Fluid and osmolyte recovery in the common pond snailLymnaea stagnalisfollowing full-body withdrawal

Abstract

SUMMARYThe common pond snail Lymnaea stagnalis sacrifices 40-60% of its extracellular fluid (ECF) including solutes to the surrounding environment to fully retract into its shell. Our objectives were to determine recovery time following such ECF loss and characterize mechanisms involved in recovering Na + , the primary cationic osmolyte in this snail. Pallial fluid was initially collected post-stimulation and again after a second stimulation on sub-groups of those snails 2·h to 10·weeks after initial sampling. Samples were analyzed for pH, osmotic pressure, and individual solute concentrations. Lost volume was recovered within 8·h with no significant changes in pH or total CO 2 . Significant decreases in osmotic pressure, [Na + ] (43% loss), and [Cl -] recovered in 48·h as a result of enhanced uptake from the water. Copper and total extracellular proteins took 5 weeks to recover. Measurements of Na + transport kinetics completed before and immediately after fluid loss revealed a near threefold increase in both affinity and capacity of the Na + uptake system. Sodium uptake was independent of ambient Cl -and HCO 3 -in both control and fluid-depleted snails. Amiloride significantly reduced recovery-phase Na + uptake rates but did not influence baseline Na + flux. Recovery uptake was significantly reduced by amiloride, ethylisopropylamiloride, bafilomycin and ethoxzolamide indicating dependency upon Na + /H + exchange, H + pump activity and H + from carbonic anhydrase-catalyzed CO 2 hydration. Thus enhanced uptake during recovery is likely via electrogenic Na + /H + exchange and/or possibly a cation channel.

Characterization of mechanisms for Ca2+ and HCO3–/CO32– acquisition for shell formation in embryos of the freshwater common pond snail Lymnaea stagnalis

“…There have also been reviews on the presence of this pathway in crustaceans (Neufeld and Cameron, 1993). Furthermore, H + -pump-driven active cation uptake has been documented in adults of this species (Ebanks and Grosell, 2008) as well as in several other freshwater species including carp (Fenwick et al, 1999), tilapia (Fenwick et al, 1999) and trout (Bury and Wood, 1999;Grosell and Wood, 2002;Lin and Randall, 1991). Thus inhibition of Ca 2+ uptake in the presence of the V-ATPase inhibitor, bafilomycin, in developing snail embryos is persistent across later time points (up to 80% reduction in post-metamorphic Ca 2+ uptake) and appears to be consistent with investigations in other species.…”

Acquisition of Ca2+ and HCO3 −/CO3 2− for shell formation in embryos of the common pond snail Lymnaea stagnalis

“…We propose that the increase in water [H + ] in the Taylor (1973) study would drastically reduce the capacity to excrete H + . Cation uptake in freshwater fish (Bury and Wood 1999; Fenwick et al 1999; Grosell and Wood 2002; Lin and Randall 1991) and in L. stagnalis (Ebanks and Grosell 2008) has been linked to an electrochemical gradient that is in part established by excretion of the H + from carbonic anhydrase-mediated hydration of respiratory CO 2 . Calcium uptake in Lymnaea exposed to low ambient pH would likely be impaired, explaining the earlier observations by Taylor (1973) of reduced [Ca 2+ ] in the perivitelline fluid.…”