Stunning photos of the mysterious sea angel (Clione limacine), a swimming sea slug, have been released by Natalia Chervyakova a marine biologist and photographer from Moscow State University.
Sea angels are translucent and swim upright with fins that look like wings giving it an angel-like appearance. Here a sea angel is pictured without its tentacles out.
A sea angel living in Russia's White Sea hunts a sea devil (Limacina helicina), another plankton mollusc also known as the sea butterfly.
Little is known about these creatures that swim under the Arctic ice. Here a sea devil is photographed with a sea angel in the background. The pictures were taken at the Arctic Circle Dive Centre located on the White Sea in Northern Russia.
Photographs of the tiny creatures, which measure 5-8mm long, were captured using specialist underwater cameras. Here two sea devils swim together.
Sea angels exclusively hunt and feed on sea devils. However, sea devils only appear for a short period of time and it is not known how sea angels survive without the smaller shelled molluscs to feed on.
To capture the images, such as this sea angel descending on a sea devil, Ms Chervyakova spent many hours in the water. The task was complicated by the fact the creatures react to any slight disturbance.
The moment of capture. Sea angels don't have eyes but use chemical senses to detect their prey. When one senses a potential victim it moves fast and raises its tentacles.
Once captured, the sea angel turns the shell of its sea devil victim around so it can pull the soft body of the smaller mollusc from its shell.
Sea angels use sharp chitinous hooks in their mouths to pull out and eat the soft bodies of sea devils.
As soon as a sea angel feels any movement in the water, it begins to swim very fast. That makes focusing on details, such as these chitinous hooks in a sea angel's mouth, very difficult.
One of Ms Chervyakova's assistants peers through their diving mask at a sea angel, which has tentacles readied to pounce.
What are these?