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This article was originally published in bioGraphic, an independent nature and conservation journal supported by the California Academy of Sciences.
The nautilus inhabited the deep waters around forest-covered Manus Island, an exclamation point at the northwestern tip of Papua New Guinea’s Bismarck Archipelago.
It lived slowly and in near-total darkness—its large eyes tuned to the blue wavelengths of bioluminescent bacteria that signaled the corpse to clear, and were sensitive enough to tell night from day 300 meters below the surface. Its 90 tentacles and superior sense of smell helped it search for food on the sea floor. And as it grew, it added new chambers to its spiral shell.
When the nautilus died—perhaps at age 20 or 30—its soft, squid-like body rotted away. Its shell lost the neutral buoyancy that allowed it to float effortlessly to any depth it chose, and floated to the surface. The currents washed it into the mangroves or onto one of the palm-fringed beaches of Manus, or perhaps a nearby coral-encrusted atoll called Ndrova Island.
Wherever it landed, the elegant cream swirl of the rust-brown-striped shell would catch the woman’s eye as she searched for clams. She took it home with her, made it useful.
Manuai Matawai grew up watching her mother, like other women in his fishing village, use the sealed outer chamber of the nautilus shell as a ladle to separate fragrant coconut oil from the fruit’s starch at the bottom of her cooking vessel. The nautilus – called kalopeu in the local language of the Titans – was also a symbol of a prophet, followed by Matauai. But like most in his coastal community, he had never seen a live one, due to his preference for the cold, dark depths.
Then, in 2015, he had his chance. Researchers from Australia and the United States came to study the creature, and Matawai, then working for the Nature Conservancy (TNC), helped organize their expedition to Ndrova. Peter Ward, a University of Washington paleobiologist widely known as “Professor Nautilus,” had last visited in 1984, when he and an associate were among the first to study a living mossy nautilus, a species belonging to a new genus that they late called Allonautilus scrobiculatus. Ward and his colleagues had returned to see if the mossy nautilus and the more famous chambered nautilus (Nautilus pompilius) were still there and to try out some new research tools.
From left, Pomat Kanaui, Gregory Barrord, Peter Ward and Manwai Matavai snorkel off Ndrova Island, Papua New Guinea, in search of the little-understood and rare nautiluses. Photo by Manuai Matawai
Only a handful of scientists study nautiluses, and many of the most basic questions about the creatures’ lives remain unresolved. Yet they have captivated humans for centuries, their form inspiring art, architecture and mathematics in many cultures. The submarine 20,000 leagues under the sea is called the Nautilus, as is the first nuclear submarine. Today, many companies, from wineries to exercise equipment manufacturers, also use the name.
“I don’t know if it’s the most mysterious well-known animal or the most famous mystery animal,” said Gregory Barrord, who joined the 2015 expedition led by Ward. The scientists hoped to dispel some of that mystery with their research in Ndrova, but what they found raised even more questions.
Soon after Ward donned his scuba gear and descended the steep walls of the reef, he noticed a change. In 1984, scientists were harassed by sharks. “They were nasty, cranky little bastards, so I was kind of afraid to go through that again,” Ward recalled. But this time they saw none, suggesting a change in the ecosystem. There was also evidence of coral bleaching and the waters, which had been pleasantly cool under the shoals, now felt uncomfortably warm.
The experience inspired Ward to pursue a new line of research, analyzing the composition of nautilus shells to track rising temperatures in the deep sea and looking to nautilus behavior to predict how these changes might affect his favorite subjects of study.
Climate change is dramatically altering life in the world’s oceans, and extreme heat is now the norm in many places. Ward believes that nautiluses may now seek refuge in cooler, deeper waters to cope. But there is only so far the molluscs will be able to swim. Below 800 meters the pressure is enough to make their shells explode.
