ISSN:
1432-1351
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary 1. When exposed to progressive hypoxia in shallow seawater,Carcinus maenas partially emerged into air and aerated its branchial chambers by reversing the direction of their irrigation. Emersion took place at a meanP I, O2 of 18 mm Hg at 6 °C, 21 mm Hg at 12 °C and 59 mm Hg at 17 °C. 2. At low oxygen tensions submerged crabs underwent a progressive bradycardia. Heart rate first became significantly lower than the rate in normoxia below aP I O2 of 30 mm Hg at 6 °C, 40 mm Hg at 12 °C and below 60 mm Hg at 17 °C. The proportion of total time spent irrigating the gills in a reversed direction increased in hypoxic seawater (P I, O2〈 50 mm Hg), but respiratory rate was unchanged. 3. Emersion into air always occurred during a reversal of irrigation and was accompanied by prolonged reversals, with consequent aeration of the branchial chambers, and by an immediate and maintained tachycardia back towards the rate in normoxic seawater. Crabs emerging into a hypoxic atmosphere ( $$P_{O_2 } $$ 〈 10mm Hg) showed neither a maintained reversal of irrigation nor a maintained tachycardia. 4. The oxygen tension of the postbranchial blood (P a,O2) was 94 mm Hg in crabs submerged in normoxic seawater (P I,O2 146 mm Hg) at 12 ° C. During progressive hypoxiaP a, O2 fell in direct proportion to the drop inP I,O2. Emersion caused no significant increase inP a, O2. 5. The mean oxygen content of postbranchial blood (C a, O2) was 0.96 vol. % at aP I,O2 of 145 mm Hg.C a, O2 fell to 0.19 vol.-% in submerged crabs at a meanP I,O2 of 25 mm Hg but rose to 0.45 vol.-% following 10 min emersion into air at a meanP I, O2 of 22 mm Hg. 6. The results provide evidence of a respiratory role for the emersion response and also of an adaptive role for the high affinity of the blood pigment inCarcinus.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00702531
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