ABSTRACT
The sodium effluxes between the blood and the medium have been studied in Blennius pholis in 10, 40 and 100% s.w. and in transfer from 40 to 100% s.w. under equilibrium conditions with the isotope 24Na. In addition the sodium influxes have been studied in 40 and 100% s.w. in a similar manner.
The total flux in 100% s.w. has been found to be 100 mm. Na/1. blood/hr., and in 40 and 10% s.w. it has been found to be 20 mm. Na/1. blood/hr.
The results are interpreted as showing that the presence or absence of exchange diffusion does not alter the estimation of the active sodium efflux across the gills in 100% s.w.
The efflux experiments showed that the animal had a rapid adaptive ability to osmo-regulate upon transference from 40 to 100% s.w.
The electric potential differences between the blood and external medium have been measured in animals adapted to 10, 40, 100 and 150% s.w. and the blood serum concentrations of sodium and chloride ions have been measured in these media.
The mean potential differences ± standard deviation in 10, 40, 100 and 150% S.w. have been found to be – 3 ± 4·5 mV., +23 + 4 mV., +23 + 3 mV. and + 29·5 ± 5 mV. respectively (external medium taken as reference).
The results are interpreted as showing that there is active outward excretion of chloride ions in animals adapted to 150, 100 and 40 % s.w. and active inward absorption of chloride ions in 10% s.w. and of sodium ions in animals adapted to 40 and 10% s.w.
The drinking rate in 100 % s.w. has been calculated to be 27 mm. Na/kg. fish/hr. or 6 % body weight/hr.
