Botryllus ascidians

Scientific name : Botryllus spp.

Encrusting ascidians, more rarely massive. Small zooids (1-4 mm) arranged in chains or ellyptical systems, making typical drawings around a common cloacal siphon. Colour may vary, as it is clear from the pictures. As the Indonesian species systematics is still unclear, we put together all the photographed species in a single page for the genus Botryllus.
Above, a species with orange-brown stripes among the oral siphons, the cloacal siphons are in white areas. All species photographed in Manado area. Botryllus species are common in the shallow areas of the back reef, lagoon and reef front. Amongst ascidians, some similarity exist with encrusting didemnids. In didemnids the oral siphons are small and uniformly distributed among the larger cloacal siphons. In Botryllus oral siphons are disposed in chains or ellypse, in systems with maximum 20 zooids each.
The similar genus Botrylloides have zoids in chains longer than 20 zoids.
At a first glance, confusion is possible with an encrusting sponge: putting a hand close, gently, if siphons close this must be an ascidian (sponges can not close their pores).

Associated organisms
Many Botryllus species are epibiotic on black coral dead stems or on leaves and rhizomes of seagrasses.