Embryonic thermosensitivity and hatchling morphology differ among three species of crocodilians farm-raised in China

We incubated eggs of three species of crocodilians farm-raised in China at three (Crocodylus porosus at 29, 31 and 33 degrees C) or four (C. niloticus and C. siamensis at 29, 30, 31 and 33 degrees C) constant temperatures to examine differences in hatching success, incubation length and hatchling morphology among species and among temperature treatments. The lowest and highest temperatures are respectively close to the lower and upper thermal limits to which embryonic crocodilians can tolerate. The three species differed morphologically at hatching. Hatching success did not differ among C. niloticus eggs incubated at 29, 30, 31 and 33 degrees C, and hatchlings hatched at these temperatures did not differ from each other in body size, mass and shape. Hatching success did not differ among C. porosus eggs incubated at 29, 31 and 33 degrees C, but the lowest temperature resulted in premature hatchlings. Hatching success at 29 degrees C was extremely low in C. siamensis. Morphologically, C. siamensis hatchlings hatched at 30 degrees C and 31 degrees C formed a group, which slightly differed from that formed by hatchlings hatched at 33 degrees C. Data from the present study and literature allow us to draw the following three conclusions. First, temperatures within the range from 29 degrees C to 33 degrees C are suitable for incubation of C. niloticus eggs. Second, temperatures within the range from 30 degrees C to 33 degrees C are suitable for embryonic development in C. porosus and C. siamensis. Third, the temperature of 29 degrees C adversely affects embryonic development in C. porosus and C. siamensis.