Starfish
Starfish, also called sea stars, are marine invertebrates in the class Asteroidea within the phylum Echinodermata.
Starfish, also called sea stars, are marine invertebrates in the class Asteroidea. They live only in saltwater and are not fish.
What it is
Starfish are echinoderms, closely related to sea urchins, sand dollars, and sea cucumbers. More than 1,600 species exist worldwide, with most having five or more arms arranged in radial symmetry.
Why it matters
They are important predators in marine ecosystems, often feeding on bivalves like clams and mussels, which helps shape ocean-floor communities. Their ability to regenerate lost arms also makes them a model for biological research.
Key details
Starfish use a water vascular system and hundreds of tube feet to move, feed, and sense their surroundings. They inhabit all oceans, from Canadian tide pools to deep-sea floors, and can reproduce both sexually and asexually.
In short
- Starfish are echinoderms, not fish.
- They live only in marine saltwater habitats.
- Many species can regenerate lost arms.
- They play a key ecological role on the ocean floor.
Starfish are found in Canadian marine waters, including the Pacific and Atlantic coasts, and are familiar to Canadian readers through tide pools, rocky shores, and cold-water marine ecosystems.
Quick questions
Are starfish actually fish?
How many arms do starfish have?
Where do starfish live?
Sources
- NOAA Ocean Service — https://oceanservice.noaa.gov/facts/starfish.htmlSupports: Starfish are not fish; they are echinoderms, live only in saltwater, and use a water vascular system.
- Smithsonian Science Education Center — https://ssec.si.edu/stemvisions-blog/all-about-starfishSupports: Classification as Asteroidea within Echinodermata and estimate of more than 1,600 species.
- Encyclopaedia Britannica — https://www.britannica.com/animal/sea-starSupports: Sea stars are marine invertebrates of class Asteroidea and are not fishes.
- Alaska Department of Fish and Game — https://www.adfg.alaska.gov/static/education/wns/starfish.pdfSupports: Habitat, ecological importance, and general biology of starfish.
- National Geographic — https://www.nationalgeographic.com/animals/invertebrates/facts/starfish-1Supports: Common name, diet, habitat range, and species diversity.