New research reveals how tiny, freshwater animals known as hydra must rip apart their skin in order to feed where scientists finally figured out how these creatures do this.

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This unique process involves changing the skin cells in the hydra's mouth for the animal to stretch out and split these cells that results in a drastic deformity. According to lead author of the study, biophysicist Eva-Marie Collins of the University of California, San Diego, for these cells to possess the ability to create a mouth opening which can be wider than its body is truly remarkable. Upon closer observation, the shape of these cells can appear as if the cell nuclei became deformed.

Collins and her team investigated this process by genetically engineering a hydra so that the two layers of its tissues could light up and reveal how their mouth and bodies function on a cellular level. Hydra are measured less than a half inch long appearing like a column where a ring of tentacles are growing from their ends. Wild hydra are often seen attaching itself to a rock or some sort of surface using these tentacles growing from this end, where it waits for its prey to pass by.

When an unsuspecting victim passes by, like small shrimp, it can brush against the hydra's tentacles as the hydra reveals and shoots out its poisoned barbs in order to sting and paralyze its prey. When the hydra is seen contracting its tentacles, this special group of cells can split apart to reveal the insides of its mouth where this predator is now ready to suck its prey in. 

After it consumes its meal, the hydra will rip open its mouth, spitting leftover materials as it seals again this mouth with a sheet of tissue, waiting for the next shrimp or prey to pass by. The team observed the genetically engineered hydra's tissues, showing that the cells of this animal change its shape as opposed to transferring in other places, in order to open its mouth.

Collins says that this complicated process is revealed a lot but in reality, this animal only uses relatively simple physics for this mechanism. When these cells are triggered, the radial pattern of the fibers inside the hydra's tissue can stretch these cells apart, which is also similar how muscles in the eye's iris contract in order to open our pupils.

Collins adds that there is no other known species on the planet that is known to feed in this unique manner. With this new information, scientists are now trying to investigate the evolutionary factors of this process and physiological effects to the animal of this shape changing in the hydra's cells.

This new study is published in the Biophysical Journal.