Creature of the Month

 
 

Bullethead Parrotfish
(Chlorurus sordidus)

 

 

 

This colourful parrotfish lives on coral reefs and lagoons to over 75 feet. It is one of the most common parrotfish seen in the Indo-Pacific from the Red Sea to Hawaii and Australia.

Parrotfish are unusual because they sleep wedged in the coral in a mucous cocoon. Until recently this was thought to mask the scent of the parrotfish from predators. But research published this month shows that the cocoon actually works as a "mosquito net". The parrotfish are targets for external parasites which feed on their blood, much as mosquitos feast off humans. During the day the fish visit "cleaner stations" where cleaner wrass remove the parasites (gnathiids).

During the night the fish spend their time building the cocoons before tucking into bed, protected from the biting gnathiids. The Bullethead parrortfish changes colour as it gets older. Initially both male and female are a drab grey, brown or reddish colour. Some of the males, though, will change into a bright blue or green primary male. Females can also turn into males, but they will not be quite as brightly coloured. These are called secondary males.

Like other parrotfish, Bulletheads have fused teeth and need to continually graze dead coral rock otherwise their teeth will grow too long. They often appear to be eating corals, but more often they're really eating algae growing on an exposed section of the coral skeleton. This benefits the coral as the algae growing on shallow reefs would otherwise smother them.

Parrotfish create a phenomenal amount of sand - the remains of the rock they crunch. This is one reason why the visibility on reefs is generally higher in the early mornings, before parrotfish have begun their rock munching.

Reprinted with permission:
Copyright SCUBA Travel - http://www.scubatravel.co.uk/