1. Department of Morphology; Federal University of Rio Grande do Norte; Cx. Postal 1524 Campus Universitário Lagoa Nova 59072-970 Natal Brazil
2. Department of Morphology; Histology Laboratory; Federal University of Amazonas; Av. General Rodrigo Octávio, 6200, Coroado I 69077-000 Manaus Brazil
3. Department of Animal Science; Federal Rural University of Semiárido; Av. Francisco Mota, 572, Costa e Silva 59625-900 Mossoró Brazil