Peacock Flounders – Transformers of the sea

In Bonaire, living on our house reef ‘Something Special’, we have a healthy population of Peacock Flounders.  This is a type of flatfish which spends most of its time living in the shallows on sandy bottoms.  They are tricky to spot due to their unusual shape, excellent camouflage and are often buried in the sand with only their eyes sticking out.

The transformation these creatures go through during the larval stage of their life is amazing. The Peacock Flounder starts life as a ‘normal’ fish. It swims upright, it has a dorsal fin on the top, two pectoral fins on its sides and an anal fin underneath. An eye on either side of its head looking forward with a mouth at the front.

Over 6-8 weeks as the Flounder descends to the seabed it goes through a miraculous transformation. Its mussels, skin, blood vessels and bones move into a flattened shape. It loses its swim bladder and rotates 90 degrees onto its side. One eye migrates round to join the other eye on the opposite side. The dorsal and anal fins join the flattened oval body leaving a lone pectoral fin extending from the center of its back.

This transformation means that when they reach the seabed they are ideally suited to living on the bottom. Each eye has independent 180-degree vision. This means it can see what is in front of it and behind it at the same time!

It has adaptive camouflage which means it can mimic the patterns of the seabed and it can perform this within a matter of seconds. This is achieved through irregular shaped cells in the skin known as chromatophores which contain different colors.

Our local flounder, the Peacock Flounder is capable of displaying more complicated patterns due to having a higher concentration of chromatophores. They can produce various types of patterns. To name a few include yellow sand, coarse gravel, flat greys and even checkerboard squares! The university of California San Diego performed tests and although the flounder could produce the checkerboard pattern. The checks were not in alignment with the ones on the board!

They are ‘lie in wait’ predators and their diet consists mainly of small ‘minnow like’ fish species. Mantis shrimp and even octopuses though have been discovered in their stomachs!

They have sex every night with a couple of ladies, during the process the female Peacock Flounder goes on top! The males fiercely protect their ladies from the advances of other males, whose territories are situated next to their own. Once the excitement is over for that day, the lady Peacock Flounders go and sleep in deeper waters, the males sleep on the same patch of sand every night!

Here is a video showing the metamorphosis of the flatfish.

Next time you are on the dive site ‘Something Special’ in the shallows performing your safety stop, keep your eyes peeled for these little transformers, a true biological marvel.