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General Session 4: Marine environment, ecosystem & sustainability |
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Distribution of the diatom Nitzschia navis-varinginca (Bacillariophyceae), a domoic acid producer from Malaysian waters
GS4-32-S
Suh Nih Tan* , Bachok Marine Research Station, Institute of Ocean and Earth Sciences, University of Malaya, 16310 Bachok, Kelantan, Malaysia
Sing Tung Teng, Faculty of Resource Science and Technology, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak
Hong Chang Lim, Tunku Abdul Rahman University College, Johor Branch, 85000 Segamat, Johor, Malaysia
Yuichi Kotaki, School of Marine Biosciences, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0373, Japan
Stephen S. Bates, Fisheries and Oceans Canada, Gulf Fisheries Centre, P.O. Box 5030, Moncton, New Brunswick E1C 9B6, Canada
Chui Pin Leaw, Bachok Marine Research Station, Institute of Ocean and Earth Sciences, University of Malaya, 16310 Bachok, Kelantan, Malaysia
Po Teen Lim, Bachok Marine Research Station, Institute of Ocean and Earth Sciences, University of Malaya, 16310 Bachok, Kelantan, Malaysia
Presenter Email: danielle_tsn0421@hotmail.com
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| Domoic acid (DA), a neurotoxin that binds irreversibly to the glutamate receptor of the vertebrate nervous system is responsible for amnesic shellfish poisoning (ASP) in human illness after consuming the DA contaminated shellfish mollusks. While toxic diatom Nitzschia navis-varingica is widely distributed in the Southeast Asian region, information on its occurrence, distribution and toxicity in Malaysian coastal waters are limited. The aim of this study was to investigate the distribution of the toxigenic N. navis-varingica along the coastal and brackish waters of Peninsular Malaysia, and their morphology, genetics and toxin production were further investigated. A total of 82 strains of N. navis-varingica were established, and their identity were confirmed morphologically using transmitted electron microscope. Frustule morphological characteristics of the Malaysian strains examined are identical to that of N. navis-varingica but consisted a sightly higher density of areolae in 1 μm (4–7 areolae). Both LSU and ITS rDNAs phylogenetic inferences supported the grouping of all the strains in the N. navis-varingica clade, with high sequence homogeneity in the LSU rDNA (0–0.3%). DA and its geometrical isomers, isodomoic A (IA) and isodomoic B (IB), were detected in the strains using FMOC-LC-FLD, and subsequently confirmed by LC–MS/MS. The cellular DA content of toxic strains ranged from 0.37 to 11.06 pg/cell. Interestingly, DA-IA type was first discovered in this study. The study indicates that the toxigenic N. navis-varingica is widely distributed in Malaysian waters, suggesting the potential risk of ASP and the safety of seafood products requires further evaluation. Keywords: Domoic acid; Amnesic shellfish poisoning; Nitzschia naris-varinginca; brackish; LSU rDNA; ITS2 |
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