9. AIR BREATHING IN FISHES
403
cance in the normally 02-deficient stagnant tropical swamps, where
stirring of surface water by wind movement or other mechanical agitation should improve the respiratory quality of the water and make
branchial breathing more efficient.
Inflation and deflation of the air bladder in Amia definitely influence
the breathing pattern. A deflation causes the fish to promptly ascend for
air, while fishes approaching the surface for air breathing interrupt their
ascent and settle to the bottom again if the bladder is artificially inflated.
This response occurs whether air, oxygen, or nitrogen is injected. This
inflation response shows striking similarity with the inflation reflex
described long ago and known as the Hering-Breuer reflex in mammals.
In higher vertebrates the inhibition of breathing caused by stretch in
the lungs is no longer held to exert any important influence in control
of breathing since such changes do not supply information to the respiratory center about the respiratory quality of the blood. In air-breathing
fishes a stretch reflex may prove to play an important role since the
volume and thus the distention of the air bladder will change during
the long intervals between air breaths because of the low gas exchange
ratio for the air-breathing organ. Since the air bladder is primarily an
O2 absorber, the change in volume with time provides a measure of
the rate of 0, depletion. If the reflex described in fishes such as Amin
proves to be homologous with the vagus-mediated inflation reflex in
higher vertebrates, the case may exemplify a basic reflex type that
exerted a more important regulatory role early in its phylogenetic history.
An important role of the air which a fish takes below the surface is
its effect on buoyancy and, indeed, in most teleosts the air bladder is
engaged mainly in buoyancy control. In fishes which use the air bladder
primarily as a respiratory organ, changes of buoyancy clearly influence
breathing behavior, Ascent for air in such fishes may be provoked simply
by tying a weight around them (Spunvay and Haldane, 1963). The airbreathing fishes consequently face the additional task of coordinating
the mechanisms for buoyancy control with those engaged in satisfying
the respiratory needs.
H. Breathing Response to Air Exposure
Only a few of the fishes adapted for air breathing make voluntary
excursions onto dry land. Estivating fishes are, of course, compelled
to subsist on air breathing when entrapped in the substratum during
drought.
403
cance in the normally 02-deficient stagnant tropical swamps, where
stirring of surface water by wind movement or other mechanical agitation should improve the respiratory quality of the water and make
branchial breathing more efficient.
Inflation and deflation of the air bladder in Amia definitely influence
the breathing pattern. A deflation causes the fish to promptly ascend for
air, while fishes approaching the surface for air breathing interrupt their
ascent and settle to the bottom again if the bladder is artificially inflated.
This response occurs whether air, oxygen, or nitrogen is injected. This
inflation response shows striking similarity with the inflation reflex
described long ago and known as the Hering-Breuer reflex in mammals.
In higher vertebrates the inhibition of breathing caused by stretch in
the lungs is no longer held to exert any important influence in control
of breathing since such changes do not supply information to the respiratory center about the respiratory quality of the blood. In air-breathing
fishes a stretch reflex may prove to play an important role since the
volume and thus the distention of the air bladder will change during
the long intervals between air breaths because of the low gas exchange
ratio for the air-breathing organ. Since the air bladder is primarily an
O2 absorber, the change in volume with time provides a measure of
the rate of 0, depletion. If the reflex described in fishes such as Amin
proves to be homologous with the vagus-mediated inflation reflex in
higher vertebrates, the case may exemplify a basic reflex type that
exerted a more important regulatory role early in its phylogenetic history.
An important role of the air which a fish takes below the surface is
its effect on buoyancy and, indeed, in most teleosts the air bladder is
engaged mainly in buoyancy control. In fishes which use the air bladder
primarily as a respiratory organ, changes of buoyancy clearly influence
breathing behavior, Ascent for air in such fishes may be provoked simply
by tying a weight around them (Spunvay and Haldane, 1963). The airbreathing fishes consequently face the additional task of coordinating
the mechanisms for buoyancy control with those engaged in satisfying
the respiratory needs.
H. Breathing Response to Air Exposure
Only a few of the fishes adapted for air breathing make voluntary
excursions onto dry land. Estivating fishes are, of course, compelled
to subsist on air breathing when entrapped in the substratum during
drought.