Harmful Algae: Pseudonitzschia (Bacillariophyceae) in southermost Argentina (Beagle Channel)
Supervisor: Emma Orive, Aitor Laza, Sergio Seoane (UPV/EHU)
Pseudo-nitzschia is a marine diatom genus which contains potentially toxic species, Domoic acid producers, agent responsible for the Amnesic Shellfish Poisoning syndrome. In the present study, by means of Morphometric and Molecular techniques, three Pseudo-nitzschia species from Beagle Channel, Argentina (54º50,38’S, 68º6,38’W) and three from the Equatorial Pacific, from the coastal area of Machala, Ecuador (3°15’1.29’’S, 80°0’9.5’’W) were identified. In both sampling sites publications on this topic are scarce or inexistent. Fourteen strains were isolated from natural samples; cultured cells were observed under Light Microscope (LM), Scanning Electronic Microscope (SEM) and Transmission Electronic Microscope (TEM). Finally molecular analysis, based on TS1-5.8S-ITS2 (internal transcribed spacer) and 28S (large subunit) rDNA regions, and pigment typification were performed. Five different genotypes were identified. The diverse techniques employed revealed the presence of, within the P. seriata complex (width > 3 μm), Pseudo-nitzschia australis and P. fraudulenta in Beagle Channel and P. pungens in Machala. Whereas from the P. delicatissima complex (width < 3 μm) P. multistriata and P. brasiliana were identified in Machala and P. plurisecta, a recently described genotype, in Beagle Channel. Five out of six of these species are potentially toxic for they are able to produce Domoic acid. ITS1-5.8S-ITS2 sequences of all P. plurisecta strains from Beagle Channel were the same and when compared to all the closest known species/strains resulted almost identical to those of the type species. P. plurisecta has been identified for the first time in Beagle Channel, whereas the other species had been previously described for this area. This is the first study performed in the area in which molecular analysis have been used for identification of species from the Pseudo-nitzschia genus.
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