For a lucky subset of vertebrates, losing an appendage is no big deal. As many an inquisitive child knows, salamanders can regenerate lost limbs or tails; and as lab investigators know, zebrafish can regrow lost fins. Of course, humans and other "higher" vertebrates must make do with repairing rather than regenerating damaged tissues. Though whole body generation (WBR) does occur, it’s typically restricted to a subset of morphologically less complex invertebrates, such as sponges, flatworms, and jellyfish.
In a new study, Yuval Rinkevich et al. discovered an unusual mode of WBR in our closest invertebrate relative, the sea squirt Botrylloides leachi.