On the involvement of mucous secretion in teleost osmoregulation

Abstract

Diffusion coefficients of ²²Na or ³⁶Cl through fish mucus (1.0–2.4 mg protein/ml) are similar (±15%) to those through control saline solutions. The ion-exchange capacity of the mucus was 70–80 μequiv./g mucus, as measured by titration with added salts. These results suggest that dilute mucous solutions could not impede the passive movement of ions sufficient to explain the sodium-retaining effect of prolactin. Other mechanisms by which mucus may act in teleost osmoregulation are discussed.