AME 64:197-203 (2011)  -  DOI:

Considerations on the toxigenic nature and prey sources of Phalacroma rotundatum

Sonsoles González-Gil1,2,*,**, Gemita Pizarro1,3,**, Beatriz Paz1,4, Lourdes Velo-Suárez1,5, Beatriz Reguera1

1Instituto Español de Oceanografía, Centro Oceanográfico de Vigo, Aptdo. 1552, 36200 Vigo, Spain
2Present address: Instituto Español de Oceanografía, Corazón de María 8, 28002 Madrid, Spain
3Present address: Instituto de Fomento Pesquero-CEQUA, Enrique Abello 0552, Casilla 101, Punta Arenas, Chile
4Present address: CACTI, Universidade de Vigo, Campus Lagoas-Marcosende 15, 36310 Vigo, Spain
5Present address: Woods Hole Oceanographic Institution, 266 Woods Hole Rd, Woods Hole, MA 02543, USA
*Email: **These authors contributed equally to this work

ABSTRACT: The heterotrophic dinoflagellate Phalacroma rotundatum (Claparède & Lachman) Kofoid & Michener is considered a toxic species, but there is controversy about its toxigenic nature. In the present study, about one-third of the toxin analyses done with liquid chromatography-mass spectrometry (LC-MS) of P. rotundatum specimens picked from field populations in Galicia (NW Spain) between 2003 and 2005 revealed traces of lipophilic toxins—okadaic acid (OA) and/or dinophysistoxin-2 (DTX2) and/or pectenotoxin-2 (PTX2) (if any)—that mimicked the toxin profile of co-occurring toxigenic mixotrophic species of Dinophysis (D. acuminata, D. acuta, and D. caudata). Thus, during the period of study, P. rotundatum was never a relevant contributor to diarrhetic shellfish poisoning (DSP) toxins contaminating shellfish resources in Galicia. Observations of phycoerythrin-like autofluorescence in P. rotundatum and in its co-occurring potential ciliate prey—Tiarina cf. fusus—led to the suspicion that P. rotundatum had taken up toxins by feeding on this ciliate prey that had previously fed on Dinophysis spp. Nevertheless, toxins in P. rotundatum specimens with orange auto­fluorescence were under detection levels, and the source of these orange pigments may be a prey different from Dinophysis spp. (e.g. Myrionecta spp.). New results here add evidence to suggest that P. rotundatum does not produce toxins de novo, but acts as a vector from toxin-containing prey to shellfish, and that M. rubra may be one of its potential ciliate prey. Conclusive testing of these hypotheses is now under investigation with laboratory cultures of Dinophysis and Phalacroma spp. and M. rubra.

KEY WORDS: Phalacroma rotundatum · Dinophysis spp. · Diarrhetic shellfish poisoning · DSP · Pectenotoxins · PTX · Lipophilic shellfish toxins

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Cite this article as: González-Gil S, Pizarro G, Paz B, Velo-Suárez L, Reguera B (2011) Considerations on the toxigenic nature and prey sources of Phalacroma rotundatum. Aquat Microb Ecol 64:197-203.

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