Aquarium visitors attend a dinner party in an underwater tunnel in Tianjin, China on September 15, 2016. Tianjin Haichang Polar Ocean World opened in the city of Tianjin, southeast of Beijing, in 2010. It gives visitors a chance to see more than 150 large animals from the Arctic and Antarctic regions, including polar bears. (Photo by Feature China/Barcroft Images)

Beneath the Swedish capital lies an intricate web of underground train lines. More than 90 of the 100 stations in the 110km tunnel system, sometimes referred to as “the world’s longest art gallery”, have been decorated with paintings, installations, mosaics and sculptures by 150 artists since the 1950s. After spending a couple of weeks exploring arctic Norway and Sweden, London-based travel photographer Conor MacNeill headed underground to capture images of the metro stations. Here: A rainbow arcs over a girl on the platform of Stadion station. (Photo by Conor MacNeill/The Observer)

“The harp seal or saddleback seal is a species of earless seal native to the northernmost Atlantic Ocean and adjacent parts of the Arctic Ocean. Newborn pups weigh around 11 kilograms (24 lb) and are 80–85 centimetres (31–33 in) long. After birth, the mother only feeds that pup. During the 12 day nursing period, the mother does not eat, losing up to 3 kilograms (7 lb) per day. Harp seal milk contains up to 48% fat, so pups gain over 2.2 kilograms (4.9 lb) per day. During this time, the juvenile's “greycoat” grows in beneath the white neonatal coat, and it weighs 80 pounds (36 kg)”. – Wikipedia

Photo: A harp seal pup lies on an ice floe in the Gulf of Saint Lawrence March 24, 2008 in Charlottetown, Canada. (Photo by Joe Raedle/Getty Images)

Commended. In late May, about a quarter of a million snow geese arrive from North America to nest on Wrangel Island, in northeastern Russia. They form the world's largest breeding colony of snow geese. Photographer Sergey Gorshkov spent two months on the remote island photographing the unfolding dramas. Arctic foxes take advantage of the abundance of eggs, caching surplus eggs for leaner times. But a goose (here the gander) is easily a match for a fox, which must rely on speed and guile to steal eggs. “The battles were fairly equal”, notes Sergey, “and I only saw a fox succeed in grabbing an egg on a couple of occasions, despite many attempts”. Surprisingly, “the geese lacked any sense of community spirit”, he adds, “and never reacted when a fox harassed a neighboring pair nesting close by”. (Photo by Sergey Gorshkov/Veolia Environnement Wildlife Photographer)

Is it a leaf? Is it tree bark? No, it’s the Satanic leaf-tailed gecko. Cleverly disguised as a rotting leaf, Madagascar’s camouflage king has red eyes, pointy horns and a taste for night hunting: it’s nature’s most devilish deceiver. The twisted body and veiny skin echo the detail of a dry leaf, which ensures the gecko blends in with its forest home. The mottled tail appears to have sections missing, as though it has withered over time. This mini-monster epitomises survival of the fittest, having adapted gradually to become today’s extraordinary leaf impersonator. (Photo by Thomas Marent/ARDEA)

Rockhopper penguins live up to their name as they navigate the rugged coastline of Marion Island in the southern Indian Ocean. (Photo by Thomas P. Peschak)