108 INDUCED BREEDING 



Properly planned, angjhi'bian eggs can be available for experimentation at all times. The 

 genus Rana is available over vride areas. 



The dose of the hormone varies somewhat, depending both on the donor and the recipi- 

 ent. In general the larger species seem to require more of the glands from the smaller 

 species. In none of the genus Bana has there been uniform success with any source but 

 other an5)hibian glands, the mammalian extracts being generally negative. 



BOTO: 



The toad will react not only to the pituitaries from other Anura but also to the 

 pituitariea from other Phyla and to the extracts of mammalian pituitaries and even to the 

 extract of pregnancy urine (antuirtin-S) and Preloban (Xenopus). The response is most 

 reliable, however, when either frog or toad pituitaries are used. 



The eggs are deposited in a manner quite different from the frog in- that they are 

 layed singly in long strings of Jelly, each egg being inseminated by the male (during 

 amplexus) as it emerges from the cloaca of the female. It is therefore necessary to in- 

 duce amplexus in toads and allow the paired animals to lay their eggs naturally. Amplexus 

 may be induced by injecting the male with doaes of pituitary glands equivalent to those 

 used for the female, and placing the pair together in a small amount of water. Several 

 changes of the water may be necessary before the eggs are layed, to eliminate the faecal 

 and other matter in the water. The water should be appropriate to survival of sperm and 

 eggs. 



HYLA : 



The tree toads and other closely related species are difficult to secure out of breed- 

 ing season but if caught during or Just before hibernation they may also be induced to lay 

 their eggs in the laboratory. The nethod is similar to that for Bufo and during amplexus 

 the male may be seen to bring his cloaca down close to the cloaca of the female as each 

 egg emerges, indicating separate insemination of each egg. The Qyla egg is small but 

 excellent for operative procedures. 



XENOPUS : 



This is the African clawed-toad which has attained fame through its use in pregnancy 

 tests. It la extremely sensitive to the pituitary hormone, and ovulation can be induced 

 by the pituitary (or gonad stimulating hormones) from any source. The method of inducing 

 the breeding reactions and caring for the early embryos has recently been described in 

 detail by Aronson (19'+'+) Weisman and Coates (19'+'+) and by Cameron (19'+7) whose papers 

 should be consulted. It is likely that the Xenopus egg and embryo will become increasing- 

 ly valuable as a laboratory form for experimentation purposes. 



URODELA 



Among the salamanders the eggs are generally inseminated as they pass through the 

 genital tract of the female, after she has picked up the sperm bundles ( spermatophores) 

 dropped in the water by the males. Artificial insemination of the Urodele egg is possible 

 but rather difficult, since the sperm found In the spermatophores are not properly acti- 

 vated. The process of artificial insemination consists of the removal of activated sperm 

 from the genital tract of the female and applying them to oviduccal eggs of a pituitary- 

 stimulated female, not Impregnated. The sacrifice of the several animals la neceasary and 

 only a few eggs are secured. 



The more satisfactory procedure, therefore, la to inject the pituitary hormone into 

 females known to carry spermatophorea, whereupon they will depoalt fertilized eggs. 



There are two methoda which may prove of practical value in the production of fertile 

 eggs of the Urodela: Flrat . pituitary atlmulation of the male two days prior to the etimu- 

 latlon of the female thereby causing it to deposit the spennatophores . If this is accom- 

 plished in a proper environment the females may be induced to pick up the spermatophores 

 with their cloacal llpa after which they may be stimulated to ovulate. Second , some suc- 

 ceae has been reported from Europe (Triton) where the paired animals are well fed, then 

 placed In the dark at hibernation temperatures (1+° - 8°C.) for a month or more, and then 

 are broi;ght out into the light at Spring temperatures (l8° - 25°C.), whereupon they will 

 spontaneously produce fertile eggs. 



