In a July 2011 expedition led by Scripps researchers and National Geographic engineers, researchers arrived at Pacific Ocean’s Mariana Trench, located in the Western Pacific, and deployed remote-controlled landers called “dropcams.”

Equipped with HD cameras and lights, the team explored a region of the trench known as the Siren Deep, 6.6 miles below the surface of the ocean. There, researchers found single-celled amoebas known as xenophyophores. The organisms can reach four inches in length.

While there are other single-celled organisms on earth, most are microscopic and are therefore classified as microorganisms. However some are visible to the naked eye, such as bacteria.

Xenophyophores are the largest known single-celled species.

“[They’re] multi-nuclei, meaning they have many nuclei, with no membranes between them,” UCSD professor of biological oceanography and director of the Center for Marine Biodiversity and Conservation Lisa Levin said.

Levin said that there are trends among some organisms to get larger in the deep sea than in shallow water for unknown reasons. These xenophyophores are consistent with that trend.

Previous xenophyophores were known to live 7,500 meters below the surface of the ocean.

According to Doug Bartlett, the Scripps marine microbiologist who organized the Mariana Trench expedition, this discovery in the deepest marine environments is of great importance to the field of studies
in biodiversity, biotechnological potential and extreme environment adaptation.

“Although it is part of Earth, the trench environment, the darkness, high pressure and low temperatures seems more like one of Jupiter’s moons [like] Europa,” Bartlett said. “We can learn a lot about how life can evolve to such as bizarre set of conditions.”

The xenophyophores — which resemble sponges or cauliflower coral — are exclusive to the deep sea, and according to Bartlett it is only the tip of the deep-sea ecosystem iceberg.

The extreme ocean depths of the expedition presented new challenges for National Geographic engineers who developed the instruments to spot the mysterious giant amoebas.

The dropcams were developed and used by National Geographic Society Remote Imaging engineers Eric Berkenpas and Graham Wilhelm.

“The dropcams are versatile autonomous underwater cameras containing an HD camera and lighting inside a glass bubble,” Berkenpas said in the Scripps News article “Researchers Identify Mysterious Life Forms in the Extreme Deep Sea” published on Oct. 21. “They were created to allow scientists and filmmakers to capture high-quality footage from any depth.”    

The gathered photographs and video of the xenophyophores were positively identified by Levin and confirmed by Andrew Gooday of the UK National Oceanography Center.