A soft translucent sea squirt, grey-green, with both siphons rimmed in dark pigment - the black mouth of the name. It reaches about 8 cm (3 in) and tucks itself under ledges and into crevices rather than standing exposed, and the tunic is soft enough that the whole animal deflates when touched.
That reaction is where the English name of the group comes from: lifted out of water, a sea squirt contracts and fires a jet from its siphons. Underwater the same contraction is a defence against anything probing at the openings. Solitary ascidians like this one live a few years, filtering continuously, and each is a hermaphrodite releasing eggs and sperm into the water - timed to avoid self-fertilisation, since the larvae need to be someone else's. Ascidians of this family are the ones that concentrate vanadium in their blood cells, at levels thousands of times higher than the surrounding seawater and for reasons still not settled. The dark siphon rims make it identifiable in a group where most identifications need dissection.
- translucent grey-green body with dark rims to both siphons
- soft tunic that collapses when the animal is touched
- tucked into crevices rather than standing in the open
- height up to 8 cm
