The Relative Importance of the Gills and Lungs in the Gas Exchange of Amphibious Crabs of the Genus Holthuisana

Abstract

Gill area increased with increasing body size in Holthuisana transversa (area in square millimetres equals 1946 times mass, in grams, to the power of 0.563). The increase in area was largely due to increase in the area of individual lamellae, at least over the size range studied (10-35 g). The area of the lungs was only 10% ofthe area ofthe gills but potentially these were at least as effective in gas exchange, due to their much shorter blood-gas diffusion distance. The volume of the lungs increased with body weight (volume in millilitres equals 0.043 times mass, in grams, to the power of 1.218), whilst tidal volume increased at a lower rate (tidal volume in millilitres equals 0.082 times mass to the power of 0.831) in the crabs examined (3-36 g).