Harmful Algae 4 (2005) 21–31 Paralytic shellfish toxin profile in strains of the dinoflagellate Gymnodinium catenatum Graham and the scallop Argopecten ventricosus G.B. Sowerby II from Bah´ ıa Concepción, Gulf of California, Mexico C.J. Band-Schmidt a , J. Bustillos-Guzmán a,∗ , I. Gárate-Lizárraga b , C.H. Lechuga-Devéze a , K. Reinhardt c , B. Luckas c a Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Apdo. Postal 128, La Paz, B.C.S. 23000, Mexico b Departamento de Plancton y Ecolog´ ıa Marina, Centro Interdisciplinario de Ciencias Marinas (CICIMAR-IPN), Apdo. Postal 592, La Paz, B.C.S. 23000, Mexico c Department of Food Chemistry, Faculty of Biology and Pharmacy, Friedrich-Schiller University, Dornburgerstraße 25, Jena 07743, Germany Received 22 December 2002; received in revised form 24 March 2003; accepted 19 October 2003 Abstract Gymnodinium catenatum Graham is a paralytic shellfish poison (PSP) producer that was described for the first time from the Gulf of California in 1943. During the last decade, its distribution along the Mexican Pacific coastline has increased. In Bah´ ıa Concepción, a coastal lagoon on the western side of the Gulf of California, G. catenatum has been linked to significant PSP concentrations found in mollusks. In this study, we describe the saxitoxin profile of 16 strains of G. catenatum, and catarina scallops (Argopecten ventricosus) from Bah´ ıa Concepción. Toxins were analyzed by HPLC with post-column oxidation and fluorescence detection. The average toxicity of the G. catenatum strains was 26.0 ± 6.0 pg and 28.0 ± 18.0 pg STX eq/cell after 17 and 22 days of growth, respectively. Ten toxins were recorded, but only dcSTX, dcGTX2, dcGTX3, C1, and C2 were always present in all strains at both growth stages. Since toxin profiles in scallops were similar to the cultures, biotransformations are not significant in catarina scallop. NeoSTX, GTX2, GTX3, and B2 were present in some G. catenatum strains and their presence varied with the age of the culture. In scallop samples, dcSTX, dcGTX2, and dcGTX3 were the most abundant toxins, and from the C-toxin group, only C2 was found. This unique toxin profile can be used as a biomarker for this population, when compared with strains of G. catenatum from other geographic regions. © 2003 Elsevier B.V. All rights reserved. Keywords: Argopecten ventricosus; Dinoflagellate; Gulf of California; Gymnodinium catenatum; Paralytic shellfish poisoning; Scallop ∗ Corresponding author. Tel.: +52-612-12-5-84-24; fax: +52-612-12-5-36-25. E-mail address: jose@cibnor.mx (J. Bustillos-Guzm´ an). 1. Introduction Gymnodinium catenatum Graham was first de- scribed in the Gulf of California by Graham (1943). Forty years later, this dinoflagellate was responsible for a red tide in the Mazatlán area and was re- 1568-9883/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.hal.2003.10.004