Chloride Regulation at Low Salinities by Nereis Diversicolor (Annelida, Polychaeta)

The ability of the common brackish water polychaete worm Nereis diversicolor O. F. Müller to regulate osmotically and ionically has been well established (Schlieper, 1929; Beadle, 1937; Smith, 1955; Hohendorf, 1963; Oglesby, 1970; and others). Jørgensen & Dales (1957) demonstrated an uptake of chloride against the concentration gradient at low salinities, with a maximum rate of exchange under steady-state conditions at external chloride concentrations of 65–120 mM/I, and a drop in uptake rate to about one-third of that maximum in fresh water (Cl = 1·4mM/l). Fretter (1955) demonstrated a comparable uptake of sodium against the concentration gradient in this species, but without the maximum shown in the chloride exchanges.