Deep Dark Sea

Hundreds of feet below the waves, an extreme cave diver confronts perils to discover rare and unusual forms of marine life.


It’s claustrophobia times 10.Photograph by Jill Heinerth

It’s cave diving, the most extreme kind, where divers go hundreds of feet below the surface into caves so dark that they are blacker than black—leaving divers with no clue what might lurk around the next corner. But in these caves live some of the most interesting and rare forms of life in the world, and Texas A&M University at Galveston researcher Tom Iliffe is the hands-down king of this underwater empire.

Iliffe has been in more underwater caves—at least 1,500—than anyone in the world and discovered several hundred new species, some of them even named after him.

One recent discovery came in the blue caves of the Tunnel de la Atlantida (“tunnel to Atlantis”)—one of the world’s longest underwater caves, located in the Canary Islands off the coast of North Africa. Iliffe discovered a type of worm about the size of a grain of rice in this mile-long cave, which was formed by a volcanic eruption 20,000 years ago.

“The small worms we discovered were found in a large, conical mound of white sand, which had filtered down from a hole in the ceiling,” Iliffe says of the discovery.

“We collected several samples of the sand, and when we examined it later, we found these new species in it.”

Fellow researchers from Spain, Germany and The Pennsylvania State University agreed to name the new species after Iliffe; thus was born Sphaerosyllis iliffei, whose tiny body has no eyes or color and is the first cave-adapted species from the worm family Syllidae.

“It’s similar to other cave-adapted worms that live in that particular cave in that they likely colonized underwater caves and cracks in older rocks on the island and invaded the water of the cave sometime after its formation 20,000 years ago,” he notes.

Iliffe also discovered a new species of crustacean, a member of the class Remipedia, believed to be among the most primitive crustaceans. It was dubbed Speleonectes (“cave swimmer”) atlantida, after the cave system it inhabits.

The remipede is about one inch long and has no eyes. Its head has specialized mouth parts and venom-injecting fangs, with a body consisting of 20 to 24 segments. Its body is almost transparent, owing to the total darkness of its environment.

Researchers have found similar species of remipedes in the northern Caribbean and in Australia, leading Iliffe to believe that Remipedia is one of the oldest crustacean groups on Earth.

“It likely had its origins during the early stages of the formation of the Atlantic Ocean millions of years ago when the continents of Europe/Asia and North/South America were in close proximity,” he adds. “So it’s thought remipedes could be at least 200 million years old—a time when dinosaurs roamed the earth.”

Resembling a centipede, remipedes have hollow-tip fangs that inject a venom potent enough to kill shrimp or other marine life but not toxic enough to harm humans. Another oddity of the creatures: They are hermaphrodites, meaning that individuals have both male and female reproductive organs.

Although Iliffe has more than 35 years of experience diving into such underwater caves, he knows they are dangerous.

“We found 80 species of new cave-adapted animals in some caves in Bermuda,” he says. “How did these creatures get there, and how do they still survive?

“Also in Bermuda, we found bones that showed us that the sea level there was 400 feet lower than it is today, so we are always learning new things from these caves,” Iliffe says. “Some of these cave systems we explore are five miles in length and go down hundreds of feet but are only a few feet wide in some places. Yes, it’s dark and it’s dangerous, but it’s worth the risk. Only a handful of people in the world have been to most of the caves, so we are seeing things almost no one has ever seen before.

“One of the great thrills about diving into these caves is that you can literally turn your head and see a creature that no one has ever seen before. These caves are like no place on Earth.”

Back to 2010 Advance Contents