Microscopic identification of the hairs of Brazilian Alouatta Lacépède, 1799 species (Primates, Atelidae, Alouattinae)

Abstract

The hair structure of five species of Brazilian howler monkeys is described. The hairs were cleared to reveal the medulla cells and impressions were made of the cuticle. A new cuticle scale pattern and four new medulla cell patterns are described. The cuticle scales in Alouatta guariba form a transverse wave pattern; their margins are ornamented and predominantly continuous, although some may be discontinuous. Alouatta caraya scales vary between two transverse wave patterns, one with alternately continuous and discontinuous margins and the other with predominantly continuous margins. Alouatta belzebul hairs have irregular wavy scales with discontinuous margins; in the apical third they adopt a transverse wave form with alternately continuous and discontinuous margins. Alouatta seniculus has scales in a transverse wave pattern with discontinuous margins, whereas A. nigerrima has narrow scales in a transverse wave pattern with discontinuous margins. The medulla cells form an isolated uniserial ladder in A. guariba, a uniserial juxtaposed stoma pattern in A. caraya, and a uniserial juxtaposed rectangular pattern in A. belzebul. In A. seniculus they are granulated, and in A. nigerrima they occur in a uniserial juxtaposed fusiform pattern, which is entire and homogeneous. Significant differences were seen among the species and a key was produced on the basis of these trichological characteristics. Hairs from young individuals were also analyzed but did not show the patterns found in adults; therefore, juveniles cannot be identified by this technique.