EARLY BEHAVIOR PATTERNS IN THE AMPHIBIA 



PURPOSE : To determine the time of onset of various types of response to external stimuli 

 in amphitian emtryos, and the succeeding appearance of integrated reactions. 



MATERIAI3 : 



Biological : Amblystoma, ^la, Sana, and Bufo emliryos from tailhud stages onward. 



Technical : Detwiler racing ring (see diagram). 



METHOD : 



Precautions : 



a. The staging of the emtryos to be tested must be exact. Even within a single 

 stage there may appear Individual differences in behavior. 



b. Repeated stimulation may lead to fatigue, particularly in the first phases of 

 response. Ample time must be allowed for recovery. In later stages the stimuliis 

 (hair loop) must be applied to the same region of the body of all larvae, pre- 

 ferably the dorso- lateral body wall, near the nyotomes. 



c. The hair loop is the most satisfactory instrument for stimulation, being pliable 

 and least likely to damage the surface cells. A ball tip or flexible glass 

 needle may be used with caution. 



d. Eliminate any extraneous stimuli such as excessive heat, light, or anisotonic 

 media. 



Controls: The response of earlier and later steiges will constitute one type of con- 

 trol, but the embryos without emy external (tactile) stimulation may be considered 

 as controls. 



Procedure : 



A. To become acquainted with the various types of response, select a group of embryos 

 such as Amblystoma stages #20 - #1+6 or Bana stages #l6 - #53. Place individuals 

 in Syracuse dishes with the appropriate medium and allow them to become adjusted 

 to the new environment for several minutes. Under low power magnification (bin- 

 ocular microscope) gently stimulate the various embryos with the hair loop to 

 elicite a response. Immediately classify the response as one of the following: 



The chronological onset of behavior patterns in the amphibian larvae has been studied 

 by Coghill (1929) by DuShane and Hutchinson (I9UI). The latter authors describe eight 

 steps as follows: 



a. Premotile stage: no response to tactile stimulation. 



b. iJlyotomic response: a non-nervous response of nyotomes as a result of direct 

 stimulation. Both response and recovery are slow. 



0. Early flexure: bending of the body away from the point of stimulation, with 

 rapid recovery. The initial evidence of this response will be at the anterior 

 end, but eventually the tail response will bring it close to the head. 



d. Coll: the early flexure response when extended so that the tail passes the head. 

 The reaction is away from the point of stimulation. There may appear a compen- 

 satory coil in the opposite direction in later stages. 



e. S-reaction: undulatory contraction wave passing down the stimulated side, but 

 not vigorous enough to result in swimming progression. 



f. Early swimming: forward progress as a result of the Integi^tion of the S- reac- 

 tions. The progression is never more than 5 body lengths. 



g. Strong swimming: forward swimming progression from 5 to 10 body lengths, 

 h. Late swimming: forward progression more than 10 body lengths. 



The data for these observations may be cumulative. It would be physically impossible 

 to complete the data in a matter of hours, for the stages are not simultaneously available. 

 For each observation (i.e., each specimen observed) a single record should be indicated on 

 the following chart, indicating the, stage and the most advanced type of response. When 

 the record is complete, there should be a minimum of 10 observations (10 specimens 

 analyzed) for each stage. 



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