THERMOREGULATION IN 3 SPECIES OF AFROTROPICAL SUBTERRANEAN MOLE-RATS (RODENTIA, BATHYERGIDAE) FROM ZAMBIA AND ANGOLA AND SCALING WITHIN THEGENUS CRYPTOMYS

The thermoregulatory characteristics of three species of Cryptomys fro m Zambia and Angola are examined and, together with published data on four other species of Cryptomys from southern Africa, used to determin e whether scaling occurs in this genus of subterranean rodents. The th ermoregulatory properties of acclimated giant Zambian mole-rats, Crypt omys mechowi (xBAR=267 g), Angolan mole-rats, Cryptomys bocagei (xBAR= 94 g) and Zambian common mole-rats Cryptomys hottentotus amatus (xBAR= 77 g) are,as follows. Mean resting metabolic rates (RMRs) within the r espective thermoneutral zones were 0.60+/-0.08 cm3 O2 g-1 h-1 (n=12) f or C. mechowi; 0.74+/-0.06 cm3 O2 g-1 h-1 (n=8) for C. bocagei and 0.6 3+/-0.06 cm3 O2 g-1 h-1 (n=21) for C. h. amatus. The thermoneutral zon es (TNZs) of all three species are narrow: 29-30-degrees-C for C. mech owi; 31.5-32.5-degrees-C for C. boeagei, and 28-32-degrees-C for C. h. amatus. The increase in mean RMR at the lowest temperatures tested (1 5-degrees-C for C. mechowi, 18-degrees-C for C. bocagei and C. h. amat us) was 2.35, 2.2 and 3.82 times their RMR in the TNZ respectively. Bo dy temperatures are low, 34+/-0.53-degrees-C (n=24) for C. mechowi, 33 .7+/-0.32-degrees-C (n=20) for C. bocagei and 33.8+/-0.43-degrees-C (n =40) for C. h amatus. At the lower limit of thermoneutrality, conducta nces are 0.09+/-0.01 cm3 O2 g-1 h-1-degrees-C-1 (n=30) in C. mechowi; 0.12+/-0.01 cm3 O2 g-1 h-1-degrees-C-1 (n=20) in C. bocagei and 0.12+/ -0.03 cm3 O2 g-1 h-1-degrees-C-1 (n=32) in C. h. amatus. The range in mean body mass among the seven species of Cryptomys examined for scali ng was 60 g (C. darlingi) to 267 g (C. mechowi). There is no clear rel ationship between RMR within the TNZ and body mass. The resultant rela tionship is represented by the power curve RMR=2.45 mass-0.259.