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worms > Phylum Platyhelminthes > Class Turbellaria > Order Polycladida
Triple-striped flatworm
Pseudoceros sp. 5*
Family Pseudocerotidae
updated Feb 2020

Where seen? This small white flatworm with three blue lines in the centre of it body is sometimes seen on many of our shores, on coral rubble near living reefs.

Features: 2-4cm long. Body white or bluish becoming dark blue at the margin. It has three non-connecting lines along the centre of the body, each line yellow with a fine blue border. Has a pair of all blue pseudotentacles (no coloured tips) made up of simple folded edges of the body.

Worms with only the centre line clear while the outer two lines are faded may be juveniles of this species.

Sometimes mistaken for the Ocher-striped flatworm which also has three lines in the centre of the body, but the lines are bordered dark brown or purplish brown.

According to Rene Ong, this flatworm resembles Pseudoceros tristriatus which also has triple-stripes. But Pseudoceros tristriatus has a blue body with three orange stripes, each bordered by black or dark purple. So far, there has been no actual record of Pseudoceros tristriatus in Singapore.

Sometimes mistaken for similar flatworms. Here's more on how to tell apart small flatworms with one central line and three central lines.

Raffles Lighthouse, Aug 06

Triple-striped flatworm (Pseudoceros tristriatus)

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

Triple-striped flatworms on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Sisters Island, May 09
Photo shared by Loh Kok Sheng on flickr.

St. John's Island, Feb 13
Photo shared by Loh Kok Sheng on his blog.

St. John's Island, Apr 22
Photo shared by Jianlin Liu on facebook.

Pulau Tekukor, Aug 21
Photo shared by Toh Chay Hoon on facebook.

Pulau Tekukor, Jun 16
Photo shared by Loh Kok Sheng on facebook.

Pulau Jong, Jun 12
Photo shared by Loh Kok Sheng on his blog.

Pulau Jong, Aug 21
Photo shared by James Koh on flickr

Pulau Semakau East, Jan 16
Photo shared by Loh Kok Sheng on facebook.

Pulau Jong, Aug 20

With grateful thanks to Leslie H. Harris of the Natural History Museum of Los Angeles County for comments on this worm and its identification.
Grateful thanks to Rene Ong for sharing details and identifying the flatworms on this page.

  • Rene S.L. Ong and Samantha J.W. Tong. 29 October 2018. A preliminary checklist and photographic catalogue of polyclad flatworms recorded from Singapore. Nature in Singapore 2018 11: 77–125.
  • D. M. Bolaños, B. Q. Gan & R. S. L. Ong. 29 Jun 2016. First records of pseudocerotid flatworms (Platyhelminthes: Polycladida: Cotylea) from Singapore: A taxonomic report with remarks on colour variation.(pdf) The Raffles Bulletin of Zoology Supplement No. 34: 130-169  Pp. 130-169.
  • Newman, Leslie and Lester Cannon. 2003. Marine Flatworms: The World of Polyclads. CSIRO Publishing. 97pp.
  • Humann, Paul and Ned Deloach. 2010. Reef Creature Identification: Tropical Pacific New World Publications. 497pp.
  • Kuiter, Rudie H and Helmut Debelius. 2009. World Atlas of Marine Fauna. IKAN-Unterwasserachiv. 723pp.
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