A Review on Histopathological Alterations Induced by Heavy Metals (Cd, Ni, Cr, Hg) in Different Fish Species

Safia Bibi1, Saima Naz1*, Saba Saeed1, Ahmad Manan Mustafa Chatha2

1Department of Zoology, The Government Sadiq College Women University, Bahawalpur- 63100, Pakistan.

2Department of Entomology, Faculty of Agriculture and Environment, The Islamia University of Bahawalpur- 63100, Pakistan.

Abstract | Industrial, domestic and other human activities are responsible for heavy metal toxicity of aquatic bodies. Metals are the major stimulators for variety of diseases in aquatic organisms mainly fishes. Chromium (Cr), mercury (Hg), nickel (Ni) and cadmium (Cd) causes histopathological variations and several diseases in various fishes of Pakistan. Extensive histopathological variations in gills, liver, kidney and skin of different fishes were noticed when exposed to heavy metals, thus indicating severity of heavy metal toxicity. The current study was focused on the toxicological effect of Cr, Hg, Ni and Cd in different type of fishes and it would be useful for the scientific community to restore different metals contaminating water.

Novelty Statement | Histopathological alterations in target fish organs functioned as fundamental indicator to assess metal toxicity in different fish species as it provides accurate data on effects of different contami-nants on fish. Hence, histopathology must be consider to monitor contaminated aquatic systems.

Article History

Received: March 17, 2021

Revised: March 29, 2021

Accepted: April 08, 2021

Published: June 13, 2021

Authors’ Contributions

SB and SS collected the data and wrote the manuscript. SN, AMMC and SS conceived the study and approved the article.

Keywords

Histopathology, Toxicity, Bioaccumulation, Toxic metals, Heavy metal pollution

Corresponding Author: Saima Naz

saima.naz@gscwu.edu.pk

To cite this article: Bibi, S., Naz, S., Saeed, S. and Chatha, A.M.M., 2021. A review on histopathological alterations induced by heavy metals (Cd, Ni, Cr, Hg) in different fish species. Punjab Univ. J. Zool., 36(1): 81-89. https://dx.doi.org/10.17582/journal.pujz/2021.36.1.81.89

Introduction

In natural environment, pollution owing to heavy metals is a major issue. Heavy metal toxicity and their bioaccumulation easily enter humans via food chain (Tahir et al., 2017) and also affect other organisms. In an ecosystem, metal residual distribution revealed contaminated area. Toxicity can easily be determine by considering various factors as to measure the level of feed and water pollution, bioaccumulation and toxicity of heavy metals along with bio magnifications in living beings (Has-Schön et al., 2006; Saleemi et al., 2019).

Heavy metals intake is a main reason for metal accumulation in different fish organs (Javed, 2015). In aquatic environment, metal toxicity not only effect aquatic life (Fish) but also humans as they are consumers in food chain (Faiza et al., 2015; Perera et al., 2015). Various fish species are used to measure health conditions of aquatic life and their ecosystem, as metal pollution is increasing day by day (Abbas and Javed, 2016). Gills and food web are directly associated for the entry of heavy metals in aquatic life and also get entry in other organs. When accumulated, metals brings oxidative stress, thus causes genotoxicity (Khan et al., 2015a, b). Different biological techniques are used to evaluate metal toxic levels and their impact on fish and other organism’s behavior, their physiological sensitivity as well as morphological indices (Yang et al., 2014; Kousar and Javed, 2015).

Different metals greatly effect cell organelles as well as metabolic and detoxifying enzymes (Wang and Shi, 2001). Metals also effect DNA and nuclear proteins, hence causes apoptosis or carcinogenesis (Beyersmann and Hartwig, 2008). Liver plays an important role in toxic material transformation (Udotong, 2015). Mercury (Hg) is a lethal metal and exists naturally in earth crust. Erosion, volcanic eruptions and anthropogenic activities (Industrial, agricultural and municipal wastes) may contaminate environment. As fish is on the top of aquatic food chain so metals from the water can easily enter the body. Increase mercury level in water brings more accumulation is fish organs.

