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D. J. RANDALL
ventral aortic pressures of 30 mni Hg in the cod, Gadus morhua; his fish
werc restrained and ventral side up, but not anesthetized. Robertson et al.
(1966) measured pressures of 82/50 mm Hg in the ventral aorta and
44/37 mm Hg in the dorsal aorta of the spring salmon. There was no
water flow over thc gills when records were taken, initiating a reflex
bradycardia as indicated by the low heart rates in these fish. Blood
pressures have been recordcd in unrestrained trout (Randall et al.,
1965; Holeton and Randall, 1967a; Stevens and Randall, 1967a), salmon
(Smith et al., 1967; Davis, 1968), and carp (Garey, 1967). Hanson
(1967) has recorded blood pressure in a number of unrestrained Chondrichthyes (skate, dogfish, and ratfish). Arterial and intraventicular pressures have been recorded in immobilized elasmobranchs by Sudak
( 1965a,b), Satchell (1961), and Satchell and Jones (1967). All values
were in the range of 30-70 mm Hg but show variability within a species as
well as between species. In general, arterial blood pressures appear to
be lower in elasmobranchs than in teleosts.
During diastole, ventral aortic pressure falls, valves in the conus or
bulbus close, and pressure declines as the blood leaves the aorta. The
pulse pressure in the ventral aorta of fishes is between 10 and 30 mm
Hg, increasing to values as high as 40 mm Hg during hypoxia ( Holeton
and Randall, 1967a).
The first appreciable drop in blood pressure occurs across the gills.
Hanson (1967) recorded dorsal aortic diastolic pressures which were 15%
in skate Raja binoculata, 20% in dogfish Squalus suckleyi, and 26% in
ratfish Hydrolagus colliei, of the ventral aortic blood pressure. The
respcctive reductions in systolic pressure were 25, 25, and 40% of the ventral aortic pressure. The recorded pressure drop in trout, Salmo gairdneri
( Holeton and Randall, 1967a; Stevens and Randall, 1967a), carp,
Cyprinus carpio ( Garey, 1967), and lungfish (Johansen and Hanson,
1968) was between 40 and 50% of the respective ventral aortic pressure.
Hypoxia probably increases the resistance to flow through the gills in
the trout ( Holeton and Randall, 1967a) and dogfish, Squalus acanthias
(Satchell, 1961), whereas exercise (Stevens and Randall, 1967a,b) and
catecholamines (Burger and Bradley, 1951) cause a decrease in resistance to blood flow through the gills.
The dorsal aorta of fishes is a long tube, running the length of the
body, which distributes blood to the systemic circulation. It is much less
elastic than the ventral aorta. Blood pressure and flow in the dorsal aorta
of the cod, Gadus morliua, is pulsatile (Shelton et d., 1969) even though
blood flows through the capillaries of the gills before entering this
vesscl. Pulsc pressures in the dorsal aorta are usually less than 50% of
those in the ventral aorta.
D. J. RANDALL
ventral aortic pressures of 30 mni Hg in the cod, Gadus morhua; his fish
werc restrained and ventral side up, but not anesthetized. Robertson et al.
(1966) measured pressures of 82/50 mm Hg in the ventral aorta and
44/37 mm Hg in the dorsal aorta of the spring salmon. There was no
water flow over thc gills when records were taken, initiating a reflex
bradycardia as indicated by the low heart rates in these fish. Blood
pressures have been recordcd in unrestrained trout (Randall et al.,
1965; Holeton and Randall, 1967a; Stevens and Randall, 1967a), salmon
(Smith et al., 1967; Davis, 1968), and carp (Garey, 1967). Hanson
(1967) has recorded blood pressure in a number of unrestrained Chondrichthyes (skate, dogfish, and ratfish). Arterial and intraventicular pressures have been recorded in immobilized elasmobranchs by Sudak
( 1965a,b), Satchell (1961), and Satchell and Jones (1967). All values
were in the range of 30-70 mm Hg but show variability within a species as
well as between species. In general, arterial blood pressures appear to
be lower in elasmobranchs than in teleosts.
During diastole, ventral aortic pressure falls, valves in the conus or
bulbus close, and pressure declines as the blood leaves the aorta. The
pulse pressure in the ventral aorta of fishes is between 10 and 30 mm
Hg, increasing to values as high as 40 mm Hg during hypoxia ( Holeton
and Randall, 1967a).
The first appreciable drop in blood pressure occurs across the gills.
Hanson (1967) recorded dorsal aortic diastolic pressures which were 15%
in skate Raja binoculata, 20% in dogfish Squalus suckleyi, and 26% in
ratfish Hydrolagus colliei, of the ventral aortic blood pressure. The
respcctive reductions in systolic pressure were 25, 25, and 40% of the ventral aortic pressure. The recorded pressure drop in trout, Salmo gairdneri
( Holeton and Randall, 1967a; Stevens and Randall, 1967a), carp,
Cyprinus carpio ( Garey, 1967), and lungfish (Johansen and Hanson,
1968) was between 40 and 50% of the respective ventral aortic pressure.
Hypoxia probably increases the resistance to flow through the gills in
the trout ( Holeton and Randall, 1967a) and dogfish, Squalus acanthias
(Satchell, 1961), whereas exercise (Stevens and Randall, 1967a,b) and
catecholamines (Burger and Bradley, 1951) cause a decrease in resistance to blood flow through the gills.
The dorsal aorta of fishes is a long tube, running the length of the
body, which distributes blood to the systemic circulation. It is much less
elastic than the ventral aorta. Blood pressure and flow in the dorsal aorta
of the cod, Gadus morliua, is pulsatile (Shelton et d., 1969) even though
blood flows through the capillaries of the gills before entering this
vesscl. Pulsc pressures in the dorsal aorta are usually less than 50% of
those in the ventral aorta.