550 



TEMPERATURE INDUCED HETEROPLOIDY 



TEMPERATURES AND EXPOSURE PERIODS 



Chromosome 

 (2N) number 



22 



28 



26 



************* 



The time/temperature ranges for optimum results (highest heteroploidy with lowest 

 mortality) have not been determined. However, for the Urodele eggs an exposure of about 

 5 hours at about 3'0°C. or an exposure of about 15 minutes at 35.0°n. may be considered as 

 optimum until exact data are available. For the Anura, the only reference is Brlggs 

 (191+7) who suggests that h minutes at 37.0°C. seems to be highly productive of triploidy. 



Rostand (1953, IS'ik^ 1956) found that hybrids between Qyla, Bufo, and Rana which 



normally go to pieces during cleavage or early blaatula stages, will respond to the cold 



treatment by producing some larvae. This type of experiment indicates that the Anura (as 



well as the Urodela) will react to low temperatures by altering the chromosomal conditions 



rcRTIUZEO ECC 



RCfRIGUATCD 



secoNo MAivftArioH 



DfVISIOH AUPPRC&iCO 



Diagram of hypothetical effect of low temperature 

 treatment on freshly fertilized salamander eggs. 

 At the time of fertilization, tlie ampliiblan egg, has 

 given off the first polar body; the second matura- 

 tion division has reached metaphase and remains in 

 this stage until fertilization occurs. Refrigera- 

 tion presumably suppresses the second maturation 

 division and produces a diploid egg nucleus. 



From Fankhauser I9I+2 : Biol. Symposia 6:21 



