Effect of food supply on the detoxification in the blue mussel,Mytilus edulis, contaminated by diarrhetic shellfish toxins

Abstract

-The objective of this study was to identify a possible effect of food on the acceleration of decontamination in blue mussels, Mytilus edulis, containing diarrhetic toxins belonging to the okadaic acid (OA) structural group. An experimental protocol was designed to describe and compare the decontamination kinetics and detoxification rates of naturally OA-contaminated mussels that had either received or not received food for three weeks. The protocol was applied in two trials (in June 2006 and June 2007, called Ker06 and Ker07), conducted one year apart on samples of mussels collected in the same area, at the same season. Okadaic acid (OA), the main lipophilic toxin produced by the toxic alga Dinophysis acuminata, was analysed over the course of the decontamination, in hydrolysed (total OA) and non hydrolysed (free OA) digestive gland extracts, in order to estimate acyl-esters (7-O-acyl-ester derivatives of OA) concentrations. OA analyses were also made for toxin presence in biodeposits and in the aqueous phase. Bivalve physiological status was evaluated by biomass measurements (dry weight of flesh) and two biochemical compounds (total lipid and glycogen concentrations). Measured physiological parameters showed that mussels did not suffer under experimental conditions. Both trials showed that the food accelerated the elimination of free and total OA. This effect cannot be attributed to a dilution of the toxin in the tissue, as results expressed in toxin burden led to the same conclusion. The kinetic models of decontamination differed between the two experiments: the model was linear for Ker06, provided that the values corresponding to the first two days were discarded, whereas data fitted a decreasing exponential curve better in Ker07. Detoxification rates increased as the food supply increased. After three weeks of experimentation, the detoxification rates for total OA in Ker06 and Ker07 were 52 and 61%, respectively, in unfed mussels and 90 and 89% in fed mussels (with the highest level in Ker07). Comparisons between the free OA and esters showed that detoxification rate was higher for free OA than for esters, whatever the level of food supply. The results of this study suggest that food increase probably accelerates elimination of OA and OA-esters but the latter are eliminated at a lower speed. Key words:Mussel / Feeding / Digestive gland / Depuration / Okadaic acid / Acyl esters / Marine lipophilic biotoxins / Mass spectrometry Résumé -L'objectif de cette étude est de mettre en évidence un effet éventuel de la nourriture sur la vitesse de décontamination de moules, Mytilus edulis, contenant des toxines diarrhéiques de la famille de l'acide okadaïque (OA). Un protocole expérimental est conçu pour décrire les cinétiques durant 3 semaines d'expérience et comparer les taux de détoxication d'une part chez des moules nourries et d'autre part chez des moules maintenues à jeun. Ce protocole est appliqué sur des moules prélevées au même endroit, à la même saison, en 2006et 2007. L'acide okadaïque, principale ...

Accumulation, transformation and breakdown of DSP toxins from the toxic dinoflagellate Dinophysis acuta in blue mussels, Mytilus edulis

“…The calculated half-life times of 5.3 and 5.8 days for OA and DTX-1b respectively, are somewhat fast compared to literature values: Marcaillou et al (2010) found a half-life time of 20 days for 4e7 cm long, unfed Mytilus edulis. However, this discrepancy could potentially be related to the size difference of the mussels used.…”

“…Depuration (or detoxification) has been studied more intensely using mussels contaminated in situ. Effects of various parameters, including food availability (Blanco et al, 1999;Svensson, 2003;Svensson and F€ orlin, 2004;Marcaillou et al, 2010), temperature (Shumway and Cembella, 1993;Blanco et al, 1999) and mussel size and lipid content (Svensson and F€ orlin, 2004;Duinker et al, 2007) have been evaluated using different mussel species. Reported toxin half-life times vary substantially, from less than a day to 25 days, but despite the efforts, depuration kinetics of DSP toxins is far from well understood.…”

Azaspiracid accumulation, detoxification and biotransformation in blue mussels (Mytilus edulis) experimentally fed Azadinium spinosum

“…Detoxification of mussels fed with T-Iso was carried out over two weeks. Supplying non-toxic diet has been previously proposed by several authors to enhance detoxification after exposure of bivalves to saxitoxin (STX) or lipophilic toxins (okadaic acid, gymnodimine) (Lassus et al, 2005;Lassus et al, 2000;Marcaillou et al, 2010;Medhioub et al, 2010). The detoxification kinetic was slow, even if toxin elimination from mussels followed a biphasic kinetic, with a rapid first and a slow second phase (figure 2 and table 3); in all cases mussels were above the regulatory limit after two weeks of detoxification when all AZAs found were taken into account and not only the three regulated AZAs.…”

Ocean modelling for aquaculture and fisheries in Irish waters

“…Contaminated shellfish can take many months, especially in winter, to depurate the HAB biotoxins. Depuration times can be highly variable and are likely related to food availability among other things, such as the metabolic rate of the bivalves (Marcaillou et al, 2010;Jauffrais et al, 2012). A HAB warning system will give farmers the opportunity to extract product before long closures occur.…”