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

Abstract

Azadinium spinosum (Elbrächter and Tillmann), a small marine dinoflagellate, has been recently described as a de novo producer of azaspiracid-1 and -2 (AZA1 and -2) diarrhoeic toxins. A culture of A. spinosum was established in our laboratory and optimised for pilot-scale production of this organism, to evaluate and understand AZA1 and -2 accumulation and biotransformation in blue mussels (Mytilus edulis) fed with A. spinosum. Adult mussels were continuously exposed to A. spinosum over 1 week in 160 L cylindrical conical tanks. Three different diets were tested for contamination: 5000, 10 000 cells mL(-1) of A. spinosum and a mixture of 5000 cells mL(-1) of A. spinosum with 5000 cells mL(-1) of Isochrysis aff. galbana (T-Iso, CCAP 927/14). During the subsequent period of detoxification (2 weeks), contaminated mussels were continuously fed with 5000 cells mL(-1) of T-Iso. Kinetics of accumulation, detoxification and biotransformation were evaluated, as well as the toxin distribution and the effect of A. spinosum on mussel digestive gland tubules. M. edulis fed on A. spinosum in the three tested conditions; this finding confirmed our recent experiments feeding A. spinosum to mussels. The original algal toxins AZA1 and -2, as well as mussel metabolites AZA3 to 12, -17, -19, -21 and -23 were found during these trials. After as little as 6 h, azaspiracid contents in mussels reached the EU regulatory limit, and metabolites were observed in all conditions at approximately 25% of the total AZA content. This fraction exceeded 50% after 24 h, and continued to increase until the end of the study. AZA17 and -19 were found to be the main metabolites, with AZA17 concentrations estimated in the same order of magnitude as that of the main algal toxin, AZA1.

Gambierol: Synthetic Aspects

“…A second set of samples from 2006 from South-West Ireland (significant year in terms of a major azaspiracid event) were also analysed via molecular methods, and again as in the Killary data set, there was a presence of A. spinosum corresponding with rapid increases in azaspiracid intoxification in mussels in the same locality. This has also been observed in earlier laboratory feeding experiments 21,41 where toxin levels rose rapidly in test shellfish in There remain many questions regarding the spatial and temporal distribution of Azadinium.…”

“…This indicates that there is an active biotransformation of the toxins in the digestive system of the mussels. These observations were subsequently confirmed, and AZA-17 and AZA19 were highlighted as two major metabolites of AZA1 and -2, respectively, over a week of contamination using A. spinosum at different cell concentrations 41 . These bioconversions pose a public health problem as AZA17 and -19 are currently not regulated (see Twiner et al, this book).…”

Amphidoma languida (Amphidomatacea, Dinophyceae) with a novel azaspiracid toxin profile identified as the cause of molluscan contamination at the Atlantic coast of southern Spain

“…It is noteworthy that new AZA-43 and AZA-3, which is a shellfish metabolite of AZA-1 (Jauffrais et al, 2012), are not only isobaric (i.e., possess the same molecular mass), but also have very close retention times (Fig. 8) implying the risk of misidentification.…”

“…), blue mussel (Mytilus galloprovincialis), clams (Ruditapes decusssatus), Venerupis senegalensis, and razor clams (Solen marginatus), but AZA levels in Portugal were rather low (1.6-6.1 mg kg in the digestive gland of blue mussels (Taleb et al, 2006). Noteworthy, toxins are highly concentrated in the digestive gland but not as much in other shellfish tissue (Hess et al, 2005;Jauffrais et al, 2012) and thus, such values cannot directly be compared with the EU regulatory limit. In summer 2006, low levels of AZA (up to 6 mg kg À1 edible tissue) were reported from the same area about 180 km south of Casablanca (Elgarch et al, 2008).…”

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.…”