50 CULTURING OF AMPHIBIAN EMBRYOS 



latlon at a minimum. For Xenopus larvae cooked, dehydrated, and finely powdered beef 

 liver is an excellent supplement to greens, and algae. Livervorst has been used suc- 

 cessfully with many Anura. Other foods used are powdered egg-yolk; bacto-beef ex- 

 tract mixed with whole wheat flour, dried and pulverized; raw liver, minced; algae 

 and Protozoa. The lettuce feeding seems to produce fewer abnormalities but develop- 

 ment is slower than with spinach ( ^man, 19'+1) • Briggs (19^+2) has shown that a pure 

 spinach diet produces certain minor abnormalities and kidney stones, so that a mixed 

 diet is recommended. On pure lettuce or spinach, or a mixture of the two, tadpoles 

 can be reared through metamorphosis with considerable ease. Anura are essentially 

 vegetarian until after metamorphosis, then they are omnivorous with a leaning toward 

 the carnivorous. 



Urodela : 



The Urodela larvae require living, moving food. At first, rich cultures of 

 Protozoa and young Daphnia are fed to the larvae after stage #4-0. The carapace of 

 the older Daphnlas will tear the gut of the larvae. The eyesight of these forms is 

 very poor and their neuro-muscular responses are slow, so that the living food must 

 be active. After a week or two of this diet, when the larvae are more hardy, they 

 can tolerate such foods as the red worm (Tubifex), the white worm (Enchytrea), 

 Daphnia (all sizes, but the young ones are better), mealflies, mealworms, wax moths 

 (Gallerla), Drosophlla (vestigial mutant), plant lice, small ants, and, best of all, 

 amphibian larvae (frog tadpoles of early stages). If not adequately fed the Urodele 

 larvae will tend to nip off each others tails and occasionally larger specimens will 

 devour the smaller ones. Beef liver favors A. tigrinum over A. punctatum while 

 Daphnia and Enchytrea favor A. punctatum over A. tigrinum. Cannibalism la common, 

 and Amblystoma larvae seem to grow best on a diet of Amblystoma. 



■)«-***-X--X-#*-X--X-*» 



If over-feeding is avoided, and any unlngested food is removed daily from the taiaka, 

 it may not be necessary to change the culture medium more than once or twice each week. 

 As the larvae grow, however, there will appear more faecal material in the tanks, and 

 this should be sucked out with a suction bulb and glass tube or the water should be changed 

 more frequently. The water must not be allowed to become turbid with bacteria. 



FOOD FOB THE POST -MET AMOKPSIC STAGES : 



After metamorphosis, with correlated changes In the histology of the digestive tract, 

 the food requirements become radically different for all amphibia. Not only must there 

 be more food, but it must represent a greater variety and should contain vitamins. 



Anura : 



After metamorphosis the situation becomes reversed in that the Anura require 

 living, moving food. Living earthworms cut into 1-inch pieces, which will continue 

 to move and attract the small frogs, are excellent as food. Blow flies, meal worms, 

 ante, spiders, roaches, caterpillars, grasshoppers, will all be eaten as long as 

 they move. Fish muscle, mammalian liver or muscle, dipped in a thin paste of Brewer's 

 yeast and cod liver oil is an excellent food for recently metamorphosed frogs. 



Xenopus is a slight exception in that it will eat anything bloody, particularly 

 strips of raw liver. This form shows little activity except in taking of food, after 

 which it settles down in the water again for as long as several days, coming to the 

 surface only occasionally to get air. 



Some of the potentially larger Anvira (e.g., B. catesbiana, the bullfrog) may 

 grow rapidly and will require more food. These forma may be fed small crayfish, 

 minnows, earthworms, and even small frogs of the same or other species. It is pos- 

 sible but difficult to train Anura to take non-living food. 



The tree frogs (^la) require a continually humid environment such as an ordi- 

 nary terrarixun and their food consists of small insects. If the terrarium is glass 

 covered, Drosophila (vestigial mutant) may be given to them, but it takes a good 

 many flies to make an adequate meal, ^la will take other living food such as earth- 

 woma. 



