Isolation and Characterization of Potential Neurotoxic Cyanobacterial Metabolites Associated with Intoxication of Captive Bottlenose Dolphins in the Florida Keys
Doctor of Philosophy (PhD)
First Advisor's Name
John P. Berry
First Advisor's Committee Title
Second Advisor's Name
Second Advisor's Committee Title
Third Advisor's Name
Anthony P. DeCaprio
Third Advisor's Committee Title
Fourth Advisor's Name
Piero R. Gardinali
Fourth Advisor's Committee Title
Fifth Advisor's Name
Fifth Advisor's Committee Title
Sixth Advisor's Name
Sixth Advisor's Committee Title
Lyngbya, Neolyngbya, cyanobacteria, Harmful Algal Bloom, Brevetoxin, Eudesmacarbonate, Tursiops truncatus, Bottlenose Dolphins, Intoxication, Florida Keys, Danio rerio, Zebrafish, Neurotoxicity
Date of Defense
Bottlenose dolphins (Tursiops truncatus) living in captivity in the Florida Keys have recently been observed grazing macrophytic algal communities, and particularly, filamentous cyanobacteria, within their enclosures, and subsequently presenting apparent signs of intoxication. Collections of a mixed assemblage of marine filamentous cyanobacteria were morphologically related to the taxonomically complex and toxigenic polyphyletic genus, Lyngbya, sensu lato. Phylogenetic characterization, using 16S rDNA methods, identified an undescribed member of the recently accepted genus Neolyngbya (Oscillatoriales) among Neolyngbya arenicola, and an unknown Oscillatoriacean species within a poorly resolved clade clustering between the genera Limnoraphis and Capilliphycus.
A dual approach was subsequently utilized to identify a putative neurotoxic metabolite from cyanobacteria associated with the intoxication events. Initial chemical screening was unable to detect recognized algal and cyanobacterial neurotoxins including anatoxin-a, brevetoxin-2 (PbTx-2), domoic acid, b-methylamino-L-alanine and saxitoxin. In tandem, however, toxicity testing – and concomitant bioassay-guided fractionation- based on early life stages (i.e., embryo, larvae) of the zebrafish (Danio rerio) as a vertebrate toxicological model, was employed to identify relevant metabolites from cyanobacterial collections. Using the latter approach, relevant toxicity including, particularly, endpoints of neurotoxicity were identified for extracts and subsequent fractions. Apparent neurotoxicity was comparatively assessed against the recognized algal neurotoxin, PbTx-2. Crude lipophilic extracts, and subsequent chemical fractions, notably aligned with observed neurotoxic effects of PbTx-2. Further bioassay-guided fractionation enabled purification and structural elucidation of a previously undocumented, neurotoxic metabolite, (4S,5R,6R,7S,10S)-eudesman-(4S,6R)-cyclocarbonate (i.e., eudesmacarbonate), from the mixed filamentous cyanobacteria (dominated by Neolyngbya sp.) which, may, in turn, contribute to the observed intoxications of captive dolphins.
Lydon, Christina, "Isolation and Characterization of Potential Neurotoxic Cyanobacterial Metabolites Associated with Intoxication of Captive Bottlenose Dolphins in the Florida Keys" (2020). FIU Electronic Theses and Dissertations. 4388.
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