Relationship Between Gonad Maturation and Heavy Metal Accumulation in the Clam, Galatea paradoxa (Born 1778) from the Volta Estuary, Ghana

Abstract

The relationship between gonadal development and the concentrations of four heavy metals Mn, Zn, Fe and Hg in the tissues of the clam Galatea paradoxa was evaluated at the Volta estuary, Ghana, over an 18-month period. Metal concentrations in the clam tissues were highly variable over the sampling period and seemed to be influenced by the reproductive cycle of the clam. Mn concentrations varied over a wide range from 49 to 867 μg/g and exhibited a significant positive correlation with gonadal development (p = 0.0146, r(2) = 0.3190). Zn and Fe concentrations ranged from 13 to 59 μg/g and 79 to 484 μg/g, respectively and both revealed negative relationships between gonad development and metal accumulation (Zn (p = 0.0554, r(2) = 0.0554) and Fe (p = 0.1040, r(2) = 0.1567)). Hg concentrations ranged from 0.026 to 0.059 μg/g over the sampling period and exhibited a slight positive relationship between gonadal development and metal accumulation (p = 0.0861, r(2) = 0.1730).

Influence of gonadal development on metal accumulation in the Portuguese oyster,Crassostrea angulata,in subtropical areas

“…This pattern could be found in Cu, Zn, Cd and Pb, and the former three metals showed a significantly negative correlation ( p < 0.05) with GSI. Several studies have described a resting phase maximum and summer pre‐spawning minimum of metal concentration in oysters, clams and mussels (Adjei‐Boateng, Obirikorang, Amisah, Madkour, & Otchere, ; Fŕias‐Espericueta et al, ; Lobe1, & Wright, ; Páez‐Osuna et al, ; Richir & Gobert, ). However, in these investigations, correlations between GSI and metal concentrations in the gonad were relatively weak.…”

“…Despite this, the tendency of gonadal metal concentration to decrease during gonad maturation is well established. This pattern may be attributed to the dilution caused by the rapid tissue growth against a relatively stable metal content in a short‐term period (Adjei‐Boateng et al, ; Phillips, ).…”

“…Tilly and Tilly () reported that the level of messenger RNA encoding Mn‐SOD acted as an antioxidant, or free radical scavenger increased during follicular maturation in female rats. However, Adjei‐Boateng et al () proposed that the accumulation of some components used for gonad tissue production during spawning had a high affinity for certain heavy metals, possibly including Mn. In these ways, the specific role of Mn in the formation of oyster gametes requires further confirmation.…”

“…Despite this, the tendency of gonadal metal concentration to decrease during gonad maturation is well established. This pattern may be attributed to the dilution caused by the rapid tissue growth against a relatively stable metal content in a short-term period (Adjei-Boateng et al, 2011;Phillips, 1980). However, regression analysis showed that the relationship between gonadal metal concentrations and GSI was not a simple linear relationship (Figure 1).…”

Differential effects of bisphenol A toxicity on oyster (Crassostrea angulata) gonads as revealed by label-free quantitative proteomics

“…Therefore, Zn 2+ homeostasis in the gonads is affected by exposure to BPA, and zinc is an essential metal ion for gonadal development in oysters. Zinc accumulation is dependent upon the developmental stage of the gonad (Adjei-Boateng et al, 2011).…”