Monster Larvae Mystery Solved: They’re Really Shrimp

A monster larvae mystery that had confused scientists and fishermen for more than 200 years has been solved — the oversized larva found in the guts of some fish are really a kind of shrimp.

Scientists had wondered why the “monster larva” pulled from these fish had looked like grown-ups rather than larvae, LiveScience reported. Now a new report published in the journal Ecology and Evolution poses an answer, that the larva, Cerataspis monstrosa, is actually a baby version of a deep-water aristeid shrimp calledPlesiopenaeus armatus.

“It’s very exciting to have solved a nearly 200-year-old conundrum,” said Keith Crandall, a biology professor at George Washington University and author of the report.

The younger version of the larva was a popular food for yellowfin and blackfin tuna, and fishermen who caught these fish often found the monster larvae in their guts.

One of the reasons the monster larvae mystery was able to last for more than 200 years was the difference between the baby and adult version of the shrimp. As Crandall noted, the two look very different, with the adult version covered in armor. Living in the deep waters of the Atlantic Ocean, the adult version looks more like a lobster than a shrimp, LiveScience noted.

To solve the monster larvae mystery, Crandall’s lab had been collecting crustacean DNA samples for years to create a database for comparison, the Daily Mail reported. It was this comparison that allowed him to correctly identify the shrimp.

“This was a project that involved having good luck with obtaining the sample, exceptional field knowledge to preserve the specimen and know that it was something special, outstanding state-of-the-art molecular and analytical tools to collect unique data that have only been available in the last 10 years,” Crandall said of the now-solved monster larvae mystery.