The Pleasing Flatworm

Pseudobiceros gratus

This species is aptly named for its pleasing, gracefully movements as it slithers over rocks and corals, producing undulating ripples along the length of its body, with a semi-transparent, white or cream coloured body and three to four long black stripes running along its length. The ruffled edges constantly shift up and down the body margin, helping the flatworm move over the surface. It also has fake ear-like pointed tentacles at one end, mimicking a nudibranch mollusc, which is much more toxic to fishes and other predators than the flatworms themselves. The Pleasing Flatworm is found under coral rubble on reef flats or in deeper subtidal waters. It purposefully slithers over the tops of encrusting invertebrates, like sponges and colonial ascidians, with its mouth open grazing them off rocks and corals to which they are attached. Its striking body pattern is highly visible to fishes and other predators which probably indicates it has noxious chemicals to deter them, and like many of its close relatives it may get its noxious chemicals from its food.

Common throughout the Indo-West Pacific including northern Australia.

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