154 



NUTRITION AND GROWTH OF LARVAE 



8. Semi-synthetic diet (Patch, 1941)- 



Purified casein 45% 



Powdered whole milk 37% 



Cooked cornstarch 



Cod-liver oil 



Baker's yeast 



Amino acids for growth and differentiation of Anura: (Gudernatsch &c Hoffman, 

 1936)** 



Glycine ^ 



Alanine > for maintenance 



Leucine J 



Aspartic acid 



, toxic, but may support maintenance 



Glutamio acid 



Arginine^l 



Lysine > for growth 



Cystine J 



Phenylalanine"] 



Tyrosine > for differentiation 



Tryptophane j 



Histidine . , ,.^^ . . 



„ ,. toxic but may support differentiation 



Proline ^ ^^ 



METHOD: 



Precautions : 



1. Any food, particularly those which become acidic, will be a source of bac- 

 terial contamination. It will be necessary therefore to change the culture 

 nnedium, and add fresh food on alternate days at first, and fir^lly, every day. 



2. Overfeeding is not possible, but maximal feeding will be achieved only by 

 providing excess food. Experience alone will determine for any group of 

 tadpoles the amount of food which is just in excess of maximal. 



3. Green vegetables must be washed to free them of arsenic used by gardeners 

 to get rid of insects. 



Control : A variety of foods should be tried, and that which provides the most rapid 

 and normal growth may be considered the control diet. All other conditions of 

 space, medium, light, temperature, etc. must be the same for all embryos. 



Procedure : 



1. Provide uniform containers, each with a measured volume of the culture 

 medium. Regulation finger bowls holding 5 tadpoles or Urodele larvae and 

 50 cc. of medium will prove satisfactory. The large (12 inch) crystallizing 

 dishes may be used with 50 tadpoles and 100 cc. of medium. Mark the con- 

 tainers adequately, and place them in a uniform environment. The temper- 

 ature should be about 14°-18°C. for Urodeles and about 5°C. higher for the 

 Anura. 



2. Select three distinctly different diets, such as carbohydrate, protein, and 

 some synthetic mixture for comparison. Set up at least 5 finger bowls (or 2 

 crystallizing dishes) for each diet offered, using a minimum of 25 tadpoles 

 (or larvae) for each diet. 



♦ Note: This diet produced catomcts in 4096 of A. trigrinum larvae living 2 months, but this effect was counteracted by adding 

 1 . 259< of the total protein of cystine. ) 



** Note; The best acid of each group is in the lowest, or most advanced^position. Most of these acids are expensive, and their 

 use in experimentol analysis of protein nutrition is prohibitive, but the paper by Gudernatsch and Hoffman should be 

 studied for its remarkable findings. ) 



