Imagine living in the sea where it is permanently dark, cold, and food is hard to find. For many animals at depth, it may be weeks to months between meals. If you find something to eat, you have to hang on to it. This is why so many deep-sea fishes have lots of big teeth. This dragonfish, spotted off the coast of Australia, even has teeth on its tongue. They would be terrifying animals ... if they weren’t the size of a banana. (Photo by Julian Finn/Museum Victoria)

Participants of the the goth festival “Wave Gothic Festival” walk in fancy costumes along the festival area in Leipzig, central Germany, Saturday, May 23, 2015. About 20,000 members of the scene are expected to attend one of the world's largest gothic and “dark” culture festivals until May 25, 2015. (Photo by Jens Meyer/AP Photo)

The bloodwood tree (Pterocarpus angolensis) is a deciduous tree with a high canopy, reaching about 15m in height and has dark bark. The red sap is used traditionally as a dye and in some areas mixed with animal fat to make a cosmetic for faces and bodies. It is also believed to have magical properties for the curing of problems concerning blood, apparently because of its close resemblance to blood. The name bloodwood for these trees stems from the dark red to brown sap that accumulates on wounds on the trunks.

A dark Devon Rex cat is held by its owner during a competition in Bucharest, Romania, Saturday, September 26, 2015. More than 300 cats entered the international feline beauty competition in the Romanian capital. (Photo by Vadim Ghirda/AP Photo)

A gallery assistant poses by a sculpture entitled “Dark Place” by Australian artist Ron Mueck displayed at Thaddaeus Ropac gallery in London, Britain, October 11, 2021. The exhibition dedicated to Ron Mueck will open to the public from Oct. 12 to Nov. 13 ahead of Frieze Week. (Photo by Matthew Childs/Reuters)

An artist applies henna on the hand or a woman during the Hindu festival of lights, Diwali, in Taipei, Taiwan, Thursday, November 4, 2021. Millions of people across Asia are celebrating the Hindu festival of Diwali, which symbolizes new beginnings and the triumph of good over evil and light over darkness. (Photo by Chiang Ying-ying/AP Photo)

A Hindu woman hold clay-lamp during a ceremony to celebrate Diwali, the festival of lights, at Krishna temple in Lahore, Pakistan, Sunday, November 12, 2023. The Hindu festival of lights, Diwali celebrates the spiritual victory of light over darkness. (Photo by K.M. Chaudary/AP Photo)

The arctic hare, or polar rabbit, is a species of hare which is adapted largely to polar and mountainous habitats. The arctic hare survives with a thick coat of fur and usually digs holes in the ground or under snow to keep warm and sleep. Arctic hares look like rabbits but have shorter ears, are taller when standing, and, unlike rabbits, can thrive in cold climates. They can travel together with many other hares, sometimes huddling with dozens or more, but are usually found alone, taking, in some cases, more than one partner. The arctic hare can run up to 60 kilometres per hour (40 mph). Its predators include the arctic wolf, arctic fox, and ermine.