Genotoxic effects of mercury chloride on the Neotropical fish Andinoacara rivulatus (Cichlidae: Cichlasomatini)

Abstract

Understanding the effects of heavy metals in aquatic ecosystems is of significant importance due to their potential to bioaccumulate at various trophic levels and induce damage in DNA. Mercury is considered one of the most dangerous heavy metals, causing chromosomal breakage (clastogenic event) or spindle dysfunction (aneugenic event), that can lead to the formation of encapsulated chromatin into a separate smaller nucleus, generally referred to as a micronucleus. We evaluated the sensitivity of the micronucleus test in the neotropical cichlid Andinoacara rivulatus (Günther 1860). The fish were divided into four groups of 16 individuals, and each group was placed in separate aquaria (140 L) provided with filtered water and constant aeration. Fish were exposed to mercury chloride (HgCl2) at doses 0.1, 0.25, and 0.50 mg/Kg body weight, administered by intraperitoneal (IP) injection. Fish from the control group were injected with a physiologic solution. The following erythrocyte anomalies were identified: erythrocytes with micronuclei varying to some extent in size and position in the cytoplasm, blebbed nucleus, binucleated cell, nuclei showing a deep invagination toward the center (notched nuclei). Examination of blood smears demonstrated a higher level of micronucleus and notched erythrocytes in fish injected with HgCl2 than in the controls. There were significant differences in the frequency of micronucleated and notched erythrocyte among the groups exposed to mercury. Linear regression analysis revealed a positive relationship between the frequency of micronucleated and notched erythrocytes (P < 0.0001), with a moderately strong correlation coefficient (r=0.737). We propose that, in addition to the two so far known mechanisms of micronucleus formation (spindle apparatus damage and chromosomal ruptures), chromatin fragmentation in notched nuclei resulting from a combination of the cytotoxic effects of mercury and mechanical stress, may be a third mechanism of micronuclei genesis. It is emphasized that although the micronucleus test is a cheap and technically simple method that requires very basic equipment, direct counting of erythrocytes using a microscope is a time-consuming task because it requires counting a high number of cells (a minimum of 1,000 to 2,000 cells) per blood smear, leading to visual fatigue. We recommend, photographing the stained blood smears at several areas at random and scoring the digital images using Adobe Photoshop software as an easy way to evaluate a large number of erythrocytes for minimizing the visual fatigue caused by many hours of direct observation through a microscope

Mercuric Chloride induced Oxidative Stress, Genotoxicity, Haematological Changes and Histopathological Alterations in Fish Channa Punctatus (Bloch, 1793).

“…However, the mechanisms responsible for formation of NAs is due to know. Further, various studies have documented that NAs can be induced in response to exposure to genotoxic agents (Braham et al, 2017;De Souza Azevedo et al, 2012;Guilherme et al, 2008;Hoshina et al, 2008;Nirchio et al, 2019). This study provides a proof that NAs may arise in the erythrocytes of sh, Channa punctatus due to oxidative stress induced by HgCl 2 .…”

“…The mechanisms of MN formation, which can be related to clastogenic and aneugenic events and their signi cance are well documented (Chondrou et al, 2018;Decordier et al, 2011;Schmid, 1975;Ueda et al, 1992). Ample numbers of investigations are there which have measured induction of MN by HgCl 2 for genotoxicity measurement in shes (Nagarajan Nagarani et al, 2009;Nirchio et al, 2019;Qureshi, Yaqoob, 2013;Yadav & Trivedi, 2009) On the other hand, very less studies are available for the utilization of other nuclear anomalies in erythrocytes for the assessment of DNA damage in aquatic organisms (De Souza Azevedo et al, 2012). Over past few years, the concurrent analyses of NA and MN frequencies in blood have received consideration in genotoxic studies.…”

“…DNA damage can best be shown by MN induction and, thus, it can be use e ciently to have sight of genotoxicity. Some studies have also mentioned, in addition to MN, the presence of other nuclear abnormalities, such as blebbed, lobed, binucleated, and notched nuclei, indicating that these abnormalities need to be seen similar to MN induction, and, thus, must be considered as potential indicators of genotoxicity (Abara et al, 2016;Anbumani & Mohankumar, 2011;Ansari et al, 2009;Çavaş & Ergene-Gözükara, 2005a;Nirchio et al, 2019;Shahjahan et al, 2020). The hematological parameters viz., RBC count, WBC count and Hb% have been used as potential indicator of stress induced by various pollutants in sh (Ates et al, 2008;Bujjamma & Padmavathi, 2018;Kumar et al, 2011).…”

Study the Impact of the Concentration of Mercury Chloride on Micronuclei Formation and Some Organs of Juveniles of Ctenopharyngodonidella

“…These results agreed with the previous. (22)(23)(24) The micronucleus test, one of the most popular and promising tests of environmental genotoxicity, has served as an index of cytogenetic damage for over 30 years. 25. The increase in micronuclei of red blood cells in the present study of (ctenopharyngodonidella) due to mercury chloride toxicity was identified as a good biological indicator of genetic toxins to monitor the influence of such elements.…”

Mercuric chloride‐induced oxidative stress, genotoxicity, haematological changes and histopathological alterations in fish Channa punctatus (Bloch, 1793)

“…Nonetheless, the mechanism responsible for the formation of NAs is due to knowing. Furthermore, various studies have documented that NAs can be induced in response to exposure to genotoxic agents (Azevedo et al ., 2012; Braham et al ., 2017; Guilherme et al ., 2008; Hoshina et al ., 2008; Nirchio et al ., 2019). This study provides a proof that NAs may arise in the erythrocytes of fish C. punctatus because of oxidative stress induced by HgCl 2 .…”