Giant single-celled animals live nearly seven miles below the ocean surface, about the deepest depth any creature has been found.

Using specially engineered cameras, scientists at Scripps Institution of Oceanography at UC San Diego in July scoped the Pacific Ocean's Mariana Trench, one of the deepest places on Earth that has been left largely unexplored.

The group found single-celled animals, also known as xenophyophores, the size of baseballs. Some were even larger and exceeded four inches.

They are fascinating giants that are highly adapted to extreme conditions but at the same time are very fragile and poorly studied, Scripps deep sea biologist and professor Lisa Levin said. These and many other structurally important organisms in the deep sea need our stewardship as human activities move to deeper waters.

Scientists say xenophyophores are the largest individual cells in existence. Recent studies indicate that by trapping particles from the water, xenophyophores can concentrate high levels of lead, uranium and mercury and are thus likely highly resistant to large doses of heavy metals. They also are well suited to a life of darkness, low temperature and high pressure in the deep sea.

The instruments used to spot the mysterious animals were Dropcams developed and used by National Geographic Society Remote Imaging engineers Eric Berkenpas and Graham Wilhelm, participants in the July voyage.

The 'Dropcams' are versatile autonomous underwater cameras containing an HD camera and lighting inside of a glass bubble, said Berkenpas. They were created by National Geographic engineers to allow scientists and filmmakers to capture high-quality footage from any depth in the ocean. The devices were baited and used 'camera-traps' to capture imagery of approaching marine life.

Scientists have found life in some of the most unexpected places including hot springs, rocks and frozen arctic regions.

The identification of these gigantic cells in one of the deepest marine environments on the planet opens up a whole new habitat for further study of biodiversity, biotechnological potential and extreme environment, said Doug Bartlett, the Scripps marine microbiologist who organized the Mariana Trench expedition.