PARABIOSIS AND TELOBIOSIS 



PUEPOSE : 



To learn the technique of grafting embryos together in various positions, and to 



study the effect of such fusion on the behavior and the morphology of paired larvae. 

 Pairs which survive metamorphosis may be studied for shared -structures, and for hor- 

 monal relations. 



MATER IAI£ : 



Biological : Anuran (stages #15 to #17) or Urodele (stages #22 to #29) larvae. 



Technical : Syracuse operating dishes with permoplast or paraffin bases. 



METHOD : 



Precautions : 



a. Moderate precautions relative to sterile conditions will prove adequate. 



b. Embryos must be held together firmly hut not so that there is displacement of 

 organs or any incurred damage. The Permoplast may be built up around the pair, 

 leaving small opening above for access to the medium and respiration. 



c. Operate In hypertonic or slightly alkaline media, or in a deficiency of Calcium 

 to facilitate adhesion. Gradually return the pair to normal medium. 



Controls : Operated but not fused embryos constitute the 

 controls, to determine whether the operation alone might 

 account for any untoward results. For pairs that sur- 

 vive metamorphosis and are to be studied for hormonal 

 relations, consult papers by Bums and by Witschi for 

 adequate controls. 



Procedure : The method consists of simply removing the 

 epidermis, some underlying mesoderm and yolk from a 

 limited area on the mirror surfaces of two embryos of 

 similar stages of development (early tail bud is the 

 best) and bringing these injured surfaces together long 

 enough to effect permanent fusion by healing. This may 

 take as little as 20 minutes, or as long as Zh hours, 

 depending a great deal on the temperature and the con- 

 stituents of the medium. 



PARABIOSIS 



Diagram illustrating 

 position of embrjos 

 (Amblystoma stage #22) 

 being fused laterally 

 in parabiosis, within 

 a Permoplast depres- 

 sion. Itijured sur- 

 faces healing together. 



Bemove several embryos of corresponding age ( see above ) 

 from their capsules and with a wide-mouthed pipette transfer 

 them to the operating Syracuse dish with a base of Permoplast 

 or very soft paraffin (containing some beeswax). Bring the two embryos together and esti- 

 mate the size of the depression which must be moulded in the Permoplast to hold the two 

 embryos closely slde-by-side. Make such a depression with a ball tip. 



In the vicinity of the depression, lay the two embryos on their sides, facing away 

 from each other. With a sterile needle, or pair of forceps, outline an oval area cover- 

 ing the region Just posterior to the gill anlage on the left side of one and the right 

 side of the other embryo. With scalpel, scissors, or forceps, excise this oval area of 

 ectoderm, mesoderm, and some yolk from each of the embryos. Quickly maneuver the embryos 

 together into the Permoplast depression, approximately their wounded areas. Build up the 

 Permoplast around them in such a manner that they cannot move, but do not distort either 

 embryo with excessive pressure. If the cilia are active, an adequate block in front of 

 the pair will impede them sufficiently. 



-2U0- 



