124 Comparative Animal Physiology 



mg./ml. ^*' Rainbow trout fed largely on canned carp developed malfunction 

 of the nervous system and melanosis, which were cured by intramuscular 

 injections of thiamine.^^- The dietary need for thiamine by trout is 0.15- 

 0.186 mg./kg./day. Man requires about 1.1-1. 5 mg. daily. Many animals 

 have in the digestive tract microorganisms which synthesize thiamine, and the 

 dietary needs may therefore be less than the actual metabolic needs. Much 

 thiamine is synthesized by microorganisms in the rumen of sheep and cattle; 

 hence these animals do not require thiamine in their diet. Calves reared on 

 synthetic milk do not have rumen microorganisms and require dietary thia- 

 mine. 



Raw fish contains a substance which destroys thiamine, so that when raw 

 fish, particularly viscera, is fed to foxes or chickens ^-^^ these animals develop 

 nerve and liver symptoms of thiamine deficiency. The active agent in the 

 fish appears to be an enzyme or thiaminase which can destroy thiamine in 

 vitro. '^^ How the fish are protected from losing their own thiamine is un- 

 known. 



Riboflavin (Vitamin B^}- Riboflavin is needed in the prosthetic group of 

 flavoprotein enzymes which act in cellular respiration between dehydrogenases 

 and either oxygen or cytochrome. Riboflavin is a constituent of Warburg's 

 "yellow enzyme," xanthine oxidase, D-amino acid oxidase and cytochrome 

 reductase. Riboflavin is an alloxazine derivative: 



CH, - (CHOH)3 - CH.OH 

 H I 



C, N N 



/\/ \ / \ 

 H3C-C C C CO 



H3C-C C C ,NH 



\ /\ /\ / 

 C N C 



H II 



O 



Riboflavin is synthesized by many microorganisms, yeasts, bacteria, and 

 probably flagellates. It stimulates multiplication of Chilomonas but is not a 

 dietary requirement. ^'^^^ Riboflavin is required by the ciliate Tetrahymena 

 strain W. '" It is required by insects— Drosophila, ^•^'' mosquito larvae, ^"'- 

 and numerous beetles (Table 24). Some beetles, e.g., Lasioderma, require 

 riboflavin when sterilized of intestinal flora, but normally the symbionts syn- 

 thesize sufficient riboflavin for the beetle. In the cockroach Blatella gervianica 

 omission of riboflavin from a synthetic diet resulted in either no retardation in 

 growth or at most a 50 per cent retardation (Noland, personal communica- 

 tion). Analyses of roaches reared to maturity on very low riboflavin, of the 

 diet, and of newly-hatched nymphs showed that a 30-fold increase in body 

 riboflavin occurred in insects reared on the deficient diets. There is probably 

 intestinal synthesis of riboflavin in the cockroach. 



Trout need 0.44-0.68 mg. of riboflavin per kg. body weight per day. '•'•'• •^'' 

 The characteristic signs of riboflavin deficiency in mammals are skin lesions. 

 Rats deficient in riboflavin develop skin lesions, some alopecia (shedding of 

 hair), graying of hair, cataracts, and ocular lesions. Pigs require riboflavin for 



