Bioaccumulation and Metabolic Effects of Zinc on Marine Rock Oyster, Crassostrea Cattuckensis

Abstract

<jats:p>The Indian rock oysters, Crassostrea cattuckensis (80-90 mm shell length) were exposed to sub lethal levels of zinc for 15 days and 30 days for metal accumulation and next 15 days for metal depuration. The oysters, which served as experimental control after 15 days showed high amount of lipid (mg/100 mg) in hepatopancreas ( 3.32) followed by gills (3.20), mantle (3.08), gonad (2.90), adductor muscle (2.78) and siphon (2.11). During 15 days metal exposed oysters to (0.65) and (0.94) ppm concentrations there was changes observed in different body parts when compared to experimental control. The decreased rate upon 15 days in (0.65 ppm) concentrations was in mantle (2.96), than gill (2.22), hepatopancreas (1.72), gonad (1.59), siphon (1.51) and adductor muscle (1.50). While in (0.94 ppm) the protein was decreased in adductor muscle (2.51), gonad (1.61), siphon (1.44), gill (1.42) and it increased in mantle (3.90) and hepatopancreas (3.34) when it was compared to experimental control. Whereas upon 30 days exposure the lipid content increased among body parts in both concentration except the gills (1.35), gonads (1.97) and hepatopancreas (1.66) in higher concentration when compared with experimental control. The lipid increased in (0.65 ppm) from gonad (2.29), hepatopancreas (2.25), adductor muscle (2.22), gills (2.20), mantle (2.14) and siphon (1.44). While in (0.94 ppm) lipid increase trend was from mantle (4.27), adductor muscle (2.46) and siphon (1.42) and decreased from gonad (1.97), hepatopancreas (1.66) and gills (1.35) when compared with 30 days experimental control. During detoxification process the lipid content was increased in both concentrations except gill (2.11) in low and adductor muscle (0.99), siphon (0.74) in high concentrations when compared with respective concentrations of 15 days exposed oysters. The increase rate in low concentration was from mantle (4.32) than from adductor muscles (4.12), gonad (3.60), hepatopancreas (2.46) and siphon (1.05). In high concentration it was more in hepatopancreas (4.93) than gonad (4.42), gills (4.08) and mantle (4.01).</jats:p>

An overview of the impact of heavy metal accumulation on marine molluscs

“…They are the filter feeders that feed opportunistically on any phytoplankton, detritus, or benthic algae available in their habitats. The heavy metals levels in molluscs and other invertebrates are often considerably higher than the other constituents of the marine environment (Hamed & Emara, 2006; [7,22,23] . Heavy metals discharged into the sea can damage both marine species' diversity and ecosystems (Ponnusamy et al, 2014) [17] due to their toxicity and accumulative behaviour (Matta et al, 1999) [13] .…”

“…This has resulted in the need to understand ecosystem interrelationships for effectively using and preserving natural and biological resources. Considerable progress has been made in understanding the heavy metals accumulation in aquatic organisms over the past decades (Mason et al, 1996; [12,23] and show the levels of heavy metals (Cu, Zn, Pb, Cr, Ni, Fe, and Mn) in the coastal water, sediments, and soft tissues of the molluscs like gastropods limpet (Patella coerulea), bivalve (Barbatus barbatus) and in the oyster (Crassostrea rhizophorae) in the Gulf of Suez. Histochemical and histopathological levels of metals have been quantified in specific tissues such as digestive glands, gills, kidneys and some target cells, which are involved in metal uptake, storage and detoxification.…”