'Phantom' Predator's Speedy Dance of Death Is Both Graceful and Creepy
An animated model of the glassworm head capsule as it opens and closes the catching basket.
Credit: Copyright 2019 Kruppert et al.

In lakes around the world, fearsome creatures attack with strikes that were recently found to be among the fastest in the animal kingdom.

High-speed footage showed the nightmarish swimmers in action; multiple-jointed mouthparts extended from their heads, revealing branching structures to catch and hold squirming prey — even when the prey sprouted "teeth" from its neck.

Fortunately for humans, these predators are positively puny, measuring just a fraction of an inch. They are the young of tiny flies in the Chaoborus genus; also known as phantom midge larvae or glassworms, they are so-named for their transparent bodies. And when researchers turned special cameras on the tiny phantom midge larvae, they discovered that the creatures' deadly attack was among the fastest seen in animals. [Tiny Grandeur: Stunning Photos of the Very Small]

Atop a glassworm's see-through body, its head is "a complex catching basket" tipped with an array of appendages for quickly trapping small crustaceans, scientists reported in a new study. 

Using high-speed video and computed X-ray tomography (CT) scans, the researchers recorded glassworms as they caught water fleas. The scientists then built 3D computer models of the "basket" of structures on the glassworms' heads, identifying grasping antenna, bristly "knife hairs," powerful mandibles and a finger-shaped structure tipped with bristles and spiky "thorns."

When a water flea floated close by, the waiting glassworm would strike, its "basket" opening outward and then quickly contracting, pushing the flea toward the glassworm's waiting mouth. The tiny predator would stuff the water flea into its esophagus, using alternating movements of its jaws; while this "chewing" action didn't seem like it was meant to shred the water fleas, they would sometimes burst from the friction, according to the study.

Animation shows multiple angles of the opening catching basket of a glassworm, based on micro-CT data and high-speed footage.
Animation shows multiple angles of the opening catching basket of a glassworm, based on micro-CT data and high-speed footage.
Credit: Copyright 2019 Kruppert et al.

A glassworm's average strike lasted about 14 milliseconds (a millisecond is one-thousandth of a second) "from start of movement to prey contact" — one of the fastest attack moves in animals, the researchers wrote.

By comparison, the attack of the praying mantis Coptopteryx viridis takes 42 milliseconds (ms). Scientists have also recorded phenomenally speedy strikes in mantis shrimp (4 to 8 ms) and in trap-jaw ants and some trap-jaw spiders (less than 1 ms), according to the study.

Despite the phenomenal speed of the glassworms' strike, water fleas aren't defenseless; special "neck teeth" pop out under their heads when a threat appears. When water fleas did not deploy their teeth, glassworm attacks succeeded approximately 80 percent of the time. However, if water fleas displayed their spiky necklace of teeth, glassworms captured only around 50 percent of their prey, the scientists reported.

The findings were published online March 22 in the journal PLOS ONE.

Originally published on Live Science.