Tim Harwood

Cawthron Institute | CI · Analytical Research and Method Development

Cyclic imines are a class of lipophilic shellfish toxins comprising gymnodimines, spirolides, pinnatoxins, portimines, pteriatoxins, prorocentrolides, spiro-prorocentrimine, symbiomines and kabirimine. They are structurally diverse, but all share an imine moiety as part of a bicyclic ring system. These compounds are produced by marine microalgal sp...

The genus Gambierdiscus produces an array of bioactive hydrophilic and lipophilic secondary metabolites that range in mode of action and toxicity. In this study, the metabolite fingerprint was mapped for thirteen Gambierdiscus, five Coolia and two Fukuyoa species (34 isolates) by assessing the production of 56 characterised secondary metabolites. G...

Paralytic shellfish poisoning is a worldwide problem induced by shellfish contaminated with paralytic shellfish toxins. To protect human health, a regulatory limit for these toxins in shellfish flesh has been adopted by many countries. In a recent study, mice were dosed with saxitoxin and tetrodotoxin mixtures daily for 28 days showing toxicity at...

Regulatory limits for toxins in shellfish are required to ensure the health of consumers. However, these limits also impact the profitability of shellfish industries making it critical that they are fit for purpose. Since human toxicity data is rarely available, the setting of regulatory limits is dependent on animal data which can then be extrapol...

It is important to decipher the diversity and distribution of benthic dinoflagellates, as there are many morphologically indistinct taxa that differ from one another in production of potent toxins. To date, the genus Ostreopsis comprises twelve described species, of which seven are potentially toxic and produce compounds presenting a threat to huma...

Background Given the recent detection of TTX in bivalve molluscs but the absence of a full collaborative validation study for TTX determination in a large number of shellfish samples, interlaboratory assessment of method performance was required to better understand current capabilities for accurate and reproducible TTX quantitation using chemical...

Identifying compounds responsible for the observed toxicity of the Gambierdiscus species is a critical step to ascertaining whether they contribute to ciguatera poisoning. Macroalgae samples were collected during research expeditions to Rarotonga (Cook Islands) and North Meyer Island (Kermadec Islands), from which two new Gambierdiscus species were...

Saxitoxin and its derivatives, the paralytic shellfish toxins (PSTs), are well known to be toxic to humans, and maximum permitted levels in seafood have been established by regulatory authorities in many countries. Monitoring of PSTs is typically performed using chemical methods which quantify the concentration of the individual PST analogues, of w...

Domoic acid (DA) is produced by almost half of the species belonging to the diatom genus Pseudo-nitzschia and causes amnesic shellfish poisoning (ASP). It is, therefore, important to investigate the diversity and toxin production of Pseudo-nitzschia species for ASP risk assessments. Between 2018 and 2020, seawater samples were collected from variou...

Paralytic shellfish toxins (PST) are found in the hepatopancreas of Southern Rock Lobster Jasus edwardsii from the east coast of Tasmania in association with blooms of the toxic dinoflagellate Alexandrium catenella. Tasmania’s rock lobster fishery is one of the state’s most important wild capture fisheries, supporting a significant commercial indus...

Regulatory limits for shellfish toxins are required to protect human health. Often these limits are set using only acute toxicity data, which is significant, as in some communities, shellfish makes up a large proportion of their daily diet and can be contaminated with paralytic shellfish toxins (PSTs) for several months. In the current study, feedi...

Molecular-based approaches for harmful algal bloom species, which can be difficult to identify by light microscopy, are important tools for detecting and predicting the blooms. In this study, 84 samples from Aotearoa/New Zealand coastal waters that contained Azadinium-like cells were analysed using an Amphidomataceae real-time PCR assay. Nineteen s...

Pinnatoxin G is a cyclic imine neurotoxin produced by dinoflagellates that has been reported in shellfish. Like other members of the pinnatoxin family, it has been shown to have its effects via antagonism of the nicotinic acetylcholine receptors, with preferential binding to the α7 subunit often upregulated in cancer. Because increased activity of...