More the amount of mercury in aquatic environment, greater will be its accumulation in fish tissues, and also in human beings (Gilbertson and Carpenter, 2004; Guilherme et al., 2008). Due to methyl mercury rapid swimming was noticed in Zebra fish (Zamorano et al., 2016). Cadmium (Cd) has teratogenic, carcinogenic and mutagenic effects on aquatic life. Freshwater ecosystem is effected by Cd owing to higher sensitivity towards aquatic life compared with mammals (Burger, 2008; Jia et al., 2011).

Nickel (Ni) also possess toxic behavior and its greater concentration causes complications in blood, respiratory system, tissues as well as mucus membranes and effect different cells and chromosomes. Thus, the European Union had offered World Trade Organization (WTO) to consider nickel as a hazardous element (Purwanti et al., 2019). Nickel can also cause metal toxicity in organs, contact dermatitis, allergy, morphological alterations in cellular systems and even chromosomal abnormalities (Coen et al., 2001; Palaniappan and Karthikeyan, 2009). Literature on nickel accumulation in fish is limited compared with other metals (Palermo et al., 2015). Chromium (Cr) toxicity may cause mucus discharge, color changes, erratic motion and even abrupt swimming as in Danio rerio (Zebra fish) (Nisha et al., 2016). Thus, the aim of current work was to estimate the effect of different heavy metals i.e. mercury, cadmium, nickel and chromium on fishes that brings histopathological variations and also causes various diseases. In Pakistan, fish species are going to reduce due to heavy metal accumulation and present study reveals that heavy metal exposure in aquatic life increases damage to fish tissues and organs.

Materials and Methods

Present study was designed to review the studies from 2000-2020 and it was based on the histopathological alterations on fish. Various articles were searched from Google Scholar and PubMed using keywords as histopathology, heavy metals, toxicity, bioaccumulation, aquatic life, fish species, and histopathological abnormalities. Latest research papers and articles were selected to avail some relevant data. All the papers were cited along with their proper references.

Aquatic toxicity

Industrial effects

Countries being developed are in front of many issues and one of them is water pollution. This is just because of industrialization which is spreading very quickly and civilization as well. Very huge number of pollutants and polluting products are released from these industries. From these pollutants, various heavy metals are on top of the list which is continually being released into adjacent water bodies without treating them. Hazardous impacts of heavy metals on water ecosystem have been considered as a global issue (Yousafzai et al., 2008). These toxic metals are allowed to be released in the environment through anthropogenic and natural activities i.e., industrial and urban discharges, mining combustion processes and mining etc. (Barone et al., 2013; Ambreen et al., 2015).

Biochemical toxicity

Chromium is considered to be exerting its toxic effects on intestinal epithelial cells and brings changes in functions regarding glucose transportation. A study on the intestine of rainbow trout revealed shortage of glucose absorption by the epithelial cells of intestine (Stokes and Fromm, 1965).

Various fish species’ osmoregulatory functions have been affected by the impact of trivalent chromium (Cr3+). A fish species named Cyprinus carpio var. communis upon chromium sulphate [Cr2(SO4)3] exposure brought variations in osmoregulation functioning in fish (Subashini et al., 2005). Heavy metals exposure up to different levels might cause various behavioral and morphological aberrations in fish (Qadir and Malik, 2011). Cd is considered as a toxic heavy metal and also have disrupting properties of endocrine (Afridi et al., 2011; Chouchene et al., 2011).

Some metals like Cd, Cr, Pb, Hg and As being non-essential elements can exert toxic effects even at very low concentration. While Co, Mn, Zn, Cu, and Ni are the essential metals producing lethal effects at high concentrations (Couture and Rajotte, 2003).

Bioaccumulation of heavy metals

Fish attained the ability of heavy metals bioaccumulation in their tissues via absorption, while humans can come into exposure of these metals by the food chain. As fish is the prior in human’s diet thus affecting humans in different ways (Dogan and Yimaz, 2007). Heavy metal’s bioaccumulation and their bio-magnification is linked with the pathway of transformation of pollutants from one trophic level to another (Ghannam et al., 2015).

In marine biota, the accumulation of Cr needs to be discovered. Marine biota which uses gill tissues for absorption is more affected by its concentration. As per known, marine organisms uses gills for the absorption process as major and main part of their body. Cr might deposit at different concentrations in different tissues. Fish gills, kidney and liver were found to be containing high concentration of Cr and muscles were not found to be affected and accumulated by the metal. However, Cr cannot be accumulated at higher trophic levels in marine food webs (Pourahmad et al., 2005).

