First report of toxic Prorocentrum rhathymum (Dinophyceae) and its pigment composition from coastal waters of the eastern Arabian Sea

Abstract

Prorocentrum rhathymum, a toxic dinoflagellate, was isolated for the first time from coastal waters of the eastern Arabian Sea. Batch cultures were grown and cell pellets were extracted in methanol for analysis of algal toxin. LCMS/MS studies exhibited presence of dinophysis toxin 1 (DTXl) with no detectable Okadaic Acid. Growth rates varied between 0.23 day sup(-1)(exponential phase) and 0.05 day sup(-1)(decline phase). Phytoplankton pigment studies revealed the presence of chlorophyll a, chlorophyll clc2, peridinin and diadinoxanthin. The average chlorophyll a production was found to be 163 pg cell sup(-1) and ranged between 73 to 223 pg cell sup(-1). Peridinin, the marker pigment of dinoflagellates, had an average value of 55 pg cell sup(-1) and ranged between 30-114 pg cell sup(-1). Further studies to identify its molecular diversity along with toxicity are presently underway. To our knowledge, this is the first report of successful isolation and culturing of Prorocentrum rhathymum from this region.