A new mouth with every meal

A view of a hydra.Photo: NYT

A view of a hydra.Photo: NYT  

A pond-dwelling hydra rips a hole through the center of its body’s outer layer everytime it finds a prey. When the dinner is done, it closes back up.

This tiny aquatic creature is not that multi-headed sea beast of Greek mythology that regenerates a head every time some daring hero chops it off. It doesn’t even have a head. But like the mythical hydra, the real hydra does regenerate, which is why scientists have been studying it for decades. Over time, researchers have learned one fact creepy enough to fuel nightmares: Every time this pond-dweller wants to eat — for example a little brine shrimp — it rips a hole through the center of its body’s outer layer. When dinner is done, it closes back up.

Researchers have been aware of the hydra’s unusual mouth for quite some time. Scientists at the University of California, San Diego, captured the hydra in action in a 25-second video clipping to show what’s going on at the cellular level.

Just seconds after the researchers applied a chemical present in shrimp, the hydra detected the possible snack and ripped open a mouth. Later, the mouth sealed back up so the hydra could digest.

“It looks a little bit like the control of the pupil in the human eye,” said Eva-Maria Collins, who led the research team, noting that the sympathetic and parasympathetic nervous systems control dilation of the pupil.

When a human detects a threat, the sympathetic nervous system prepares the body to respond, dilating the pupils to help see better. In the absence of the threat, the parasympathetic nervous system brings the pupil back to normal. Dr. Collins thinks the hydra opens and closes its mouth for food by a similar process.— New York Times News Service

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