Journal of Comparative Physiology B

, Volume 162, Issue 4, pp 375–382

Carapace movements aid air breathing in the semaphore crab, Heloecius cordiformis (Decapoda: Brachyura: Ocypodidae)

  • David P. Maitland


While on land and recirculating branchial water the Australian semaphore crab Heloecius cordiformis (Decapoda: Ocypodidae), a semi-terrestrial airbreathing mangrove crab, sequentially depresses and elevates its carapace in a regular pump-like manner. The functional role of these carapace movements in aerial oxygen consumption is investigated. Carapace immobilisation (reversible and non-injurious) did not appear to affect branchial water circulation. In “dry” crabs (branchial water removed) carapace immobilisation had no effect on the rate of oxygen consumption (VO2), heart rate or whole-body lactate (WBL) levels. In “wet” crabs (with branchial water) carapace immobilisation caused VO2 to drop by 38% from 81 to 46 μl O2 · g-1 · h-1, heart rate to decline by 32%, from 2.5 to 1.7 Hz, and WBL levels to increase over 2.5-fold, from 0.27 to 0.67 mg · g-1, after 3 h of carapace immobilisation. The (VO2) of carapace-immobilised crabs with branchial water was similar to lung-occluded crabs with branchial water. Severe hypoxia induced physiological responses similar to those of carapace-immobilised crabs with branchial water. After 3 h of severe hypoxia, heart rate had declined by 80%, from 2.2 to 0.43 Hz, and the incidence of carapace pumping slowed by 85%, from 2.4 to 0.37 cycles · min-1. It is concluded that in the absence of carapace movements branchial water in some way inteferes with lung ventilation. Under normal circumstances water circulation and lung ventilation are mutually exclusive processes (due to their singular dependence on the scaphognathites), yet in Heloecius these processes must be carried out simultaneously. Carapace movements may alleviate this conflict.

Key words

Air breathing Lung ventilation Scaphognathite Water circulation Carapace movements Crab, Heloecius 



fast-forward, fast-reverse, slow-forward, slow-reverse scaphognathite pumping


Milne Edwards aperture


rate of oxygen consumption


whole-body lactate


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Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • David P. Maitland
    • 1
  1. 1.School of Biological ScienceUniversity of New South WalesKensingtonAustralia
  2. 2.Department of Physiology, Medical SchoolUniversity of the WitwatersrandJohannesburgSouth Africa

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