Aquatic Toxicology 183 (2017) 94–103 Contents lists available at ScienceDirect Aquatic Toxicology journal homepage: www.elsevier.com/locate/aquatox Research Paper Transcriptional changes in oysters Crassostrea brasiliana exposed to phenanthrene at different salinities Flávia Lucena Zacchi a , Daína de Lima a , Fabrício Flores-Nunes a , Jacó Joaquim Mattos b , Karim Hahn Lüchmann c , Carlos Henrique Araújo de Miranda Gomes d , Márcia Caruso Bícego e , Satie Taniguchi e , Silvio Tarou Sasaki e , Afonso Celso Dias Bainy a,∗ a Laboratory of Biomarkers of Aquatic Contamination and Immunochemistry − LABCAI, Federal University Santa Catarina, Florianópolis, Brazil b Aquaculture Pathology Research Center – NEPAQ, Federal University of Santa Catarina, Florianópolis, Brazil c Laboratory of Biochemistry and Molecular Biology – LBBM, Fishery Engineering Department, Santa Catarina State University, Laguna, Brazil d Laboratory of Marine Mollusks – LMM, Federal University of Santa Catarina, Florianópolis, Brazil e Laboratory of Marine Organic Chemistry – LABQOM, Oceanographic Institute, University of São Paulo, São Paulo, Brazil a r t i c l e i n f o Article history: Received 18 August 2016 Received in revised form 15 December 2016 Accepted 17 December 2016 Available online 21 December 2016 Keywords: Estuaries Mangrove oyster PAHs Phenanthrene qPCR Salinity a b s t r a c t Euryhaline animals from estuaries, such as the oyster Crassostrea brasiliana, show physiological mecha- nisms of adaptation to tolerate salinity changes. These ecosystems receive constant input of xenobiotics from urban areas, including polycyclic aromatic hydrocarbons (PAHs), such as phenanthrene (PHE). In order to understand the influence of salinity on the molecular responses of C. brasiliana exposed to PHE, oysters were acclimatized to different salinities (35, 25 and 10) for 15 days and then exposed to 100 g L −1 PHE for 24 h and 96 h. Control groups were kept at the same salinities without PHE. Oysters were sam- pled for chemical analysis and the gills were excised for mRNA quantification by qPCR. Transcript levels of different genes were measured, including some involved in oxidative stress pathways, phases I and II of the xenobiotic biotransformation systems, amino acid metabolism, fatty acid metabolism and aryl hydrocarbon receptor nuclear translocator putative gene. Higher transcript levels of Sulfotransferase-like gene (SULT-like) were observed in oysters exposed to PHE at salinity 10 compared to control (24 h and 96 h); cytochrome P450 isoforms (CYP2AU1, CYP2-like1) were more elevated in oysters exposed for 24 h and CYP2-like2 after 96 h of oysters exposed to PHE at salinity 10 compared to control. These results are probably associated to an enhanced Phase I biotransformation activity required for PHE detoxification under hyposmotic stress. Higher transcript levels of CAT-like, SOD-like, GSTm-like (96 h) and GST˝-like (24 h) in oysters kept at salinity 10 compared to organisms at salinities 25 and/or 35 are possibly related to enhaced ROS production. The transcription of these genes were not affected by PHE exposure. Amino acid metabolism-related genes (GAD-like (24 h), GLYT-like, ARG-like (96 h) and TAUT-like at 24 h and 96 h) also showed different transcription levels among organisms exposed to different salinities, suggesting their important role for oyster salinity adaptation, which is not affected by exposure to these levels of PHE. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Mangroves and estuaries are characterized by constant fluctua- tions in the mixture of freshwater and seawater, being among the most productive and valuable ecosystems worldwide. Salinity is an ∗ Corresponding author at: Laboratory of Biomarkers of Aquatic Contamination and Immunochemistry − LABCAI, Federal University Santa Catarina, Servidão Cam- inho do Porto, 88034−257 Florianópolis, Brazil. E-mail addresses: afonso.bainy@ufsc.br, afonsobainy@pq.cnpq.br (A.C. Dias Bainy). important factor determining the structure and functional charac- teristics of aquatic biota in these areas (Elliott and McLusky, 2002). Euryhaline animals, such as bivalves, possess physiological mech- anisms to regulate the osmotic pressure in order to adapt to these salinity changes (Berger and Kharazova, 1997). One of these mech- anisms is the use of free amino acids (FAAs) and inorganic ions, such as Na + , K + and Ca 2+ , as intracellular osmolytes (Hosoi et al., 2007; Pierce et al., 1992). Over the past decades, the role of amino acids in osmoregulatory processes in bivalves has been widely studied (Deaton, 2001; Kube et al., 2007; Matsushima et al., 1987; Powell et al., 1982; Shumway et al., 1977). More recently, genome and tran- scriptome studies have been carried out in bivalves under salinity http://dx.doi.org/10.1016/j.aquatox.2016.12.016 0166-445X/© 2016 Elsevier B.V. All rights reserved.