Paralytic Shellfish Toxins by Alexandrium (Dinophyceae) in seawater, cultures and bivalve molluscs: case study in Sicily.

In the last years the presence of algal toxins in the aquatic environment has attracted great interest, with increasing geographical spread in marine waters of toxic dinoflagellates producing Harmful Algal Blooms. Marine biotoxins can accumulate in filter-feeders bivalve molluscs, such as the Mediterranean mussel Mytilus galloprovincialis, that ingest large quantities of planktonic organisms. Thus, molluscs may represent a source of potential health problems being vectors of toxins that are transferred to humans through their consumption. Birds and fish can also be affected by PSP toxins and bivalve species exhibit a wide range of responses and sensitivities to them. HABs impact on aquaculture may give also economic losses due to temporary closures of contaminated shellfish harvest and marketing. Toxic blooms of dinoflagellates, such as several Alexandrium species, A. minutum and A. catenella, re-named in 2014 as A. pacificum, and occasional contamination of mussels, are reported in this study from a Mediterranean area, in the Ionian coast of Sicily (Syracuse Bay, 2011-2014) where shellfish farms are located. These species produce a suite of potent PSP neurotoxins (Paralytic Shellfish Poisoning), known collectively as "saxitoxins" which include pure saxitoxin (STX), neosaxitoxin (NSTX), gonyautoxins (GTX), and other derivatives, specifically binding the voltage-gated sodium channel, blocking the passage of nerve impulses with consequent paralysis. In the framework of our project on algal toxins, supported by the Italian Ministery of Heath (Project RF-IZI-2008-1139874, Algal toxins contaminating water and fish products), the taxonomic identity of the two PSP-species was confirmed through the use of ribosomal markers (5.8S rDNA e ITS regions) in real time-PCR on field samples. Toxin profiles of the Alexandrium Ionian clones isolated from Sicily were obtained by HPLC chemical method and compared with the available data on PSP-toxins in mussels from our target location. Toxins profiles in the different samples revealed the presence of gonyautoxins (GTX1,4, GTX2,3, GTX5), C-group toxins (C1,2), and minor percentages of saxitoxins (STX, dcSTX).