Fascinating facts about starfish
Starfish( sea stars) or Asterozoa are beautiful marine life fauna.
(scientific name: Asteroidea) belong to the echinoderm family, which includes starfish, brittle stars, sea urchins, sea cucumbers, sea lilies, and feather stars have around 7,000 extant species of invertebrates.
It is an enormous phylum that covers around 95% of marine animals.
There are about 2,000 species of starfish that add beauty to our oceans. They all resemble each other; they live in all types of ocean waters, from coral reefs to the deep sea, up to 6 km deep.
They commonly have five arms, but some grow up to 40 arms. Starfish do not have blood a brain, or a heart. They have two stomachs. Starfish can live up to 35 years. They can regenerate themselves.
Although they are not actual fish, they are simple marine animals. We often see them at the seashore while diving when they are attached to rocks. That’s a brief introduction to starfish.
But have you ever wondered if Can starfish swim? If they can’t swim, how do they move?
In this blog post, we will explore the biological facts about sea star locomotion in detail. We will also cover the anatomy of their organs related to their “swimming” or movement.
But first, let’s start with a quick answer.
Starfish(sea stars) can’t swim like many other sea animals. Instead, they move by walking or gliding along the sea floor.
They do this using special tube-like feet on the bottom of their bodies. However, when starfish are very young (in their larval stage), they can swim or float in the water.
How Starfish Move?
Starfish, or sea stars, have tiny tube feet on their underside that help them move along the seafloor or reef.
How it works?
Starfish have a unique internal system of water-filled canals.
Seawater enters through a small structure called a madreporite and flows through canals to reach the tube feet.
Each arm of a starfish has thousands of tube feet. Most starfish species have five arms, with a few exceptions having more.
Interestingly, these tube feet can move in any direction independently. During my research work in Florida, I used to do extensive work on florida starfish species in a large aquarium.
I picked up a sea star, Gray Sea Star (Luidia clathrata ). I felt the organs and tube feet of this sea star for the first time; the tube feet felt quite silky.
You know, Tube feet can extend and contract. When a tube foot touches the ground, it releases a particular adhesive substance to stick to the surface.
By controlling water pressure in the tube feet, the starfish can make them extend, adhere, and contract, moving them forward.
Any arm can lead the movement. Although starfish don’t have a brain, their nervous system cannot learn or plan, but it helps them react to stimuli, like coordinating the tube feet across different arms.
Tube feet have multiple functions including helping in the starfish breathing process, sensing the environment, and capturing food.
The adhesive on their tube feet can be quickly released and reapplied, allowing starfish to move on various surfaces.
Thanks to their flexible tube feet, Starfish can adapt to rough or smooth surfaces.
How Does The Water Vascular System Work?
The water vascular system in starfish is suitable for their movement.
1. Ring Canal
This circular canal surrounds the starfish mouth.
2. Madreporite
also called the sieve plate, it is a small plate on the upper side of the body that helps water enter the system and helps equalize pressure differences.
3. Stone Canal
Water from the madreporite flows into the stone canal.
4. Tiedemann Bodies
These structures produce phagocytic cells called coelomocytes.
5. Polian Vesicles
These vesicles store fluid for the water vascular system.
6. Radial Canals
Five (or multiples of five) radial canals branch out from the ring canal.
Each radial canal has many lateral canals that lead to the tube feet.
7. Tube Feet
Internally, the tube feet end in bulb-like muscular ampullae.
When an ampulla contracts, it pushes water into the tube foot, causing it to extend.
The tube feet often have suction cups at their ends to attach to surfaces.
Water Flow Process
1. Madreporite to Stone Canal
Water enters through the madreporite and flows into the stone canal.
2. Stone Canal to Ring Canal
Water flows from the stone canal into the ring canal, which is a five-sided structure around the starfish’s center.
3. Ring Canal to Radial Canals
Water then moves into the radial canals, one extending through each arm.
4. Radial Canals to Lateral Canals
Radial canals branch into lateral canals, which end at the tube feet.
5. Tube Feet Extension
Each lateral canal has a valve to prevent backflow.
The lateral canals connect to the ampullae at the base of the tube feet.
When an ampulla contracts, water is forced into the tube foot, extending it.
6. Tube Feet Function
The tube foot’s suction cup attaches to a surface.
The contraction of muscles in the suction cup creates a vacuum, allowing the starfish to adhere to surfaces.
Functions
1.Feeding
The original function of the water vascular system was likely feeding, helping the starfish capture prey.
2.Locomotion
The system allows starfish to move in any direction by coordinating their tube feet.
3. Gas Exchange
The movement of water through the system also aids in gas exchange and helps the starfish get the oxygen it needs.
This coordinated system allows starfish to climb or attach to rocks, aiding in their survival in various marine environments.
Do Starfish Swim? Free-Swimming Starfish Larvae
Starfish start their lives as tiny larvae.
They can drift around in the ocean currents for days or even weeks.
These tiny starfish float alongside other super-small creatures called plankton. Then, male starfish release sperm, and female starfish release eggs into the water at the same time.
