When we hear names like starfish and jellyfish, it’s easy to think that both are fish because of the word fish in their names. However, the truth is quite surprising. Which OF These IS A Fish: Starfish OR Jellyfish? Despite their names, neither a starfish nor a jellyfish is a true fish. In this article, we’ll explore what makes them different, how they live, and why their names can be confusing.
🐠 Understanding What a True Fish Is
Before we decide whether a starfish or jellyfish is a real fish, we must first understand what a fish actually is.
✅ Features of True Fish
True fish belong to a group called vertebrates, which means they have a backbone. Other features include:
- They live in water.
- They breathe through gills.
- They have fins to swim.
- Their bodies are usually covered with scales.
- Most lay eggs to reproduce.
Examples of true fish are goldfish, tuna, sharks, and salmon. Now that we know what a real fish is, let’s look at starfish and jellyfish.
⭐ What Is a Starfish?
A starfish, also known as a sea star, is a sea animal that lives at the bottom of oceans.
🧬 Scientific Facts About Starfish
- Type: Echinoderm (same family as sea urchins)
- Body: Radial symmetry, usually has five arms
- Skeleton: No bones, but a tough outer skin
- Breathing: Uses small tubes to absorb oxygen
- Movement: Moves slowly using tiny tube feet
🪸 Why Starfish Is Not a Fish
A starfish does not have a backbone, gills, or fins. It also cannot swim like fish do. Instead, it crawls along the ocean floor using hundreds of small tube feet.
Because of these reasons, scientists no longer use the word “fish” for them — the correct name is sea star.
🪼 What Is a Jellyfish?
A jellyfish is another ocean animal that looks soft and wobbly, often transparent. They float freely in the sea and are known for their tentacles that can sting.
🌊 Scientific Facts About Jellyfish
- Type: Invertebrate (no bones or backbone)
- Body: Gel-like structure made of 95% water
- Movement: Moves by pulsing its bell-shaped body
- Breathing: Absorbs oxygen directly through its skin
- Diet: Eats small fish, plankton, and shrimp
⚠️ Why Jellyfish Is Not a Fish
Even though it swims in water, a jellyfish:
- Has no bones or backbone
- Has no gills or fins
- Does not have a brain or heart
So, scientifically, a jellyfish is not a fish either. It belongs to a group called Cnidarians, which also includes corals and sea anemones.
🧠 Why Are They Called “Fish” Then?
The names “starfish” and “jellyfish” were given long ago, before scientists understood these creatures well. People used the word “fish” for almost any creature that lived in water.
- The starfish got its name because of its star-like shape.
- The jellyfish got its name because of its jelly-like body.
Today, scientists try to use more accurate names:
- Starfish → Sea Star
- Jellyfish → Jellies or Sea Jellies
🌍 Differences Between Starfish and Jellyfish
FeatureStarfish (Sea Star)JellyfishTypeEchinodermCnidarianBodyHard, with armsSoft, jelly-likeMovementCrawls on the sea floorFloats or drifts in waterBackboneNoNoFins/GillsNoNoHabitatBottom of the oceanOpen waterDanger to HumansHarmlessSome can sting painfully
As you can see, both creatures are very different from real fish and from each other.
🧩 Interesting Facts About Starfish and Jellyfish
⭐ Starfish Fun Facts
- They can regrow lost arms — sometimes even an entire new body.
- There are over 2,000 species of sea stars.
- They eat by pushing their stomach out to digest food outside their body.
🪼 Jellyfish Fun Facts
- Jellyfish have existed for over 500 million years — older than dinosaurs.
- Some jellyfish can glow in the dark.
- The box jellyfish is one of the most dangerous sea creatures on Earth.
🧬 What Scientists Say
Modern marine biologists classify:
- Starfish as Echinoderms.
- Jellyfish as Cnidarians.
Both are invertebrates, meaning they do not have a backbone. Real fish, on the other hand, are vertebrates.
So, while both live in the ocean and have “fish” in their names, neither is truly a fish.
Final Answer
So, which of these is a fish: starfish or jellyfish?
👉 Neither!
Both are amazing sea animals but belong to very different families from true fish. The “fish” in their names is just a leftover from old times when people didn’t know much about sea life.
Today, scientists prefer calling them sea stars and sea jellies to avoid confusion.
FAQs
1. Is a starfish a fish?
No, a starfish (sea star) is not a fish. It’s an echinoderm and does not have gills, fins, or a backbone.
2. Is a jellyfish a fish?
No, a jellyfish is not a fish. It’s an invertebrate and belongs to the cnidarian family.
3. Why do starfish and jellyfish have “fish” in their names?
They were named before scientists understood their biology. The term “fish” was used for any water-dwelling animal.
4. Do starfish have hearts or brains?
No, starfish don’t have a heart or brain. They use water pressure to move and react to their surroundings.
5. Are jellyfish dangerous to humans?
Some jellyfish stings can be painful or dangerous, but most species are harmless.
6. What should we really call them?
We should say sea stars for starfish and sea jellies for jellyfish — these names are more correct scientifically.
