9. AIR BREATHING IN FISHES
383
less than 10% of the total oxygen uptake in adult fish (Johansen and
Lenfant, 1967; Lenfant and Johansen, 1968). Aquatic breathing remains
very important in CO, elimination and is, in Protopterus (Lenfant and
Johansen, 1968), about 2.5 times more effective than the lungs in removing CO,. In many fishes the skin plays an important role in gas exchange,
particularly in CO, elimination. Cunningham (1934) reported a gas
exchange ratio in excess of 10 for the skin of Lepidosiren in water. During air exposure the skin is also important in gas exchange and marked
cutaneous vasodilation has been reported for the common eel, Angtiillu
(Berg and Steen, 1965) and Lepidosiren (Johansen and Lenfant, 1967).
In Cobitis fossilis, an intestinal air breather (Calugareanu, 1907), and
Gillichtys mirabilis, a marine gobiid fish practicing accessory air-breathing with the buccopharyngeal cavity (Todd and Ebeling, 1966), Oz
absorption is the dominant feature of air breathing (Table 111).
The large variation of total 0, uptake, apparent in Table 111, may be
related to feeding. Oxygen uptake in Protopterus has been reported to
decline rapidly between 24 and 48 hr after the last food intake, and a
constant metabolic rate was maintained only as long as the intake of
food exceeded the prevailing oxidation rate (Smith, 1930).
A labile oxygen uptake was also apparent during air exposure of
juvenile Lepidosiren (Johansen and Lenfant, 1967) and adult Amia. In
Lepidosiren the 0, uptake fell to 20% of the value in water in less than 6
Neocemiodur
Amio IO'C
Anguillo
I
2
3
4
5
Time (minutes)
Fig. 8. Rate of O? depletion from air-breathing organs in various fishes. The
slopes represent average values. Information selected from Lenfant et al. ( 1966),
Neoceratodus; Johansen et al. ( 1970), Amio; Berg and Steen (1965), Aiigtiilk;
Johansen (1966), Symbranchus; Todd and Ebeling ( 1966), Gillichtys; Lenfant and
Johansen ( 1968), Protopterus; Johansen and Lenfant ( 1967), Lepidosiren; and
Johansen et al. ( 1968 ) , Electrophorus.
383
less than 10% of the total oxygen uptake in adult fish (Johansen and
Lenfant, 1967; Lenfant and Johansen, 1968). Aquatic breathing remains
very important in CO, elimination and is, in Protopterus (Lenfant and
Johansen, 1968), about 2.5 times more effective than the lungs in removing CO,. In many fishes the skin plays an important role in gas exchange,
particularly in CO, elimination. Cunningham (1934) reported a gas
exchange ratio in excess of 10 for the skin of Lepidosiren in water. During air exposure the skin is also important in gas exchange and marked
cutaneous vasodilation has been reported for the common eel, Angtiillu
(Berg and Steen, 1965) and Lepidosiren (Johansen and Lenfant, 1967).
In Cobitis fossilis, an intestinal air breather (Calugareanu, 1907), and
Gillichtys mirabilis, a marine gobiid fish practicing accessory air-breathing with the buccopharyngeal cavity (Todd and Ebeling, 1966), Oz
absorption is the dominant feature of air breathing (Table 111).
The large variation of total 0, uptake, apparent in Table 111, may be
related to feeding. Oxygen uptake in Protopterus has been reported to
decline rapidly between 24 and 48 hr after the last food intake, and a
constant metabolic rate was maintained only as long as the intake of
food exceeded the prevailing oxidation rate (Smith, 1930).
A labile oxygen uptake was also apparent during air exposure of
juvenile Lepidosiren (Johansen and Lenfant, 1967) and adult Amia. In
Lepidosiren the 0, uptake fell to 20% of the value in water in less than 6
Neocemiodur
Amio IO'C
Anguillo
I
2
3
4
5
Time (minutes)
Fig. 8. Rate of O? depletion from air-breathing organs in various fishes. The
slopes represent average values. Information selected from Lenfant et al. ( 1966),
Neoceratodus; Johansen et al. ( 1970), Amio; Berg and Steen (1965), Aiigtiilk;
Johansen (1966), Symbranchus; Todd and Ebeling ( 1966), Gillichtys; Lenfant and
Johansen ( 1968), Protopterus; Johansen and Lenfant ( 1967), Lepidosiren; and
Johansen et al. ( 1968 ) , Electrophorus.