Date of Award


Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy



First Advisor

Dr. Kevin J. James


This research was initiated to examine the Diarrhetic Shellfish Poisoning (DSP) toxin profiles in mussels (Mytilus edulis) in south-west Ireland. Extensive sampling and testing of shellfish was conducted during the toxic periods of 1991 to 1994. This was the most comprehensive study ever undertaken of toxin profiles in shellfish from a single cultivation area.

A new toxin named dinophysistoxin-2 (DTX-2), which is an isomer of okadaic acid (OA), was the major toxin during prolonged DSP episodes. This toxicity in shellfish occuired soon after high cell counts of Dinophysis acuta were observed. As well as seasonal variability in toxin levels, substantial variations were also observed both horizontally and vertically, within the water column.

DTX-2 was isolated from mussel hepatopancreas using extensive chromatographic procedures. It was found to be a potent inhibitor of protein phosphatase and its activity is similar to that of OA. Another new compound, code-named DTXB-91, was also isolated in small quantities. This was confrrmed to be a diarrhetic toxin from its potent inhibition of protem phosphatase activity and was determined to be an isomer of okadaic acid by LC-MS/MS analysis. These potent bioactive compounds have been made available to a number of research institutes for biochemical studies of cellular reactions.

The confirmation of DTX-2 in Portuguese shellfish has been made possible by the availability of toxin standard. Furthermore, reports of the presence of DTX-2 in the dinoflagellate, Prorocentrum lima, has been shown to be incorrect.

Two commercially available ELISA methods and a rapid cytotoxicity test, designed to detect okadaic acid, have been evaluated for their potential use as a DSP toxin screening method for European shellfish.

Four fluorescent HPLC methods, used to analyse for DSP toxins in shellfish, have been evaluated. 1-Bromoacetylpyrene (BAP) has been successfully used as a derivatising agent for the analysis of okadaic acid, DTX-1, DTX-2 and DTXB-91.

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