Tuesday, 6 May 2008

Mangrove invertebrates

Mangrove swamps teem with invertebrates. You don't have to go very far in to discover that. Insects make themselves known the moment you step under the canopy. Green tree ants. Mosquitoes. Sand flies. All your blood are belong to us. (Although, strictly speaking, the ants don't feed on blood. But they would, you know, if they could ...)

Green tree ants (Oecophylla smaragdina)

Butterflies are abundant in the sunny patches, especially when the trees are in flower. The orange mangrove (Bruguiera) is near the end of its flowering period but there are enough blossoms to keep both the insects and the friarbirds happy.

Eggfly (Hypolimnas)

Orange mangrove (Bruguiera) flower

But most of the animal life loves the mud. Every footfall and shadow sends crabs scurrying into their burrows. The most noticeable are the maroon mangrove crabs (Perisesarma messa) with their burgundy-coloured claws and eyes like pearls. They aren't as nervous as the other species, so they hang around for longer before finally diving into burrows or scuttling under logs. Even so, they're not easy to photograph in the gloom of the forest — dark glistening carapace against dark glistening mud.

Maroon mangrove crabs

At the water's edge, orange-clawed fiddler crabs (Uca coarctata) pick through the mud for tasty tidbits.

Orange-clawed fiddler crab

Perhaps the most obvious crustaceans are the ones you never see. Snapping shrimp make popping and clicking noises from their burrows in the mud. They're distributed throughout the mangroves but down in the Rhizophora zone, where the mud is sloppy and moist, they perform like an orchestra of percussionists.

Here be snapping shrimp

Molluscs are also plentiful. And they don’t move as fast as crabs. The most obvious species are Terebralia and Telescopium, which graze on the microscopic algae on the surface of the mud. Other species live among the tree roots or on the leaves in the canopy.


Snails aren't the only things you sometimes find in the canopy …