Turbellaria  

Turbellarians are flatworms with a bilateral symmetry. Eyes and tentacle-like outgrowths are often found at the anterior end. The mouth is situated on the underside and is the only opening of the digestive system. Most species are hermaphroditic and as well as sexual reproduction they can reproduce asexually. Flatworms move by creeping or flowing across the substratum using cilia on the underside of the body. They can be predators, scavengers, commensals or parasitic.

Free-living flatworms can be found in rock crevices, living amongst coral debris, and in sand along Ranong shores. Specimens encountered during this study varied in colour from brightly banded species to uniform buff or grey. Identification depends on microscopic examination of external features such as number of eyes, marginal outgrowths (called tentacles), position of the mouth and genital pores, together with anatomical examination of internal features.

The species collected in Ranong were found in Ao Khloei from rock crevices or in coral debris in Ko Ra. A number of very small species are common in intertidal sand. It should be noted that many more species are likely to encountered.