These cells fertilize into each other in the water.
When this happens, fertilization occurs.
After fertilization, the eggs start to grow and change into those tiny swimming larvae we talked about earlier.
As the larvae float around, they eat even smaller organisms to get the energy they need to grow.
With all that good food, the larvae slowly develop their arms, which will help them move and eat when they grow up.
After a while, the larvae find a nice spot on the ocean floor they like and settle down. Once settled, they go through a significant change and become adult starfish, ready to explore the ocean bottom.
How Fast Can Starfish Swim?
Starfish, or sea stars, move very slowly across the ocean floor.
It was early evening in Florida. Around 6 p.m., the tides were low. We noticed some sea stars walking around the sand near the water. Some were enjoying the tides, whereas some were strolling on the sand very slowly.
Being a marine life lover, I decided to relocate them back to the ocean water so they could feel comfortable and easy. The other people also became fascinated with them; they followed me in relocating a large number of sea stars to the water.
Some of the sea stars’ movement was even so slow that it was hard to notice they were moving.
Sea stars are one of the slowest-moving animals in the ocean, after garden snails or sloths.
They have hundreds of sensors or feelers under their legs. These sensors also help them sense oceanic waves. Maybe they like it very much; of course, they are inhabitants of oceanic waters.
Fun fact
If a sea star has all its legs cut off(don’t do it), it can regenerate all its legs again if only its central disk remains intact.
Speed and Species
The speed at which a starfish moves depends on its species and the conditions around it. Some starfish can move faster than others.
For example, the leather star (Dermasterias imbricata) can move about 6 inches (15 cm) per minute.
How Can Starfish Swim?
Starfish use a unique system called the water vascular system to move. This system works like a hydraulic pump, which consists of canals that carry water through the sea star body.
When the proper signals are given to their nervous system, the seawater carrying nutrients forcefully enters the tube feet, allowing them to extend and pull back their tube feet.
Arachnids like Spiders, the arthropods, also work in the same kind. Their legs basically work like hydraulic arms controlled by their unique blood pressure. You noticed that when a spider dies, their legs are curled up above their body.
Tube feet help starfish stick to surfaces, crawl, and grab food. You can feel their little legs underwater. But always use clean hands because dirty and bacterial hands can make them unhealthy.
Examples of Movement
1. (Asterias vulgaris ) moves around 30 cm in one minute, which is around 18 meters (59 feet) in an hour.
2. The sunflower star (Pycnopodia helianthoides) moves four times faster than Asterias specie. According to National Oceanic and Atmospheric Administration(NOAA), an adult sunflower (Pycnopoda helianthoides) can travel at around 3 feet per minute using its 15,000 tiny tube feet.
Why Do Starfish Swim?
Sea stars, like some of us, move around to find food. They eat clams, mussels, and oysters. Some even eat dead plants and animals.
Just like us, they need a safe place to stay. Coral reefs are great for that. They have tiny light-sensitive spots on their arms that help them find dark places to hide, like their own little sea star homes.
They also hide in the sand, some in sand rocks, or some attach to rocks with their suction tubes to protect themselves from predators.
Overall, starfish move in search of food.
Also Read:
Decomposers of the Ocean? 06 Important Types Scientifically Explained
Best Beaches for Seashells in Florida (A Local’s Guide with Expert Tips)
FAQs (Frequently Asked Questions)
How Do Sea Stars Move?
Sea stars move using numerous tiny tube feet that extend, contract, and suction to surfaces, allowing them to glide across the ocean floor.
Can Starfish Swim In Salty Waters?
Starfish cannot swim. They live in saltwater but are adapted to crawl on the seafloor using their tube feet, not to swim in open water.
Do Starfish Swim Easily in the Larval Stage?
Yes, starfish larvae swim quickly. They’re free-swimming plankton that use tiny hair-like structures to move through water before settling on the seafloor and transforming into adults.
Does Starfish Swim In Deep Water?
Starfish don’t swim in deep water. They crawl on the ocean floor at different depths, from shallow areas to deep seas, using their tube feet to move around.
5 Characteristics Of Starfish?
1. Radial symmetry (star shape)
2. Tube feet for movement
3. Spiny exoskeleton
4. Regeneration ability
5. Water vascular system
Do starfish have eyes?
Yes, starfish have simple eyes at the ends of their arms. These eyes can see light and movement, help them find their way, but they don’t see clearly like other animals.
Do starfish have brains?
No, starfish do not have brains. They have a simple nervous system made up of nerves that spread out from a ring around their mouth. This helps them sense their surroundings, but it’s much simpler than a brain.
Conclusion
In conclusion, can a starfish swim? No, adult starfish cannot swim. Starfish move using tube feet to crawl on the ocean floor, but their larvae can swim freely. They use a water vascular system for movement, feeding, and respiration. Starfish are found at various depths, moving slowly to find food and shelter. Key features include radial symmetry, regeneration ability, and an exoskeleton.
Resources:
Triterpenoids in Echinoderms: Fundamental Differences in Diversity and Biosynthetic Pathways
