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In some species, in which the human is included, the influence of age in the variation in the number of micronucleated erythrocytes (MNE) is known. In the present work we show how the process of aging influences the number of spontaneous MNE in the gray squirrel (Sciurus aureogaster). Because of the difficulty of knowing the age of each animal, 69 animals were weighed at their arrival to the laboratory and at the start of sample taking, with the supposition that the heaviest animals were the oldest and those with the lightest weight were the youngest. The major number of MNE was found in the younger animals, whereas the adults displayed less MNE (P < 0.0001). A group of 11 animals were sampled every 15 days over a period of 6 months, and the number of MNE were found to decrease with an increment in the weight in conformity with the time elapsed. These results showed that in the gray squirrel, the number of spontaneous MNE in peripheral blood depend on age. An additional interesting datum about the increment of MNE after the administration of colchicine is shown.

Nuclear abnormalities in erythrocytes, as micronuclei and nuclear buds (BE), are considered potential biomarkers of genotoxic exposure. We described previously the frequency of spontaneous micronucleated erythrocytes (MNE) in the species Aratinga canicularis. Here, we have used this species to evaluate the induction of MNE and BE by mitomycin-C. Animals were given a single intracoelomic injection of 0, 2, 3 or 4 mg/kg mitomycin-C on two consecutive days. A drop of blood was obtained after 0, 24, 48 and 72 h, and stained smears were used to count micronucleated polychromatic erythrocytes (MNPCE) and polychromatic erythrocytes with buds (BPCE)/1000 polychromatic erythrocytes. The number of MNE and BE in 10 000 total erythrocytes was also counted. MNPCE and BPCE frequencies were elevated at 24, 48, and 72 h after the administration of the lower dose (P B/0.03). At a 3 mg/kg dose, the frequency of MNPCE increased at 48 and 72 h (P B/0.04) whereas the number of BPCE increased, but not significantly. Administration of 4 mg/kg mitomycin-C increased the number of MNE observed at 72 h (P B/0.03), the number of MNPCE at 48 h (P B/0.01) and 72 h (P B/0.006), the BE frequency at 72 h (P B/0.05), and the frequency of BPCE at 48 and 72 h (P B/0.001). While mitomycin-C appears to produce a parallel increase in MNPCE and BPCE frequencies, the MNE seemed to be a more sensitive indicator of genotoxicity than the BE. This suggests that evaluating BE and MNE in routine haematological analysis should be considered to evaluate environmental genotoxic exposure.