Mysterious Undersea Circles Finally Explained

After 22 years speculations regarding the mysterious, strangely appealing circles on the seafloor, the mystery has finally been solved.It turns out that the undersea circles are created by a newly discovered pufferfish species to attract female mates.

In 1995, a number of divers found attractive, strange circular structures on the seafloor near Japan’s Oshima Island. These circular pattern formations would then disappear after a while and new ones would appear after some time.

All those years, no one really knew who/what formed them or how they were created. Finally, scientists made an intriguing discovery. The beautiful undersea formations were created male pufferfish thought to be a new species in the Torquigener genus.

According to scientists, the male pufferfish creates the circular structures, which are actually nests, to woo female pufferfish.

The Actual Creation Process

The male pufferfish which measures about 13 centimeters (less than 5 inches) long flaps its fins while swimming along the sandy seafloor in a circular manner to create peaks and valleys.

He does this by swimming towards the center of the circle in a straight line, and then back around in a circular motion.

He also carefully decorates the peaks of the ridges with shells and coral fragments. The result is amazingly unique circular patterns.

These formations are said to measure approximately 7 feet (2 meters) in diameter and take about 10 days to complete.

Once complete, the female pufferfish come to inspect them. If they feel pleased with the structures, they lay their eggs. According to Hiroshi Kawase, the Coastal Branch of Natural History Museum and Institute’s
curator, no one really knows what the females are attracted to in these beautiful formations.

Female Lays Eggs

Once the female deems the formation satisfactory, she then lays her eggs in the fine sediments at the center of the circle and then vanishes.

The male then fertilizes the eggs externally.

Interestingly, once the female leaves, the male takes up the parenting role where he remains in the nest, perhaps to guard the eggs until they hatch which takes about six days.

Once they hatch, the male repeats the same process all over in another place mainly because these formations don’t stay intact for long as the underwater currents washes them away pretty quickly.

Also, the fact that all the fine sediment within the area is used up prompts him to look for a fresh place to construct another nest.

Small Fish, Large Formations

Initially, scientists assumed that only a much bigger fish would be able to make such large formations. No one would have really thought that such a small fish would be able to make such an amazingly large structure.

However, some scientists suggest various possibilities such as improving the visibility of their nests for females to find them easily or poor visibility at depth.

Formations Similar to Bowers

Bowerbirds are known to build display sites “bowers” to show-off before mating. This behavior is also exhibited in some other animals.

Pufferfish formations are now considered as very rare in biology. And the fact that such a small animal is capable of creating such large nests makes it very interesting.

Additionally, why the male pufferfish tediously spends about 10 days to create a large nest and repeat the process over and over makes it even more intriguing.

All in all, it’s good to know that this decades long mystery has finally been solved.

Featured image by Animal Wire