Histopathological alterations

Histopathological studies are thought to be consistent and comprehensive biomonitoring tool to analyze the fish health and its survival rate in accumulated aquatic ecosystems (Deore and Wagh, 2012). Effects of metals i.e. Cd, Cr, Ni and Hg in different fish species present in Pakistan were noticed along with their histopathological changes (Table 1).

Heavy metals and diseases

Cadmium

Metals uptake primarily occurs by gills but it can also occur through intestinal epithelium (Mohamed, 2008). Some of the aberrations were observed in the intestine of Oreochromis nioticus and Lates niloticus. It was noticed that there were various severe degenerative and necrotic alterations in their intestinal mucosa. Kaoud et al. (2011) studied some pathological changes in the intestine of Oreochromis niloticus exposed with Cd along with atrophy in muscularis, necrotic and degenerative alterations in mucosa and sub mucosa. As the liver is associated with biotransformation and detoxification processes so due to these functions, its location, and its access to the body supply, it is an organ which is mostly affected by the water contamination (Camargo and Martinez, 2007; Mohamed, 2009).

Nickel

Generally, Ni present in trace amounts in the fish, if its concentration increases; it would be a risk for the survival of water organisms (Rauf et al., 2009). An extensive use of Ni, in various activities like, ceramic, steel industries and electroplating which are making Ni containing products, releasing waste materials into adjacent water channels without treating them (Jabeen and Javed, 2011). Fish accumulates heavy metals in its body by various ways i.e., through respiratory system, digestive system and skin directly (Ma’ruf, 2007). One of a fish named Barbonymus gonionotus, is considered to be sensitive to the environmental fluctuations and that’s why they act as bio indicator of environmental changes in the aquatic ecosystem (Wajiya and Yazid, 2009).

Chromium

Cr has deteriorating effects on fish survival and its growth (Shaheen et al., 2012). It just not only damage fish fertility but also produces aberrations in their progeny as well. Breeders’ exposure before spawning induced cumulative impact on fish gonads and it results in meager, weak and retarded off-springs just because of the malfunctioning of trophic hormones (Kobayashi and Okamura, 2005). It was noticed that, any decrease in activation of mitogen induced lymphocytes and a noticeable change in shape and phagocytic functions of neutrophils. These alterations may reflect the reduced power of resistance to pathogens chronic exposure of Cr in fish (Steinhagen et al., 2004).

Mercury

Studies revealed that, Hg ions increases the formation of vacuole in hepatocytes and hepatic disintegration occurs in severe cases. Damage increases with persistent exposure of Hg, indicating its accumulation in fish body. This study also in the favor of Kuang et al. (2007), who studied the roles on heavy metal’s ions in A. japonica under the water. Toxicity of heavy metals may lead to various pathological alterations in various fish tissues and these changes also has been addressed in Labeo rohita when exposed to mercuric chloride and Channa puntatus when exposed to phenyl mercuric acetate (Karuppasamy, 2000). Some major diseases caused by heavy metal toxicity are:

Necrosis

Hepatocytes necrosis and its degeneration might be due to the cumulative effects of metals and an increase in their concentrations in liver. Liver cellular degeneration might be due to oxygen deficiency as a result vascular dilation along with intravascular haemolysis was noticed in blood vessels (Mohamed, 2001). Lesions as degeneration, blood vessels dilation and necrosis in hepatocytes were detected in Mugil cephalus, Tilapia mossambicus and Clarias gariepinus (Ibrahim and Mahmoud, 2005).

Oedema

Labeo rohita gills when exposed to tannery effluent indicated fusions and primary lamellar epithelium clumping (Fanta et al., 2003). Some degenerative alterations in edema and lamellar were observed in fish gills when exposed to heavy metals (Osman et al., 2009). The lamellar epithelium lifting is a change of tissues, might be induced by any incidence of severe edema (Pane et al., 2004; Schwaiger et al., 2004).

