[Effect of hypercapnia on the acid base states of the blood in the crab Carcinus maenas (L.) (Crustacea-Decapoda)]

When the crab Carcinus maenas respires in hypercapnic water, a respiratory acidosis occurs, which is progressively compensated by a rise of the blood bicarbonate concentration. The CO2 partial pressure in the blood increases in proportion to the change in ambient CO2 partial pressure. Therefore, the regulation of the acid-base status depends mainly on non-respiratory adjustments of the blood bicarbonate concentrations.

[Control of the respiration in teleostean fish: respiratory reactions to abrupt changes in the oxygenation of the medium]

In the trench, carp and trout, an abrupt change in the partial pressure of ambient oxygen leads to a change in arterial oxygen tension which, within 1.5-2.6 seconds, elicits cardiac and ventilatory reactions. By their short latency, these responses may be explained as a modification of chemoreceptor activity, and resemble respiratory chremoreflexes of higher vertebrates.