Creatures of the polar deep

Scientists conducted a series of expeditions during International Polar Year 2007-08 to collect data that they will contribute to the Marine Life Census, the most comprehensive study of life in the oceans ever conducted. By comparing notes, scientists studying both poles found 235 species living in both polar regions despite being 6,800 miles (11,000km) apart. Marine life that both poles share includes these shelled pteropods, Limacina helicinia Photograph: Russ Hopcroft, University of Alaska Fairbanks/Census of Marine Life

Scientists say the discovery opens a host of future research questions over where they originated and how they ended up at opposite ends of the earth. The ghost-like sea-angel Platybrachium antarcticum, flies through the deep Antarctic waters hunting the shelled pteropods (another type of snail) on which it feeds. This 3cm long slug was photographed during a 2008 expedition aboard the Umitaka Maru to the Antarctic Photograph: Russ Hopcroft, University of Alaska Fairbanks/Census of Marine Life

Sand fleas (amphipod crustaceans) under nearshore ice in the Beaufort Sea. Ice-associated amphipods are a major food source for Arctic cod, in turn the main prey for ice seals Photograph: Shawn Harper, University of Alaska Fairbanks/Census of Marine Life

The nemertean Pelagonemertes rollestoni hunts for zooplankton prey that it will harpoon with a dart attached to the tongue coiled within it. Its yellow stomach reaches out to feed all parts of the body. About 3cm long, it was photographed during an Antarctic expedition in 2008 Photograph: Russ Hopcroft, University of Alaska Fairbanks/Census of Marine Life

Arctic krill, Thysanoessa raschii, is found in high densities under sea ice in the Arctic and its marginal seas, where it feeds seasonally on algae associated with the sea ice Photograph: Russ Hopcroft, University of Alaska Fairbanks/Census of Marine Life

Calycopsis borchgrevinki, is one of the more common hydromedusae encountered in Antarctic waters Photograph: Russ Hopcroft, University of Alaska Fairbanks/Census of Marine Life

Chionodraco hamatus, one of the Antartic's ice fish, can withstand temperatures that freeze the blood of all other types of fish Photograph: Census of Marine Life/Russ Hopcroft, University of Alaska Fairbanks

Sand-fleas such as Hyperoche capucinus, are common predators swimming in polar waters. This specimen - about the width of a finger - was photographed during an Antarctic expedition Photograph: Russ Hopcroft, University of Alaska Fairbanks/Census of Marine Life