Membranous ascidians

Scientific name : Didemnide spp.

Many undescribed didemnids have in common the encrusting form, membrane like, with common cloacal siphons larger and surrounded at different distance by many individual oral siphons. Often the cloaca is higher.
The above species is whitish-violet, with black siphons edges.
Another undescribed species, with yellow and grey colour and slimy aspect. Many Didemnid species are similar between them. All can be identified by the oral siphons opening at all levels around a common cloaca.
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).
When the colony is not feeding, can be thinner and membranous. Identification then can be more difficult

Associated organisms
This species, often associated with large ascidians, has a purple colour with whitish areas next to siphons. In these areas there is an higher concentration of spicules, to make the colony more robust.