Freshwater spider crab
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Halicarcinus lacustris Chilton, 1882 |
The freshwater spider crab, Halicarcinus lacustris, is a spider crab of the family Hymenosomatidae found in lakes and slow-flowing streams and rivers in south east Australia including the Norfolk Islands, and New Zealand. It is the only species of freshwater crab in New Zealand. It grows to around 10 mm in shell width.
Unlike marine crabs, the young hatch directly from the eggs carried under the folded tail of their mothers, as with freshwater crayfish. They are detritivores, feeding on both animal and vegetable material found in the organic silt of their habitat. Freshwater spider crabs have small pincers, not very effective as protection against predators like eels and other fish, causing them to spend daylight hours in crevices in fallen logs and under rocks. Their eyes are not very effective in bright sunlight, and they prefer shaded areas.