Abstract

Haemocyanin oxygen affinity, respiratory gas exchange and haemolymph 02 levels were measured in three burrowing crayfish; Cambarus diogenes diogenes, Cambarus fodiens, and Procambarus clarkii, a temporary burrower and compared with those of an essentially fluviatile species Orconectes obscurus. Burrowing crayfish were acclimated to a transparent artificial burrow which allowed video analysis of burrowing behaviour. Although water was present at the base of the burrow all three burrowers spent a substantial proportion of their time in air. Haemocyanln oxygen affinity of O. obscurus measured in vitro (P₅₀=7.6 torr at 15C, pH 7.85) was similar to literature values for other non-burrowing crayfish: that of burrowing species was substantially higher (P₅₀=3.2-3.8 torr at 15C, pH 7.85). The Bohr shift was moderate in each case ( = -0.497 Oo,-0.497 cdd,-0.475 cf,-0.348 pc). In resting immersed crayfish circulating haemolymph (blood) O₂ partial pressures were relatively low in all cases but were substantially lower in the three burrowing species. Circulating O₂ levels increased following 24h emersion into air but remained low compared to those reported for marine crustaceans. Haemolymph pH decreased substantially on emersion and the resulting Bohr shift maintained O₂ delivery to tissues. The haemocyanin of burrowing crayfishes seems well adapted to pick up O₂ from depleted burrow water. These crayfish are also well able to saturate the O₂ carrier and deliver O₂ to tissues alter 24h air exposure.

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