MUCUS AS A DIFFUSION BARRIER TO OXYGEN - POSSIBLE ROLE IN O2 UPTAKE AT LOW PH IN CARP (CYPRINUS-CARPIO) GILLS

1. 1. The standard Vo of carp (Cyprinus carpio) is reduced at low pH, concurrently with the formation of mucus on the gills. 2. 2. The rate of diffusion of oxygen through mucus produced by carp in response to low pH was measured in a diffusion chamber and found to be 2.60 × 10-5 cm2/min per atm. The diffusion constant for water measured with the same apparatus was 3.60 × 10-5cm2/min per atm. 3. 3. The inhibition of the diffusion of oxygen into the gill bloodstream, and the inhibition of the flow of respiratory water between the secondary lamellae, are calculated for a gill with assumed dimensions. At thicknesses of mucus on the gills up to 5 μm the effects are similar, but at greater thicknesses the effect of slowing the water flow predominates. We conclude that mucus on the gills contributes to the hypoxia observed in fish subjected to high acidities. © 1979.