Ciguatera poisoning has caused illnesses in New Zealand through the consumption of contaminated reef fish imported from Pacific Islands. In May 2020 five people became ill and one was hospitalised following the consumption of Fiji Kawakawa (camouflage grouper; Epinephelus polyphekadion). The fish was purchased in New Zealand but imported from Fiji....

Understanding the toxicity and production rates of the various secondary metabolites produced by Gambierdiscus and cohabitating benthic dinoflagellates is essential to unravelling the complexities associated with ciguatera poisoning. In the present study, a sulphated cyclic polyether, gambierone, was purified from Gambierdiscus cheloniae CAWD232 an...

Portimine, a recently identified cyclic imine produced by the dinoflagellate Vulcanodinium rugosum, has been described as a potent apoptotic agent in contrast to most of the cyclic imines that are well-known to be neurological toxins. As apoptosis can be a consequence of a high level of DNA lesions, we investigated the responses of portimine on sev...

Two different types of polycyclic ether toxins, namely brevisulcenals (KBTs) and brevisulcatic acids (BSXs), produced by the red tide dinoflagellate Karenia brevisulcata, were the cause of a toxic incident that occurred in New Zealand in 1998. Four major components, KBT-F, -G, -H, and -I, shown to be cytotoxic and lethal in mice, were isolated from...

Pectenotoxins (PTXs) are produced by Dinophysis spp., along with okadaic acid, dinophysistoxin 1, and dinophysistoxin 2. The okadaic acid group toxins cause diarrhetic shellfish poisoning (DSP), so are therefore regulated. New Zealand currently includes pectenotoxins within the DSP regulations. To determine the impact of this decision, shellfish bi...

The Tasmanian abalone fishery represents the largest wild abalone resource in the world, supplying close to 25% of the annual wild-caught global harvest. Prompted by the need to manage Paralytic Shellfish Toxin (PST) contamination of Blacklip Abalone (Haliotis rubra rubra) from east coast Tasmania, the uptake of toxins by this species is investigat...

Tetrodotoxin (TTX) is a heat-stable neurotoxin typically associated with pufferfish intoxications. It has also been detected in shellfish from Japan, the United Kingdom, Greece, China, Italy, the Netherlands and New Zealand. A recent European Food Safety Authority (EFSA) scientific opinion concluded that a level of <0.044 mg TTX/kg in marine bivalv...

Ciguatera fish poisoning (CFP) is prevalent around the tropical and subtropical latitudes of the world and impacts many Pacific island communities intrinsically linked to the reef system for sustenance and trade. While the genus Gambierdiscus has been linked with CFP, it is commonly found on tropical reef systems in microalgal assemblages with othe...

Rome, 19-23 November 2018, Food Safety and Quality Series, 9

Benthic dinoflagellates produce a diverse range of phycotoxins, which are responsible for intoxication events in marine fauna. This study assessed the hemolysis associated toxicities of six species of benthic dinoflagellates from the genera Coolia, Fukuyoa, Amphidinium and Prorocentrum. Results demonstrated that Amphidinium carterae, Coolia tropica...

Genetic diversity in marine microbial eukaryotic populations (protists) drives their ecological success by enabling diverse phenotypes to respond rapidly to changing environmental conditions. Despite enormous population sizes and lack of barriers to gene flow, genetic differentiation that is associated with geographic distance, currents, and enviro...

Up to 13.6 mg STX.2HCl equiv. kg⁻¹ of paralytic shellfish toxins (PST) have been found in the hepatopancreas of Southern Rock Lobster, Jasus edwardsii, on the east coast of Tasmania. Blooms of the toxic dinoflagellate Alexandrium catenella have been reported in this region since 2012. Experimental work was undertaken to improve the understanding of...

Background Paralytic shellfish toxins (PST) are a significant problem for the Tasmanian shellfish and Southern Rock Lobster (Jasus edwardsii) industries, and the introduction of a rapid screening test in the monitoring program could save time and money. Objective The aim was to perform a single-laboratory validation of the Neogen rapid test for PS...

