Nudibranchs or “Sea Slugs” of Koh Tao

Nudibranchs or sea slugs is a name normally given to any marine gastropod without a shell or a reduced one, such as nudibranchs, Pleurobranchs, Sea Hares, Sap Sucking slugs and the Bubble Snails and Headsheild Slugs. Members of each of these species can be found around Koh Tao. Nudibranchs are the most diverse and variable of this type of species to be found are the island.  Nudi meaning naked and branches refers to gills!..Naked Gills!


They come in a great variety of shapes, colours, sizes and body styles.  For example the rhinophores (ear-like structures that can sense and taste) that can be smooth, retractable, sheathed, lamellate, or papillate.  The oral tentacles could be short and blunt, long and exposed or heavily reduced.  Some have cerata (sort of horns that extend the surface area of nudibranchs and aid in respiration) while others have dorsal appendages and others may be smooth or bumpy that may do the same job.  We still have a lot to learn.

Many don’t grow longer than a few millimeters but some can grow to 20cm.

where to go scuba diving in koh

Phyllidia picta, it grows no bigger than 4cm

Where can you find it?

They under the sand, crawl along the sea floor, swim in the water column,  some like plankton living just below the waves.

One of the most widespread and abundant nudibranch found around Koh Tao

Jorunna funebris, one of the most widespread and numerous species. It feeds solely on the common blue sponge, which grows in abundance around the island.

What do they do

One of the common traits of these creatures is how they defend themselves, they have chemicals with which to protect themselves from predators.  Some do retain an internal or external shell to some degree as well as chemical protection.   Also, they are widely studied as an important indicator of biodiversity in a healthy marine ecosystem.

Want to do more Diving on Koh Tao ?

So if you are interested in learning about marine life you can study the Fish Identification or Marine Ecology courses online.
If you would like to more about Koh Tao diving contact us and you can find out more about the diving we offer by clicking on the links below or follow us on Facebook or Instagram.

Koh Tao Diving Courses

Want to know more?

Find out more about SSI here: Dive SSI