Análise citogenética e genotóxica de Caiman crocodilus (Linnaeus, 1758) provenientes de ambiente natural e antropizado dos arredores de Manaus

Abstract

Crocodilians are chain top predators and play an important role in the ecosystems in which they live. Species that occur in Brazil, the most abundant is the spectacled Caiman (Caiman crocodilus), which is found in many different environments. Alligators in the Amazon region are the least studied in relation to other species, occurring in other parts of the world where the few studies are confined to protected areas, excluding the populations of C. crocodilus occurring within the city limits, which are continuously exposed the anthropogenic environments, generating an incipient knowledge about them. Although there is description for the diploid number of the species, a more specific approach as banding chromosome techniques, fluorescent in situ hybridization (FISH), micronucleus test and comet assay are necessary for a better understanding of pollution effect in the genome of these animals. Thus, we collected specimens in non anthropic environment and anthropic for domestic effluents to assess the genotoxic potential of these pollutants in the genome of alligators. For chromosomal analyzes were used 12 Caiman crocodilus (6 ♂, ♀ 6), caughts in Lake Catalão, in the Mindu stream and the Assua stream in the Amazon state. Where, from the conventional staining subspecies showed diploid number of 42 chromosomes (24t+18m/sm and NF=60) with little complexity and heteromorphisms. The pattern observed in C. crocodilus in relation to the distribution of heterochromatin is shown maintained, presenting in the centromeric regions of chromosomes, but more so in pair 21. The nucleolus organizer region (Ag-RON) is simple, where your location the pair 13 coincides with the heterochromatic centromeric region, and with the location of hybridization sites with 18S rDNA probe. These hybridization sites showed a doubling in one of the pair of chromosomes 13 in C. crocodilus. Cytogenetic characteristics suggested the possibility of variation for the species in relation to North America, differentiated by chromosomal fissions, common rearrangement to other species of the genus. For genotoxic analysis of Comet Assay were captured 8 C. crocodilus (4 ♀, 4 ♂) Lake Catalan and 7 (2 ♀, 1 ♂ and 4 indeterminate) of urban streams of Manaus - AM. Using the Mann-Whitney U test, it was observed that the p value was significant for levels 3 (p=0.007) and 5 (p=0.010) when comparing the different environments, where the level 3 is considered damage moderate, and level 5 that the cell is undergoing apoptosis. As for the micronucleus test, 15 C. crocodilus were captured (7 ♀, 8 ♂) on Lake Catalão and 15 (8 ♀, 9 ♂) of Mindu stream - AM. Note that when comparing the amount of micronuclei with the size of the animals, the value of p=0.04 was significant. Our study demonstrates that the impact of pollution on the aquatic environment can be significant in the long term for the emergence of mutations and differentiation in the karyotype of the species occurring in the Amazon. Our results can significantly contribute to the crocodilian conservation strategies within the city limits of the city of Manaus.