Starfish are beautiful marine creatures with a distinct shape that makes them easy to recognize. But did you know they don’t always have a five-pointed figure? They come in all different shapes, sizes, and colors—and their appearance changes widely based on their species. This is just one of many interesting facts about starfishes you might not know.
Starfish are very important members of the marine ecosystem and play a vital role in keeping our oceans regulated. They’re found all over the world, from the tropical waters of the state of Hawaii to the cold polar regions.
If you want to learn more interesting facts about starfishes, like why their skin is so hard, how fast they can move, or the unique way they eat, you’ll enjoy this comprehensive list of information.
43 Interesting Facts About Starfish
A starfish might look like a simple creature, but these underwater animals have many fascinating features. In fact, some of their characteristics might just surprise you.
1. There Are Approximately 2,000 Species of Starfish
There are about 2,000 species of starfish in the world’s oceans today.
2. Starfish Come in a Variety of Colors
Starfish come in all sorts of different colors—like red, blue, purple, green, orange, pink, black, and white. And they’re not limited to a single shade; some species have patterns made up of several colors.
3. Orange is the Most Common Color of a Starfish
Although starfish come in a wide variety of colors, orange and orangish-brown is the most common color of a starfish.
4. Starfish Are Not Fish
Starfish live underwater, but that’s where their similarity to fish ends. They do not have fins, scales, or gills. They are echinoderms, which are a phylum of marine invertebrates.
5. Starfish Are Related to Sand Dollars
Sea stars are related to all the other members of the echinoderms family, which includes sand dollars, sea urchins, brittle stars, crinoids, sea lilies, and sea cucumbers. All members of this group have five-point radial symmetry.
6. These Underwater Creatures Are Referred to by Two Different Names
In most European countries, these underwater creatures are referred to as sea stars. In other parts of the world, they’re usually called starfish.
7. Starfish Don’t Have a Brain
Although starfish don’t have brains, they have complex nervous systems. This allows them to feel pain, and it also coordinates their movement.
8. Starfish Don’t Have Blood in Their Body
Starfish don’t have blood in their body; instead, they have a water vascular system that pumps seawater throughout their tube feet and body.
9. Starfish Can Have Hundreds or Thousands of Feet
Depending on the size of a starfish, they can have hundreds to thousands of little tube feet located on the underside of their arms. To get where they need to go, they fill their feet with seawater, which helps propel movement. Their tube feet also help them hold onto their prey and attach to things in their environment.
10. Starfish Are Slow Movers
Most starfish move relatively slowly; they typically crawl at speeds of about 6 inches per minute. Sunflower sea stars are thought to be the fastest in the species. An adult can move at top speeds of about 3.2 feet per minute.
11. Starfish Have Eyes
Although different from human eyes, starfish can see. Their “eyes” are located on the tip of each of their arms and are usually red or black in color. Although they’re very small, they are visible to the naked eye. Their eyes can’t make out full details, but they can sense the differences between light and dark.
12. Starfish Can Live For Many Years
There are many different species of starfish, and each can live for a different number of years. But starfish can generally live for up to 35 years in the wild.
13. Starfish Don’t Do Very Well in Captivity
Starfish do much better living in the wild; the ocean has everything they need. In captivity, they usually live for 5 to 10 years.
14. The Size of a Starfish Can Determine How Long It Lives
In general, the larger starfish species tend to live longer than the smaller starfish species.
15. Starfish Can Be Heavy
Starfish come in all different sizes, but some of the larger species can weigh up to 11 pounds.
16. Starfish Are Found in Many Marine Environments
Starfish can be found in many different ocean habitats, like rocky shores, kelp beds, seagrass, coral reefs, sand, and tidal pools.
17. Starfish Can’t Live in Fresh Water
The oceans around the world are home to starfish. They need the calcium found in salt water to form their bodies. In fresh water, the levels of this mineral are too low for starfish to survive.
18. Starfish Occupy Different Depths of the Ocean
Starfish live in all depths of the ocean floor, from shallow waters to as deep as 19,500 feet below the surface.
19. Starfish Have a Hard Shell
If you’ve ever stroked the body of a starfish, you’re familiar with the fact that they have an extremely hard body. Their skin consists of a calcium carbonate plate. This is the protective armor that helps shield them from predators.
20. Starfish Are Radially Symmetrical
Starfish are radially symmetrical, which means their arrangement of body parts is centered around a single main axis. If a starfish is cut from one side of its body through the center to the other side, this cut can produce two equal halves.
Other marine animals that are radially symmetrical include jellyfish, sea anemones, and coral.
21. Starfish Are Carnivorous
Starfish are carnivorous; they mostly eat clams, oysters, mussels, scallops, and coral.
22. Starfish Sometimes Eat Other Starfish
Starfish can be cannibalistic; they have been documented eating smaller starfish. Baby starfish will cannibalize their own, smaller siblings too.
23. Starfish Have Several Predators
The main predators of starfish include sharks, manta rays, sea turtles, snails, crabs, and otters.
