7. GAS EXCHANGE IN FISH
255
(1967), Randall et aZ. ( 1967), Robin and Murdaugh (1967), Dejours
et al. ( 1968), and Piiper and Baumgarten-Schumann ( 1968a,b) have
discussed aquatic gas exchange in detail; they have shown how the design of the exchanger can be related to the properties of the media on
either side of the respiratory epithelium, in this case blood and water.
The diffusion of gases in both tissues and water is extremely slow
(Table I ) , and the design of the gas exchange system is such that
diffusion is kept to a minimum and largely restricted to the movement of
oxygen and carbon dioxide across the gill epithelium. Gas molecules
are delivered to or removed from the gill epithelium by the bulk flow
of water and blood.
Except for some larval forms, gills are ubiquitous in fish. The fine
structure of the gills of tcleosts has been described by Hughes and
Grimstone ( 1965), Rhodin ( 1964), Newstead ( 1967), and Hughes and
Datta Munshi (1968). Other groups of fish have received less attention,
references and a general description of the anatomy of the gills of elasmobranchs, cyclostomes, and Dipnoi can be found in Daniel (1922),
Fry (1957), Chapman et al. (1963), and Johansen and Strahan (1963).
The gills form a sievelike structure placed in the path of the respiratory water flow. The secondary lamellae form the side walls of this sieve
(Fig. 1) and probably represent the major respiratory portion of the
gill structure (Hughes, 1966a; Muir and Hughes, 1969). The total surface area of the secondary lamellae is about 5 cm’/g body weight (Gray,
1954; Hughes, 1966a). There is a countercurrent (van Dam, 1938;
Hughes and Shelton, 1962) or multicapillary (Piiper and Schumann,
1967) arrangement of the flows of blood and water on either side of the
gill epithelium; the epithelium is usually between 1 and 5 p in thickness.
The ratio of the flows of blood and water is somewhere between 1 : l O
(Piiper and Schumann, 1967; Garey, 1967) and 1:80 (Stevens and Randall, 196713). The ratios of the content per mm Hg partial pressure of
both oxygen and carbon dioxide in water and blood are between 1: 10
and 1:20 (Black et al., 1966; Beaumont and Randall, 1968).
1. DIMENSIONS OF THE GILLS
A number of workers (see Muir, 1969, for reference) have measured
the dimensions of the gills of teleost fish and estimated the total surface
area of thc secondary lamellae, which is generally considered to represent the anatomical respiratory surface area. The surface area of the
gills discussed below refers to the total surface area of the secondary
laniellae.
The average surface area of the gills of teleosts, compiled from the
255
(1967), Randall et aZ. ( 1967), Robin and Murdaugh (1967), Dejours
et al. ( 1968), and Piiper and Baumgarten-Schumann ( 1968a,b) have
discussed aquatic gas exchange in detail; they have shown how the design of the exchanger can be related to the properties of the media on
either side of the respiratory epithelium, in this case blood and water.
The diffusion of gases in both tissues and water is extremely slow
(Table I ) , and the design of the gas exchange system is such that
diffusion is kept to a minimum and largely restricted to the movement of
oxygen and carbon dioxide across the gill epithelium. Gas molecules
are delivered to or removed from the gill epithelium by the bulk flow
of water and blood.
Except for some larval forms, gills are ubiquitous in fish. The fine
structure of the gills of tcleosts has been described by Hughes and
Grimstone ( 1965), Rhodin ( 1964), Newstead ( 1967), and Hughes and
Datta Munshi (1968). Other groups of fish have received less attention,
references and a general description of the anatomy of the gills of elasmobranchs, cyclostomes, and Dipnoi can be found in Daniel (1922),
Fry (1957), Chapman et al. (1963), and Johansen and Strahan (1963).
The gills form a sievelike structure placed in the path of the respiratory water flow. The secondary lamellae form the side walls of this sieve
(Fig. 1) and probably represent the major respiratory portion of the
gill structure (Hughes, 1966a; Muir and Hughes, 1969). The total surface area of the secondary lamellae is about 5 cm’/g body weight (Gray,
1954; Hughes, 1966a). There is a countercurrent (van Dam, 1938;
Hughes and Shelton, 1962) or multicapillary (Piiper and Schumann,
1967) arrangement of the flows of blood and water on either side of the
gill epithelium; the epithelium is usually between 1 and 5 p in thickness.
The ratio of the flows of blood and water is somewhere between 1 : l O
(Piiper and Schumann, 1967; Garey, 1967) and 1:80 (Stevens and Randall, 196713). The ratios of the content per mm Hg partial pressure of
both oxygen and carbon dioxide in water and blood are between 1: 10
and 1:20 (Black et al., 1966; Beaumont and Randall, 1968).
1. DIMENSIONS OF THE GILLS
A number of workers (see Muir, 1969, for reference) have measured
the dimensions of the gills of teleost fish and estimated the total surface
area of thc secondary lamellae, which is generally considered to represent the anatomical respiratory surface area. The surface area of the
gills discussed below refers to the total surface area of the secondary
laniellae.
The average surface area of the gills of teleosts, compiled from the