A study by Dr. Alexandra Grutter, the University of Queensland, Australia and his team unraveled the secret behind coral parrot fish sleeping in its unique cocoons. The research revealed that the coral reef parrot fish, the coral reef sand maker, builds cocoons at night to guard itself from the blood sucking parasites.

The bullet head, coral reef parrot fish builds cocoons at night using the mucous secreted from a small glad under its gills. This process takes at least 45 minutes to 1 hour. This cocoon forms a protective cover around the fish securing it onto one place, helps hide its scent from enemies and also acts as a warning system.

The large amount of antioxidants found in this cocoon also helps the fish replenish its lost energy by morning. "The amount of effort that goes into building these cocoons, which requires fish to have developed very large glands, is extraordinary," said Dr Grutter.

Scientists and divers were surprised to find the bullet head parrot fish hiding inside a cocoon at night. They could not understand this unusual behavior pattern in this coral reef parrot fish and the use of its cocoon. In order to unravel the mystery they have conducted an overnight research.

The study revealed that the cocooned parrot fish survived the blood sucking parasite gnathiids better than those without cocoons. "What I find most exciting about these results is the unique way these fish deter parasites at night while still being able to sleep, an approach not used to my knowledge by any other animal,” said Dr Grutter.

According to the scientists, the parasite menace was too much for the parrot fish to force physiological evolution in the species. There are no other animals in the world which uses cocoons to ward off enemies.

The research was published in the Royal Society journal Biology Letters.