Water Fleas are the Real Transformers

Image: Linda Weiss
Image: Linda Weiss

Consider the water flea. They don’t seem like the flashiest animals, but it turns out they can grow helmets and spines to beat their enemies, and can even customize the defenses based on which predator they’re fighting.


Linda Weiss, a professor at Ruhr-University Bochum in Germany, is leading research on how water fleas, or Daphnia lumholtzi, developed this ability, and presented it at the most recent meeting of the Society for Experimental Biology. Apparently, the fleas have the ability to detect the unique chemical traces left in their environment by predators such as phantom midge larvae and fish. Depending on which chemical traces the water flea detects, they will develop different types of armor.

“These defences are speculated to act like an anti-lock key system, which means that they somehow interfere with the predator’s feeding apparatus,” says Dr. Weiss.


For example, many freshwater fish can only eat small prey so the water fleas who detect freshwater fish will grow head and tail spines to make themselves larger and harder to eat. Her team has detected the specific neurotransmitters that detect the chemical traces and then activate the process that causes the spines or helmets to grow.

Future research will look at how the water flea’s “arming” abilities affect the local ecosystem, but for now we’re just wishing there were a way that we could do the same thing.


Angela Chen is the morning editor at Gizmodo.

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Didn’t protect them from the tropical fish we used to feed them to in industrial quantities when I was a kid.

“Look! I have a helmet!”

“Om nom nom nom.”

It does make them look pretty goddamn horrifying, though. My nightmares tonight are on you.