Thalassophryne maculosa (Batrachoididae: Thalassophryninae) as a Bioindicator of Mercury-Induced Genotoxicity

Abstract

Environmental monitoring requires reliable bioindicators to assess the genotoxic effects of pollutants in aquatic ecosystems. In this study, the marine fish Thalassophryne maculosa was evaluated as a bioindicator of genotoxicity through the application of the micronucleus test. Fish were exposed to varying concentrations of mercuric chloride (HgCl₂) (0.1, 0.25, and 0.5 µg HgCl₂/g body weight) over different time intervals (24, 48, 72, and 96 h). A dose- and time-dependent increase in nuclear abnormalities, including micronuclei, was observed, with significant chromosomal damage detected at 0.25 and 0.5 µg HgCl₂/g body weight. These results demonstrate the sensitivity of T. maculosa to mercury exposure, even at concentrations below regulatory safety thresholds, emphasizing its suitability as a bioindicator for detecting genotoxic contamination in coastal ecosystems. This study provides critical insights into the ecological risks posed by mercury and highlights the potential of T. maculosa to enhance environmental monitoring programs, particularly in regions vulnerable to heavy metal pollution.

Keywords: Thalassophryne maculosa; bioindicator; genotoxicity; marine pollution; mercury; micronuclei.

Figure 1

Nuclear abnormalities in peripheral blood of Thalassophryne maculosa. (a,b) Mature micronucleated erythrocytes (MMEs) with micronuclei of varying sizes; (c) immature binucleated erythrocytes (BIEs); (d) mature binucleated erythrocytes (MBEs); (e) immature binucleated erythrocytes with a cytoplasmic bridge (BIECBs); (f) erythrocytes with vacuoles or cytoplasmic loss (VLCs).

Figure 2

A three-dimensional representation of the variation in micronucleated cells (MN/2000 cells) in response to HgCl₂ concentration (µg/body weight) and exposure time (hours). Darker colors (blue/green) indicate fewer micronucleated cells, while lighter colors (yellow) denote higher frequencies.