Air breathing crabs of trinidad: Adaptive radiation into the terrestrial environment—I. Aerobic metabolism and habitat

Abstract

1. 1. Nine species of tropical air breathing crabs were collected from a diverse range of semi-terrestrial habitats: marine/terrestrial (rocky shore, Grapsus; sandy shore, Ocypode), brackish water/terrestrial (estuarine mud-flat, Uca; mangrove swamp, Ucides, Goniopsis, Aratus; coconut grove, Cardisoma); freshwater/terrestrial (lowland freshwater swamps and rivers, Dilocarcinus; mountainous tropical rain forest, Pseudothelphusa). 2. 2. Rates of aerial oxygen uptake ( V o 2 , 25°C) of these semi-terrestrial crabs are remarkably similar (interspecific live wt/ V o 2 b value = 0.6). 3. 3. “Excitement” induces maximal factorial increases in V o 2 of × 3.3 − × 5.6 in committed air breathing crabs. 4. 4. The active V o 2 of the “lungcrab”, Pseudothelphusa, does not exceed that of land crabs with diffusion limited “cutaneous lungs”. 5. 5. The perfusion limited, invaginated lung of Pseudothelphusa functions in optimising respiratory gas exchange/water balance during quiescent air breathing ( V o 2 depressed by 30–40%).