Ion-exchange phenomena regulate the environment of embryos in the eggs of freshwater fish

Studies on the fish-gill microclimate: interactions between gill tissue, mucus and water-quality

“…It could arise as a result of selective permeability of the mucus to cation diffusion from the filament; it could be the result of unequal K+ and Cl-mobilities within the charged mucus, leading to a liquid-junction potential at the 3M KCl, mucus interface (Overbeek 1961); it is, however, most easily interpreted as a 'Donnan potential' arising as a result of immobile negative charges within the mucus and in equilibrium with a dilute external solution. The situation is comparable to that in the perivitelline fluid of fish eggs (Peterson 1984, Shephard 1987 and in snail mucus (Schlichter 1982).…”

“…Interactions between ion exchange 'equilibria' and diffusion gradients have, however, been mode lied from in situ measurements in a similar material. ; the perivitelline fluid of fish eggs (Shephard 1987, Shephard & McWilliams 1989.…”

Studies on the fish-gill microclimate: interactions between gill tissue, mucus and water-quality

“…It could arise as a result of selective permeability of the mucus to cation diffusion from the filament; it could be the result of unequal K+ and Cl-mobilities within the charged mucus, leading to a liquid-junction potential at the 3M KCl, mucus interface (Overbeek 1961); it is, however, most easily interpreted as a 'Donnan potential' arising as a result of immobile negative charges within the mucus and in equilibrium with a dilute external solution. The situation is comparable to that in the perivitelline fluid of fish eggs (Peterson 1984, Shephard 1987 and in snail mucus (Schlichter 1982).…”

“…Interactions between ion exchange 'equilibria' and diffusion gradients have, however, been mode lied from in situ measurements in a similar material. ; the perivitelline fluid of fish eggs (Shephard 1987, Shephard & McWilliams 1989.…”

An analysis of the ion-exchange characteristics of fish-egg chorions

“…Although it is difficult to predict the in fluence of this equilibrium on the physiology of the developing embryo, some features of this system must be examined. These include elevated cation activity and decreased pH within the chorion, with respect to external solutions; factors that also probably extend to the perivitelline fluid due to the presence there of charged colloids (Shephard 1987b). It is important to note that ion exchange sites ensure the existence of high cation activities in the immediate environ_ment of the embryo, evep in extremely dilute solutions, but that this stability is lost in the presence of low pH and high concentrations of divalent and trivalent cations.…”

“…For both solutions the equivalent ionic fraction for calcium within the chorion lies between 0.90 and 1.0, indicating that at least 90~ of the anionic sites are neutralised by calcium ions. On this basis it is reasonable to predict the Donnan ratio for potassium from the ion exchange calculations for calcium as described previously (Shephard 1987b). This has been done for both solutions (I mM K +, ImM Ca ?+ , pH 8.35; 0.1raM K +, 0.1raM Ca 2+, pH 7.70) and the predictions are shown in Fig.…”

Studies on the fish-gill microclimate: interactions between gill tissue, mucus and water-quality

“…It could arise as a result of selective permeability of the mucus to cation diffusion from the filament; it could be the result of unequal K+ and Cl-mobilities within the charged mucus, leading to a liquid-junction potential at the 3M KCl, mucus interface (Overbeek 1961); it is, however, most easily interpreted as a 'Donnan potential' arising as a result of immobile negative charges within the mucus and in equilibrium with a dilute external solution. The situation is comparable to that in the perivitelline fluid of fish eggs (Peterson 1984, Shephard 1987 and in snail mucus (Schlichter 1982).…”

“…Interactions between ion exchange 'equilibria' and diffusion gradients have, however, been mode lied from in situ measurements in a similar material. ; the perivitelline fluid of fish eggs (Shephard 1987, Shephard & McWilliams 1989.…”

An analysis of the ion-exchange characteristics of fish-egg chorions

“…Although it is difficult to predict the in fluence of this equilibrium on the physiology of the developing embryo, some features of this system must be examined. These include elevated cation activity and decreased pH within the chorion, with respect to external solutions; factors that also probably extend to the perivitelline fluid due to the presence there of charged colloids (Shephard 1987b). It is important to note that ion exchange sites ensure the existence of high cation activities in the immediate environ_ment of the embryo, evep in extremely dilute solutions, but that this stability is lost in the presence of low pH and high concentrations of divalent and trivalent cations.…”

“…For both solutions the equivalent ionic fraction for calcium within the chorion lies between 0.90 and 1.0, indicating that at least 90~ of the anionic sites are neutralised by calcium ions. On this basis it is reasonable to predict the Donnan ratio for potassium from the ion exchange calculations for calcium as described previously (Shephard 1987b). This has been done for both solutions (I mM K +, ImM Ca ?+ , pH 8.35; 0.1raM K +, 0.1raM Ca 2+, pH 7.70) and the predictions are shown in Fig.…”

Studies on the fish-gill microclimate: interactions between gill tissue, mucus and water-quality

“…It could arise as a result of selective permeability of the mucus to cation diffusion from the filament; it could be the result of unequal K+ and Cl-mobilities within the charged mucus, leading to a liquid-junction potential at the 3M KCl, mucus interface (Overbeek 1961); it is, however, most easily interpreted as a 'Donnan potential' arising as a result of immobile negative charges within the mucus and in equilibrium with a dilute external solution. The situation is comparable to that in the perivitelline fluid of fish eggs (Peterson 1984, Shephard 1987 and in snail mucus (Schlichter 1982).…”

“…Interactions between ion exchange 'equilibria' and diffusion gradients have, however, been mode lied from in situ measurements in a similar material. ; the perivitelline fluid of fish eggs (Shephard 1987, Shephard & McWilliams 1989.…”

An analysis of the ion-exchange characteristics of fish-egg chorions

“…Although it is difficult to predict the in fluence of this equilibrium on the physiology of the developing embryo, some features of this system must be examined. These include elevated cation activity and decreased pH within the chorion, with respect to external solutions; factors that also probably extend to the perivitelline fluid due to the presence there of charged colloids (Shephard 1987b). It is important to note that ion exchange sites ensure the existence of high cation activities in the immediate environ_ment of the embryo, evep in extremely dilute solutions, but that this stability is lost in the presence of low pH and high concentrations of divalent and trivalent cations.…”

“…For both solutions the equivalent ionic fraction for calcium within the chorion lies between 0.90 and 1.0, indicating that at least 90~ of the anionic sites are neutralised by calcium ions. On this basis it is reasonable to predict the Donnan ratio for potassium from the ion exchange calculations for calcium as described previously (Shephard 1987b). This has been done for both solutions (I mM K +, ImM Ca ?+ , pH 8.35; 0.1raM K +, 0.1raM Ca 2+, pH 7.70) and the predictions are shown in Fig.…”