12U 



EARLY BEHAVIOR PATTERNS IN THE AMPHIBIA 



Youngstrom (1958) has added a few, more advanced stages in response. These are: 



a. The larva becomes free swimming - tactile stimuli unnecessary. 



b. Beginning of spontaneous eye movements. 



c. Body resists rotation. 



d. Hind leg buds appear. 



e. Hind leg buds become motile. 



f . Beginning of withdrawal leg reflex. 



B. It is suggested that the student determine the onset of response to light stimu- 

 lation. The more highly pigmented Anura may respond earlier than the lighter 

 colored Urodela; or neither may respond to variations in light until the retina 

 develops . 



A regulation Spencer diaphragm microscope lamp with heat- absorbing, water- 

 filled, round bottom (500 cc.) flask will provide an adequate spot light. After 

 proper focusing of the light onto the binocular microscope stage, turn off the 

 light and In the dim (ceiling) light of the room orient the embryos of various 

 stages within the field of the microscope. After a minute or two, turn on the 

 spot light while observing the embryo through the microscope and note any reac- 

 tion to the light. The embryos should be oriented toward and also away from the 

 source of light. 



C. Detwiler (19'<-6) has devised a method of quantltatlng the distance travelled by 

 the individual Amblystoma larvae (stages #39 and upwards) which are normal and 

 those which have had parts of the embryonic central nervous system removed. He 

 found that larvae lacking the midbrain began to show a failure in locomotor 

 capacity at stage #'+1, and that the hemispheres were relatively unimportant in 

 the general locomotor activity of the larvae. 



It is recommended that the student remove parts of the brain anlage at stage 

 #21 (Amblystoma), allow the larva to develop to stage #59 or later and determine 

 the locomotor capacity as compared with the controls, using the figure below. 

 The operation should be performed in 0.51^ sodium sulfadiazine (Detwiler and 

 Eobinaon, I9U5). The Syracuse dish in which is placed a glass ring, providing a 

 "moat" for the swimming larva, can be placed directly over the figure below and 

 readings of the distance moved can be recorded in sectors. Ablation experiments 

 are qualitative in that no two operated larvae could possibly be Identical. 

 Sketches of the excision and later larva should be made. 



An improved device placed beneath a Syracuse 

 dish for quantltatlng the distance traveled 

 Dy individual AmDlystoma larvae (stages 39 

 to 46+). The outer heavy circle corresponds 

 to the inner wall of the dish; the inner 

 lieavy circle indicates a glass ring the 

 heiglit of tlie dlsli. The space between the 

 two represents a "moat" approximately 7 mm. 

 In diameter. Each larva was placed in tlie 

 moat and stimulated twenty-five successive 

 times at approximately o-second Intervals, 

 and the total distance was recorded In units 

 (sectors of arc) . The glass ring has been 

 added to the original device (Detwiler, 1945, 

 Ma;. 1) , to prevent larvae from occasionally 

 sliort-cuttlng as t)iey swim along the wall of 

 the dish. 



From Detwiler, I9U6: Jour. Exp. Zool. 102:521. 



