Prorocentrum borbonicum sp. nov. (Dinophyceae), a new toxic benthic dinoflagellate from the southwestern Indian Ocean

Abstract

A new toxic benthic marine dinoflagellate, Prorocentrum borbonicum Ten-Hage, Turquet, Quod, Puiseux-Dao & Couté sp. nov., isolated from the fringing coral reef of St Leu from La Réunion Island (France, southwest Indian Ocean) is described from light and scanning micrographs. The species was identified based on shape, size, surface micromorphology, ornamentation of thecal plates, and architecture of the periflagellar area and intercalary band. Prorocentrum borbonicum is a small species (18–24 μm long and 16–20 μm wide) with a broadly ovate shape. Thecal depressions are numerous (950–1020 per valve). Two sizes of valve pores were recognized: large pores, which are scattered on the valve surface, except in the central area, and smaller pores, which are localized chiefly in the centre of the valve and at the periphery, along the intercalary band. The periflagellar area is V-shaped and accommodates a flagellar pore and an auxiliary pore, the latter being the smaller of the two. Prorocentrum borbonicum is photosynthetic, containing a golden-brown chloroplast with a centrally located pyrenoid. Prorocentrum borbonicum produces toxic compounds that are lethal to mice. The symptoms induced in mice by methanolic crude extracts indicate neurotoxicity.