Hyperplasia

Epithelial cells which undergo the lamella fusion and hyperplasia can go on to cause a huge decrease in gill surface area for respiration. It also disrupts blood flow in gills, alters the functioning of metabolism and may cause fish mortality (Purwanti et al., 2019). Recently, some of the researchers demarcated the gill injuries of two types. First type of injury comes from defense response and it includes hyperplasia of gill epithelium filaments while the second type is direct injuries which include shedding and necrosis of gill epithelium (Fanta et al., 2003).

 

Table 1: Effects of metals (cadmium, chromium, nickel and mercury) in different fishes of Pakistan.

Fish species	Metal	Concentration	Exposure type	Exposure time	Organ	Histopathological changes	References
Wallago attu	Cadmium	1/3, 1/4, 1/5 of LC50	Sub-lethal	14days	Liver	Protein level decreased	(Batool et al., 2018)
Catla catla	Nickel	70.40 mg/L	Sub-lethal	60days	…..	Total length, fork and weight increased	(Safina et al., 2020)
Labio rohita		71.99 mg/L				Weight increment
Cirrhinus mrigala		79.9 mg /L				Weight increment
Channa striata	Nickel	1/3, 1/4, 1/5 of LC50	Sub-lethal	14days	….	CAT activity reduced	(Arshad et al., 2018)
Catla catla	Cadmium	…..	Acute	96hrs	Blood	Hemoglobin, hematocrit and RBCs decreased	(Hassan et al., 2018)
Channa marulius	Cadmium	101.25mg/L	Acute	96hrs	Liver	Liver sensitivity increased	(Javed et al., 2016)
Mystus seenghala
Wallago attu
Ctenophary-ngodon idella	Chromium	25.5mg/L	Acute	24hrs	Gills, muscle tissues	Swelling in gills cells, fusions, inflammation. muscle cells necrosis, RBCs and hemoglobin decline.	(Shah et al., 2020a)
		22.5mg/L		48hrs
		20mg/L		72hrs
		18mg/L		96hrs
Oreochromis niloticus	Mercury	0.044 mg/L	Sub-lethal	48hrs	Liver	Hepatocytes destruction, sinusoids, pyknotic nuclei	(Pervaiz et al., 2019)
				96hrs		Cellular necrosis, melano-macrophages centers appearance, pyknotic and karyolosis nucleus, hepatic cords disorganization.
		0.055 mg/L		48hrs		Tissue degeneration, hepatic cords disorganzation, bile ducts degeneration, pyknosis
				96hrs		Bile duct inflammation, cellular necrosis, pyknotic nuclei, hemopoietic tissue degeneration.
		0.073 mg/L		48hrs		Pyknotic nuclei, hemopoietic tissue degeneration, bile duct degeneration, vacuolization, necrosis.
				96hrs		Pyknosis, necrosis, degeneration of tissue, bile duct inflammation, vacuolization.
Carassius auratus	Chromium	4ppm	Sub-lethal	24hrs	Gills Intestine Skin	Increased breathing rate. Increased mucus secretion. Tissue residues.	(Fawad et al., 2017)
		6ppm		48hrs
		8ppm		72hrs
		12ppm		96hrs
Oreochromis niloticus	Cadmium mixture	183.4 ml	Chronic	2weeks	Kidney	Renal CAT activity increased firstly, decreased finally.	(Ahmed et al., 2016)
Ctenophary-ngodonidella	Chromium	45.5, 43.5, 41.5, and 39 mg /L	Lethal	96hrs	Blood	RBCs and hemoglobin level decreased	(Shah et al., 2020)
Labeo rohita	Nickel	0.32 - 1.22 mg/L	Sub-lethal	River water	Gills	Hyperplasia, necrosis, Blood vessels congestion	(Sultana et al., 2016)
					Intestine	Atrophy,
					Liver	Necrosis
					Table continue on next page......................
Fish species	Metal	Concentration	Exposure type	Exposure time	Organ	Histopathological changes	References
Tilapia nilotica	Cadmium-cobalt mixture	37.93 mg/L	Acute	96hrs	Tissues	Exhibited sensitivity higher	(Ambreen and Javed, 2016a)
Cyprinus carpio	Chromium	5 mg/Land 10mg/L	Sub-lethal	16 days	Liver	Blood congestion, necrosis, parenchyma cell degeneration.	(Rana et al., 2015)
					Kidney	Pyknotic nuclei reduction, haemolysis.
Gibelion catla	Chromium	1/3rd of LC50	Chronic sub-lethal	12 weeks	Liver	Growth performance affected.	(Azmat et al., 2018)
Labeo rohita					Kidney
Cirrhinus mrigala					Gills
Cyprinus carpio	Chromium	25 to 150mg/L	Sub-lethal	30days	…..	Deleterious effects on growth produced.	(Shaheen and Jabeen, 2015)
Cyprinus carpio	Cadmium	10.42, 7.81, 6.25 and 5.21mg/L	Sub-lethal	30days	Blood	DNA damage	(Ambreen and Javed, 2016b)
Cyprinus carpio	Cadmium-lead mixture	78.94 and 82.22 µgg-1	Lethal	96hrs	Kidney	Higher accumulation, increase sensitivity.	(Ambreen et al., 2015)

