Date of Award
Alison Robertson, Ph.D.
Ciguatera poisoning (CP) is one of the most prominent seafood-borne illnesses worldwide, affecting between 25,000–500,000 people annually. Ciguatera is caused by the ingestion of seafood contaminated with algal-derived ciguatoxins (CTX), the precursors of which are produced by benthic and toxigenic dinoflagellates in the genera Gambierdiscus and Fukuyoa. These compounds enter marine food webs through herbivory and are subsequently transferred to higher trophic levels, undergoing complex metabolic biotransformations, which produce structurally related CTX derivatives. Consumption of CTX induces a variety of severe neurological, gastrointestinal, and/or cardiovascular symptoms beginning within hours and lasting for weeks to months following exposure. Despite the impact of CP on human health, marine resources, and the socioeconomic stability of coastal communities, relatively little is known about the complex movement or metabolic fate of CTX within individual organisms and throughout marine food webs. While progress has been made in studying the derivatives, distribution, and toxicology of CTXs in the Pacific, relatively little has been reported for the CTXs that occur in the Caribbean (C-CTX). To fill this knowledge gap, this dissertation focuses on improving methods for the detection and identification of C-CTX in Caribbean herbivorous reef fish (Chapter II) – a critical, yet understudied, link in the fate of CTX in marine food webs. In Chapter III I employed a multi-dietary tracer approach using stable isotope and fatty acid analyses to explore the dietary niches of Caribbean herbivorous fish as a prerequisite to understanding the trophic and ecological drivers potentially affecting toxin accumulation in lower marine food webs. Metabolic biotransformation pathways of C-CTX were evaluated in ecologically relevant fish species from the northern Gulf of Mexico (Chapter IV) using an in vitro approach to better understand the toxin profiles and fate of CTX derivatives in marine food webs. Applying similar microsomal and analytical tools to study biotransformation of the structurally and toxicologically related brevetoxin (BTX) from the pelagic dinoflagellate, Karenia brevis, we not only validated the approaches and results of our research into C-CTX metabolism but also contributed to work on BTX, tentatively identifying several novel metabolites in fish and providing evidence of interspecific variation in BTX metabolism (Chapter V). Through the novel work presented in this dissertation, we have gained new insights into the chemical diversity of C-CTX and BTX in marine fish and trophic niche differentiation potentially driving differences in exposure and toxicity. This knowledge provides critical information to marine resource and human health managers to aid in the biomonitoring and analysis of seafood products, predicting the movement and fate of C-CTX and other harmful algae toxins in marine ecosystems, and prevention of human illness associated with the consumption of contaminated fish.
Gwinn, Jessica K., "Linking the metabolic and ecological fate of Caribbean ciguatoxins and related neurotoxins in reef herbivores" (2023). Theses and Dissertations. 155.
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