438
JOHAN B. STEEN
E. Gas Deposition in Fishes with Poorly Developed Rete
The situation becomes more difficult when we attempt to explain
the high concentration of inert gases found in many physostomes, the
above-mentioned whitefish of Hufner is an example. The swim bladder
of these fishes possesses only a very poorly developed rete; in many
cases, it consists of only a few arteries and veins (Fange, 1958; Fahlkn,
1967). One possibility is that inert gases in these fishes are concentrated
by an entirely different process. However, Wittenberg (1958) showed
that even in these fishes the freshly deposited gas contained predominantly O?. This indicates that the final high tension of inert gases may
result from secondary reabsorption of 0,. The presence of Hb would
certainly increase the rate of 0, reabsorption above that of inert gases.
It is most likely, as concluded by Wittenberg (1958) and substantiated
by Sundnes (1963), that the high partial pressures of inert gases found
in these fishes result from the interaction between a countercurrent
mechanism of lower capacity than that found in physoclists and a reabsorptive process with a high capacity.
Gas deposition in the herring, which lacks a rete altogether (Fahlkn,
1967), has not been investigated. Most likely it depends on acidification
alone. Variation in gas composition will be accomplished by the interplay between the rate of deposition and that of reabsorption. The
problem is obviously in need of experimental data.
VII. NERVOUS CONTROL OF THE HYDROSTATIC
FUNCTION OF THE SWIM BLADDER
The volume of the swim bladder may be considered to be steadily
controlled by two reflex mechanisms: an inflatory reflex (gas deposition)
and a deflatory reflex (gas reabsorption). Both these reflexes seem to be
complex processes involving reactions of several categories of effectors
in the swim bladder.
Treatments that increase the specific gravity of the fish act as stimuli
initiating the inflatory reflex. Thus gas deposition (inflation) can be
produced experimentally by an increase of the external hydrostatic
pressure, by removal of a part of its gas content, or by attachment of
small weights to the fish (see Fange, 1953). All these treatments reduce
the degree of stretch in the bladder wall.
Treatments that lower the specific gravity of the fish, or increase the
JOHAN B. STEEN
E. Gas Deposition in Fishes with Poorly Developed Rete
The situation becomes more difficult when we attempt to explain
the high concentration of inert gases found in many physostomes, the
above-mentioned whitefish of Hufner is an example. The swim bladder
of these fishes possesses only a very poorly developed rete; in many
cases, it consists of only a few arteries and veins (Fange, 1958; Fahlkn,
1967). One possibility is that inert gases in these fishes are concentrated
by an entirely different process. However, Wittenberg (1958) showed
that even in these fishes the freshly deposited gas contained predominantly O?. This indicates that the final high tension of inert gases may
result from secondary reabsorption of 0,. The presence of Hb would
certainly increase the rate of 0, reabsorption above that of inert gases.
It is most likely, as concluded by Wittenberg (1958) and substantiated
by Sundnes (1963), that the high partial pressures of inert gases found
in these fishes result from the interaction between a countercurrent
mechanism of lower capacity than that found in physoclists and a reabsorptive process with a high capacity.
Gas deposition in the herring, which lacks a rete altogether (Fahlkn,
1967), has not been investigated. Most likely it depends on acidification
alone. Variation in gas composition will be accomplished by the interplay between the rate of deposition and that of reabsorption. The
problem is obviously in need of experimental data.
VII. NERVOUS CONTROL OF THE HYDROSTATIC
FUNCTION OF THE SWIM BLADDER
The volume of the swim bladder may be considered to be steadily
controlled by two reflex mechanisms: an inflatory reflex (gas deposition)
and a deflatory reflex (gas reabsorption). Both these reflexes seem to be
complex processes involving reactions of several categories of effectors
in the swim bladder.
Treatments that increase the specific gravity of the fish act as stimuli
initiating the inflatory reflex. Thus gas deposition (inflation) can be
produced experimentally by an increase of the external hydrostatic
pressure, by removal of a part of its gas content, or by attachment of
small weights to the fish (see Fange, 1953). All these treatments reduce
the degree of stretch in the bladder wall.
Treatments that lower the specific gravity of the fish, or increase the