Having to completely rip your once sealed mouth every time you want to enjoy a taco seems like a lot of work. But, that's exactly how the hydra consumes most of its meals. The hydra is a small freshwater creature that has to tear its mouth, a sealed (and re-sealing) piece of skin, each time it wants to eat. link
The hydra lack bones, measure less than half an inch, and live underwater. They typically exist attached to an underwater plant stem. Their tubular bodies, which end in tentacles and stingers, are the perfect bio-weapon for spearing microscopic crustaceans and corepods. Eva-Maria Collins, a cell biologist and physicist that led the study comments, "We were really struck by the fact that it can open its mouth wider than its body...nobody actually knows how it achieves this feat".
Through some serious microscope sleuthing, the team realized that the cells are not actually moving relative to each other when it opens its mouth. Instead, each cell keeps its neighbor and both stretch together. The stretching is allowed by the muscle-like cells in the mouth's outer later. The process, they say, is similar to how muscles in the iris of a human eye contract to widen the pupil. Additionally when the researchers decided to add a muscle relaxant to the hydras, they couldn't open their mouths at all!
Biophysicists have jus recently filmed these hydras and their eating process as a hope to finding more clues about tissue regeneration.
This photo is licensed under Wikimedia Commons and Public Domain.