Annelids are a phylum of segmented worms. Well known members of this phylum are the earthworms and leeches. The classification of this phylum and related phyla needs further research.
According to reference number 1 below, there are 19 species of earthworm in Singapore, three of which could be native.
Less well known members of this phylum are the polychaete worms (Class Polychaeta), which include the tubeworms. Tubeworms are common in the mudflats of Chek Jawa. They are so called because they build a breathing tube out of their underground burrow. Two main types can be easily distinguished. The one with the leaves or debris stuck to the breathing tube are the Diopatra, while the one without can be any of a wide range of polychaetes.