EFFECTS OF TEMPERATURE AND WATER ON CRITICAL OXYGEN-TENSION OF TURTLEEMBRYOS

The influences of temperature and water on the ability of turtle embry os to tolerate hypoxia were investigated by measuring critical oxygen tension, P-c, at different levels of temperature (22, 27, and 32 degre es C and hydric conditions (3 and 13% gravimetric water content). Eggs were half-buried in sand with 3 or 13% gravimetric water content and incubated at a constant 30 degrees C. Using a closed metabolic chamber , oxygen consumption, V-O2, was measured at decreasing oxygen tensions . Embryonic V-O2 varied as a function of incubation day and temperatur e, whereas the P-c differed among temperatures but not among incubatio n days. At a given incubation day, the P-c increased in direct proport ion to temperature. Eggs incubated in sand with 13% gravimetric water content achieved greater mass at days 30 and 39 than did those in sand with 3% gravimetric water content. However, V-O2, P-c, and masses of yolk-free hatchlings were similar in the two hydric conditions, indica ting that hypoxic tolerance of turtle eggs is not curtailed by excessi ve water absorption. The similarity in P-c is likely attributable to t he small V-O2/surface area ratio of turtle eggs. Within the range of p arameters studied, temperature, but not water, can modify the P-c of t urtle embryos. (C) 1994 Wiley-Liss, Inc.