A shop in the Philippines sells piles of spiral nautilus shells from a large container. More than 100,000 nautilus shells were imported into the United States alone between 2005 and 2014. Photo: Greg Barrord
At the same time, human desire for the animals’ beautiful mother-of-pearl shell has led to overfishing in some parts of their tropical Pacific home. “The bad luck of the nautilus is that it has this beautiful symmetry,” says Ward. Their shells can fetch up to US$1,000 on eBay. Between 2005 and 2014, trade data compiled by the US Fish and Wildlife Service showed that more than 100,000 whole nautilus shells and 800,000 parts were imported into the United States alone. Some once-abundant populations in the Philippines — where nautiluses are also sometimes hunted for food — may already be extinct.
As climate change looms, so does one question among all others for nautiluses: can they survive us?
Nautiluses have certainly always survived. Ancient and cunning, their lineage was adaptable enough to last through all five of Earth’s greatest past extinction events. Their ancestors, the nautiloids, appeared half a billion years ago. They were the first cephalopods, a group of molluscs that today includes octopuses, cuttlefish and squid.
Back then, most life crawled along the seafloor, but nautiloids could float suspended in the water, a key innovation they achieved by removing the fluid from their innermost chambers to match the density of the seawater around them. making them essentially weightless. The earliest nautiloids had straight, cone-shaped shells, but soon evolved the coiled spiral with interconnected internal chambers seen in nautiluses today. In their current incarnation, they have been criss-crossing the oceans for at least 100 million years.
It was in this form that they withstood the asteroid that ended the age of the dinosaurs. Debris from the impact and ash from the fires that raged afterward hid the sun for two years, killing most of the photosynthesizing plankton that form the base of the shoals’ food web. The Nautilus species that lived near the surface probably died out of starvation along with their relatives, the ammonites.
Same but different: a chambered nautilus swims next to a mossy nautilus with a slimy outer layer. Photo by Peter Ward
But in the eternal twilight known as the Mesopelagic Zone, between 200 and 1,000 meters below the surface, other species of nautilus persist. And since today’s nautiluses are thought to be primarily scavengers, the mass death and destruction may have even benefited them, Ward suggests. After all, he says, “What was left after the end of the Cretaceous? Dead bodies.”
A more personal tragedy kept Ward from Nautilus field research for several decades. During an expedition to New Caledonia in late 1984, his diver friend drowned while the two were checking nautilus traps. The 2015 expedition was his first foray back into Papua New Guinea.
The team, which included Barord’s Richard Hamilton and TNC, traveled to Ndrova aboard a 14m two-masted canoe that Matawai had built for a climate change awareness trip a few years earlier. The island is a particularly good place to study nautilus: the seabed falls away so sharply from its shores that a trap placed on the bottom hundreds of meters below the surface can simply be tied to a coconut tree.
Ndrova Chief Peter Kanawi welcomed the researchers and 18 community members joined the expedition as assistants. Each evening, as the tropical sun sank into the sea, the team set out in small motorboats and lowered the traps – cubic metal frames covered with chicken wire and fed with tuna. At dawn, they pulled the lines by hand — a grueling exercise that took almost an hour per trap — stopping when the cage was within snorkeling distance of the surface.
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Researchers studying nautiluses off Papua New Guinea capture the animals with their shells to weigh, measure, sex and take samples before returning them to the water. Video by Dave Abbott
The traps caught nothing the first night. Some locals speculated that the foreigners were not properly acquainted with the ancestors. But an older fisherman who had taken part in the previous expedition recalled that the traps were set in a different location in 1984, at a slightly shallower depth. On their next outing, the team did as he suggested. In the morning, Hamilton dived overboard to check the trap.
A coral reef biologist accustomed to studying the shoals, he looked forward to this daily discovery. “You feel like a little kid making luck.” These were all things I hadn’t seen before – sort of a visual assessment of how much you don’t know.” Sometimes there were the odd eel and Hamilton was particularly fond of the ‘strange-looking crabs’. But that day he was thrilled to count three fuzzy nautiluses and three chambered nautiluses.
Nautiluses are accustomed to the depths and cannot survive long in the warm surface waters of tropical seas. So, once back aboard the outrigger, the scientists placed the animals in a seawater-filled cooler cooled with frozen water bottles.
It was obvious who the mossy nautiluses were. Their shells were covered with a sticky, hairy periostracum, or outer layer, which is completely absent in other nautilus species. “It feels kind of…
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