Marine flatworms are a group of organisms that have a soft, flattened, unsegmented form which resembles a leaf. They are extremely primitive, lack organs and body cavities, and have a very basic, incomplete digestive system. They breathe directly through their body's surface through a process called diffusion for which it is necessary for all cells of their body to be in contact with the water all the time, making their flattened form important. Flatworms feed on a variety of things ranging from algae to small fish and other invertebrates. They are brightly coloured, and thus, sometimes called "butterflies of the sea". Interestingly, some flatworms can mimic the appearance of sea slugs for camouflage, and some may even contain some minor concentrations of toxins for defence!
Sudhanshu Dixit, ZSI
( Pseudobiceros hymanae )
Like most of the flatworms, the black flatworm can also be found moving along reefs and coral rubble.
They can grow up to 10 cm in size and get their name from their jet black colour that appeals to the observer immediately. In contrast to this, their margins which are orangish-red in colour.
They feed on tunicates and small crustaceans by protruding their stomach out which secretes fluids that then digest the prey.
Sudhanshu Dixit, ZSI
( Pseudoceros bifurcus )
They can be found at depths between 1-20 m around coral reefs.
Usually found crawling along coral reefs, the stunning racing stripe flatworm is named so because of its distinctive single stripe on its body like those on racing cars. They can grow up to 6cm in length. In terms of their colour, they usally have a solid blue but can sometimes be bluish-purple as well. The central line or racing stripe is whitish yellow in colour.
Their diets manily consist of tunicates that they feed on while moving across coral rubble.
Sudhanshu Dixit, ZSI
Sudhanshu Dixit, ZSI
( Pseudoceros rubrotentaculatus )
The triple striped flatworm is a common species found along the Indian coasts swimming along coral rubble or close to corals themselves in shallow warm water.
They grow up to between 2-4 cm long, they have a whitish blue body with darker blue margins. They have three yellow lines in the centre of their body with a dark blue border on each line.
They feed on small invertebrates.
Sudhanshu Dixit, ZSI
Sudhanshu Dixit, ZSI
( Pseudoceros meenae )
They can be found at depths between 1-20 m around coral reefs.
The white flatworm, named so because of it's distinctive white colour can grow up to 4-5 cm in length. Crawling and moving around coral rubble, to add to their white colour along their margins are lines of black, yellow and grey.
They feed on various small invertebrates.
Phalguni Ranjan
( Pseudoceros sp. )
These species of flatworm can be found in tropical regions on or around coral reefs and seagrass meadows.
They get their name from their easily identifiable yellow line going across their body. Like other flatworms, males of these speicies can be seen 'fencing' or fighting with their extensions as a show of authority or territory, the loser of this duel will become a female!
They feed on various small invertebrates.
Joydeep Sarkar
( Acanthozoon sp )
They can be found moving along coral rubble, living near reefs.
Growing up to about 8-12 cm in length the worm can be as large as a human palm. They have a black body with many bumps on their skin which are yellow or orange on the tips with a white base and white margin.
They are known to feed on copepods, small worms and molluscs.