The Effects of emersion and hypoxia on the hemolymph acid-base and oxygenation states of the horseshoe crab limulus polyphemus
Date
1989
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The effects of both emersion and hypoxic exposure
(followed by recovery) on hemolymph acid-base and oxygenation states of the horseshoe crab Limulus polyphemus were examined using both in vitro and in vivo measurements. In vivo studies involved sampling of hemolymph from animals exposed to emersion or hypoxia for 48h, followed by a 48h recovery period. To assess the effects of the repetitive sampling regime, h polyphemus exposed to normoxic seawater were also sampled for a 96h period.
The in vitro determinations confirmed the presence of a reversed Bohr effect of comparable magnitude to that previously reported for h polyphemus hemolymph. In agreement with previous measurements made at similar hemolymph c1ยท, cooperativity of o2 binding to hemocyanin
(n50 ) was low {1.4). Hemocyanin 02 affinity was, however, higher than previously measured at comparable levels of
hemolymph Cl and pH (e.g. P50 = 5 torr at pH 7.6). This series also demonstrated that h polyphemus hemolymph lacks a Haldane effect.
The in vivo studies demonstrated that repetitive sampling of hemolymph from animals in normoxic water had little effect on acid-base state. Mean hemolymph pH, Pco2, and Cco2 were stable throughout the sampling regime. Although ventilatory rate remained lower than has previously been reported, a hyperventilatory response was observed in response to sampling. This hyperventilation probably caused the elevation of hemolymph oxygen tensions, most marked during periods of intense sampling. The resultant increase in hemolymph 02 delivery to the tissues during the sampling regime was sufficient to fuel any increase in energy requirements caused by disturbance to the animal; the stable values for hemolymph lactate demonstrated that anaerobic metabolism was not utilized.
In contrast to the stability of acid-base state of h polyphemus sampled in normoxic water, animals sampled during emersion demonstrated a marked respiratory acidosis. The elevation of hemolymph CO2 tensions and the decrease in 02 tensions to below 10 torr, both suggested that diffusion of gases across the emersed book gills was limited. The high affinity of h polyphemus hemocyanin for 02, however, allowed similar amounts of o2 to be delivered to the tissues as occurred in animals sampled in normoxic seawater.
Although no compensation for acid-base disturbance occurred during emersion, potential hemolymph alkalosis during prolonged moderate hypoxic exposure was averted by elevation of hemolymph bicarbonate concentrations. This compensation prevented a decrease in hemocyanin 02 affinity from occurring via the reversed Bohr effect. Again, delivery of 02 to the tissues was not compromised.
Description
Bibliography: p. 152-163.
Keywords
Citation
Gallagher, K. L. (1989). The Effects of emersion and hypoxia on the hemolymph acid-base and oxygenation states of the horseshoe crab limulus polyphemus (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/15623