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Seven strains of Protoceratium reticulatum isolated from Spain and the USA were cultured in the laboratory. Yessotoxins (YTXs) quantification and toxin profile determination were performed by LC-FLD and LC-MS/MS. The four Spanish strains were found to produce YTX and known YTX analogs, however, YTX was not detected in any of the three USA strains. Among the strains that produced YTXs, toxin production ranged between 2.9 and 28.6pg/cell. The YTX profile was substantially different between strains, in three out of the four Spanish strains YTX was the main toxin and in the fourth homoYTX was the prominent toxin. This work demonstrates that YTX is not always the main toxin in P. reticulatum and a high variability in YTX amounts and profile found in other locations is confirmed.

In the present study the geographical distribution, abundance and composition of Gambierdiscus was described over a 600km longitudinal scale in the Canary Islands. Samples for cell counts, isolation and identification of Gambierdiscus were obtained from five islands (El Hierro, Tenerife, Gran Canaria, Fuerteventura and Lanzarote). Average densities of Gambierdiscus spp. between 0 and 2200cellsg blot dry weight of macrophyte were recorded. Morphological (light microscopy and SEM techniques) and molecular analyses (LSU and SSU rDNA sequencing of cultures and single cells from the field) of Gambierdiscus was performed. Five Gambierdiscus species (G. australes, G. caribaeus, G. carolinianus, G. excentricus and G. silvae), together with a new putative species (Gambierdiscus ribotype 3) were identified. These results suggest that some cases of CFP in the region could be associated with the accumulation of ciguatoxins in the marine food web acquired from local populations of Gambierdiscus. This unexpected high diversity of Gambierdiscus species in an area which a priori is not under risk of ciguatera, hints at an ancient settlement of Gambierdiscus populations, likely favored by warmer climate conditions in the Miocene Epoch (when oldest current Canary Islands were created), in contrast with cooler present ones. Currently, warming trends associated with climate change could contribute to extend favorable environmental conditions in the area for Gambierdiscus growth especially during winter months.

A cell cycle-analysis method based on morphological recognition of cytokinesis and sulcal list regeneration was chosen to estimate in situ division rates (µ) of 4 dinoflagellate species of the genus Dinophysis, associated with diarrhetic shellfish poisoning (DSP), following 2 different models. Sampling over 24 h was conducted on 4 mini-cruises in the Galician rías during spring and autumn proliferations of these species. Frequencies of paired and recently divided cells in integrated water samples (0 to 20 m) were measured at 30, 60, or 120 min intervals. Cellular division was phased in D. acuminata, D. acuta, D. caudata and D. tripos, but the shape of the phase fraction curves and the values of estimated division rates varied considerably between seasons and cruises for the same species. Frequencies of paired plus recently divided cells were maximal at dawn in D. acuminata, and 2 to 3 h later in the other species. The results presented here confirm that the cytokinetic (paired) phase can be very fast in Dinophysis spp. (0.3 to 2.7 h), but sulcal list regeneration was shown to be a more stable process and an unambiguous marker of cellular division. This 'postmitotic index' allowed estimates of µ at low field concentrations (10 2 to 10 3 cell l -1 ) of the target species and required a short time for sample processing (1 to 2 h per sample). Moderate (0.24) to high (0.57) values of µ were found under oceanographic conditions considered unfavourable for growth of Dinophysis spp., and the phase in the population growth season seemed to be a key factor affecting this value. A critical revision of previous results of asynchronous division obtained in cell cycle studies of Dinophysis spp. is presented. It is suggested that monitoring the content of DNA per cell through the cell cycle in Dinophysis spp. is not a reliable method until a reasonable knowledge on the nuclear behaviour during sexual processes and other nonmitotic processes is available for these species, and that even accepting that mitosis is a non-return process, cell division may be arrested in one of its phases, adding further inconsistencies to µ measurements based on quantification of DNA per cell.