Rates of water loss in four crabs from different habitats

1. 1. The water loss was determined for both sexes in crabs from mangrove Ucides cordaius and Goniopsis cruentata, supralittoral Ocypode quadrata and intertidal Pachygrapsus transversus under aerial desiccation conditions (19.63 ± 2.77% r.h. and 25.50 ± 0.34°C) for several hours. 2. 2. The water loss rate increased linearly with exposure time. The smaller P. transversus have the faster rate, 3.50 ± 0.20 and 3.03 ± 0.25 g/100g/hr, followed by U. quadrata, 1.03 ± 0.07 and 0.65 ± 0.07 g/100 g/hr, G. cruentata, 0.53 ± 0.02 and 0.50 ± 0.04 g/100 g/hr, V. cordatus, 0.43 ± 0.03 and 0.29 ± 0.02 g/100g/hr, females and males, respectively. 3. 3. The surface-volume ratio appears to be the most important factor related to the water loss. The terrestrialness of the four species could be indirectly inferred from their water loss rates.