Chapter IV 



MARINE ANIMALS THAT ARE POISONOUS TO EAT 



In the skin diver's quest for new adventures, many are finding 

 that the "pastures on the other side of the fence" contain warmer 

 and clearer water, and more abundant sea life. Venturing into 

 strange tropical waters is not without some danger. In this chapter 

 we are not concerned about what might hurt us from without, but 

 rather the dangers from within — those sea foods likely to be eaten 

 by the skin diver while in the field. Fortunately, most sea foods are- 

 edible and nourishing, but there are those which are known to con- 

 tain some of the most violent organic chemical poisons known to 

 science. Note that we are not discussing illnesses due to bacterial 

 food poisoning, but rather, a group of marine animals whose flesh, 

 under certain circumstances, may contain poisonous chemical sub- 

 stances. It is to some of these toxic agents that we will direct our 

 attention. 



There are two major groups of marine organisms poisonous to 

 eat. They are (1) molluscs, and (2) fishes. In rare instances, sea 

 turtles and certain marine mammals have also caused serious 

 poisonings. 



POISONOUS MOLLUSCS 



Under ordinary circumstances, most molluscs, or shellfish, are 

 edible. However, at certain seasons of the year, bivalve molluscs 

 may feed on poisonous microscopic marine animals, called dino- 

 flagellates. The red tide phenomenon in which extensive areas of 

 water take on a reddish hue and kill off large numbers of fishes, is 

 a good example of some of these effects. The discoloration of the 

 water is Hue to the presence of these minute creatures in great 

 abundance. There are many different species of dinoflagellates, 

 and several kinds of poisons are produced. The poison affecting 

 fishes is probably a different one than that causing paralytic shell- 

 fish poisoning in man. Toxic dinoflagellates are ingested by the 

 molluscs and the toxic materials are stored in various parts of the 

 body of the shellfish. Strange to say, the poison is lethal to man, 

 but does not seem to affect the mollusc. If a person should eat one 

 of these molluscs containing a sufficient amount of the poison, 

 violent intoxication, or death, may result. The toxicity of the shell- 

 fish is, therefore, dependent upon the food that it eats. 



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