The influence of body weight on gas exchange in the air-breathing fish, Clarias batrachus

Beta-adrenergic control of plasma glucose and free fatty acid levels in the air-breathing African catfishClarias gariepinusBurchell 1822

“…For Clarias, aquatic oxygen is still the primary source of oxygen as they are normally classified as a facultative airbreathers (Magid, 1971;Jordan, 1976;Bevan and Kramer, 1987). Apparently, air-breathing in this species did not lead to an evolutionary change in the control of lipolysis as we hypothesised.…”

“…Therefore, in the present study the effect of β-adrenoceptor stimulation on plasma FFA levels was investigated in the airbreathing African catfish Clarias gariepinus. Clarias species are among the best-known air-breathing fish species (Graham, 1997) and are mostly classified as facultative air-breathers (Magid, 1971;Jordan, 1976;Bevan and Kramer, 1987), meaning that they can live indefinitely on aquatic oxygen and breathe air only when necessary. When African catfish are subjected to low aquatic oxygen tensions, the air-breathing frequency increased, resulting in a constant total oxygen consumption (Magid, 1971;Jordan, 1976).…”

“…Clarias species are among the best-known air-breathing fish species (Graham, 1997) and are mostly classified as facultative air-breathers (Magid, 1971;Jordan, 1976;Bevan and Kramer, 1987), meaning that they can live indefinitely on aquatic oxygen and breathe air only when necessary. When African catfish are subjected to low aquatic oxygen tensions, the air-breathing frequency increased, resulting in a constant total oxygen consumption (Magid, 1971;Jordan, 1976). In this way, African catfish can sustain a complete aerobic metabolism at low aquatic oxygen tensions and it is thus unlikely that it experiences functional hypoxia in its natural surroundings.…”

Microcirculation of gills and accessory respiratory organs of the walking catfish Clarias batrachus

“…ARO in Clariidae enable these fish to survive in hypoxic water (Bevan and Kramer, 1987;Das, 1927;Ghosh et al, 1990;Jordan, 1976) and they support gas exchange during brief terrestrial sojourns (Das, 1927;Jordan, 1976) and during drought when the gills may be covered with viscus mud (Bruton, 1979). Superficially, Clarias ARO appear to be complex and highly specialized organs.…”

“…Clarias batrachus is a facultative air-breather and may survive total submersion indefinitely in aerated, temperate water (Jordan, 1976;Munshi et al, 1976). Well-developed gills are supplemented by additional, modified gills (fans), two pairs of tree-like arborescent (dendritic) organs, and respiratory epithelium lining the suprabranchial chamber (Das, 1927;Munshi, 1961).…”