Monster larva’s identity revealed

For centuries, an elusive larval creature with armor-like horns has kept its true identity a secret. That mystery has been solved, thanks to a team of researchers led by FIU Assistant Professor Heather Bracken-Grissom.

The oceanic creature, first identified by a marine scientist in 1828, was originally described as monstrous and misshapen. It was assigned the scientific name Cerataspis monstrosa.

For nearly two decades, scientists have been unable to identify what the Cerataspis monstrosa grows up to become. FIU researcher Heather Bracken-Grissom and a team of scientists have solved the mystery.
Photo courtesy of D.L. Felder.

“Monster isn’t a term necessarily indicative of its size, but rather its bizarre, monster-like appearance. It’s really crazy when you see it,” said Bracken-Grissom, who joined FIU’s Department of Biology this year.

Rarely seen since that initial discovery, scientists did not know what this monster larva matured into as an adult. In several instances, specimens were found in the guts of ocean predators including dolphin fish and tuna. However, most of these specimens were damaged, degraded, and unsuitable for molecular studies. But a chance discovery on a 2009 research cruise changed all that. Researcher Nicole Vollmer with the University of Louisiana at Lafayette came upon an intact, freshly collected specimen in the Gulf of Mexico.

“The fact that it was recently collected and preserved correctly made it suitable for molecular-type testing,” Bracken-Grissom said. “We were able to use genetic techniques — DNA methods — to determine what exactly this monster larva is.”

So what exactly is this monster lurking in our oceans?

“A shrimp. It’s a rare deep sea shrimp,” Bracken-Grissom said.

Heather Bracken-Grissom, assistant professor of Biology, says she hopes, by providing a definitive link between the mysterious larva and its adult counterpart, it will spur more conversations about biodiversity.

Acknowledging the humor in the discovery, Bracken-Grissom said she totally appreciates the oxymoron of a monster larva that grows up to be a shrimp. Now identified as Plesiopenaeus armatus, the adult form is almost as elusive as its larval counterpart. Making its home in the abyssal depths of the ocean, the shrimp is difficult to track and study.

“In the larval form, we think it has an extended existence in the water column because of its unusual physical characteristics,” she said. “We know that it’s a food source for some large, predatory fish. But there’s so much we just don’t know about it.”

While Bracken-Grissom has linked this larva to its adult form, she said the discovery barely puts a dent in what people don’t know about the world’s oceans.

“A lot of people in the marine community have asked the question of what this little bugger becomes. Surprisingly, that’s not that uncommon,” she said. “There are so many instances where we have documented creatures in infant or larval stages and have no idea they become as adults. It’s just further evidence of how vast the oceans are. I hope this discovery helps keep the conversation going about the importance of biodiversity.”

Bracken-Grissom’s research, “Phylogenetics links monster larva to deep-sea shrimp,” was published August 27 in Ecology and Evolution. The research was funded by the National Oceanic and Atmospheric Administration, National Science Foundation, Southeast Fisheries Science Center, Department of Interior-Bureau of Ocean Energy Management, and the Gulf of Mexico Research Initiative.