Habitat characteristics of tropical rainforest freshwater crabs (Decapoda: Brachyura: Potamidae, Gecarcinucidae) in Singapore

Abstract

Little is known about the ecology of freshwater crabs in streams in the equatorial tropics, making it difficult to implement conservation measures. This study characterises the habitats of freshwater crabs in Singapore’s tropical rainforests – Irmengardia johnsoni, Johora singaporensis, Parathelphusa maculata, and Parathelphusa reticulata, three of which are threatened with extinction. Non-metric multidimensional scaling revealed that pH, organic substrate cover, dissolved oxygen content, surface flow velocity, and elevation are important habitat characteristics. These together with comparisons of environmental ranges provide quantitative evidence that confirm anecdotal accounts of the habitats of these crabs and differences between them. Although the crabs persist in patches of forest, they remain vulnerable to many threats. The revealed differences in stream characteristics make it necessary to conserve a range of habitats for the survival of all four species. The findings of this study thus provide important baseline data for informing conservation and management strategies.