### Abstract

1. When the ambient oxygen tension of the water was lowered, unrestrained shore crabs acclimated to 15, 20 and 25°C emerged into air to ventilate the branchial chambers when the inspired oxygen tension ( {Mathematical expression}) was reduced to mean values of 37±4 mmHg, 51±6 mmHg and 119±3 mmHg respectively. There is a positive correlation between {Mathematical expression} at emersion and acclimation temperature (Fig. 1). 2. The extent to which the {Mathematical expression} of the water in the branchial chambers was increased by emersion was related to the length of time emerged (Fig. 2), and inversely proportional to the {Mathematical expression} at emersion (Fig. 3). 3. Following 60 s emersion at 15°C there was a marked increase in oxygen content of the postbranchial haemolymph ( {Mathematical expression}), pHa was reduced and {Mathematical expression} increased (Table 1). The same trend in acid-base balance was observed at 25°C but {Mathematical expression} was unchanged as emersion was from virtually normoxic water (Table 2). 4. Emersion from water at 25°C into air at 25°C and 60% R.H. caused no significant change in heart rate or core temperature. Emersion into air at 17°C was accompanied by a decreased heart rate and core temperature. 5. At relatively low temperatures emersion from hypoxic water serves to aerate the branchial chambers and lead to an increase in {Mathematical expression}, which together with a recovery tachycardia restores the oxygen supply to the tissues. CO_{2} accumulates during emersion but to a lesser extent than during air-breathing, so that CO_{2} exchange with water is retained during emersion. At 25°C emersion into cool air may serveto reduce the crab's temperature thus reducing its oxygen demand.

Original language | English (US) |
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Pages (from-to) | 305-311 |

Number of pages | 7 |

Journal | Journal of Comparative Physiology □ B |

Volume | 132 |

Issue number | 4 |

DOIs | |

State | Published - Dec 1 1979 |

Externally published | Yes |

### ASJC Scopus subject areas

- Ecology, Evolution, Behavior and Systematics
- Biochemistry
- Physiology
- Animal Science and Zoology
- Endocrinology