Background: An ultrahigh-performance LC (UHPLC)-tandem MS (MS/MS) method for determination of paralytic shellfish poisoning toxins and tetrodotoxin (TTX) in bivalve molluscs was developed. To be used for regulatory testing, it needed to be validated through collaborative study. Objective: The aim was to conduct a collaborative study with 21 labo...

Approximately 70 species of Prorocentrum are known, of which around 30 species are associated with benthic habitats. Some produce okadaic acid (OA), dinophysistoxin (DTX) and their derivatives, which are involved in diarrhetic shellfish poisoning. In this study, we isolated and characterized Prorocentrum concavum and P. malayense from Broome in nor...

In marine ecosystems, dinoflagellates can become highly abundant and even dominant at times, despite their comparatively slow growth. Their ecological success may be related to their production of complex toxic polyketide compounds. Ostreopsis species produce potent palytoxin‐like compounds (PLTX), which are associated with human skin and eye irrit...

Tetrodotoxin (TTX) is a potent neurotoxin responsible for countless human intoxications and deaths around the world. The distribution of TTX and its analogues is diverse and the toxin has been detected in organisms from both marine and terrestrial environments. Increasing detections seafood species, such as bivalves and gastropods, has drawn attent...

http://hab.ioc-unesco.org/index.php?option=com_content&view=article&id=22&Itemid=0

Tetrodotoxin (TTX) is a potent neurotoxin responsible for many human intoxications globally. Despite its potency and widespread occurrence in taxonomically diverse species, the primary source of TTX remains uncertain. Paphies australis, an endemic clam found in New Zealand, has been found to contain TTX in several locations. However, it is unknown...

A new analogue of gambierone, 44-methylgambierone, was isolated from the benthic dinoflagellate Gambierdiscus australes collected from Raoul Island (Rangitahua/Kermadec Islands). This molecule has been previously reported as maitotoxin-3. The structure of 44-methylgambierone was elucidated using 1D- and 2D-nuclear magnetic resonance spectroscopy an...

Background: The recently identified alternate, or backdoor, pathway of DHT synthesis provides important novel information on androgen biosynthesis beyond the classical pathway. We report a rapid and versatile liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to simultaneously and accurately quantify key steroids in human or mouse se...

A range of natural products from marine invertebrates, bacteria and fungi have been assessed as leads for nature-inspired antifouling (AF) biocides, but little attention has been paid to microalgal-derived compounds. This study assessed the AF activity of the spirocyclic imine portimine (1), which is produced by the benthic mat-forming dinoflagella...

To date Paralytic shellfish toxin (PST) variants in cyanobacteria have primarily been characterized using high performance liquid chromatography coupled with fluorescence detection. In this study we re-evaluated the PST profiles of five cyanobacterial cultures (Dolichospermum circinale AWQC131C, Aphanizomenon sp. NH-5, Raphidiopsis raciborskii T3,...

Ciguatera fish poisoning is a serious human health issue that is highly localized to tropical and sub-tropical coastal areas, affecting many of the indigenous island communities intrinsically linked to reef systems for sustenance and trade. It is caused by the consumption of reef fish contaminated with ciguatoxins and is reported as the most common...

Tetrodotoxin (TTX) is a potent neurotoxin associated with human poisonings through the consumption of pufferfish. More recently, TTX has been identified in bivalve molluscs from diverse geographical environments, including Europe, and is therefore recognised as an emerging threat to food safety. A recent scientific opinion of the EFSA Panel on Cont...

Dinoflagellates of the genus Gambierdiscus are known to produce neurotoxins that cause the human illness ciguatera, a tropical and sub‐tropical fish poisoning. Some species from the Gambierdiscus genus were recently re‐classified into a new genus, Fukuyoa based on their phylogenetic and morphological divergence, however, little is known about their...

http://hab.ioc-unesco.org/index.php?option=com_content&view=article&id=22&Itemid=0

Paralytic shellfish toxin (PST) producing microalgal blooms have a significant economic impact on the Southern Rock Lobster ( Jasus edwardsii) fishery in Tasmania, Australia. The regulatory level of 0.8 mg of saxitoxin (STX) eq/kg in place for bivalve shellfish fisheries is applied to lobster hepatopancreas during blooms of toxic algae, resulting i...

