Sea urchins move with their spines attached to the test. The spines work mainly on the water vascular system, allowing them to contract and expand easily. The spines are articulated through a ball and a socket joint. The walk of urchins is coordinated through spines as a team.
The feet of the sea urchin are called tube feet. The feet help them stick to the ground while feeding. They move, yes, and they can move fast, walking on their feet, spines and sometimes even their teeth.
Can Sea Urchins Move?
Sure, they can. And to be more specific, they have an interesting way of moving along the sea with their spines and tube feet.
You won’t exactly distinguish the movement unless you observe the spiny bush closely around the little spike ball called a sea urchin.
Looking closely, you can see tiny bumps on the sea urchin test. Through these bumps, the spines are attached closely or, you say, very tightly near the base.
This helps the spines move freely with the strength to the extreme limit. The skin and muscles cover the test in a live sea urchin. The fitting of the spines to test is better observed having a dead sea urchin with you.
The diagram above shows the position of the spines on the urchin’s body. This defines how a ball-like figure moves using multiple feet in a low gravitational pull.
How Do Sea Urchins Move?
The body structure amuses us and arouses our curiosity about the movement of a sea urchin. See how smooth the walk of the urchin is in the sea.
The movement of sea urchins is also labeled as Brownian motion, which is a random spread in all directions.
Where Do Sea Urchins Move?
Sea urchins shun the light. They are mainly found in colder offshore waters, but you can sometimes look for them in shallow waters.
You would find them in armies when they search for food. Here are some locations to let me clarify your idea about their mobility.
- New England’s green sea urchin is also in the tide pool and below the low-tide line.
- They move on the seabed.
- They move on the ocean floor from zero depth to the deepest trenches.
- More specifically, they move to 100 feet in depth in an intertidal zone.
- At low tide, they take shelter from waves in rock cavities.
How Do Sea Urchins Move Their Spines?
To know how they move, it is better to see the spine’s structure and how amazing nature has sculpted the urchin’s body (source).
The Sea Urchin’s spines are like wedge-based cylinders. The bridge and the pores in the spine help control the tension during its movement.
The spine not only waves but contracts and expands more like the tentacles of an octopus to balance the walking movement and clutch the prey.
The torsion helps it remain firm yet bend to the maximum. Torsion is when one end bends towards the other end while the other end remains firm and moves to the opposite side.
Also See: Are Sea Urchins Alive?
How Fast Do Urchins Move?
There are different aspects of the urchin movement. It depends on the smell of the predator or no stimuli. It also depends on the need to get the feed from the urchin.
A study says that the urchins move at the speed of 11-15 cm per minute when they smell a predator.
On the contrary, the speed reduces to 8 cm per minute when there are no such stimuli as a predator’s smell ~ Notes Jordi Pagès, member of the Department of Evolutionary Biology, Ecology and Environmental Sciences (Source).
How Often Do Sea Urchins Move?
Urchins are nocturnal. They avoid light, so they hide in crevices during the day and come out moving in the nighttime to feed. There are normally two instances when the urchins move.
- From the predator, if the urchins smell them
- In search of food
A red sea urchin moves 7.5 cm a day when there is enough supply of food nearby and 50cm a day when the food is yet to be found by the urchin.
Can Urchins Flip Themselves?
Yes, they can. If the sea urchins are flipped for some reason, they can right themselves using the spine and tube feet.
However, having poor oxygen or less water, they would have difficulty flipping themselves. High temperatures also make them less efficient in doing so.
They turn themselves right because they fear being eaten by the reef fish or tossed against the rocks by the waves.
Also See: How Do Sea Urchins Reproduce? [Explained]
Why Do Sea Urchins Move Their Spikes?
The sea urchins’ spikes are not only for protection but also for navigation. They move because of their ability to sense touch and light.
The fact that the urchins don’t have eyes clarifies this statement. They have sensitive skin on the tips of the spikes, making them move once touched.
The spikes also point toward the light direction to help urchins move toward the light.
Can Sea Urchins Swim?
They walk, crawl or move fast in the ocean bed but do not swim. This is the reason why you will find them on the ocean floor as they walk with tube feet on the ocean floor rather than swimming in the water.
Their special spine mechanism reflects the fact that they are made for walking and using the spines to survive in water.
Can Sea Urchins Poop?
Yes, is the answer. They poop; interestingly, the poop is healthy for the sea environment.
As per the study of Dr. Robert Scheibling at Dalhousie University in Nova Scotia, Canada, the poop, when examined, had many facts to share:
- The feces aren’t big, but thousands of them excrete these in small bits, almost covering the seabed.
- The poop starts breaking down and releases components that give the seawater nutrients back. The nutrients are carbon, nitrogen and lipids. The decrease in the carbon-to-nitrogen ratio makes it good for the invertebrates of the sea for feeding.
FAQs
1. Do Sea Urchins move a lot?
The sea urchins move on purpose. It is when they search for food or avoid predators.
2. What do Sea Urchins do if you touch them?
Don’t panic that they will stab you instantly. They aren’t intended or quick enough to point the spines at you. But a hard push would give punctures in your fingers.
It also depends on the species. Some of the species have blunt spines, which can but stab you.
3. How Long Can Sea Urchins survive out of water?
Normally, sea urchins cannot stay out of water. However, some species can stay out of the water for hours.
Conclusion
Unlike my imagination, sea urchins move in the ocean bed, not swim. Yet the speed and balance are awe-inspiring.
The body of the urchin is boneless, yet the strong movement mechanism of sea urchins with wedge-based cylindrical spines allows them to feed and stay safe.
The spines even provide them with a flipping technique that is more characteristic of fish. It is a unique creature that confuses you with its multidimensional qualities of land and sea animals both.
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