Responses ofHelix pomatia to anoxia: Changes of solute activity and other properties of the haemolymph

Summary

• 1) The following variables were measured in the haemolymph ofHelix pomatia, during periods of anoxia lasting up to 45 h and during recovery in air after 24 h of anoxia:d-lactate, succinate, propionate, acetate, Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, protein, total osmolarity.

• 2) d-lactate and succinate appear in the haemolymph immediately after the onset of anoxia and may reach concentrations of 60 and 40 mM, respectively. In the period 10 to 30 h following the onset of anoxia the two endproducts accumulate in the haemolymph at approximately the same rate. Propionate is not formed. Acetate may occur in the liver but its concentration is unrelated to the duration of anaerobiosis.

• 3) Complete recovery after 24 h of anoxia takes a further 24 h. Changes in the concentration ofd-lactate and succinate suggest that these two end-products are metabolized in the liver.

• 4) No significant changes of Na⁺, Cl⁻ and protein occur during anoxia, suggesting that haemolymph volume remains more or less constant. However, the concentration of K⁺ in the haemolymph increases up to 3-fold.

• 5) Ca²⁺ increases at a rate which corresponds to the rise ofd-lactate and succinate concentrations. Mg²⁺ shows only a modest increase and remains constant after 10 h of anoxia.

• 6) Solute activity during anoxia increases initially, from an average of 160 to 270–280 mOsm, and then drops to approximately 220 mOsm. After 40 h of anoxia the difference between solute activity and concentration of all measured solutes amounts to approximately 160 mM.

• 7) In the haemolymph of anaerobic snails the activity of Ca²⁺ is reduced by up to 60% but this is not sufficient to account for the reduction of total solute activity.

• 8) In a buffer system resembling the haemolymph of anaerobic snails (containing 50 mM NaCl, 60 mM Ca²⁺, 60 mMd-lactate, 40 mM succinate, pH 6.9) the haemocyanin ofH. pomatia displays a negative Bohr shift (Δlogp₅₀/ΔpH-0.14) with respect to aerobic haemolymph (pH 7.8) over the whole$P_{O_2 }$ range considered. Cooperativity is identical under both conditions.

• 9) It is concluded that none of the speculations so far advanced concerning mechanisms which might control the flow of metabolites along the major pathways of anaerobiosis, can completely explain the responses ofH. pomatia to anoxia.