Venomous Animals and Their Toxins 



By FiNDLAY E. Russell 



Director, Laboratory of Neurological Research, School of Medicine 

 Loma Linda University, Los Angeles, Calif. 



[With 2 plates] 



Venomous animals are fomid in every phylum except the birds. 

 While it would be difficult to propose a figure for the nmnber of species 

 of venomous animals, because we do not as yet know about the possible 

 venomousness of a score of arthropods and fishes, we do have some 

 idea of the approximate number of poisonous species in most of the 

 phyla. Of the 2,500 or so species of snakes found throughout the 

 world, only about 250 are dangerous to man. Table 1 gives the names 

 of some of the more important venomous snakes of the world, their 

 adult average lengths, the approximate amount of dried venom con- 

 tained within the venom glands of adult specimens, and the intra- 

 peritoneal and intravenous LD50 (the dose required to kill 50 percent 

 of the test animals of a given group), expressed in milligrams per 

 kilogram (mg./kg.) weight of test animal. 



In the marine animals there are many venomous forms ; at least 200 

 species of marine animals and freshwater fishes are known to be 

 venomous or poisonous. Table 2 gives the names of a few venomous 

 aquatic animals. The lethal doses for the marine toxins vary con- 

 siderably. The geographer cone, Conus geographus, has an LD50 of 

 less than 5 micrograms per kilogram ; the venom of the round stingray, 

 Urolojyhus halleri^ has an LD50 of approximately 25 mg./kg. while the 

 LD50 for the toxin of certain catfishes is of the order of 200 mg./kg. 



Among the arthropods at least 700 species are known to be venomous. 

 These include the black widow spider {Latrodectus) ^ funnel web spider 

 {Atrax robiistus), the spiders Lycosa rciftona and Plioneutria fera, 

 the scorpions, particularly Centrurokles sculpturatus.^ Tityus hahien- 

 sis, and T. serridatus, the bees, wasps, hornets, certain centipedes, 

 millipedes, caterpillars, moths, ticks, beetles, and ants. Even among 

 the mammals there are several venomous forms, the platypus and sev- 

 eral of the shrews. 



1 Printed by permission from The Times Science Review (London), Autumn 1963. 



477 



