Morphology, molecular characterization and habitat preference of harmful Benthic dinoflagellate gambierdiscus (Dinophyceae) in Malaysia / Nurin Izzati Mustapa

Nurin Izzati , Mustapa (2020) Morphology, molecular characterization and habitat preference of harmful Benthic dinoflagellate gambierdiscus (Dinophyceae) in Malaysia / Nurin Izzati Mustapa. Masters thesis, Universiti Malaya.

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Abstract

Ciguatera fish poisoning (CFP) is a type of illness that causes human intoxication after consuming contaminated coral fishes. The neurotoxins, ciguatoxins, are produced by species of Gambierdiscus, one of the harmful benthic dinoflagellates. Identification of harmful dinoflagellate species is important to gain further insights into the global dispersion. In this study, morphological characteristics of species in the genus Gambierdiscus and their habitat preferences were investigated. Field sampling was undertaken at Pulau Rawa, Terengganu and Pulau Sibu, Johor. Single cells of Gambierdiscus were isolated and clonal cultures were established. Morphology of Gambierdiscus was examined by using light and scanning electron microscopes. Taxon sampling on the small subunit (SSU) and large subunit (LSU) ribosomal RNA genes (rDNAs) of Gambierdiscus was performed for phylogenetic reconstruction using branch swapping algorithm. Morphological character states were coded and mapped onto the molecular phylogenetic tree (MP tree) to investigate the character state evolution of Gambierdiscus species. Morphological information and the distribution of Gambierdiscus species were used to develop a comprehensive taxonomic database of Gambierdiscus, and a 3I web-based interactive identification key for species identification is presented. Based on the morphological observation and molecular characterization, G. caribaeus and G. balechii were identified in Pulau Rawa, Terengganu and a new ribotype designated as Gambierdiscus sp. type 7 was identified from Pulau Sibu, Johor. Field survey on the habitat preference of Gambierdiscus in Pulau Rawa was conducted; the results showed that Gambierdiscus abundance was positively correlated with the habitat of coral rubbles covered with turf algae as compared to other substrates. The epiphytic behavior of Gambierdiscus species towards macroalgae hosts were further examined in the laboratory setting. The results demonstrated that different species of Gambierdiscus preferred different macroalgal host and attachment of Gambierdiscus cells were also differed among various macroalgal hosts. This study provides an inventory of toxic Gambierdiscus species in Malaysian water, which is useful in identifying the hotspot of CFP in the region. Future study on the trophic transfer mechanism of the toxins in the marine food webs is needed to better understand the source and fate of these potent neurotoxins.

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