Physiological Responses of the Bivalves Mytilus galloprovincialis and Ruditapes decussatus Following Exposure to Phenanthrene: Toxicokinetics, Dynamics and Biomarkers Study

Abstract

The aim of the current study was to assess the multifaceted effects of the polycylic aromatic hydrocarbon phenanthrene, mainly used in the colouring, explosive, and pharmaceutical industries, on the physiology of two bivalve species with economic value as seafood, namely, the Mediterranean mussel Mytilus galloprovincyalis and the European clam Ruditapes decussatus. The current study assessed how the phenanthrene affected several biomarkers and biometric endpoints in both bivalves, based on an in vivo experiment in silico approach. The bivalves were exposed during four time slots (i.e., 7, 15, 21, and 28 days) to two concentrations of phenanthrene in water (50 µg/L and 100 µg/L). For the clam R. decussatus, an additional contamination of sediment was applied due their typical benthic lifestyle (50 µg/kg and 100 µg/kg). The phenanthrene significantly reduced the ability of bivalves to tolerate desiccation and their Median Lethal Time, and also inhibited the activity of the enzyme acetylcholinesterase in a time-dependent manner. The activity of catalase indicated that bivalves also experienced oxidative stress during the first 21 days of the experiment. The significant decline in catalase activity observed during the last week of the experiment for the mussel M. galloprovincyalis supported a depletion of enzymes caused by the phenanthrene. The phenanthrene has also toxicokinetic and toxicodynamic properties, as assessed by the in silico approach. Overall, the results obtained suggest that the bivalves Ruditapes decussatus and M. galloprovincyalis can be used as a sentinel species in monitoring studies to assess the environmental impact of phenanthene in marine ecosystems. The significance of our findings is based on the fact that in ecotoxicology, little is known about the chronic effects, the simultaneous use of multiple species as bioindicators, and the interactions molecular modelling.

Keywords: biomarkers; bivalves; chronic toxicity; in silico modelling; polycyclic aromatic hydrocarbons; stress on stress.

Figure 1

Graphical summary of steps and methodology adopted.

Figure 2

Regressions relating linear parameters in bivalve species Mytilus galloprovincialis and Ruditapes decussatus. Length (L); Width (W); Thickness (T).

Figure 3

Regressions relating length and masses in bivalve species Mytilus galloprovincialis and Ruditapes decussatus. Total Fresh Mass (TFM); Fresh Chair Mass (FCM); Fresh Shell Mass (FSM), Length (L).

Figure 4

Percentage of survivors in bivalves’ species Mytilus galloprovincialis and Ruditapes decussatus in open air after being exposed to an Untreated control (Ut) and two concentrations of phenanthrene in water [50 µg/L (WC1) and 100 µg/L (WC2)] and sediment [50 µg/kg (SC1) and 100 µg/kg (SC2)] over 28 days.

Figure 5

Average biomarker responses (± standard deviation) in bivalves’ species Mytilus galloprovincialis and Ruditapes decussatus after exposure to an Untreated control (Ut) and two concentrations of phenanthrene in water [50 µg/L (WC1) and 100 µg/L (WC2)] and sediment [50 µg/kg (SC1) and 100 µg/kg (SC2)] over 28 days. Catalase (CAT); Acetylcholinesterase (AChE). Different letters (a, b, c, d, and e) above bars indicate significantly differences from controls represented by ‘a’ after mutiple comparisions using Tukey’s HSD test.

Figure 6

The chemical structure of phananthrene (A) and the average biomarker responses related to its toxicodynamics as compared to the average of class compounds (B). Cytox: Cytotoxicity; Mutagen: Mutagenicity; Immunotox: Immunotoxicity; Carcino: Carcinogenicity; Hepatotox: Hepatotoxicity; ATAD5: ATPase family AAA domain-containing protein 5; TS-p53: Tumor Supressor (Phosphoprotein) p53; MMP: Mitochondrial Membrane Potential; HSE: Heat shock factor response element; Nrf2/ARE: Nuclear factor like 2/antioxidant; PPAR-γ: Peroxisome Ploriferator Activated Receptor Gamma; ER-LBD: Estrogen Receptor Ligand Binding Domain; ERα: Estrogen Receptor Alpha; AR-LBD: Androgen Receptor Ligand Binding Domain; AR: Androgen Receptor; AhR: Aryl hydrocarbon Receptor.