Copper is a trace element necessary for the normal growth and metabolism of living organisms. If exceeds its limit it becomes pollutant and causes pathological effects. Asian sea bass (Lates calcarifer) was exposed to sublethal concentrations of copper for 28 days and histopathological alterations were noticed in the gill, liver, muscle and intestine. Epithelial necrosis, hypertrophy, rupture of gill epithelium and haemorrhage at primary lamellae were observed after 7 days of exposure. Lifting of epithelium, oedema and fusion of adjacent secondary lamellae were conspicuous at 28 days of exposure. The experimental liver tissue showed reduction in the size of hepatocytes, vacuolisation, and hypertrophy. The intestine displayed fused microvilli, sloughing of mucus membrane and swollen cells. Muscle bundles with severe oedema and their thickening and separation were more pronounced in sublethal treatment of copper in the muscle. Several histopathological changes observed in various fish organs would serve a useful purpose in evaluating the toxic effects of copper. The present study clearly demonstrated that all the treated body organs exhibited significant damage with response; amongst the body organs the liver is an important target organ for copper toxicity in L. calcarifer and this species could be possibly used as a model organism for toxicity studies.

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The tissue damage induced by various organic pollutants in aquatic animals is well documented, but there is a dearth of information relating to the histological alterations induced by copper in the spiny lobster. In the present study, intermoult juveniles of the spiny lobster Panulirus homarus (average weight 150-200 g) were exposed to two sublethal concentrations of the copper (9.55 and 19.1 μg/l) for a period of 28 days. The muscle, hepatopancreas, midgut, gills, thoracic ganglion and heart of the lobsters were then dissected out and processed for light microscopic studies. Exposure to copper was found to result in several alterations in the histoarchitecture of the muscle, hepatopancreas, midgut, gills, thoracic ganglion and heart of P. homarus. The alterations included disruption and congestion of muscle bundle in muscle tissue; blackened haemocytes; distended lumen and F cell; necrosis of the tubules of the hepatopancreas; disarrangement of circular muscle of the midgut; accumulation of haemocytes in the haemocoelic space; swelling and fusion of lamellae; abnormal gill tips; hyperplastic, necrotic, and blackened secondary gill lamellae of the gills; damaged neurosecretory cell and sensory and motor fibre; necrotic of the thoracic ganglion; dispersedly arranged muscle bands; clumped satellite cells and nucleus of the heart. The results obtained suggest that the muscle, hepatopancreas, midgut, gills, thoracic ganglion and heart of lobsters exposed to copper were structurally altered. Such alterations could affect vital physiological functions, such as absorption, storage and secretion of the hepatopancreas, digestion of gut and respiration, osmotic and ionic regulations of the gills, which in turn could ultimately affect the survival and growth of P. homarus. Thus, all possible remedial measures should be adopted to prevent the occurrence of copper contamination in the aquatic environment.

Surface ultrastructure of the gill and liver of 3-month-old Asian sea bass, Lates calcarifer, after copper exposure, was investigated by scanning electron microscopy (SEM). Fish samples were exposed to copper concentrations of 6.83 and 13.66 ppm (sublethal) for 28 days with parallel untreated control. These structures showed structural modifications in both low and high concentrations of copper exposure. Oedema, hyperplasia, desquamation, necrosis, epithelial lifting, lamellar fusion, collapsed secondary lamellae, curling of secondary lamellae and aneurism in the secondary lamellae were observed in gill tissues exposed to copper. Hepatic lesions related to cloudy swelling of hepatocytes, congestion, vacuolar degeneration, dilation of sinusoids and nuclear hypertrophy were evident in the exposed sea bass liver tissue.

Spiny lobster Panulirus homarus which had been exposed to cupric ion at 9.55 and 19.1 μg/l for 28 days was examined for sub-lethal effects including morphology, wet weight, and induced genotoxic effect on the chromosome. Following cupric exposure, the color of lobster P. homarus changed from yellowish-brown to greenish black in the hepatopancreas, changed from normal creamy white to yellowish white in the muscle, and changed to greenish black in the gill. A significant change in the percentage of wet weight of muscle (28.70 ± 0.41-23.47 ± 0.45), hepatopancreas (4.03 ± 0.12-2.63 ± 0.17), and gills (3.63 ± 0.45-3.87 ± 0.12) were observed in the copper-treated lobsters. The diploid number of chromosomes of P. homarus was over 200 metaphases from ten lobsters, as 2n = 58, and consisted of 16 acrocentric, seven metacentric, and six sub-metacentric chromosomes. The lobsters exposed to cupric ion at 9.55 and 19.1 μg/l showed different types of chromosomal aberrations such as centromeric gaps, chromatid breaks, centromeric fusion, stickiness, ring chromosomes, and acrocentric association region. The frequency of aberrations increased with duration of exposure. In conclusion, it was suggested that cupric ion interacts with the spindle formation and consequently distorts the normal karyomorphology, indicating cytogenetic effect on lobster.