297
8. THE REGULATION OF BREATHING
will be returned to later. However, the concept is a useful one provided that the full extent of interaction between pumps in producing
flow into the system, through the gills, and out to the environment is
appreciated.
The experiments of Hughes and Shelton (1958) were done on anesthetized animals held in a clamp which, although not interfering with
the breathing, was somewhat restricting. The pressures were measured
via fine metal tubes passed through the mouth and opercular openings.
These unnatural circumstances may have affected the overall respiratory
behavior of the fish since this is notoriously sensitive to interference
of all types (Fry, 1957). Saunders ( 1961) avoided these difficulties by
implanting flexible polyethylene cannulae in the buccal cavity through
the ethmoid region of the skull and in the opercular cavity through the
cleithrum. The cannulae were then connected to the manometer system
but were sufficiently flexible to permit free movement of the unanesthetized fish. This cannulation technique of Saunders, or modifications of
it, has since been used extensively (e.g., Holeton and Randall, 1967a;
Smith et al., 1967). Saunders did not measure the characteristics of his
manometers, and it seems possible that their frequency response was
low. However, in the case of Catostomus, the sucker, and Zctalurus, the
bullhead, the results differ only in details from those of Hughes and
Shelton (1958). In the case of Cyprinus, the carp, the differences were
marked since the resting animal was found to breathe intermittently
with a double excursion of pressure in both cavities for each cycle of
activity (Fig. 2a). There is some resemblance to the cough recorded in
the roach by Hughes and Shelton. The heavy breathing pattern was also
different and showed no gradient reversal in phase 4 (Fig. 2b).
b. Ecological Variation. Baglioni ( 1907) suggested that marine teleosts fell into four ecological categories between which there were
fairly clear differences in respiratory mechanism. The variation was
mainly in the degree of development of the branchiostegal apparatus
below the opercular flap. Hughes (196Ob) recorded breathing movements and pressure in a range of marine teleosts and, in general, confinned the validity of Baglioni’s classification.
In his first group are pelagic fish which never rest on the bottom
and in which the operculum is well developed with a small branchiostegal apparatus. Hughes (1960b) found a great deal of variation in
the pressure characteristics of fish in this category. In wrasse, Crenilabrus,
and herring, Clupea, the two pumps were balanced (Fig. 3a), but the
buccal pump predominated in the horse mackerel, Trachurus, and the
opercular pump in the whiting, Gadus. There has been very little work
8. THE REGULATION OF BREATHING
will be returned to later. However, the concept is a useful one provided that the full extent of interaction between pumps in producing
flow into the system, through the gills, and out to the environment is
appreciated.
The experiments of Hughes and Shelton (1958) were done on anesthetized animals held in a clamp which, although not interfering with
the breathing, was somewhat restricting. The pressures were measured
via fine metal tubes passed through the mouth and opercular openings.
These unnatural circumstances may have affected the overall respiratory
behavior of the fish since this is notoriously sensitive to interference
of all types (Fry, 1957). Saunders ( 1961) avoided these difficulties by
implanting flexible polyethylene cannulae in the buccal cavity through
the ethmoid region of the skull and in the opercular cavity through the
cleithrum. The cannulae were then connected to the manometer system
but were sufficiently flexible to permit free movement of the unanesthetized fish. This cannulation technique of Saunders, or modifications of
it, has since been used extensively (e.g., Holeton and Randall, 1967a;
Smith et al., 1967). Saunders did not measure the characteristics of his
manometers, and it seems possible that their frequency response was
low. However, in the case of Catostomus, the sucker, and Zctalurus, the
bullhead, the results differ only in details from those of Hughes and
Shelton (1958). In the case of Cyprinus, the carp, the differences were
marked since the resting animal was found to breathe intermittently
with a double excursion of pressure in both cavities for each cycle of
activity (Fig. 2a). There is some resemblance to the cough recorded in
the roach by Hughes and Shelton. The heavy breathing pattern was also
different and showed no gradient reversal in phase 4 (Fig. 2b).
b. Ecological Variation. Baglioni ( 1907) suggested that marine teleosts fell into four ecological categories between which there were
fairly clear differences in respiratory mechanism. The variation was
mainly in the degree of development of the branchiostegal apparatus
below the opercular flap. Hughes (196Ob) recorded breathing movements and pressure in a range of marine teleosts and, in general, confinned the validity of Baglioni’s classification.
In his first group are pelagic fish which never rest on the bottom
and in which the operculum is well developed with a small branchiostegal apparatus. Hughes (1960b) found a great deal of variation in
the pressure characteristics of fish in this category. In wrasse, Crenilabrus,
and herring, Clupea, the two pumps were balanced (Fig. 3a), but the
buccal pump predominated in the horse mackerel, Trachurus, and the
opercular pump in the whiting, Gadus. There has been very little work