolaelaps wolffsohni/Oryzomys nigripes, Polygenis pradoi/Oxymycteurs sp. and Amblyopinus sp./Oxymycteurs sp. The following represent new host records: Polygenis (Polygenis) tripus from Akodon serrensis and Hoplopleura sciuricola from Sciurus aestuans. New geographic records are given for two species of flea and one sucking lice.