Toxic Pseudo-nitzschia multistriata (Bacillariophyceae) from the Gulf of Naples: morphology, toxin analysis and phylogenetic relationships with other Pseudo-nitzschia species

Abstract

The genus Pseudo-nitzschia includes a number of species responsible for blooms in coastal and open waters worldwide. P. delicatissima, a species reported as a potential source of amnesic shellfish poisoning (ASP), reaches high concentrations in the Gulf of Naples (Mediterranean Sea), where it regularly blooms in spring and, at times, in autumn. We assessed both intra-and interindividual genetic diversity of this species before and during a bloom (February to April 2001) by sequencing the internal transcribed spacer regions (ITS1 and ITS2) and the 5.8S gene of the nuclear ribosomal DNA. PCR products obtained from 70 strains were cloned and several ITS copies were sequenced for each strain to assess intra-individual polymorphism. Phylogenies showed the presence of 5 distinct, well-supported lineages within what was considered to be a single morphospecies. Genetic diversity was higher in pre-bloom conditions, while all strains collected at the height of the bloom clustered within a single major clade. Ultrastructural investigations carried out on selected strains revealed morphological features slightly different from the ones typical for P. delicatissima only in 1 strain, outside the major clade. Our results, supported by the analysis of the hypervariable domains of LSU (large subunit) rDNA carried out on selected strains, suggest the presence of cryptic diversity within P. delicatissima. Such diversity could in fact explain the existence of toxic and nontoxic strains within the same species and the occasional mismatches between 'species-specific' molecular probes and target species. KEY WORDS: Diatoms · Pseudo-nitzschia delicatissima · ITS nDNA · Cryptic diversity · BloomResale or republication not permitted without written consent of the publisher

Spatio-temporal distribution of the dominant Diatom and Dinoflagellate species in the Bay of Tunis (SW Mediterranean Sea)

“…OUNISSI & FRÉHI (1999) reported high abundances of Pseudo-nitzschia multiseries (>1000 cells ml -1 ) on the eastern coast of Algeria. Recently, ORSINI et al (2002) confirmed the presence of toxic species of Pseudo-nitzschia in the Tyrrhenian coasts. This genus requires further investigation in the Bay of Tunis.…”

Pseudo-nitzschia physiological ecology, phylogeny, toxicity, monitoring and impacts on ecosystem health

“…The toxin has now been detected in shellfish from many European countries, particularly UK, Ireland and France (EFSA, 2009). European strains of several Pseudo-nitzschia species have been found to be toxic: P. australis, P. calliantha, P. galaxiae, P. multiseries, P. multistriata, P. pseudodelicatissima, P. pungens and P. seriata (Table 3; Lundholm et al, 1994;Sarno and Dahlmann, 2000;Cusack et al, 2002;Orsini et al, 2002;Fehling et al, 2004a,b;Moschandreou et al, 2010;E. Keady, pers.…”

Pseudo-nitzschia Peragallo (Bacillariophyceae) diversity and domoic acid accumulation in tuberculate cockles and sweet clams in M’diq Bay, Morocco

“…calliantha, P. delicatissima, P. fraudulenta, P. multistriata, P. pungens, P. galaxiae, P. cacciantha, P. mannii, P. arenysensis (QUIJANO-SCHEGGIA et al 2008 and P. australis (ZAPATA et al 2011). In Italy, P. calliantha and P. delicatissima (CAROPPO et al 2005, ZINGONE et al 2006, P. galaxiae, P. multistriata (SARNO and DAHLMANN 2000), ORSINI et al 2002, CERINO et al 2005, ZINGONE et al 2006, P. fraudulenta (ZINGONE et al 2006) were identified. Pseudo-nitzschia calliantha (SPATHARIS et al 2007) was identified in Greece.…”