Chlorophyll c pigment patterns in 18 species (51 strains) of the genus Pseudo-nitzschia (Bacillariophyceae)

Abstract

The pigment composition of 18 species (51 strains) of the pennate diatom Pseudo-nitzschia was examined using HPLC. The carotenoid composition was typical for diatoms, with fucoxanthin (the major xanthophyll), diadinoxanthin, diatoxanthin, and β,β-carotene. However, a diverse array of chl c pigments was observed in the studied strains. All Pseudo-nitzschia strains contained chl a and chl c2, traces of Mg-2,4-divinyl phaeoporphyrin a5 monomethyl ester (MgDVP), and traces of a chl c2–like pigment originally found in the haptophyte Pavlova gyrans. The distribution of chl c1 and chl c3 was variable among species (present in seven and 14 species, respectively). Based on chl c distribution, three major pigment types were defined: type 1 (chl c1 + c2, four species: P. australis, P. brasiliana, P. multiseries, and P. seriata), type 2 (chl c1 + c2 + c3, three species: P. fraudulenta, P. multistriata, and P. pungens), and type 3 (chl c2 + c3, 11 species: P. arenysensis, P. calliantha, P. cuspidata, P. decipiens, P. delicatissima, P. galaxiae, P. mannii, P. pseudodelicatissima, P. subcurvata, P. cf. subpacifica, and a novel Pseudo-nitzschia species). Type 1 and 2 species also shared the absence of a particular morphological character, the central nodule in the raphe, with the only exception of P. fraudulenta. The implications of such pigment diversity in chemotaxonomy, HAB monitoring, ecology, and phylogeny of Pseudo-nitzschia species are discussed.