CULTURING OF AMPHIBIAN EMBRYOS 51 



Toads require a rather warm and dry environment, live on insects at first and 

 then they will accept worms and even strips of beef, if the food is shaken before 

 their nostrils. 



Urodela : 



Salamanders are aquatic or semi -aquatic, and a few are actually terrestrial, 

 hence the food requirements will vary somewhat with the species. 



In general, the salamanders should be removed to a large crystallizing diah dur- 

 ing feeding. The food at first may consist of cliunps of white worms (Enchytrea), 

 small earthworms or larger earthworms cut into 1-inch lengths suitable for ingestion. 

 As the salamanders grow they can be trained to accept strips of beef or calves liver, 

 if the liver is held in forceps and dangled before their nostrils. These forms act 

 as though they are blind, but their olfactory senses are acute. After the feeding, 

 remove all excess food, rinse off the specimens in fresh water, and return them to 

 their tanks. Uningested or regurgitated food in the tank necessitates frequent com- 

 plete change of medium, and occasional sterilization of the entire tank. 



Triturus pyrrhogaster, the Japanese fire salamander, should be fed about three 

 times each week, and each adult specimen should receive the equivalent of about 1 

 inch of liver, the diameter of a small pencil. With this routine they may be kept in 

 healthy condition for many years, producing eggs (luider pituitary stimulation) when 

 desired by the Investigator. 



SPACE AND OXYGEN 



The space factor in development has not been adequately recognized but it plays a 

 very important role in the rate of development. In general, the larvae will grow the 

 faster in less crowded conditions, all other factors being equal. It is suggested that a 

 ratio of 1 egg to 2 cc. of medium be used In finger bowls with a maximum of 25 eggs to 

 50 cc. of medium. As the embryos develop into larvae (tadpoles) this ratio will have to 

 be changed so that at the beginning of feeding there are no more than 10 tadpoles per 

 finger bowl of 50 cc. of medium. At this time it is better to transfer the tadpoles to a 

 larger tank to allow for greater activity (see Rugh, 195'*-)- 



The amount of water per specimen is not the vital consideration, however. It is the 

 surface area that is Important, so that in a tank measuring 6 x 12 x 2l4- inches one can 

 place 200 tadpoles in water not more than 1 inch in depth. Evaporation from this tank 

 should be compensated for by adding distilled water once each week, but under no condi- 

 tions should tadpoles be placed in deep water. 



Amphibian embryos can tolerate a wide range of oxygen tension but they are very sen- 

 sitive to anerobic conditions. Artificial aeration is not necessary but it is well to 

 place in the tanks some aquatic plants such as Elodea, Nltella, etc. which will continual- 

 ly add some oxygen to the medium. Anuran larvae seem to require more oxygen than do the 

 Urodele larvae. 



LIGHT 



There is no evidence that light is necessary for normal amphibian development (Eugh, 

 1955) . However, since larvae can derive nourishment from algae and they do require oxygen, 

 it is well to provide normal light so that plant food can grow and can provide some of the 

 necessary oxygen. Direct sunlight Is not advised because of the heat factor. 



TEMPERATURE 



The temperature tolerance of various forms is given in the section on Temperature. 

 The range of tolerance for the various forms is about 2l+°C., but the scale is high for 

 some and low for others. The Urodela, for Instance, develop better at the lower tempera- 

 tures while the Anura seem to develop better at the higher temperature levels. 



