This unidentified species of Spirobranchus is smaller than S. corniculatus and is nearly always found in the coral Acropora palifera, which appears to be a more dense, harder coral than the Porites species where S. corniculatus lives. The two also differ in that S. sp. 1 has no easily visible operculum to cover the hole when it retracts, although it is possible it is too small or hidden to notice in these photos.
Retracted into their tubes.
A couple of worms on coral that has died.
Created 5 February 2019