Coral reefs: Underwater pharmacies

These kaleidoscopes of colour and life cover less than 0.1% of the planet but are home to a quarter of all marine species. As a result, it’s a crowded place to live and underwater warfare reigns as animals vie for space and food. Since many of the creatures on the reef are stationary, many have evolved chemical defences to protect themselves from predators. These potent weapons may also hold the key to new medicines to treat everything from cancer and Alzheimer’s disease to viruses and arthritis.