THERMAL TOLERANCE AND HEAT-SHOCK PROTEIN-SYNTHESIS DURING DEVELOPMENTIN THE ANURAN LEPIDOBATRACHUS-LAEVIS

Development of the Paraguayan anuran Lepidobatrachus laevis is unusual in that the larvae are obligate carnivores, facultative cannibals and apparently exist at high environmental temperatures in their natural habitat. In the present study, the effect of environmental temperature on the rate or anuran development was investigated. The larvae have a thermotolerance range of 18 degrees C for normal development between 19 and 37 degrees C. The effect of temperature on the rate of developm ent was dramatic; larvae that were incubated at 36.8 degrees C develop to stage 24 (Gosner) in approximately 9 h compared with 24 h for larv ae incubated at 19 degrees C. The ability of larvae to survive heat sh ock was also examined; larvae did not survive a shock of 45 degrees C for 15 min when it was administered at stages 3, 5, 9, 10 or 20. Howev er, using the same heat shock conditions, 50% survival was observed wh en larvae were shocked at stage 16. To study protein synthesis during heat shock, larvae were pulsed with [S-35]-methionine during heat shoc k and labeled proteins were analyzed by electrophoresis under reducing and denaturing conditions. Larvae synthesized two sets of heat-shock proteins at doublet molecular weights of 83/78 and 62/59 kDa. These pr oteins were synthesized independently of the stage of development at w hich the shock was administered or the magnitude of the heat shock.