Diadema setosum is a special kind of sea urchin. It has very long, hollow, and thin spines. It’s part of the Diadematidae family.
The Diadema setosum sea urchin has five white dots on its body, which makes it different from others of its kind. It lives in the Indo-Pacific region, places like Australia, Africa, Japan, and the Red Sea.
What Does Diadema setosum Look Like?
Imagine a sphere with lots of long spikes sticking out. That’s what Diadema setosum looks like!
Diadema setosum’s body, or test, is black and a bit squashed. The spikes, or spines, are very long and thin compared to its body.
The spines are often black, but can also be brown, and they are hollow with a weak venom inside.
The Diadema setosum sea urchin has five white spots on its body that make it easy to identify.
What Are Some Other Features of Diadema setosum?
There is a bright, orange ring around the Diadema setosum sea urchin’s ‘anus’, which is a word for its waste hole. It also has blue spots on its body.
Diadema setosum sea urchin doesn’t have an apical ring or calcareous platelets on its apical cone.
Grown-up Diadema setosum weighs between 35 to 80 grams. They are no bigger than 70 millimeters in width and 40 millimeters in height.
Where Can Diadema setosum Be Found?
Diadema setosum lives in many different places. It’s found from the Red Sea to the Australian coast, and from Japan to the southern tip of Africa.
In 2006, two Diadema setosum sea urchins were found in waters off the coast of Turkey. This was a big deal because it was the first time this kind of sea urchin was found in the Mediterranean Sea.
How Did Diadema setosum Get to Turkey?
There are a few theories about how the Diadema setosum sea urchins got to Turkey.
One theory is that the baby Diadema setosum sea urchins traveled through the Suez Canal from the Gulf of Suez, where there are many Diadema setosum.
Another theory is that ships brought Diadema setosum over in their ballast, which is a part of the ship that helps keep it stable.
The last theory is that people who keep fish as pets let them go on purpose.
What Kind of Places Does Diadema setosum Live In?
Diadema setosum likes to live near coral reefs, but it can also live on sandy flats and in seagrass beds. It eats a lot of different kinds of algae that are found on tropical coral reefs.
In Hong Kong, there are a lot of Diadema setosum sea urchins. This might be because there aren’t many of their predators, the blackspot tuskfish, left due to overfishing.
What Can You Tell About the Biology of Diadema Setosum?
Diadema setosum can spawn, or produce eggs, all year round or only at certain times, depending on where they live. It seems like when the water is warmer than 25°C, the sea urchins spawn more.
In the Philippines, Diadema setosum spawn all year round. But in the Persian Gulf, they only spawn in April and May. They also seem to spawn more when there’s a full moon.
What Else Is Interesting About Diadema setosum’s Biology?
Diadema setosum is one of the oldest kinds of sea urchins we know about. It’s the most basic, or ‘basal’, kind of sea urchin in its group.
Diadema setosum’s venom is mild and not dangerous to humans, but the spines can be hard to remove if they get stuck in your skin.
What Is Special About Diadema setosum’s Behavior?
When Diadema setosum is in danger, it can flip over and ‘run’ on its longest spines. It rolls when it hits small things in its path.
This sea urchin also has very good eyesight for an urchin and can move its spines toward fish that come too close.
But we’re not sure how Diadema setosum can see so well. We think light might enter each spine and get sensed at the base. We need to do more research to find out.
Scientific Classification
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Echinoidea |
| Order: | Diadematoida |
| Family: | Diadematidae |
| Genus: | Diadema |
| Scientific Name: | Diadema setosum |
| Also Known As: | Black Longspine Urchin |
| Conservation Status: | Unknown |