Meet Phronima – A Parasitic Predator from the Deep

Meet Phronima – A Parasitic Predator from the Deep

Picture a predator with four eyes, two pincer-like claws, and a set of sharp jaws. Its body is transparent, allowing it to blend fully into its surroundings. Its home is transparent too – providing protection while also allowing the creature to stalk its prey from within.

Sound like something from your nightmares? You’re not alone. A popular (though possibly unfounded) rumor is that this critter served as the inspiration for the alien queen in the movie “Aliens”. Its appearance and lifestyle certainly seem to lend some credibility to the argument.

Meet Phronima, a small amphipod found in all the world’s oceans, outside of the Polar Regions. Phronima may be scary, but only if you are a salp. Females hunt salps for both food and a residence. After hollowing out and eating the inside of a salp, they retain the animal’s husk as a convenient mobile home. Phronima use their pincers and clawed legs to snatch food, generally zooplankton, through the open ends of the hollowed-out salp.

Female phronima recycle parts of salps or jellies, building barrels to raise their progeny.

Their four, complex eyes allow them to watch out for predators and prey lurking above, while at the same time possibly scanning for bioluminescent cues from food sources floating below. The walls of the salp also provide a safe place for Phronima’s eggs and hatchlings. Females use their brush-covered posterior legs to propel their salp homes through the sea, ensuring access to food and fresh water as they go.

The Phronima is a parasite that hitches a ride on a barrel-shaped salp and drifts through the open ocean. They are found in all of the world’s oceans except for the polar regions.

Not a whole lot more is known about the life of these strange and wonderful creatures, giving us yet another reason to further explore and protect their wide blue world. Who knows what other horror movie inspirations await us in the depths?

Contributor: Andrea Greene Liberatore