Gender influences molecular and histological biomarkers in mature oysters Crassostrea gasar (Adanson, 1757) after pyrene exposure.

Oysters are frequently used as sentinel organisms for monitoring effects of contaminants due to their sessile, filtering habits and bioaccumulation capacity. These animals can show elevated body burden of contaminants, such as pyrene (PYR). PYR can be toxic at a molecular level until the whole oyster, which can show reproductive and behavioral changes. Considering that biologic parameters, such as gender or reproductive stage can interfere in the toxic effects elicited by contaminants uptake, the aim of this study was to evaluate some molecular and histological responses in females and males of oyster Crassostrea gasar exposed to PYR (0.25 and 0.5 µM) for 24 h at the pre-spawning stage. PYR concentrations were analyzed in water and in tissues of female and male oysters. Gene transcripts related to biotransformation (CYP3475C, CYP2-like, CYP2AU1, CYP356A, GSTO-like, GSTM-like, SULT-like), stress (HSP70), and reproduction (Vitellogenin, Glycoprotein) were quantified in gills. In addition, histological analysis and histo-localization of CYP2AU1 mRNA transcripts in gills, mantle and digestive diverticulum were carried out. Females and males in pre-spawning stage bioconcentrated PYR in their tissues. Males were more sensitive to PYR exposure. CYP2AU1 transcripts were higher in males (p < 0.05), as well as tubular atrophy was observed only in males exposed to PYR (p < 0.05). As expected, vitellogenin transcripts were lower in males (p < 0.05). Given these results, it is suggested that levels of CYP2AU1 be a good biomarker of exposure to PYR in oyster C. gasar and that it is important to consider the gender for the interpretation of biomarker responses.

Comparison of the antioxidant defense system in Crassostrea rhizophorae and Crassostrea gigas exposed to domestic sewage discharges.

Oysters Crassostrea rhizophorae and Crassostrea gigas were kept for fourteen days at four sites in São José, SC, Brazil, chosen according to a sewage discharge contamination gradient. Enzymatic activities of CAT, GST, G6PDH and GR were evaluated in gills and digestive glands. Higher CAT activity was observed in tissues of C. rhizophorae in response to sewage contamination possibly indicating peroxisome proliferation induction. C. gigas showed elevated G6PDH activity in digestive gland, and GR in gills, after domestic sewage exposure. In conclusion, C. rhizophorae and C. gigas showed different biochemical responses after in situ exposure to domestic sewage. However, C. rhizophorae showed more significant changes in CAT suggesting that this organism could be a better monitor to this kind of effluent.