CHAPTER 3
THE RELATIONSHIP BETWEEN TEMPERATURE AND THE RESTING RATE OF
METABOLISM IN Protopterus aethiopicus
Introduction
Few of all environmental factors known to affect metabolism are as significant as
temperature. The study of this relationship, from both a molecular and whole organism
perspective, yields insight into the intimate connection between animal energetic and the
environment. A derivation from first principles of the association between temperature
and the resting rate of metabolism has been a topic of rich conversation ever since August
Krogh and his co-workers attempted to formulate such a relationship for poikilothermic
organisms (Krogh 1914, 1916). His quantitative expression of this relationship for a
single species, the goldfish (Cassius auratus) led to his derivation of what came to be
known as "Krogh's normal curve" (Ege and Krogh 1914). The normal curve expressed an
exponential increase in metabolic rate as a function of increasing temperature.
Winberg (1956), examining resting metabolic rates in fishes, compared values
drawn from the literature to Krogh's normal curve in an effort to compare metabolic rates
from different species measured at different temperatures. Using the normal curve for
orientation, Winberg (1956) derived a series of coefficients that could be used to adjust
metabolic rates of temperate fishes by applying the Van't Hoff equation,
[Qio=(K2/K)(10 t2-1t)]
where Ki and K2 are the metabolic rates measured at two different temperatures ti
and t2, for changes in temperature across intervals of 10 'C. This permitted adjustment of