Bottle ascidian

Scientific name : Sigillina signifera

Colonies of small (1 cm) zooids, bottle green colour, with dark lines around the siphons. Even large colonies.
The bottle green colour is exclusive. Confusion is possible with Oxycorynia fascicularis, the latter opaque and stalked.

Associated organisms
Colonies can grow very fast, colonizing large reef areas. Sometimes this species can cover living hard corals, sometimes maybe killing them.