TEMPERATURE INDUCED HETEROPLOIDY 



555 



DISCUSSION : 



Heteroploldy in plants has long been recognized but not until recently has its normal 

 incidence among animals been determined (See Fankhauaer's excellent review In 19'*^5 Qwart. 

 Bev. Biol. 20:20). It is now believed that triploidy in Triturus viridescens occurs 

 naturally to an extent of about O.T^. In some batches of eggs (or, more accurately, eggs 

 from certain females) will respond to cold treatment by producing almost 100^ triploids, 

 among those which survive the treatment. It must be emphasized that the mortality of all 

 eggs, treated by these extremes of temperature, is very high, often as much as 50^. 



ABNORMALITIES FOUND IN HAPLOID EMBRYOS AND LARVAE OF AMPHIBIANS 



Table from Fankhauser I'^k'i: Quart. Rev. Biol. 20:20 



It is now believed that the temperature shift at this particular time in maturation 

 affects the kinetic movements of maturation so that the formation of the second polar body 

 is suppressed. It is difficult to explain the infrequent haploids achieved by this treat- 

 ment, but the vast majority of abberatlons are in the direction of triploidy, tetraploldy, 

 etc. The survival of Bostand's (I936) hybrids beyond the normal stage of termination of 

 development, following exposure to cold, fits in perfectly with the concept of polar body 

 retention and the further possibility that amphimixis (in this case, with the foreign 

 sperm) is prevented. If the drastic temperature treatment is delayed for more than 30 

 minutes (Triturus viridescens) the larvae which result are all diploid. 



DIRECT EVIDENCE OF HAPLOIDY 

 Diagrammatic drawing of the metaphase chromosomes of a dividing, 

 epidermal cell from the amputated tail tip of 19-day haploid 

 larva. The haploid chromosome number in this species Is twelve; 

 normal diploid tissue having twelve pairs of chromosomes. 

 (Triturus pyrrhogaster) 



j)rom Fankhauser 1957: Jour. Heredity 28:1 



