GROWTH, METABOLISM, AND CHORIOALLANTOIC VASCULAR DENSITY OF DEVELOPING SNAPPING TURTLES (CHELYDRA SERPENTINE) - INFLUENCE OF TEMPERATURE

In developing vertebrates the effects of temperature on physiological rates are not necessarily predictable. Chelydra serpentina eggs were i ncubated at either 24 degrees or 30 degrees C on vermiculite with a wa ter potential of approximately - 150 kPa. Measurements of oxygen consu mption rate (VO2), yolk-free mass, and chorioallantoic membrane (CAM) vascular density index (VDI) were made. Measurements began when the CA M completely covered the inside of the shell and were continued until just before hatching. Eggs incubated at 24 degrees C had a significant ly longer incubation time than eggs incubated at 30 degrees C (70 d vs . 51 d, respectively). Embryonic mass and VO2 of 24 degrees C-incubate d eggs increased and peaked Inter than in 30 degrees C-incubated eggs. Temperature did not affect peak egg VO2, embryonic mass, or CAM VDI. Graphical overlay and regression analysis of embryonic mass and VO2 da ta against time revealed the presence of similar patterns at both temp eratures. These data indicate that 24 degrees C-incubated eggs experie nced a slowing of development at the beginning of incubation but that growth and VO2 following CRM development (late in incubation) were ess entially the same as in eggs incubated at 30 degrees C. These results indicate that temperature has its effects primarily during the early p ortion of development and that Inter acclimation mitigates temperature effects. It is suggested that investigators should not treat reptilia n development as a single homogenous period, but rather as two separat e periods.