Acid-base responses to changes in CO2 in two pacific crabs: The coconut crab,Birgus latro, and a mangrove crab,Cardisoma carnifex
✍ Scribed by Cameron, James N.
- Publisher
- John Wiley and Sons
- Year
- 1981
- Tongue
- English
- Weight
- 724 KB
- Volume
- 218
- Category
- Article
- ISSN
- 0022-104X
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✦ Synopsis
Abstract
The blood pH was depressed in the terrestrial coconut crab, Birgus latro, by about 0.3 units when the animals were forced to breathe 3% CO~2~ in air. This hypercapnic acidosis was compensated over 24 hours by a 15.4 mM · L^−1^ increase in blood bicarbonate, but little amelioration of the pH depression was achieved (less than 0.15 units). The increased base excess could not arise from ion exchange with water, and did not apparently involve antennal gland excretion either. The distribution of injected DMO changed in a way that indicated that the intracellular compartment was supplying about half of the observed base excess. In an amphibious, or bimodally breathing crab, Cardisoma carnifex, a reduction of the normal blood P by forced water breathing led to an opposite hypocapnic alkalosis, the blood P dropping from 10.6 to 7.0 torr. This led to a progressive metabolic acidosis, which maintained the blood pH within 0.1 unit of control (air‐breathing) values. The distribution of injected DMO in C. carnifex did not indicate any participation of the intracellular bicarbonate pool in the adjustment to the hypocapnia. It appears that only in the fully terrestrial crabs, deprived of an aquatic medium enabling ionic exchange processes, are other mechanisms for acid‐base regulation brought into play.