## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Species**} & \multirow{2}{*}{**Exposure**} & \multirow{2}{*}{**Day**} & \multirow{2}{*}{**Cum \% acc**} & \multicolumn{2}{c}{**Amount of Ingesgested**} & \multicolumn{2}{c}{**Amount of MC**} & \multirow{2}{*}{**Cum \% acc**} \\  & & & & & **MC (ng/Mosaic)** & & **Accounted (ng)** \\  & & & & & **between Two** & & **between the Same** \\  & & & & & **Sampling Times** & & **Sampling Times** \\ \hline \multirow{8}{*}{_A. anatina_} & \multirow{4}{*}{10 ug MC/L} & E1 & ND & E1–E0 & ND & ND & ND \\  & & E3 & 38.8 \(\pm\) 16.5 & E3–E1 & ND & ND & ND \\  & & E7 & 7.3 \(\pm\) 1.3 & E7–E3 & 5525.6 & \(-\)742.4 & \(-\)13.4 \\  & & E14 & 21.2 \(\pm\) 6.0 & E14–E7 & 136023 & 4158.5 & 30.6 \\  & & E21 & 1.4 \(\pm\) 0.5 & E21–E14 & 6375.4 & \(-\)4427.7 & \(-\)69.45 \\ \cline{2-8}  & & & E1 & 61.6 \(\pm\) 2.55 & E1–E10 & 111.10 & 6845.4 & 61.6 \\  & & E3 & 13.4 \(\pm\) 4.8 & E3–E1 & 4620.3 & \(-\)4742.0 & \(-\)102.6 \\  & & E7 & 10.6 \(\pm\) 7.3 & E7–E3 & 37,6047.4 & 3567.5 & 9.5 \\  & & E14 & 12.4 \(\pm\) 2.3 & E14–E7 & 28,684.05 & 4496.9 & 15.6 \\  & & E21 & 3.3 \(\pm\) 0.3 & E21–E14 & 53,9921.5 & \(-\)1222.3 & \(-\)0.6 \\ \hline \multirow{8}{*}{_D. polymorpha_} & \multirow{4}{*}{10 ug MC/L} & E1 & \(0.2\pm\) 0.2 & E1–E0 & 745.8 & 1.6 & 0.2 \\  & & E3 & ND & E3–E1 & 3327.6 & \(-\)1.6 & \(-\)0.05 \\ \cline{1-1}  & & E7 & 0.1 \(\pm\) 0.03 & E7–E3 & 24,670.0 & 16.8 & 0.1 \\ \cline{1-1}  & & E14 & 0.05 \(\pm\) 0.03 & E14–E7 & 14,366.2 & 3.3 & 0.02 \\ \cline{1-1}  & & E21 & \(0.2\pm\) 0.05 & E21–E14 & 18,644.35 & 72.8 & 0.6 \\ \cline{1-1} \cline{2-8}  & & & E1 & \(0.1\pm\) 0.1 & E1–E0 & 2639.1 & 2.1 & 0.1 \\ \cline{1-1}  & & E3 & 0.05 \(\pm\) 0.02 & E3–E1 & 12,449.7 & 4.8 & 0.04 \\ \cline{1-1}  & & E7 & 0.04 \(\pm\) 0.03 & E7–E3 & 62,256.7 & 27.6 & 0.04 \\ \cline{1-1}  & & E14 & 0.1 \(\pm\) 0.03 & E14–E7 & 49,661.9 & 63.0 & 0.1 \\ \cline{1-1}  & & E21 & 0.1 \(\pm\) 0.04 & E21–E14 & 50,245.35 & 10.8 & 0.02 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Cumulated percentage of total MC accumulation (cum % acc), amount of ingested MC (ng) per mussel between two sampling times, difference in the amount of total MC accumulated (ng) between the same sampling times, and temporary percentage of total MC accumulation (temp % acc) of the same time range. Data not shown due to technical difficulties are referred as ND (not determined). Secondly, the triggering of detoxication pathways may have fluctuated between exposure concentrations. The most described pathway of MC detoxification by bivalves involves the glutathione S-transferase (GST) and glutation (GSH). MC can be conjugated to GSH [60], reducing MC toxicity and potentially enhancing its excretion [61]. This conjugation is catalysed by GSTs, a multigene family of enzymes responsible for phase II biotransformation processes, representing a defence mechanism against xenobiotics [62]. GST is known to catalyze the conjugation of MC to glutathione in bivalves [63]. Another mechanism involves the multi-xenobiotic-resistance (MXR) phenomenon, based on the overexpression of transmembrane P-glycoprotein that prevent the cellular accumulation of various substances by actively pumping them out of cells [64]. MXR was suggested as a possible explanation for the insensitivity of _D. polymorpha_ towards MC [65]. Here, it is possible that the detoxification was triggered while _A. anatina_ were exposed to 10 \(\mu\)g MC/L, as reflected by the variations of the cumulated accumulation factor over the exposure period. This hypothesis is also supported by _A. anatina_ negative temporal accumulation ratio observed between some days (e.g., between day one and three in mussels exposed to an equivalent of 100 \(\mu\)g MC/L), whereas the ingestion of filaments continued during this time range. Therefore, _A. anatina_ may not have decreased their ingestion rate of _P. agardhi_ during this period but have far less accumulated MC, probably via MC metabolization and/or detoxification.