24. Some Cultures Eat Starfish
A handful of Asian countries eat starfish. In Japan and China, they are sold in street food markets. The edible part of a starfish is the meat in its legs; its shell and feet are not edible, and can actually be poisonous.
They’re not very common seafood, and many people that have eaten them describe them as being an acquired taste.
25. The Way a Starfish Eats Is Very Unique
After a starfish has claimed its prey, it’ll extend its stomach outside of its mouth and envelop the edible parts of its prey’s body. When they’ve finished digesting their meal, they’ll draw their stomach back into their body to swallow it.
26. Starfish Aren’t Social
Starfish are not social creatures. They spend most of their life alone but will occasionally congregate in groups to feed during certain times of the year.
27. Starfish Can Reproduce Sexually and Asexually
Starfish can reproduce in two ways. Sexually, fertilization occurs by spawning. This is where males and females release millions of eggs and sperm into the water. When an egg meets with the sperm, fertilization occurs.
Asexual reproduction takes place when fission or autotomy of arms occurs. This is when a central disc or a portion of their arm breaks off and a new piece grows to replace the missing part.
28. Female Starfish Release Millions of Eggs
A female starfish can release up to 2.5 million eggs into the water at one time. The majority of their eggs are eaten by marine creatures, so only a fraction of this number will live to maturity.
29. Starfish Can Change Their Gender
Some species of starfish can switch their gender. The cushion star, for example, only births male babies. Once the males mature, they stop producing sperm and instead start creating eggs.
30. There Are Square Starfish
Not all starfish have five arms. A mutation in the square starfish caused one of its arms to be removed, making it square.
31. There’s a Starfish Species With a Circular Appearance
Culcita novaeguineae, whose common name is the cushion star, is a species of starfish that resembles a pin cushion. Its inflated appearance is due to its having very short arms that make it look circular. They vary in color and mostly inhabit the warm, tropical waters in the Indo-Pacific region.
32. Starfish Don’t Live Long Out of Water
Most starfish species can’t last more than 3 to 5 minutes outside of water. They are unable to breathe and suffocate within a matter of minutes.
33. Starfish Shouldn’t Be Picked Up
Even though starfish can survive for a few minutes outside of the ocean, you should never pick them up from the water if you see one. Other factors, like sunscreen, lotion, perfume, and other chemicals on your skin can harm them.
34. The Sunflower Sea Star Is One of the Largest Starfish Species
Pycnopodia helianthoides, whose common name is the sunflower sea star, is among the largest starfish in the world. It has a maximum arm span of about 3.2 feet. At full maturity, it usually has between 16 and 24 limbs.
Unfortunately, as of 2020, the sunflower sea star is listed as critically endangered on the International Union for Conservation of Nature (IUCN) red list of threatened species.
35. The Pink Starfish Is Another One of the Largest Starfish Species
The pink starfish is another one of the largest starfish species in the world. They typically have a diameter of 13 inches; however, they’ve been recorded measuring up to 35 inches.
36. The Smallest Known Starfish Species Can Fit on Your Fingernail
Parvulastra parvivipara is the smallest known species of starfish. They typically grow to be about 0.4 inches in diameter. They are an orange-yellow color and live in South Australia
Another interesting fact about this small starfish species is that they give birth to live young.
37. The Bat Starfish Has Webbed Arms
The bat starfish’s name comes from its appearance. They have webbing in between their arms, similar to a bat. Although their scientific name is Patiria miniata, their common name is the bat starfish, sea bat, or webbed star.
In terms of the other parts of their appearance, they can have from five up to nine arms and their color varies from orange to green to purple.
38. The Royal Starfish Is One of the Most Interestingly Colored Starfish
The royal starfish is one of the most beautifully hued starfish species. The outline of their body is a gold or orange color and the inside is usually bold purple. This species is mostly found along the east coast of North America.
39. There’s a Species of Starfish Named After Jewelry
Fromia monilis, whose common name is necklace starfish, is another striking species of starfish. They have a red or orange body dotted with little white spots that resemble pearls. They are mostly found in the Indian Ocean and Western Pacific.
40. There’s a Species of Starfish Named After a Sweet
Protoreaster nodosus is commonly called the chocolate chip sea star. Its body has small black dots with little spikes coming from them, which makes it look like it’s topped with chocolate chips. They’re found in the warm, shallow waters of the Indo-Pacific region.
41. One Species of Starfish Has Spikes on Its Body
Acanthaster planci, known commonly as the crown-of-thorns starfish, has long spikes that cover the outer surface of its upper body. The spikes are venomous to both marine creatures and humans.
42. The Crown-Of-Thorns Starfish Are Threatening Coral Reefs
The crown-of-thorns starfish inhabits the coral reefs in the Indo-Pacific region, including the Great Barrier Reef. They can eat their way through about 107 square feet of coral in one year. In regular numbers, they have a positive impact on the ecosystem, but recently, their budding population has resulted in a major coral loss.
43. Starfish Are a Keystone Species
Starfish are a keystone species and are very important for the marine ecosystem. They prey on animals that don’t have other natural predators. If there were no starfish, their prey would overgraze on kelp, which would create a shortage of food and habitat for the marine life that relies on it for survival.