Ghost Shark Prompts Questions About Deep Sea Exploration

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Ghost Shark Prompts Questions About Deep Sea Exploration

Off the coasts of California and Hawaii, scientists recorded the ghost shark, also known as the pointy-nosed blue chimera, in its natural habitat for the first time.

The ghost shark is a strange deep-sea creature—the video shows its blank eyes, large and flexible fins, and dotted heads. The fish, a distant relative of the shark and considered to be a living fossil, has other unusual features, including a retractable sex organ located on the head of males and flat tooth plates instead of teeth. Also known as Ray Troll’s chimera, named after an Alaskan artist whose images often feature the alien-looking fish, the Hydrolagus trolli lives at crushing depths up to 6,500 feet below the ocean’s surface.

Although the video was taken in 2009, it was just released to the public by the Monterey Bay Aquarium Research Institute (MBARI). Previously, the ghost shark had only been found near Australia, New Zealand, and New Caledonia.

“The interesting thing about this particular finding is that the fish has been observed in the Northern Hemisphere, a long way from the place where it was originally described,” said Dominique Didier, the ichthyologist who first identified Hydrolagus trolli as a new species in 2002.

This could mean the ghost shark migrates or is more common than originally thought. MBARI’s video also shows the pointy-nosed blue chimaera near a rocky seafloor, which could point to the fish’s preferred habitat. In previous findings, pointy-nosed blue chimeras were typically observed on sedimented seafloor.

Another possibility is that the fish recorded is a new species.

“We are finding new species of chimaeras—and all kinds of other fish—all the time,” Didier said.

But a new species can’t be proven until a specimen is obtained. Having a specimen of the fish is so important to species identification that the fish in the video is cautiously described as Hydrolagus cf. trolli: the additional “cf.” means that the fish in question should be compared to Hydrolagus trolli, as it might not be the same species.

Joshua Drew, who researches aquatic ecosystems at Columbia University, defined the specimen as the arbiter of whether or not an observed species is a new species.

“This very special specimen, called the ‘holotype,’ is the representation of that organism, and we compare it to all the other kinds of things that it might be,” he said. “When we don’t have a specimen in hand, we have to make do with what we have.”

Even if the Hydrolagus cf. trolli isn’t a new species, it still gives scientists plenty of new information—and new questions to ask. Didier pointed out that although the search for chimaeras doesn’t drive research, new information can be found when research is conducted for other purposes, such as during pipeline and geological surveys or when checking an area’s biodiversity.

“We know more about the surface of Mars than the depths of our oceans,” she said.

The vastness of the oceans means that new discoveries are frequently uncovered, she added.

“Every time we send down an ROV (remotely operated underwater vehicle), it’s like looking at a pinpoint of the entire ocean. I like to use the analogy that taking a sample at one place in the ocean is like trying to understand all the Great Lakes using a Dixie cup.”

Deep sea exploration presents many challenges to researchers such as Didier and Drew. Exploring the depths of the oceans is expensive work, and few organizations have the funds and equipment to do so. Funding for deep sea exploration is difficult to obtain as national priorities move away from science and education, Didier said.

“I worry about our long-term ability to be a scientific contributor to the global community, ” Drew said. “ … However, people will fund what fascinates them, and I hope that finding out that there are new and amazing things in the deep will help us stay funded and continue to do the work that’s necessary to understand our oceans.”

Because the oceans largely remain unexplored, there are many opportunities for new discoveries. Plus, the price of ROVs is declining, which could allow scientists to map more of the ocean, Drew said.

Also, new technology being developed for deep sea exploration, such as exosuits, one- or two-person manned submarines, and advanced photography promises improved documentation, Didier said.

“I’m excited every day about what new things scientists will discover.”

Top image: Monterey Bay Aquarium Research Institute

Nicole Lipitz is a science communicator and sci fi writer living in Brooklyn, New York.

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