worms > Phylum Platyhelminthes > Class Turbellaria > Order Polycladida
Dawn flatworm
Pseudobiceros uniarborensis*
Family Pseudocerotidae
updated Aug 10

Where seen? This elegant flatworm is sometimes seen on coral rubble near living reefs on many of our Southern shores. Like the first light of dawn, the dark to black flatworm has orange and white edges.

Features: 5-8cm long. Body dark brown to black. Marginal bands are orange, on a transparent greyish band with thin white line on the outermost edge. There is a ridge on along the centre of the body, and a short white stripe on the head.

It has a pair of erect pseudotentacles at the front made up of folded edges of the body. The pseudotentacles have white edges at the pointed tips. The edge of the body is slightly ruffled.

According to Leslie Harris, this is possibly Pseudobiceros uniarborensis. Another worm that looks very similar is Pseudobiceros hancockanus which has an outer margin that is solid bright white; the outer margin of Pseudobiceros uniarborensis is translucent gray with a white line on the outside.

The members of the genus Pseudobiceros have two penises!

Kusu Island, May 05

Marginal band: orange, grey, white.

Pulau Hantu, Sep 08

It can swim!

Upper and underside.

Dawn flatworms on Singapore shores


St. John's Island, Jan 06


Tanah Merah, Aug 09

Swimming.


Pulau Semakau, Sep 05

more photos of dawn flatworms on Singapore shores
northern shores
southern shores part 1 | part 2

*Tentative identification. Species are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience of display.

Acknowledgement
With grateful thanks to Leslie H. Harris of the Natural History Museum of Los Angeles County for comments on this worm and its identification.


References
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