The occurrence of domoic acid linked to a toxic diatom bloom in a new potential vector: The tunicate Pyura chilensis (piure)

Abstract

The tunicate Pyura chilensis (Molina, 1782); Phylum Chordata; Subphylum Urochordata; Class Ascidiacea, common local name “piure” or sea squirt; a filter-feeder (plankton and suspended particles) sessile species; may play an important role in monitoring domoic acid (DA) the principal toxic component of Amnesic Shellfish Poisoning (ASP). Significant DA concentrations have been determined in tunicate samples, collected during a recent ASP outbreak in Bahía Inglesa, an important scallop ( Argopecten purpuratus) farming area. Several infaunal species were tested for the presence of DA, in addition to the usual scallop monitoring programme. DA was found at sub-toxic levels in filtering bivalves such as mussels ( Mytilus chilensis), large mussels ( Aulacomya ater) and clams ( Protothaca thaca) (6.4, 5.4 and 4.7 μg DA/g tissue respectively). Of particular interest was the observation of significant accumulations of toxic Pseudo-nitzschia sp. diatoms in the internal siphon and atrium spaces of the tunicate. Toxin distribution within major tunicate organs was heterogeneous with 8.7–15.5 μg DA/g in edible tissues, 14.9–17.9 μg DA/g in the fecal material and 13.6–32.7 μg DA/g in the gut content. DA was determined by HPLC–UV and confirmed by diode-array detection and LC–MS/MS analysis. This is the first report of the presence of DA in a tunicate that is regularly consumed by coastal populations. These results confirm the need to include these organisms in sanitation programs for marine toxins.