MARINE TOXINS

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MARINE TOXINS

• Many structurally different toxic compounds are
  biosynthesised by marine organmisms.
• They are useful as chemical defense substances to
  the organisms which produce them but are toxic to
  other animals when ingested.

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MARINE TOXINS

• Toxic marine algae - dinoflagellates
  cyanobacteria (blue-green algae)
• Ciguatera - derived from dinoflagellate
  Gambierdiscus toxicus. Only certain clones of
  this algae are genetically capable of producing
  ciguatoxins.
• Ciguatera is a global disease caused by the
  consumption of fishes contaminated with orally
  effective levels of sodium channel activator
  toxins (ciguatoxins).
• Less than 1 ppb causes illness.

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• Gambiertoxins are oxidised to ciguatoxins in the
  fish.
• Ciguatoxins accumulate in the fish flesh.
• Global warming results in coral bleeching and
  consequent coral reef death.
• Dead coral is covered by benthic algae.
• G. toxicus colonises the benthic algae and is
  consumed by herbivorous fish.
• Global warming thus contributes to an increased
  incidence of ciguatera fish poisoning.

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Ciguatoxicity of Gambierdiscus dinoflagellates
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• Dinoflagellate toxins that poison
• okadaic acid family
• brevetoxins
• ciguatoxins
• palytoxin
• azaspiracid
• pectenotoxins
• pinnatoxin
• spirolides maitotoxin prorocentrolide
  gymnodimine yessotoxin

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A MARINE TOXIN
Brevetoxin B
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Paralytic Shellfish Poisons (PSPs)

• 1973 - two ship crew died from shellfish around
  Vancouver Is.
• Produced by dinoflagellate, Alexandrium catenella
  other Alexandrium species. Also Gymnodinium
  catenatum and Pyrodinium bahamense.
• Results in muscular paralysis, respiratory
  difficulty and death within 2-24 hrs after
  ingestion.
• The dinoflagellates are consumed by clams and the
  toxins are distributed in various parts of
  shellfish.
• PSPs are also associated with crabs and lobsters.

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Diarrhoetic Shellfish Poisons (DSPs)

• Produced by dinoflagellates of the genus
  Dinosphysis.
• DSP produces gastrointestinal symptoms from 30
  mins - 2 hrs after ingestion of sea food.
• Shellfish - mussels oysters and in Australia the
  pipi - Donax deltoides.
• Toxins include okadaic acid, dinophysis toxins
  and pectenotoxins, azaspiracids.

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Amnesic Shellfish Poisoning (ASPs)

• The causative organism is Pseudo - nitzschia
• ASP can be life-threatening and is characterised
  by both gastrointestinal and neurological
  disorders.
• GI symptoms develop within 24 hrs of consumption
  of toxic shellfish neurological symptoms appear
  within 48 hrs.

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• Neurotoxic shellfish poisoning.
• Toxic aerosols produce asthma like symptoms.
• Toxin, brevetoxin, is a polyether, also produces
  fish kills.
• Toxin DOMOIC acid produces amnesic shellfish
  poisoning (ASP).
• Sea food affected mainly is shellfish such as
  mussels and also fish and crab viscera can also
  contain the toxin DOMOIC ACID.

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Lyngbya toxins

• Produced by Lyngbya majuscula
• Main toxins Lyngbya toxin-a and debromoaplysia
  toxin - they are potent cytotoxins.
• Lyngbya majuscula can contaminate Gracillaria
  which is consumed as food.
• Lyngbya majuscula is consumed by turtles,
  dugongs, and certain fish such as Siganus
  species.
• Lyngbya majuscula can live amongst sea grass.

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• A number of algal toxins can be present in sea
  food.
• Algal toxins are produced in all climates around
  the world.
• Harmful algal blooms can be due to some human
  activities.

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MARINE TOXINS

• These have toxic effects on other marine
  organisms, humans or both.
• So far, the emphasis has been on compounds toxic
  to humans.
• Chemical defence substances
• Pahutoxin, a chlorine ester of ?-acetoxypalmitic
  acid, from the skin of the Hawaiin box fish,
  Ostracion lentiginosis, is a toxic to some fish
  but not to humans.

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• Some fish died when confined with boxfish.
• Pahutoxin is non-toxic towards warm-blooded
  animals.
• Pahutoxin shows hemolytic activity
• Holothurin Toxins - These toxic saponins in sea
  cucumbers they are glycosides.
• The sugars identified from Holothurin A from the
  sea cucumber Actinopyga agassizi are D-xylose,
  D-glucose, 3-O-methyl-D-glucose and D-quinovose.

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• Holothurin and holothurin fractions have been
  found to be toxic to many marine animal species
  including protozoan, sea anemones, echinoderms,
  crustaceans, molluscs, planarians, earthworms,
  fish and some mammals.
• Since these compounds are hemolytic, it can be
  lethal to humans if injected!
• Asterosaponins from the sea star Asterias
  amurensis are also hemolytic. One of the
  saponins, Asterosaponin A, when hydrolysed
  yielded two moles of D-quinovose, two moles of
  D-fucose H2SO4

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TOXINS FROM SEA HARES

• Aplysins have been isolated from the Sea hares of
  the family Aplysiide, class gastropoda.
• These cause eye irritation in rabbits and dogs
  and caused muscular paralysis when injected into
  coelenterates, annelids, frogs and other
  cold-blooded animals.