Botulina poisoning has been definitely excluded as 

 a possible cause of these bird deaths . It seems 

 highly possible that many instances of water fowl 

 deaths in the past were not caused by botulina as 

 claimed. In one year 7000 Franklin gulls and 60 

 mallard ducks were killed by Anabaena flos-aquae 

 in Iowa . 



In addition to these animal deaths, there are 

 many instances on record of the killing of fish by 

 algal toxins. Carl (1937) reported fish deaths in 

 British Columbia from Anabaena flos - aquae . Prym - 

 nesium parvum secretes a toxin which kills gill- 

 breathing organisms. Also, it has been found 

 (Ryther, 1954; Lucas, 1936) that extracellular sub- 

 stances have a profound effect on the biology and 

 feeding habits of microorganisms. AA^ereas these 

 cannot be construed as highly detrimental, they do 

 constitute examples of disturbances that may have 

 far-reaching and ramifying effects on aquatic biota. 



Mention should be made here of the critical 

 studies of Abbott and Ballantine (1957) on the 

 toxins of the dinoflagellate, Gymnodinium vene- 

 ficum which plays a role in the wholesale death of 

 fish. Material obtained from laboratory cultures of 

 the flagellate was found to be toxic to the nervous 

 system of animals by depolarizing nerve and mus- 

 cle membranes . 



Although in need of further study and con- 

 firmation, evidence indicates that fish are killed 

 in Iowa lakes by toxins and scanty but strong in- 

 ferential evidence is at hand to support the belief 

 that epidemics of human intestinal disturbances 

 are caused by them. (See Spencer, 1930; Tisdale, 

 1931) . That there are not more cases of this sort 

 of disturbances is related to the simple fact that 

 domestic drinking water is seldom allowed to de- 

 velop concentrated algal blooms . Persons would 

 naturally refrain from drinking water directly from 

 ponds which are obnoxiously overgrown with algae, 

 especially blue-green species which produce dis- 

 agreeable tastes and odors. 



That toxins actually exist in extracellular 

 excretions has been demonstrated by both labora- 

 tory and clinical tests. Fitch, et al (19 34) are the 

 first to have investigated waters after an epidemic 

 of cattle deaths . The toxins with which they 

 worked were produced by Aphanizomenon , Ana- 

 baena and Microcystis in Minnesota . They fed 

 animals in the laboratory with algal material 

 taken fresh from the lake and also administered 

 injections . The animals died within a matter of 

 minutes in some instances, or after 12 hours in 

 others . 



Mason and Wheeler (1942) also found that 

 small animals were killed within three hours after 

 being injected with Microcystis medium. Veteri- 

 narians in Iowa injected 10-15 cc . of a bacteria- 

 free filtrate from Anabaena flos - aquae into guinea 

 pigs which lived but 12 minutes. Only 0.04 cc . 

 injected into a mouse caused its death in four 



minutes . They also found that after one year the 

 filtrate was ineffective. Olson (1951) points out 

 that only 0.02 cc . of raw algal material injected 

 into a 20-gram mouse produced death in one hour. 

 More time is required for death to occur when lab- 

 oratory animals are given algal material orally. 

 An interperltoneal injection of 10 cc . killed a 

 chicken in 20 minutes, whereas 50 cc . fed to a 

 chicken produced death one and one-half hours 

 later according to Olson (1. c). 



Shelubsky (195 1-b) obtained toxin from Mi - 

 crocystis by drying the plants and by precipitating 

 it with phosaphotungstic acid at a pH of 2.0 . 

 Also, he demonstrated a toxin to be present in 

 living cells experimentally and that it was not an 

 antigen. Living Microcystis injected in several 

 small animals, including carp, produced death. 



The deaths mentioned above are supposedly 

 caused by exotoxins present in the water in which 

 algae have been living (in a bloom condition) . 

 These exotoxins have not been Isolated. This is 

 understandable since extracellular substances in 

 quantities sufficient for analyses would have to be 

 separated from the other substances in solution 

 within the medium. Can they be filtered, or pre- 

 cipitated, or distilled? It is known that the exo- 

 toxins are alkali-labile, which indicates a possi- 

 bility that a technique can be developed that will 

 permit chemical analysis. Laboratory tests using 

 water and/or algal material have determined that 

 the toxins of Microcystis and Anabaena occur in 

 the medium of healthy cells; that they are non- 

 filterable; that like endotoxins , they are non-ionic, 

 are not alkaloid, nor albuminoid, are non-volatile 

 and are heat stable . They have a low molecular 

 weight and may be soluble in alcohol . Exotoxins 

 are not destroyed by air-drying, by freezing or by 

 ultra-violet radiation. Louw (1950) claims to have 

 detected two alkaloids from Microcystis , however. 

 One of these has a suspected formula of C^oHig 

 NO2. The other is a picrate and is the one that 

 acts as a hepatotoxin. 



Molecules of chlorellin are smaller than 

 15 A in diameter. The exotoxin effects of Micro- 

 cystis have been shown by Ashworth and Mason 

 (1946) to be similar to the symptoms of poisoning 

 by Amanita . From a marine alga a toxin has been 

 identified as a form of polysaccharide. 



Some workers have found that decayed blue- 

 green algae are toxic , a fact which might be ex- 

 plained by the presence of endotoxins which have 

 been released. Thus, it is clear that either living 

 or in a decomposed state algal substances are 

 toxic. Louw (1950), for example, found that fil- 

 trations of decayed algae were toxic, whereas 

 fresh or living plants were non-poisonous to lab- 

 oratory animals . It has been found also that the 

 'maturity' of the alga involved is related to varia- 

 tions in the strength of the toxin. Just what this 

 age-time factor is, has not been determined, but 



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