 

Results and Discussion

Different metals (Hg, Cr and Cd) are considered as systemic toxicants, thus affect various organs even at low level (Olsson et al., 1998). Cellular organelles as well as enzymes involved in detoxification, damage repair and metabolic process are greatly influenced by heavy metals (Wang and Shi, 2001). Metallic ions effect nuclear proteins and DNA molecule, hence brings apoptosis or carcinogenesis (Beyersmann and Hartwig, 2008).

Histological biomarkers regarding fish organs toxicity are important indicators of environmental pollution. Biomarkers permits to examine specific target organ (gills) that are responsible for their vital function as respiration (Gernhöfer et al., 2001; Peebua et al., 2008). Gills are mainly involved in entry of heavy metals that brings lesions and gill damage and structural variations in gills of exposed fish are responsible for deaths (Bols et al., 2001; Obomanu et al., 2007). A study indicated that histopathological changes in gill tissues of Channa might cause hypoxic disorders, thus affecting their locomotory ability (Begum et al., 2006). Various organic compounds causes toxicopathic lesions in liver of fish. Cloudy swelling, hydropic degenerations as well as karyolysis, pyknosis and karyorrhexis of nuclei occurs due to acute toxic injury (Paul et al., 2014; Jiraungkoorskul et al., 2003). Cytoplasmic vacuoles of hepatocytes containing glycogen and lipids are associated with normal liver functioning (Camargo and Martinez, 2007). Hepatocytes vacuolation brings metabolic changes when exposed to contaminated water. Similarly, histopathological variations with Cu and Cd were noticed in liver of teleostean fishes (Pacheco and Santos, 2002; Ibrahim and Mahmoud, 2005; Tayel et al., 2008).

Fish can even cope with increased level of heavy metals in their bodies but is not safe for human consumption. Thus, time duration of contact with toxic elements and fish species as well as concentration rate must be considered before establishing basics for tolerable levels in ecological studies (Usero et al., 2004). The oedema can lead to tissue swelling due to fluid accumulation and cause cell organelles to decrease cell permeability (Rennika and Nurlita, 2013). Oedema may cause hyperplasia occurrence which may lead to interlamellae being clogged, thus causing the entire space to be filled with new cells and thicken the epithelium present at lamellae base (Robert, 2001). Epithelial degeneration, inflammatory cell infiltration in sub mucosa along with sub mucosal edema was detected in the intestine of tilapia when exposed to carbofuran (Soufy et al., 2007). Histopathological changes in the intestine of Oreochromis niloticus and Lates niloticus indicated severe degenerative and necrotic variations in the intestinal mucosa. Edema may be due to absorption of toxic metals (Hanna et al., 2005). Thus, various studies reported heavy metal accumulation in different fish organs and changes were noticed regarding particular heavy metal.

Conclusions and Recommendations

The current review indicates that exposure of heavy metals such as Cr, Cd, Ni and Hg at various concentrations brings histopathological changes in different fish organs. Such histopathological variations would be supportive to determine effect of heavy metals on fish species. Hence, present research served as experimental tools for the estimation of environmental pollution.

Acknowledgments

We are thankful to the digital library of HEC (higher education commission) Pakistan for providing the platform to search the literature and provision of full text articles to write this review.

Conflict of interest

The authors have declared no conflict of interest.

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