SREL Reprint #2138
 

Estimating Energy Metabolism of Goldfish (Carassius
auratus) and Southern Toads (Bufo terrestris) from^{ 86} Rb
Elimination Rates I evaluated the potential use of ^{86}Rb elimination rate constants (^{86}Rb k_{b}'s) as a
predictor of oxygen consumption rates (Vo_{2}'s) for two ectotherms: the goldfish
(Carassius auratus) and the southern toad (Bufo terrestris). I injected the
goldfish intraperitoneally with ^{86}Rb and measured the amount of the radionuclide
remaining in the fish every 24 d for 1428 d (eight measurements/treatment). I
gave the toads subcutaneous injections of ^{86}Rb and measured the remaining
radionuclide every 34 d for 22 d (seven measurements/treatment). I measured
'Vo_{2}'s and ^{86}Rb k_{b}'s of C. auratus at five temperatures (10.0, 12.9, 17.0, 21.2,
and 24.0 C), salinities (280, 800, 1550, 2300, and 2800 µM each of Na+, K+,
and Cl ), and food intake rates [0, 41, 100, 159, and 200 mg (dry) every 2 d] to
determine the sensitivity of this method to environmental conditions. I measured
Vo_{2}'s and ^{86}Rb k_{b}'s of B. terrestris at 20.0 and 27.5 C., and assessed the
sensitivity of the k. estimates to sampling interval by comparing simulated 3point
(1012 d between measurements) and 2point (22 d between measurements)
elimination curves. Elimination curves were best described by a single exponential
model. Carassius ^{86}Rbk_{b}'s increased with temperature and salinity, decreased
with increased body mass, and were not significantly affected by food intake rate.
Bufo ^{86}Rb k_{b}'s increased with temperature. There were significant relationships
between Vo,'s and ^{86}Rb k_{b}'s in both species, but this relationship lacked sufficient
predictability (rl < 0.20) to permit accurate estimates of C. auratus energy
metabolism. However, the relationship between Vo,'s and ^{86}Rb k_{b}'s in B.
terrestris was sufficiently predictive (rl = 0.68) to suggest that this method might
be used to estimate FMRs of amphibians. Comparisons of the B. terrestris ^{86}Rb
k_{b}'s with 2point and 3point elimination curves indicated that relatively infrequent
recaptures of individuals would be sufficient for field application of this method. SREL Reprint #2138 Peters, E.L. 1996. Estimating the energy metabolism of goldfish (Carassius auratus) and southern toads (Bufo terrestris) from ^{86}Rb elimination rates. Copeia 4:791804.
