Footage of rarely seen, nearly transparent, alien-looking cephalopods—glass octopuses—is making waves across the internet. But the unprecedented look at the elusive glass octopus (footage scientists will study for insights into the species known as Vitreledonella richardi) is just one of many mesmerizing findings made during the deep-sea expedition of the remote Pacific Ocean. 

“We have likely discovered about a dozen candidates for new [animal] species,” including never-before-seen crabs, corals, and jellyfish, says Randi Rotjan, the Boston University marine biologist who led the expedition with the help of coprincipal investigator Tim Shank of the Woods Hole Oceanographic Institute. Their team—comprising BU student researchers and a postdoctoral fellow as well as other scientists from Woods Hole and Boston Children’s Hospital—also documented more than 100 species living symbiotically with deep-sea corals, including more than 10 symbiotic relationships between corals and other organisms that had never been observed before. On top of that, she says, they collected samples of deep-sea bacteria that have never before been analyzed: “We might be talking about hundreds of new species of bacteria.”

Sorry, glass octopus. But those new species of bacteria could be the real star of the show, in Rotjan’s eyes. 

How deep-sea bacteria could fuel marine conservation

In a recently-published paper in Science Immunology, she and her Boston Children’s collaborators reported that some of these bacteria aren’t recognized by the human immune system. That could make them effective new vehicles for delivering drugs or therapeutics in people, without triggering an attack from the human immune system. The medical promise of these “silent” bacteria, Rotjan believes, could even unlock a new avenue for financing marine exploration and conservation.

Randi Rotjan aboard the research vessel Falkor. Photos courtesy of Schmidt Ocean Institute.

“If there are medical uses for these deep-sea bacteria, it could help us conserve swaths of the ocean that are currently unprotected,” says Rotjan, a BU College of Arts & Sciences research assistant professor of biology. Such protection is critical, because so little is yet understood about the ecology of the deep-sea floor yet it plays such a large role in helping to regulate Earth’s planetary processes and its climate.

Over the course of the expedition, the team mapped 45,000 square kilometers of seafloor, including the terrain of 10 underwater mountains, or seamounts, whose undersea peaks and features had not yet been known in any detail. “They just were known as [topographic] blobs before we got there,” Rotjan says. Five of them are located in high-seas waters that aren’t allocated to any country, and five of them are in US-owned waters. “We’ll have the opportunity to name some of the seamounts, which will be really fun.”

During the expedition—which took place aboard the research vessel Falkor and was supported by the Schmidt Ocean Institute—Rotjan, BU PhD candidate Anna Gauthier, and Boston Children’s collaborator Jon Kagan also conducted 48 experiments, looking for new evidence of how corals’ and sponges’ immune systems interact with deep-sea bacteria. 

“Deepwater corals [and sponges] live for hundreds or sometimes even thousands of years; there are even some corals living today that predate major moments in human history, like the start of Christianity,” Rotjan says. “[As these] corals get slowly eaten by predators, they have open wounds for long periods of time, likely weeks, months, or even years. Despite this, we don’t see outward signs of infection.”

She explained that by studying how the immune systems of these primitive corals and sponges respond, scientists may uncover new insights into how their immunity developed alongside the very origins of multicellular life on Earth.

Some of the questions the researchers hope to answer include: Do deepwater corals and sponges recognize different bacteria that human immune systems do not? Can coral immune systems recognize E. coli, a human gut pathogen? And just how similar are human immune systems to those of deepwater corals and sponges, which represent one of the most ancient branches of the animal evolutionary tree?

Rotjan also hints that corals and sponges could hold new clues to understanding longevity, since despite being slowly eaten by predators throughout their lifetimes, many of these organisms continue to survive and grow indefinitely. “Looking at deepwater corals and sponges challenges us to think differently about how organisms grow and live through time. They live so long and grow so slowly, it’s a very different situation [from humans and most other animals],” Rotjan says.

With more than 250 hours of footage from the seafloor, Rotjan and her team will analyze the films, documenting many things, including all the different types of predators observed feeding on corals, something that has not been surveyed before. Down in the ocean’s darkest depths, “no one knows who exactly is eating who,” she says.

Why “incredible” discoveries risk destruction without protection

Which brings us back to the ghostly, glassy, eight-armed creature that first brought the spotlight to Rotjan’s expedition. Predation—and the attempt to avoid becoming prey—is likely why the glass octopus is as translucent as it is, scientists believe. Its appearance makes it difficult for the octopus to be spotted by would-be predators, and helps it conceal itself from prey that it’s stalking for its own meals. 

During the expedition, researchers discovered more than 10 new symbiotic relationships between corals and other creatures. Photos courtesy of Schmidt Ocean Institute.

“We did so many amazing things on this expedition, and have so many samples to analyze and characterize back in the lab now—and on top of all those successes, we were lucky enough to observe two glass octopuses,” Rotjan says. Both creatures, she notes, were seen in unprotected parts of the ocean.

Those areas, however, are incredibly important to our planet’s functioning and its ability to absorb and release carbon to support life. “The deep sea provides [so many life-sustaining functions] for the planet, yet so many deepwater areas are not protected—areas that we haven’t even explored yet,” she says.

Rotjan hopes that the treasure trove of new knowledge stemming from this expedition will demonstrate why marine conservation is important. “Even though many areas of the sea are not protected yet doesn’t mean they should be ignored—just look at the incredible things we saw down there,” she says.