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Algal Toxins
| Question | Answer |
|---|---|
| Where do marine algal toxins originate from? | Marine algal toxins originate from unicellular algae which produce pharmacologically active subtancese.g. proteins and peptides. About 1/3 of blooming species produce potent toxins. Dinoflagellates are the dominant toxin producing group. |
| What are the 5 seafood poisoning syndromes which result from the consumption of contaminated seafood? | PSP, NSP, ASP, DSP and Ciguatera fish poisoning. |
| Define 'Poison'. | Pharmacologically active substance which is chemically stable to around 200C. Have a wide range of toxicities when introduced to a living organism, varying in efficiency and effectiveness. |
| What are HABs? | Harmful algal blooms which include a broad range of phytoplankton species which produce algal toxins. |
| Why are HABs increasing on a global and spatial scale? | 1) increased awareness of issues and establishment of research programmes 2) consequence of anthropogenic activities - introduction of new species in ship ballast water and shellfish transplantation, global climate change, eutrophication. |
| What are NABs? | Nuisance Algal Blooms - not toxic but can rpoduce impacts on ecosystems |
| What are the main causative organisms of PSP and what toxins are produced? | Alexandrium, Gymnodinum, and Gyrodinium. Main toxins produced are saxitoxins and neosaxitoxins. |
| What are saxitoxins? | Group caused by PSP toxins. They are specific and potent sodium channel blockers, preventing the propagation of action potentials therefore muscle fibres can't contract. Dose of ~0.2mg can be fatal. |
| What is epimerization? | The isomer change of H & S groups of the saxitoxin which alters potency. May be changed during digestion when going through different biological processes. |
| What are PSP concentrations in algal cells influenced by? | The algal clone, temperature, nitrogen levels, phosphorus levels, age of bloom, feeding rate of shellfish. |
| What is depuration? | The selective retention and secretion of toxins - this is species and temperature specific. |
| What is the maximum permitted PSP toxin level when harvesting shellfish? | 80μg/100g shellfish tissue. |
| What are the main causative organisms of DSP and what toxins are produced? | Dinophysis, Porocentrum lima. Toxins produced include okadaic acid. |
| What effects does okadaic acid have? | OA is a potent protein phosphate inhibitor, inhibiting the phosphorylation of proteins when they are being manufactured. |
| What are the causative organisms of NSP and what toxins are produced? | Causative organisms include Karenia brevis, and toxins produced include brevetoxins. |
| What effects can brevetoxins have? | They target voltage sensitive sodium channels, producing respiratory asthma like symptoms. Fragile waves are capable of breaking the cell structure, producing toxic aerosols. |
| What are the causative organisms of ciguatera fish poisoning and what toxins are produced? | Causative organisms include G.toxicus and Prorocentrum spp. Toxins include ciguatoxins (CTX) and maitotoxins (MTX). |
| How can humans be affected by Ciguatera fish poisoning? | Consumption of herbivorous fish which has fed on CTX producing algae e.g. parrot fish. CTX = efficient at bioaccumulation - predatory fish contain highest levels. CTX = Na+ and Ca2+ activator. |
| What affects do maitotoxins have? | Increases Ca2+ membrane influx which leads to hormone stimulation and neurotransmitter release. Accumulates in the liver - once contaminated it is very dangerous to eat more contaminated fish. |
| What are haptophytes? | Used by species e.g. Prymnesium as an attack weapon if grazer is present. Primarily ichthyotoxic. |
| What is Pfiesteria poisoning? | Estuarine dinoflagellate with a resistant cyst stage which flourishes with eutrophication. Produces potent neurotoxins against fish - can also affect humans. Highly influenced by climate. |
| What is bioaccumulation? | The accumulation of chemicals within a biological system. Occurs if input is greater than removal processes. Is divided into bioconcentration and biomagnification. |
| Define 'half-life'. | Defines how long a chemical will stay within a biological system until they are lost, excreted, degraded or react into something different. |
