Cerataspis monstrosa, on the left, and Plesiopenaeus armatus, on the right (Photo : George Washington University )

A researcher from George Washington University has solved a 200-year-old mystery about the origns of 'monster' larva Cerataspis monstrosa by cracking its DNA.

Based on genetic evidence, researcher Keith Crandall found how the larva found in the guts of other fish looked like in their adulthood. He revealed that the adult counterpart of the C. monstrosa is the deep-water aristeid shrimp known as Plesiopenaeus armatus.

"It's very exciting to have solved a nearly 200-year-old conundrum," Dr. Crandall said in a statement. "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 to answer this question and to have an outstanding database of reference sequences to compare against."

It wasn't easy for the researchers to connect a link between the larva and the aristeid shrimp as both looked completely different. They said that the C. monstrosa had a thick body and was covered with armor and exceptional horn ornamentation. It was the preferred meal of predators like blackfin tuna, yellowfin and dolphins.

But the Plesiopenaeus armatus looked more like a crab or lobster which is very elusive. It had been a very difficult task for the researchers to search for the Plesiopenaeus armatus which calls the Atlantic Ocean its home. Earlier studies have suggested a link between the C. monstrosa and the deep-water shrimp, mainly the penaeoid shrimp.

Hence, experts compared the samples of DNA sequence belonging to the family of Aristeidae based on the data collected over the years. They found that the C. monstrosa and Plesiopenaeus armatus are one and the same.

"Because previous studies suggested an affinity between Cerataspis and penaeoid shrimp, and more specifically the family Aristeidae, we sampled heavily within these groups," Crandall said.

Experts hope such studies will help in understanding the ecology of an organism.

The findings of the study are published in the journal "Ecology and Evolution."