Species list

Flatworms (phylum Platyhelminthes) may be more frequently mistaken for sea slugs than any other animals. Some of them are brilliantly colored and many have folds of the body margin or small projections from the dorsal surface that resemble rhinophores. A few even have elongate papillae on the dorsal surface that may be mistaken for cerata. However, they are usually proportionately flatter and move more rapidly than sea slugs (either by ciliary action or undulation). They lack the molluscan foot and an anus. All or nearly all are predators and some of the larger species may feed on sea slugs. Others mimic sea slugs that concentrate toxic or distasteful chemicals from their food. Most of those that are readily mistaken for sea slugs are in the order Polycladida.

A few of the species most frequently mistaken for sea slugs:
Pseudoceros cf. dimidiatus
PF; La Perouse Bay, Maui

Pseudobicero gratus
Pseudobiceros gratus
CP: Hekili Point, Maui;
March 30, 2007
Pseudoceros ferrugineus
Pseudoceros ferrugineus
PF: Makena, Maui;
Sept. 20, 2008

Pseudobiceros sp. #5
Pseudobiceros sp. #5
CP: Maui;
May, 2005

Pseudobiceros sp. #14
Pseudobiceros sp. #14
CP: Hekili Point, Maui;
March 23, 2007
Thysanozoon tentaculum
Thysanozoon tentaculum
CP: Maalaea Bay, Maui;
Oct. 22, 2007
For more information see:
John Hoover's flatworm page
Keoki Stender's flatworm page
Marshall Islands Flatworms by Scott & Jeanette Johnson
Jim Anderson's flatworm pages
Gustav Paulay's Guam flatworms
Flatworms on the Sea Slug Forum
Discover Life flatworm pages by Marian K. Litvaitis
Flatworms at Umiushi-zukan
Reunion Flat Worms by Philibert Bidgrain
Guam Flat Worms by Dave Burdick
Flatworms by Teresa Zubi
Australian flatworms by Denis Riek

Marine Flatworms Facebook Group
Species list