Avaliação de parâmetros ecotoxicológicos e organossomáticos em tubarões-martelo do Rio de Janeiro

Abstract

Elasmobranchs currently comprise the second most threatened vertebrate taxon in the world and the lack of data impairs conservation actions establishment. Among the multiple threats against the group, the extension of chemical contamination is poorly known and underestimated. In this regard, the present study proposed to assess the effect of contamination by metals (Ti, Zn, Cu, Mn, and Se) on the health of hammerhead sharks landed on the coast of Rio de Janeiro using ecotoxicological, morphometric and fluctuating asymmetry tools (FA). The sharks were sampled opportunistically on artisanal fishing colonies in Copacabana, Recreio dos Bandeirantes and Cabo Frio. The animals were dissected, and their tissues (muscle, liver, kidney, brain, and ampullae of Lorenzini) were processed for the detection of metals and metallothioneins using specific protocols. Principal Component Analysis (PCA), Permutation Analysis of Variance (PERMANOVA), Redundancy Analysis (RDA), and Spearman correlations were performed as the statistical treatment set. Nine hammerhead sharks were sampled and classified as juveniles. All metals were detected in all tissues, with selenium representing the highest concentrations, while manganese had the lowest. The tissue dynamics trends of metals were illustrated by PCA analysis (p = 0.0001; PC1 =70.1%; PC2 = 12.5%) and confirmed by PERMANOVA (F = 11.6; p < 0, 0001), both significant, and the tissues were organized in the following descending order: Kidney > Liver > Brain = Muscle = Ampullae. Differences between biological matrices were more relevant to metals accumulation than sex or size in S. lewini from Rio de Janeiro coast. The RDA analyzes yielded significant results between the hepatosomatic index and the concentrations of metals on muscle. Significant correlations of fluctuating asymmetry and the analyzed variables resulted in increased concentrations of Zn in the liver associated with greater variation in the asymmetry of the cephalofoil, while values of FA1 of pelvic fins and FA1 of pectoral fins decreased with muscular Se and Cu concentrations, respectively. The FA1 of eye diameter was correlated with the metallothionein concentrations in muscle. It was possible to conclude that IHS has sufficient sensitivity to be considered a good proxy of metal effects on the hammerhead sharks’ health in Rio de Janeiro while fluctuating asymmetry needs further applications to better understand its role as a health indicator in elasmobranchs. The present study invests in innovative approaches for the locality, performing methodologies that have never been tested before for elasmobranchs, such as analysis of contamination in ampullae of Lorenzini and application of fluctuating asymmetry, giving ecotoxicology predictive capacity for animal health assessment. The findings presented herein elucidate some aspects of the coastal contamination process but reinforce the need to feel the great scientific gap regarding the impact of metals on the development of large marine predators.