306
G. SHELTON
The work done in breathing a unit volume of water would be -Pi +
D + P,. If the data available in work cited previously are used, this
total would usually be between 1 x lo6 and 2 x loG ergs/liter of water
ventilated. Assuming 20% efficiency in the respiratory muscles, 0.025-0.05
ml of oxygen would be needed to pump 1 liter of water. Under normal
conditions this would represent only 0 5 1 % of the oxygen taken from
that amount of water by the fish. Considerable increases in these figures
are found if the calculations are repeated for active fish or for animals in
a poorly aerated environment ( Alexander, 1967).
The fact that the pressures in all parts of the system vary during
both inspiration and expiration will make the real system less efficient
than the model. In addition, there is often considerable reflux through
the mouth during expiration and through the opercular openings during
inspiration. This means that the ventilation volume is not the same as
the overall volume changes. It seems very doubtful that these factors
could account for the discrepancy between oxygen consumption measurements and the calculations.
2. THE PUMP MUSCULAWE AND SKELETON
Several accounts have been published of the head skeleton and its
musculature in teleosts, some of which refer specifically to ventilation
( Ballintijn and Hughes, 1965; Henschel, 1941; Hughes and Ballintijn,
1968; Hughes and Shelton, 1962; Kirchhoff, 1958). Interactions occur
between the skeleton, muscles, and tendons so that movements of one
component tend to cause complementary movements in many others.
Because of these interactions it is very difficult to determine the precise
role of any muscle in the overall pattern. Anatomical studies, extirpation of muscles, and movement recordings all provide valuable information, but the recent studies of Ballintijn and Hughes (1965) and Hughes
and Ballintijn ( 1968) using electromyography give the most convincing
picture of the sequences of muscle contraction. The level of electrical
activity in a muscle can also be used as a guide to the relative contribution of that muscle in the total mechanism, and in Callionymus Hughes
and Ballintijn ( 1968) have demonstrated a clear relationship between
stroke volume and electrical activity as shown by the height of the integrated electromyogram.
The following brief account is based on a generalized scheme of the
teleost respiratory musculature ( Fig. 6 ) . Details of the musculature obviously vary from species to species as will their mode of action (Hughes
and Ballintijn, 1968). One of the interesting conclusions of Ballintijn
and Hughes (1965) is that the same breathing pattern is maintained
G. SHELTON
The work done in breathing a unit volume of water would be -Pi +
D + P,. If the data available in work cited previously are used, this
total would usually be between 1 x lo6 and 2 x loG ergs/liter of water
ventilated. Assuming 20% efficiency in the respiratory muscles, 0.025-0.05
ml of oxygen would be needed to pump 1 liter of water. Under normal
conditions this would represent only 0 5 1 % of the oxygen taken from
that amount of water by the fish. Considerable increases in these figures
are found if the calculations are repeated for active fish or for animals in
a poorly aerated environment ( Alexander, 1967).
The fact that the pressures in all parts of the system vary during
both inspiration and expiration will make the real system less efficient
than the model. In addition, there is often considerable reflux through
the mouth during expiration and through the opercular openings during
inspiration. This means that the ventilation volume is not the same as
the overall volume changes. It seems very doubtful that these factors
could account for the discrepancy between oxygen consumption measurements and the calculations.
2. THE PUMP MUSCULAWE AND SKELETON
Several accounts have been published of the head skeleton and its
musculature in teleosts, some of which refer specifically to ventilation
( Ballintijn and Hughes, 1965; Henschel, 1941; Hughes and Ballintijn,
1968; Hughes and Shelton, 1962; Kirchhoff, 1958). Interactions occur
between the skeleton, muscles, and tendons so that movements of one
component tend to cause complementary movements in many others.
Because of these interactions it is very difficult to determine the precise
role of any muscle in the overall pattern. Anatomical studies, extirpation of muscles, and movement recordings all provide valuable information, but the recent studies of Ballintijn and Hughes (1965) and Hughes
and Ballintijn ( 1968) using electromyography give the most convincing
picture of the sequences of muscle contraction. The level of electrical
activity in a muscle can also be used as a guide to the relative contribution of that muscle in the total mechanism, and in Callionymus Hughes
and Ballintijn ( 1968) have demonstrated a clear relationship between
stroke volume and electrical activity as shown by the height of the integrated electromyogram.
The following brief account is based on a generalized scheme of the
teleost respiratory musculature ( Fig. 6 ) . Details of the musculature obviously vary from species to species as will their mode of action (Hughes
and Ballintijn, 1968). One of the interesting conclusions of Ballintijn
and Hughes (1965) is that the same breathing pattern is maintained