**4. Conclusions**

authors, the biological parameters discussed are verified at the cellular level and provide two types of analyses that reveal damage to the genetic material: the micronucleus test. The increase in the frequency of micronucleated cells is a marker of genotoxic effect that may reflect a exposure to agents with clastogenic mode of action (chromosome breakdown [25]. In the present study, the effect of the antigen on the chromosome number was not significant.

**Figure 2.** Photomicrograph (×1000) of erythrocytes of *H. pusarum* and *M. duriventre* stained with Giemsa from the São Romão and Prata Waterfall, Chapada das Mesas National Park, Brazil, showing (A) lymphocytes and normal cells erythrocytes (arrow), (B) binucleated nucleus (arrow) and micronucleus (arrow), (C) eosinophils (arrow) and (D)

The incidence of NM to the PNCM sampling points was lower than NMA. These data differ from studies performed by Pinheiro-Sousa [8] and Carvalho-Neta et al. [26] who found a higher incidence of MN for the Environmental Protection Area of Maracanã. Thus, despite the low frequency of NMA and MN, especially of micronuclei, it is suggested that the Waterfalls

The presence of nuclear morphological changes (NMA) should be considered as complementary data to micronucleus records and as changes resulting from the induction by cytogenotoxic agents [18, 27] or by induction of pollutants. In fish, several types of nuclear anomalies do not yet have their origin completely understood. However, Carrasco et al. [28] and Galvan [29] have described and photographed some morphological changes found in fish erythrocyte nuclei. These alterations were classified as follows: [1] binucleate nuclei: nuclei that present cuts of two nuclei and nuclear membrane bounded and [2] nucleus vacuolizados: these nuclei present a region that resembles the vacuoles inside. These vacuoles are devoid of any visible

of São Romão and Prata still do not suffer from point sources of pollution.

material along the nuclear structure [29].

vacuolated nucleus (arrows).

92 National Parks - Management and Conservation

Means and standard deviations (SDs) of the biometric data of *H. pusarum* showed length and total weight are greater than *M. duriventre*. Nuclear morphological changes (NMAs) were identified in the two sampled species for the two collection points. Among the NMAs found, binucleated nucleus (BN), vacuolated nucleus (VC) and micronucleus (MN) were also found in both species; however, in *M. duriventre*, the frequency of MN and NMA was higher than *H. pusarum*. Probably, the cascudo (*H. pusarum*), considered a benthic species and resistant to environmental conditions, presented a lower frequency of genotoxic alterations than the Pacú (*M. duriventre*), that is, a species that presents a migratory habit and sensitive to environmental variables. Besides, the frequency of MN and NMA was not significant to indicate possible environmental impacts in the two sampled areas. The presented data show that methodologies based on biomarkers and bioindicator species can be used in future biomonitoring and park management programs.
