Hypoxic survival differs between two mole rat species (Spalax ehrenbergi) of humid and arid habitats

1. 1. Two chromosomal species, 2n = 52 and 2n =60 of the mole rat superspecies (Spalax ehrenbergi), occupy humid (2n = 52) and arid (2n = 60) habitats in Israel. 2. 2. Gas conductivity of the soil of the 2n = 52 mole rat is lower than that of the 2n = 60 mole rat, and the 2n = 52 mole rat is better adapted to hypoxia. 3. 3. The hypothesis that the 2n = 52 mole rat can survive to a lower pO₂ than the 2n = 60 mole rat was tested. 4. 4. Terminal pO₂ (Torr) of four females 2n = 52 was lower, 18.0 ± 2.9 (SD), than the terminal pO₂ of five females 2n = 60, 28.2 ± 5.1 (SD). 5. 5. The hypoxic survival of the 2n = 52 mole rat as compared to that of the 2n = 60 mole rat correlates with other physiological traits: breathing and heart frequencies, blood hemoglobin and tissue gas tensions.