Two new ASP toxin production types in strains of Nitzschia navis-varingica from the Philippines

Nitzschia navis-varingica, a diatom widely distributed in brackish waters of Japan and Southeast Asia, was found to pro- duce domoic acid (DA) and its derivatives isodomoic acids A (IA) and B (IB) as the major toxin components. The toxin composi- tion of N. navis-varingica has previously been classified into three types namely DA type (produces DA and IB with an IB ratio of less than 10%), DA-IB type (the IB ratio is 20-80%) and IA-IB type (produces no DA). In the latter type, the ratio of IB tends to be higher in southern areas. In order to investigate more detailed distribution of ASP toxin types of N. navis-varingica, a screening was performed in three localities on Luzon Island, the Philippines. All isolates from one locality, Bulacan, were the DA-IB type. Isolates from the other two localities, Alaminos and Cavite, were found to make up two different and never described toxin composition types, the IB and the DA-IA-IB types, respectively. Sub-strains established from a representative parent of each new toxin composition type showed the same toxin composition as the parental strains. These results suggest that ASP toxin compo- sition types of N. navis-varingica are more complex than previously reported.