Identification of the brazilian species of Akodon (Rodentia: Cricetidae: Sigmodontinae) through the microstructure of the hair

Abstract

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.