In October 2012, paralytic shellfish toxins (PST) were detected in the hepatopancreas of Southern Rock Lobsters (Jasus edwardsii) collected from the east coast of Tasmania, Australia. This resulted in the first commercial closure in Australia for this species. Questions were raised on how the toxins were transferred to the lobsters, how long the to...

Ciguatera Fish Poisoning (CFP) is a human illness caused by the consumption of marine fish contaminated with ciguatoxins (CTX) and possibly maitotoxins (MTX), produced by species from the benthic dinoflagellate genus Gambierdiscus. Here, we describe the identity and toxicology of Gambierdiscus spp. isolated from the tropical and temperate waters of...

– Members of two classes of marine polycyclic ether compounds, brevisulcenals (KBTs) and brevisulcatic acids (BSXs), were isolated as causative toxins from a red tide (Karenia brevisulcata) bloom event in New Zealand in 1998. The new analogues, brevisulcenals (KBTs)-G, -H, and -I, were isolated from neutral lipophilic extracts of bulk dinoflagellat...

https://authors.elsevier.com/c/1WBBu5aloFJpU8 Ciguatera fish poisoning is a food-borne illness caused by the consumption of seafood contaminated with ciguatoxins (CTXs) produced by dinoflagellates in the Gambierdiscus genus. Since most surveillance programs currently rely on the survey of Gambierdiscus cell densities and species composition, supple...

In August 2014, a puffer fish poisoning incidence resulting in one fatality was reported in New Caledonia. Although tetrodotoxin (TTX) intoxication was established from the patients' signs and symptoms, the determination of TTX in the patient's urine, serum or plasma is essential to confirm the clinical diagnosis. To provide a simple cost-effective...

Paralytic shellfish toxins (PSTs) in bivalve molluscs represent a public health risk and are controlled via compliance with a regulatory limit of 0.8 mg saxitoxin (STX)⋅2HCl equivalents per kilogram of shellfish meat (eq/kg). Shellfish industries would benefit from the use of rapid immunological screening tests for PSTs to be used for regulation, b...

Detection of paralytic shellfish toxins (PSTs) in bivalve shellfish by analytical methods is complicated and costly, requiring specific expertise and equipment. Following extensive blooms of Alexandrium tamarense Group 1 in Tasmania, Australia, an investigation was made into commercially available screening test kits suitable for use with the toxin...

Species in the genus Gambierdiscus produce ciguatoxins (CTXs) and/or maitotoxins (MTXs), which may cause ciguatera fish poisoning (CFP) in humans if contaminated fish are consumed. Species of Gambierdiscus have previously been isolated from macroalgae at Rangitahua (Raoul Island and North Meyer Islands, northern Kermadec Islands), and the opportuni...

Ciguatoxins (CTXs), and possibly maitotoxins (MTXs), are responsible for Ciguatera Fish Poisoning, an important health problem for consumers of reef fish (such as inhabitants of islands in the South Pacific Ocean). The habitational range of the Gambierdiscus species is expanding, and new species are being discovered. In order to provide information...

Ciguatera Fish Poisoning (CFP) is a tropical disease caused by the consumption of fish contaminated with ciguatoxins (CTXs). Currently, the only feasible prevention methods for CFP are to avoid the consumption of fish of certain species from some regions, avoid larger fish of certain species, or avoid all fish caught from specific regions. Here, we...

Two isolates of a new tropical, epiphytic dinoflagellate species, Gambierdiscus honu sp. nov., were obtained from macroalgae sampled in Rarotonga, Cook Islands, and from North Meyer Island, Kermadec Islands. Gambierdiscus honu sp. nov. had the common Gambierdiscus Kofoidian plate formula: Po, 3′, 6″, 6C?, 6 or 7S, 5‴, 1p and 2⁗. The characteristic...

Paralytic shellfish poisoning results from consumption of seafood naturally contaminated by saxitoxin and its congeners, the paralytic shellfish toxins (PSTs). The levels of such toxins are regulated internationally, and maximum permitted concentrations in seafood have been established in many countries. A mouse bioassay is an approved method for e...