*Genomic Instability and Cyto-Genotoxic Damage in Animal Species DOI: http://dx.doi.org/10.5772/intechopen.99685*

The number of MNi in peripheral blood is practically null in humans [22]. However, they can be observed in impaired splenic function secondary to pathologies that directly affect it, for example, when patients have been splenectomized or were born prematurely. Since it is ethically not allowed to carry out biomonitoring programs in humans, these type of bioassays provide the opportunity to test genotoxic agents [14, 17, 22].

The organism's age influences the variability in the number of MND [23] demonstrated when analyzing their frequency in splenectomized patients since adults showed a higher frequency than children [24, 25]. Similar results are described in rodent spermatids, where old mice and hamsters have more MNi than young ones, probably because genetic damage continually accumulates throughout the organism's life [25, 26]. Some organisms present a higher frequency of MNi in juvenile stages due to the immaturity of their nuclear phagocytic system; upon reaching adulthood, their system becomes efficient and prevents the visualization of MNi [14, 25].

## **3.3 Selection of a suitable peripheral red blood micronucleogenicity bioindicator**

To properly select a biomonitor for the MNi test in peripheral blood, at least six MNi in a total count of 10,000 erythrocytes should be identified [25]. The analyzed tissue must meet the following requirements: be in constant division, have abundant quantified cells, sufficient cytoplasm-nucleus relationship to identify MNi clearly, and a regular shape of the nucleus without lobes must be present to facilitate their observation [27]. This assay has been applied in a broad diversity of organisms to take advantage of the available resources in the environment (**Table 1**). The investigations carried out by Dr. Zúñiga's group concluded that the organisms with the best potential are felines, the capuchin monkey, and the atolero parakeet, among others [4, 14, 19, 38, 39].
