Uncharismatic Fact of the Day
Gills are for usually for breathing- but not for the lancelet! These primitive animals diverged from fish-- and all other chordates-- during the Cambrian era, so even though they share plenty of traits with modern vertebrates, they've undergone a process known as exaptation, in which certain traits change function. For example, rather than use their gill slits to breathe, they exclusively use them to filter out plankton for feeding.
(Image: A trio of Mediterranean amphioxus (Branchiostoma lanceolatum) by Vincent Moncorgé)
















