Ionic permeabilities of the gill lamina cuticle of the crayfish, Astacus leptodactylus (E).

Abstract

SUMMARY1. The cuticle of the gill lamina of the crayfish AstacUs leptodactylus (E), mechanically isolated, was mounted in an Ussing chamber and examined for its electrical properties. The cuticle ofthe gill lamina obtained from exuviae had similar properties.2. When perfused with artificial fresh water (AFW) outside and Van Harreveld solution (VH) inside, the transcuticular potential VjI was negative with respect to the inside, and close to the equilibrium potential for Cl-(EC1-). CH3COO-, HCO-, S042-and cations (Na+, K+, Ca2+, Mg2+ and NH4+) behaved as impermeant ions with respect to Cl-. A decrease of pH (brought about with C02) from 8-5 to 6-0 in AFW, VH or both had no effect on the potential. 3. The cuticle area specific conductance was 20-30 mS/cm2 when superfused with AFW outside and VH inside. The conductance decreased linearly with log [Cl-] when Cl-was replaced by CH3COO-. Rectification was obvious when internal Cl-was reduced to 5 mmol/l.4. The Cl-selectivity of the cuticle could also be demonstrated in perfusing the cuticle with a single salt (NaCl, KCl, CaCl2, MgCl2 or LaCl3) and in diluting that salt on one side of the preparation or in replacing Cl-by CH3COO-, SO42-and HC03-.The potential changed almost linearly with log [Cl-] and was close to EC1-. The inner face of the cuticle was found to be slightly less selective than the outer face. The relative permeabilities were calculated to be: PC,-= 1, PNa+ = 0-001, PHCO3-= 0 0006, PCH3COO-= 00002.5. The dilution of a Cl--free salt resulted in a cationic potential. The relative permeabilities of cations (NH4+, K+, Na+, Ca2+ and Mg2+) were found to range within a factor 2. The permeability of the cuticle to HCO3-, CH3COO-and SO42-was 2-5 times lower.6. The cuticle conductance was linearly related to the activity of the salt perfusing the two sides of the preparation at equal concentrations. The molar area specific conductance to chloride salts was 14 (mS/cm2)/(mmol/l). That ofCl--free salts ranged from 1 to 20 (fUS/cm2)/(mmol/l) depending on the salt used. It was deduced that PC,-is 2 x 10-3 cm/s and that all the other ions tested have permeabilities of 10-7_10-6 cm/s. 7. With large intensity current pulses the cuticle exhibited rectifying properties and an asymmetrical behaviour. P. A VENET AND J. M. LIGNON 8. Increasing the pH of the perfusing solution reduced the transcuticular potential established with a Cl-gradient. In Cl--free media and at high pH, large potentials were obtained with a pH gradient. The conductance of the cuticle increased with pH and a permeability to OH-of about 10-3 cm/s was computed.9. The soft thorax and abdomen cuticle of the crayfish had no selective properties and its conductance was low. The soft cuticle of the gill lamina of the lobster had no selective properties but its conductance was high.10. Our results show a high selectivity of the gill lamina cuticle to Cl-and OHover other ions normally present in the haemolymph and in the fresh water. This selectivity is likely to be located in the epicuticular layer and is speci...

Ammonia excretion in aquatic and terrestrial crabs

“…The main site for ammonia excretion by aquatic crabs is the phyllobranchiate gill (Claybrook, 1983;Kormanik and Cameron, 1981;Regnault, 1987), featuring a single-celllayered epithelium covered by an ion-selective cuticle (Avenet and Lignon, 1985;Lignon, 1987;Riestenpatt, 2002, Weihrauch et al, 2002). The gills of aquatic crabs are multifunctional organs.…”

The mechanism of sodium chloride uptake in hyperregulating aquatic animals

“…It was shown some years ago that the lamellar cuticle is permeable to Cl -and OH -but nearly impermeable to cations and to other anions. Relative permeabilities were calculated to be: PCl=1; PNa=0.001; PHCO 3 =0.0006 (Avenet and Lignon, 1985). By contrast, the cuticle covering the filaments is cation permeable, with permeabilities in the order K + >NH4 + >Na + >Li + ӷCl -and SO4 2- (Lignon and Lenoir, 1985).…”

Immunolocalization of Na+,K+-ATPase in the branchial cavity during the early development of the crayfish Astacus leptodactylus (Crustacea, Decapoda)

“…Moreover, differences in ionic permeabilities of the cuticle in A. leptodactylus have also been demonstrated depending on whether the lamina or the gill filaments are considered. As hypothesized by Dunel-Erb et al (1997), the lamina with a cuticle selectively permeable to Cl -and OH - (Avenet and Lignon, 1985) and whithout Na + ,K + -ATPase (Barradas et al, 1999b and this study) might be involved in the movements of anions.…”

“…The ion-transporting filaments which possess Na + ,K + -ATPase (Barradas et al, 1999b and this study) and possibly H + V-ATPase Greenaway, 1997, 1998) might be involved in the movements of Na + , K + , NH 4 + , and Ca 2+ to which the cuticle is highly permeable (Avenet and Lignon, 1985;Lignon and lenoir, 1985;Lignon and Péqueux, 1990). …”