These “Mysterious Underwater Circles” of Amami Oshima became a hot topic when a TV program introducing them was broadcasted. Originally found by an underwater photographer in 1995, he didn’t know who made them and for what purpose they were there. It was in 2011, that we finally discovered that it was made by small pufferfish.
The Amami Oshima’s “Mysterious Underwater Circle” is often made nearly 30m deep, so it is hard to observe for long at that depth; and the seasons and tides limit the divers’ abilities to observe these circles, so it took 16 years before we were able to meet its creator, the pufferfish.
This is the male pufferfish, Torquigener albomaculosus, the creator of the circle. In 2014, this pufferfish was registered as a new species. The Japanese name “Amami Hoshizorafugu” is named so because of the dotted pattern on its back, like the many stars in the beautiful night sky of Amami Oshima. (In Japanese “Hoshizora”= starlit night sky, “fugu” = pufferfish)
We observed this white-spotted pufferfish over five days, as it was constructing the circle. In this photo, the pufferfish is decorating the outer edge of the circle with shells. It seems that the fish shapes the shell by chewing on a larger shell in its mouth.
The first step in creating the circle, is for the pufferfish to choose a spot that it likes and begin by removing and seaweed from the area. Then it will make a groove which will be the basis of the circle. For the making of the outer circle, the groove is formed by the small fish using its pectoral fins to roll up the sand moving from side to side. Slowly, the sand is piled up on both sides to form a deeper groove.
The center of the circle, where the eggs will be laid, is made into a gentle shallow area using its stomach.
White-spotted pufferfish which has finally finished making its circle. But even then, it’s very busy with maintenance to keep the shape.
Now it is just a waiting game, until a female pufferfish comes by and likes his circle!
At this time in May 2022, during high tide there were seven circles in the diving area. This morning, one male had success as there were some eggs in the middle of the circle! The gray color mass in the middle of the photo are the eggs.
As soon as the female lays the eggs, she disappears and the male will take care of the eggs in his circle. He will consistently move the eggs and sand with its fins and continue to send them fresh seawater.
A male white-spotted pufferfish who is busy taking care of his eggs. The maintenance of the circle stops and therefore the shape is starting to collapse a little.
So, in this 30m deep area where we were diving, we could see 6 of the 7 circles had eggs. But the one that had no eggs yet, which we nicknamed “Fuguta,” this was the circle that I thought was “the most beautiful and splendid circle” but sadly, it wasn’t chosen by a female pufferfish. I am sure there is a difference between the pufferfish and our senses, but even so, I was disappointed that it was not selected…it was like a Japanese saying that “it was the crowd favorite, but it failed to qualify for the finals.”
Our little “Fuguta,” who was dedicated to the maintenance of his circle. He was laboring over it, however, he wasn’t as energetic as yesterday.
“Fuguta” would not give up! The breeding season will continue for another two months. I left the seabed praying for him, that he’ll be able to attract another female during the next high tide.
Of the 15 dives over a 5 day period, 10 dives were spent observing the white-spotted pufferfish. We observed all the various stages from circle construction, the maintenance, and then of taking care of the eggs. It looks a very smart fish.
Photos & text: Mariko SAWADA
Observation: May 2022, Amami Oshima
Special Thanks: Dive Species Amami, Mr. Homare SUWA
Tags: Dive in Japan, Scuba diving tour in Japan, Wildlife tour of Japan, amami hoshizora fugu, Diving tour of Japan, amamihoshizora fugu, アマミホシゾラフグ, Wildlife in Japan, White-Spotted Pufferfish, Scuba diving in japan, Scuba diving in amami oshima, Torquigener albomaculosus, T. albomaculosus, mystery circles, Wildlife of Japan, mistery circles in Amami Oshima