| What are the main causative organisms of ASP and what toxins are produced? | Causative organisms include the diatoms P.pungens and P.australis. Toxins produced include domoic acid, acting as a grazing deterrent. |
| How can algae avoid autotoxicity by compartmentation? | Intracellular partitioning of substances and metabolic activities by membranes locks substance away from organelles. Can be released from compartments if needed. E.g. saxitoxins are compartmented in chloroplasts of Gonyaulax. |
| What are 'activated reactions'? | Plant-defence system. Grazer initiated signal disrupts compartmented enzyme substrate systems, causing a rapid reaction that produces a feeding deterrent. Avoids self toxicity and minimises energetic cost of defence capability. |
| What effects can toxic aldehydes have on food web dynamics? | Diatoms produce oxylipins upon physical stress - these target reproductive stage in copepods, inhibting fertilisation, embryo-genesis and hatching & larval fitness. Can present serious invertebrate recruitment issues. |
| What is the transfer of PSP to zooplankton affected by? | Toxin cell and grazer abundance, zooplankton community composition and the algal toxin cell quota. |
| What effects the accumulation of toxins? | Sloppy feeding, defecation, feeding mode & rate, detoxification, gut retention time, dilution effects, body retention time and temperature. |
| How do shellfish become toxic? | Filter feeding mollucs accumulate toxins from the water, showing no ill effects. When ingested, acid hydrolysis in stomach makes STX 6X more toxic |
| What are examples or toxin accumulation in non filter feeding invertebrates? | Domoic acid in Portuguese cephalopods, PSP accumulation in shore crabs, DSP accumulation in eduble crabs, microcystins in silver carp, accumulation of domoic acid in sardines, accumulation of PSP toxins in Atlantic mackerel. |
| Name the main vectors associated with the transfer of sequestered toxin to higher trophic levels. | Filter feeding shellfish, zooplankton and herbivorous fish. |
| What are the main problems associated with HABs? | Mass ecosystem dysfunction, public health rish and enormous economic loss due to effects on tourism. |
| How is domoic acid becoming an increasing problem in the Southern Ocean? | P.australis blooms able to dominate for ~3months. Krill act as an effective vector after P.australis consumption, transferring it to higher trophic levels - threatening one of the most important ecosystems on the planet. |
| What does LD50 mean? | Defined as the dose of poison which kills 50% of a given population over a given time period (usually 24hr). Defines the specific activity of a toxin. |
| How can lectin probes be used as an algal biotoxin detection technology? | Non-enzymatic secreted proteins (lectin) recognise and bind to carbohydrate at cell surface - binds to characteristic signature and then fluoresces. Can be used to determine if toxic cells are present. Relatively quick ~1day. |
| How can antibodies be used as an algal biotoxin detection technology? | Specific antibodies bind to specific antigens (peptides, glycoproteins, carbohydrates, toxins etc.) and then fluoresce. Antibodies which are then produced can be harvested. Expensive and time consuming process. |
| How can DNA probes be used as an algal biotoxin detection technology? | Used to obtain and compare rRNA and/or rDNA sequences from organisms of interest. Takes around 30mins - quickly determine how many toxic cells are present. |
| How can flourometric assays be used as an analytical techniques for shellfish poisoning? | PSP toxin fluorescence can be increased to provide a screening assay - not good for quantitative purposes however. |
| How can chromatographic methods be used as an analytical techniques for shellfish poisoning? | HPLC combined with fluorescence detection allows for identification of PSP components on a sample. |
| What in vitro assays can be used for detection of phycotoxins? | Immunoassays, enzyme assays, receptor assays and cytotoxicity assays. These are highly sensitive and specific towards toxic analyte. E.g. Jellet rapid test for PSP - detects all saxitoxins as low as 40μg/100g shellfish tissue quickly. |
Created by:
jenniferwarner
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