SALAMANDERS have a cool trick if they lose their tail: they simply grow a new one. Yet they are some way off the top of the league when it comes to such running repairs. Some creatures can regenerate an entire body from mere fragments of the old one.
It was thought that only simple beasts such as jellyfish and sponges have this talent. Now sea squirts (Botrylloides leachi), the closest invertebrate relative to vertebrates, have been found to do it, too.
Inhabiting shallow coastal waters, sea squirts form colonies of genetically identical individuals. Ram Reshef and Yuval Rinkevich of the Israel Institute of Technology in Haifa and colleagues took fragments of blood vessels from the animals and watched under a microscope. Out of 95 fragments they examined, 80 underwent whole body regeneration (WBR). Cells first grouped into hollow spheres, then cell layers infolded and organs developed, until after two weeks an adult sea squirt had grown, capable of sexual reproduction (PLoS Biology, DOI: 10.1371/journal.pbio.0050071).
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鈥淭o think that even one attached blood vessel survives storm damage and regenerates the entire colony,鈥� says Reshef. 鈥淲hat an advantage this provides!鈥�
In other animals, the signals that trigger WBR are transmitted from a central point, but in sea squirts they arise from multiple locations. Reshef suggests the discovery may help illuminate regeneration abilities that have been lost or suppressed in vertebrates.
