Starfish - Facts for Kids

Basic Information

Starfish belong to the scientific class Asteroidea, which comes from the Greek words “aster” (star) and “eidos” (form or shape)!

A group of starfish is commonly a “galaxy” — just like the stars in space!

There are over 2,000 species of starfish divided into seven different orders based on their body structure!

Baby starfish are called “larvae” when they’re floating and “juveniles” once they settle on the ocean floor!

Male and female starfish look exactly the same from the outside — even scientists need special tests to tell them apart!

The smallest known adult starfish species is Parvulastra parvivipara, only about as wide as your fingernail — measuring just 0.4 inches (1 cm) across!

Most adult starfish weigh about 3 to 7 pounds (that’s 1.5 to 3 kilograms), but some giants can grow as heavy as 11 pounds (5 kilograms)!

Starfish can be found from the tropical waters of the equator to the freezing polar regions — that’s every ocean on Earth!

Most starfish live about 5 to 35 years in the wild. In tanks, they usually survive only a few years — because it’s tricky to copy their ocean home!

Starfish are mainly carnivores (meat-eaters), but some species are omnivores that also eat algae and plant material!

Some starfish species live in the intertidal zone where they’re exposed to air twice daily, while others live in the deep ocean at depths of over 20,000 feet (6 km)!

The family Asteriidae includes some of the most common starfish species, like the North Pacific Sea Star!

Starfish belong to the phylum Echinodermata, which means “spiny-skinned” in Greek — a perfect description of their texture!

If a starfish loses an arm, it can grow a new one! For most species, this takes about 6 to 12 months, though some tropical starfish can regrow arms even faster.

Physical Characteristics

A starfish isn’t actually a fish at all — scientists call them “sea stars” because they’re really part of the echinoderm family, just like sea urchins and sand dollars!

Most starfish have five arms, but some species can have up to 50 arms — that’s like having enough arms to hug eight friends at once!

The largest starfish in the world is the sunflower sea star, which can grow as wide as a kitchen table — up to 3.3 feet (1 meter) across!

Starfish don’t have blood like we do — instead, they use seawater to move nutrients through their bodies in a special system called a water vascular system!

A starfish’s body is covered in tiny pincer-like structures called pedicellariae that help keep their skin clean from parasites and debris — like having thousands of tiny automatic cleaners!

Starfish have tiny eyes at the tip of each arm that can detect light and dark, helping them navigate the ocean floor!

The skin of a starfish feels rough because it’s covered in calcium carbonate plates and spines — like wearing a suit of underwater armor!

A starfish’s mouth is located on its underside, right in the center of its body — imagine having to eat your dinner from your belly button!

Starfish have thousands of tiny tube feet under each arm that work like suction cups, allowing them to grip rocks and move around!

Behavior & Intelligence

When a starfish finds food, it can push its stomach out through its mouth to digest food outside its body — like having a portable kitchen!

Starfish can detect food using chemical sensors on their tube feet, helping them find meals even in complete darkness!

Some starfish can move really fast—sunflower sea stars crawl about 3 feet (1 meter) per minute, and sand stars can zoom over 9 feet (3 meters) per minute!

Starfish don’t have a brain, but they have a complex nervous system that forms a network throughout their bodies!

Some starfish species can hibernate during times when food is scarce, slowing down their metabolism to survive!

Starfish use hundreds of tiny tube feet with suction cups to crawl slowly over rocks, making them steady climbers in the ocean!

Habitat & Survival

Starfish can be found in every ocean on Earth, from tropical coral reefs to the freezing waters of the Arctic!

Some starfish live in tide pools where the temperature swings wildly between high and low tide — and they’ve got clever ways to cope!

The deepest living starfish have been found at depths of 20,000 feet (6,000 meters) — that’s deeper than 65 football fields stacked on top of each other!

Some starfish can create special slime trails that help them glide more easily across rocky surfaces!

Starfish can regenerate their arms if they lose them to predators — it takes about 6–12 months for a new arm to grow back completely!

Life Cycle

Baby starfish start life as tiny larvae floating in the ocean, smaller than a grain of sand!

A single female starfish can release up to 2.5 million eggs at once during breeding season!

Starfish larvae spend about two months swimming in the ocean before settling down and transforming into their star shape!

Unlike crabs that shed their shells, starfish don’t molt. They carry a tough, comfy skeleton under their skin that just gets bigger as they grow — bit by bit — like a hidden building that grows with them!

Some species of starfish can reproduce without a mate through a process called fission, where they split their body in half and each half grows into a complete starfish!

Starfish eggs are super tiny — about 0.16 mm wide, which is still thinner than some human hairs! Even though you can’t see them without a microscope, each one can grow into a whole new starfish.

Baby starfish are excellent swimmers, using tiny hairs called cilia to move through the water until they’re ready to settle on the ocean floor!

Diet & Feeding

Starfish are opportunistic feeders, meaning they’ll eat almost anything they can find — from tiny plankton to large mollusks!

When eating clams or oysters, a starfish can apply pressure with its arms for hours until the shell opens — even just a fraction of an inch is enough!