Diversity and Toxicity of the Genus Meunier in Brazil, and Detection of 44-Methyl Gambierone in .

is a genus of marine benthic dinoflagellates which is widely distributed in tropical and temperate zones. Toxicity has been reported in selected species, although the identity of causative compounds is still controversial. In this study, we investigated the taxonomical and toxicological aspects of species from Brazil. Since light- and electron microscopy-based morphology was not enough to distinguish small-celled species, ITS and LSU D1-D3 phylogenetic analyses were used for species definition. Cultures of and were established from samples collected along the northeastern Brazilian coast, the first record of both species in South Atlantic waters. Cultures of and were also established and exhibited acute toxicity to adults of , while and were non-toxic. The presence of 30 yessotoxin analogues, 7 metabolites of and 44 metabolites was screened in 14 strains of . 44-methyl gambierone (formerly referred to as MTX3) and a new isomer of this compound were detected only in , using both low- and high-resolution LC-MS/MS. To our knowledge, this is the first report of gambierone analogues in dinoflagellates other than ; the role of in ciguatera poisoning thus deserves to be considered in further investigations.