Nudibranchs or “Sea Slugs” of Koh Tao
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 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.
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.