52 CULTURIN6 OF AMPHIBIAN EMBRYOS 



Within the normal tolerance range it is possible to retard or accelerate the normal 

 rate of development of any of the forms without altering the developmental processes in 

 any way. For Instance, one can keep Eana pipiens eggs at 15°C., 20°C., and 25°C. and have 

 three different stages of development simultaneously, all from the same original hatch of 

 fertilized eggs. 



The maximum range for all amphibian larvae is 0°C. to it-0°C., with the optimum range 

 between 120C. and 25°C. Most laboratories are kept at between 25°C. and 25°C. which is 

 satisfactory for the Anura but somewhat high for the Urodela. 



BACTERIA AND PARASITES 



The most common infection for adult frogs is Eed-Leg. Numerous attempts have been 

 made to control this disease. The best method is to eliminate any infected animals upon 

 receipt; to keep the tanks cool and the animals in running water, and occasionally to 

 treat possibly infected animals with weak KMNOij^ solution. Copper lined tanks will reduce 

 the incidence of Eed-Leg. Saprolegnia is another infection of high mortality and unknown 

 cure. The symptoms include body swelling or bloating. Infected animals should be de- 

 stroyed immediately and the tank sterilized with permanganate. It is a practice in many 

 laboratories to place several copper pennies in the tanks with the frogs, enough copper 

 ions passing into the water to keep down these infections and yet not enough to be toxic 

 for the adults. (In even minute concentrations, copper, lead, zinc, mercury, and bronze 

 are toxic to embryos.) 



Salamanders are sometimes seriously affected by a fungus, Monilia batrachus, which 

 attacks the lips and causes open sores. Frogs and toada seem to be immune. This growth 

 is contagious but if treated early by painting the lips with 2^ mercurochrome, the disease 

 may be checked. 



Parasites are often brought in with living food. These include worms, flies, and 

 mites. However, these infected animals normally comprise the food of most amphibia so 

 that there is little or no danger for them. If Tubifex (red worm) is used as food, it la 

 well to keep them in running cold water for several days because they grow in sewage and 

 are apt to bring in an excess of bacteria. 



Oedema, or swelling of tissues with water, may be due to a malfunctioning of the 

 embryonic kidneys although it is known to occur even before such organs are developed. 

 Early tadpoles often develop an apparent oedema, but the swelling is due to an accumulation 

 of dissolved gases in the digestive tract with some consequent bloating of the body. 

 Generalized oedema can sometimes be relieved by placing the embryos in slightly hypertonic 

 medium. If the oedema is localized, it can be relieved by puncturing with a needle to al- 

 low the escape of the excess fluid. 



