Most tunicates have a relaxing life, sucking water in and filtering out plankton. The Predatory Tunicate is more active and go-getting, even though it's got a stalk and is stuck to the sea floor.
It's perfectly clear what they do. They have what is effectively a big mouth. When little creatures wander in, the big mouth closes. Clearly, their guts are held somewhere in the stalk. There's simply nothing else to it!
Once they've sucked their food in they reset the trap and wait for more.
This strategy allows the Predatory Tunicate to eat small Copepods and the like who might be swimming about just above the sea floor. A tiny crustacean might not seem like much to us, but compared to the microscopic bits and bobs that is the food of their shallow water cousins, a meal that we can actually see is quite the feast!
They reach about 13 cm (5 in) across and live at depths of 200 to 1,000 metres (650 to 3,300 feet). They're also hermaphrodite, where each individual simply releases sperm and eggs into the sea and hopes for the best. They can even fertilise their own eggs if need be.
In short, when a Predatory Tunicate closes its massive gob, that's about all the exercise it ever gets.
And of course, it really is a tunicate. Which means it's a chordate. Which means that, like the Salp, this mouth-on-a-stalk is a relative of all vertebrates, including humans.