Indicadores de genotoxicidade e pesquisa de hemogregarina em cágados (Phrynops geoffroanus) de diferentes ambientes hidrográficos do Parque Nacional do Iguaçu

Abstract

This study aimed to identify and quantify erythrocytes with genotoxic indicators and to assess hemogregarine infection in association with leech infestation in individuals of Phrynops geoffroanus. Freshwater turtles were sampled from four distinct hydrographic environments in the Lower Iguaçu River, Paraná, Brazil, including: two tributaries, the Silva Jardim River (SJr) and Floriano River (FL-r); and two river islands, Ilha do Sol (SOL-i) and Ilha do Geninho (GEN-i). A total of 56 animals were evaluated for indicators of genotoxic damage based on erythrocyte alterations, and 58 were screened for hemoparasites through blood smear analysis. Linear biometric data were recorded for all individuals, including maximum carapace and plastron length and width along with body mass, sex, and the presence of anatomical lesions or abnormalities. Blood was collected via dorsal cervical venous sinus puncture, and blood smears were stained using the May-Grünwald Giemsa method. To determine the frequency of micronuclei (MNs) and nuclear abnormalities (NAs), as well as the occurrence and parasitemia of hemogregarine, 3,000 erythrocytes were analyzed per animal. Mean MN frequencies varied slightly among the four sites (0.29 ± 0.63 in SJ-r, 0.38 ± 0.50 in FL-r, 0.25 ± 0.39 in SOL-i, and absent in GEN-i), with no significant differences (p = 0.32). NAs were observed in 32 of 56 individuals (mean frequency of 7.2 per 1,000 cells), also without significant variation among sites (p=0.81). Hemogregarina infection was highly prevalent (82.76%), though the mean parasitemia was only 0.33% of erythrocytes. No significant differences in parasitism rates were detected among sampling sites (p=0.18), but a positive correlation was identified between infection and body size (p<0.001). Leech infestation was recorded in 20.69% of turtles and was also positively correlated with both body size (p<0.001) and hemogregarine infection (p=0.043). The absence of spatial differences in genotoxic indicators or parasitological parameters may reflect the ecological buffering effect of Iguaçu National Park, which likely reduces contaminant influx from neighboring agricultural zones. At the same time, the presence of leeches suggests that conditions favorable for vector persistence are maintained within the park. These findings highlight P. geoffroanus as a valuable sentinel species for freshwater ecosystem monitoring and emphasize the importance of surveillance at the interface between protected and anthropogenically impacted areas.