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Journal of Experimental Biology 128,307-322 (1987)
Published by Company of Biologists 1987

The Effects of Aerial Exposure on the Distribution of Body Water and Ions in the Freshwater Crayfish Austropotamobius Pallipes (Lereboullet)

E. W. TAYLOR ¹, R. TYLER-JONES ¹, and M. G. WHEATLY ²

¹ Department of Zoology and Comparative Physiology, University of Birmingham, Birmingham B15 2TT, England
² Department of Zoology and Comparative Physiology, University of Birmingham, Birmingham B15 2TT, England; Department of Zoology, University of Florida, Gainesville, FL 32611, USA.

1. Submerged crayfish had a total body water content of 76% body mass. Haemolymph volume was around 30% and was dependent on mass, the relationship being described by the regression equation y (volume) = 3.98+0.177x (mass). The inulin space was greater than the copper space in abdominal muscle, suggesting the existence of an interstitial component of the extracellular fluid into which haemocyanin does not penetrate.

2. Crayfish exposed to water-saturated air (100% relative humidity, RH) did not lose mass and haemolymph levels of K⁺ and Na⁺ were unchanged from the submerged values.

3. When exposed to air (70-80% RH) crayfish progressively dehydrated at the rate of 0-38 % body massh^-1 (0.5 % body water h^-1) and died after 72 h when 27 % of initial mass had been lost.

4. After a 10 % reduction in mass, haemolymph volume was significantly reduced to about 75 % of its submerged value in 10-g animals and to 65 % in 60-g animals, the decrease in volume being approximately equivalent to the mass lost. After 48 h in air (19% reduction in mass) haemolymph volume was further reduced to 24% of the submerged volume.

5. The total water content of the abdominal muscles showed a small but significant reduction when animals were dehydrated which could be accounted for by a reduction in the extracellular fluid volume, including the interstitial space.

6. After 48 h dehydration in air the osmolarity of the haemolymph increased by 36%, [K⁺] by 47% and [Cl^-] by 57% above the submerged levels whilst [Na⁺] showed an insignificant decrease of 10%. In the abdominal muscle [K⁺] increased by 15 %, [Na⁺] increased by 23 % and [Cl^-] decreased by 27 %.

7. [Ca²⁺] levels in the haemolymph doubled after 24 h in air, an increase which was independent of the degree of dehydration. The increase is thus a result of emersion and not dehydration and may be due to a mobilization of CaCO₃ from the exoskeleton to buffer a respiratory acidosis, as it corresponds to a doubling in [HCO₃^- + CO₃^2-].

8. A substantial loss of ions from the haemolymph during dehydration cannot be fully accounted for by uptake into the tissues or by urinary losses, but a 500 mmoll^-1 increase in the Na+ concentration of the proventricular contents suggests that the foregut may play an important role in ionoregulation.

Key words: crayfish, aerial exposure, dehydration, water and ion distribution

Accepted on September 30, 1986

This article has been cited by other articles:

				D. Jackson, T Wang, P Koldkjaer, and E. Taylor Lactate sequestration in the carapace of the crayfish Austropotamobius pallipes during exposure in air J. Exp. Biol., January 3, 2001; 204(5): 941 - 946. [Abstract] [PDF]