Toxicon 49 (2007) 1182–1192 Toxicity to medaka fish embryo development of okadaic acid and crude extracts of Prorocentrum dinoflagellates Nicolas Escoffier a , Julien Gaudin a , Karim Mezhoud a , He´le`ne Huet b , Sophie Chateau-Joubert b , Jean Turquet c , Franc - ois Crespeau b , Marc Edery a,Ã a USM 0505 Ecosyste`mes et Interactions Toxiques, Muse´um National d’Histoire Naturelle, RDDM, 12 rue Buffon, F-75231, Paris Cedex 05, France b Laboratoire d’Anatomie Pathologique, Ecole Nationale Ve´te´rinaire d’Alfort, 7 Avenue du Ge´ne´ral de Gaulle, F-94704 Maisons-Alfort Cedex, France c ARVAM, 14, Rue du Stade de l’Est, F-97490 Sainte Clotilde, La Re´union, France Received 13 December 2006; received in revised form 5 February 2007; accepted 6 February 2007 Available online 24 February 2007 Abstract Chronic and subchronic toxicity following exposure to the DSP (Diarrhetic shellfish poisoning) toxin okadaic acid (OA) is receiving increasing attention as a public human health biohazard. However information on ecological impacts induced by proliferation of the OA producing dinoflagellate Prorocentrum is scarce. In order to analyse the toxicity of these substances, in vivo experiments were conducted on medaka fish (Oryzias latipes) embryos used as an experimental model. The study was focused on two strains of benthic Prorocentrum species, P. arenarium and P. emarginatum, naturally found in the Indian Ocean. Sample extracts (crude extracts, CE) were obtained from algal cultures and their toxic potential was explored. Their OA (and derivatives) content was evaluated by two methods: one based on chemical analysis using HPLC- MS, the other based on screening the inhibiting effect on protein phosphatase PP2A. P. arenarium extracts inhibit PP2A and the active toxin was confirmed as being OA by HPLC-MS. In contrast, P. emarginatum showed negative results regardless of the method used. The development of medaka fish embryos kept in medium containing pure OA or Prorocentrum CE was examined. Survival rates were reduced up to 100% depending on the concentrations used of both OA and CE of P. arenarium, while no effect was observed with CE of P. emarginatum. Anatomopathological studies of surviving embryos indicate that OA treatment resulted in significant increases in liver and digestive tract areas compared to controls. P. arenarium treated surviving embryos exhibited significant quantitative increases of global body and vitellus areas. Together, our results indicate that the toxic effects to medaka embryos development of pure OA and P. arenarium extracts containing OA are distinguishable. The differences may indicate the presence of additional toxic substance(s) (or molecules able to modulate OA impact) in the P. arenarium CE that probably are not present in P. emarginatum. r 2007 Elsevier Ltd. All rights reserved. Keywords: Okadaic acid; Prorocentrum; Medaka; Diarrhetic shellfish poisoning (DSP); Anatomo-pathological studies 1. Introduction Diarrhetic shellfish poisoning (DSP) is a human gastrointestinal illness caused by a group of polyether ARTICLE IN PRESS www.elsevier.com/locate/toxicon 0041-0101/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.toxicon.2007.02.008 Ã Corresponding author. Tel.: +33 1 40 79 31 79; fax: +33 1 40 79 35 94. E-mail address: medery@mnhn.fr (M. Edery).