328
G. SKELTON
V. THE CHEMICAL REGULATION OF RESPIRATION
The metabolic rate in fish, as measured by oxygen consumption, can
be influenced by a large number of internal or external factors (Fry,
1957). Temperature and size (Job, 1955; Beamish and Mookherjii, 1964;
Beamish, 1964a), pollution of various types (Erichsen Jones, 1964),
season ( Beamish, 1964b), and activity ( Brett, 1964; Stevens and Randall,
1967b) have been examined in some detail. Although they all change
the animal's demand for oxygen there is no evidence, except perhaps
in the case of changes in activity (Stevens and Randall, 1967a), that
they are directly involved in the modifications of ventilation and perfusion which result in the demand being met. It seems likely that factors
such as these operate primarily, although not exclusively, at the level
of the cell. Other changes, most notably of oxygen concentration, carbon
dioxide concentration, and pH level in the ventilation stream and/or the
blood, also influence oxygen consumption but in a more complex way.
All three factors may be involved to varying degrees in mechanisms
important in the regulation of gas exchange. The degree of internal
change in the oxygen, carbon dioxide, or pH levels as a result of environmental fluctuations in these parameters would therefore depend
on the characteristics of the total regulatory system. Variations in
metabolic rate in this case would be a function of the metabolic cost of
regulation, the overall efficiency of regulation, and ultimately the direct
effect of any changes at the tissue level, although these would be
small if the regulation were efficient. It is probable that regulatory systems of this general type, sensitive to respiratory gas concentrations
within the body, and perhaps in the environment as well, would be
directly involved in the responses which cope with the respiratory requirements of the cells under a wide variety of different conditions,
including those of temperature, size, season, and activity mentioned
above.
A. Oxygen
1. EFFECT OF OXYGEN CONCENTRATIONS ON OXYGEN
CONSUMPTION AND GILL VENTILATION
a. Respirato y Dependence. Progressive depletion of oxygen in the
water breathed by a fish at first produces no change (respiratory independence) but eventually leads to a greater and greater restriction of
G. SKELTON
V. THE CHEMICAL REGULATION OF RESPIRATION
The metabolic rate in fish, as measured by oxygen consumption, can
be influenced by a large number of internal or external factors (Fry,
1957). Temperature and size (Job, 1955; Beamish and Mookherjii, 1964;
Beamish, 1964a), pollution of various types (Erichsen Jones, 1964),
season ( Beamish, 1964b), and activity ( Brett, 1964; Stevens and Randall,
1967b) have been examined in some detail. Although they all change
the animal's demand for oxygen there is no evidence, except perhaps
in the case of changes in activity (Stevens and Randall, 1967a), that
they are directly involved in the modifications of ventilation and perfusion which result in the demand being met. It seems likely that factors
such as these operate primarily, although not exclusively, at the level
of the cell. Other changes, most notably of oxygen concentration, carbon
dioxide concentration, and pH level in the ventilation stream and/or the
blood, also influence oxygen consumption but in a more complex way.
All three factors may be involved to varying degrees in mechanisms
important in the regulation of gas exchange. The degree of internal
change in the oxygen, carbon dioxide, or pH levels as a result of environmental fluctuations in these parameters would therefore depend
on the characteristics of the total regulatory system. Variations in
metabolic rate in this case would be a function of the metabolic cost of
regulation, the overall efficiency of regulation, and ultimately the direct
effect of any changes at the tissue level, although these would be
small if the regulation were efficient. It is probable that regulatory systems of this general type, sensitive to respiratory gas concentrations
within the body, and perhaps in the environment as well, would be
directly involved in the responses which cope with the respiratory requirements of the cells under a wide variety of different conditions,
including those of temperature, size, season, and activity mentioned
above.
A. Oxygen
1. EFFECT OF OXYGEN CONCENTRATIONS ON OXYGEN
CONSUMPTION AND GILL VENTILATION
a. Respirato y Dependence. Progressive depletion of oxygen in the
water breathed by a fish at first produces no change (respiratory independence) but eventually leads to a greater and greater restriction of