In coral reefs into the night, corals competing for space are no match for the crawling crown of thorns starfish, unless they have the help of some very special friends, who will defend their home with determination - crabs.

Originally released by BBC Worldwide Learning, 2011. Streaming video file encoded with permission for digital streaming by Infobase on April 18, 2015.

Crown of Thorns Starfish (3:00); .