Approved Abstracts

Molecular responses in Crassostrea gigas (Thunberg, 1793) oysters collected in potentially contaminated areas in the North and South Bays of Santa Catarina Island (Florianópolis, Brazil)



Author(s): Bastolla CLV; Saldaña-Serrano MA; Lima D; Mattos JJ; Righetti BPH; Piazza CE; Reis IMM; Cella H; Deconto VS; Gomes CHAM; Lanzarin LS; Boas LOBV; Brocardo GS; Zacchi FL; Taniguchi S; Bainy ACD;
Presenter: Camila Lisarb Velasquez Bastolla

The precariousness of sewage treatment systems in coastal regions contributes to the pollution of the aquatic environment and significantly impacts various activities, such as aquaculture. The Pacific oyster Crassostrea gigas is responsible for more than 90% of the oyster farming in Santa Catarina. Furthermore, the species is an important sentinel organism in environmental monitoring. The aim of this study was to evaluate the molecular responses of C. gigas oysters collected in aquaculture areas potentially contaminated by sanitary sewage in Florianópolis, SC. In February 2020, C. gigas oysters were collected in Santo Antônio (SAL), Sambaqui (SAM), Serraria (SER), Caieira (CAI), Tapera (TAP), Imaruí (IMA) and had their gills dissected (n=10) to evaluate the levels of gene transcripts involved in xenobiotic biotransformation (phase I and II) and antioxidant defense. Transcript levels of four cytochrome P450 isoforms (CYP1A1-like, CYP2-like, CYP2AU2-like and CYP356A1), Sulfotransferase (SULT-like), Superoxide Dismutase (SOD-like) and Catalase (CAT-like) were evaluated by means of quantitative reverse transcription PCR (qRT-PCR). The total RNA was extracted from 80 mg of gills samples using Qiazol reagent. The concentration and purity of total RNA were quantified in a NanoDrop®ND-1000 spectrometer. Reverse transcription was performed from 1 µg of Total RNA using QuantiTect Reverse Transcription kit and the total cDNA concentration was determined. Results were analyzed with the 2-Cq method and normal carried out using the cDNA load effectively used in the reaction. Data were computed as mean (± standard deviation), submitted to normality tests and according to results, submitted to one-way ANOVA (Tukey’s posttest) or non-parametric test Kruskal-Wallis (Dunn‘s posttest). The oysters collected at SER showed higher levels CYP1A-like transcripts (4.7-fold) (p < 0.05) comparing to SAL. CYP356A1-like transcript levels were lower in SAL, SAM, CAI, TAP (0.4-fold) and SER (0.5-fold) compared to IMA (p < 0.05). CYP2AU2-like transcript levels were 3.2-fold higher in IMA compared to CAI and TAP (p < 0.05). The oysters collected at SER, TAP and IMA showed higher transcript levels of CYP2-like (3-fold, 3.1-fold and 3-fold) in relation to SAM (p < 0.05). Regarding phase II of biotransformation, no significant changes were observed in SULT-like transcript levels between the evaluated areas. SOD-like transcript levels in IMA were 2-fold higher in relation to SAL and SAM, 2.6-fold compared to CAI and 1.5-fold in relation to TAP. The transcript levels of CAT-like were 2.2-fold and 2.5-fold higher in SER in relation to SAL and CAI, respectively (p < 0.05). Microbiological analysis of water showed values above those allowed by law for total and thermotolerant coliforms in TAP, SER and IMA suggesting contamination by untreated sanitary sewage. Chemical analysis in soft tissues of oysters showed the presence of PAH in all monitored aquaculture areas. Subsequent chemical analyses of sediment and molecular analysis (GST isoforms) are being carried out to verify other organic contaminants and their influence, qualitatively and quantitatively, in phase II of biotransformation. By integrating chemical analysis with molecular biomarkers, our approach provides insight into contamination of organic pollutants and potential impacts on the health of oysters farming in Grande Florianópolis. Financial Support by CNPq.

Keywords: monitoring; biotransformation; aquaculture

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