Joanne Froggatt
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Learn about starfish, also known as sea stars or asteroids, which are marine invertebrates with a central disc and usually five arms. Discover their anatomy, life cycle, ecology, fossil record and cultural significance.
- Sea Stars Are Not Fish
- Sea Stars Are Echinoderms
- There Are Thousands of Sea Star Species
- Not All Sea Stars Have Five Arms
- Sea Stars Can Regenerate Arms
- Sea Stars Are Protected by Armor
- Sea Stars Do Not Have Blood
- Sea Stars Move Using Their Tube Feet
- Sea Stars Eat with Their Stomachs Inside-Out
- Sea Stars Have Eyes
- GeneratedCaptionsTabForHeroSec
Although sea stars live underwater and are commonly called "starfish," they are not true fish. They do not have gills, scales, or fins like fish do. Sea stars also move quite differently from fish. While fish propel themselves with their tails, sea stars have tiny tube feet to help them move along. Because they are not classified as fish, scientist...
Sea stars belong to the phylum Echinodermata. That means they are related to sand dollars, sea urchins, sea cucumbers, and sea lilies. Overall, this phylum contains approximately 7,000 species. Many echinoderms exhibit radial symmetry, meaning their body parts are arranged around a central axis. Many sea stars have five-point radial symmetry beca...
There are about 2,000 species of sea stars. Some live in the intertidal zone, while others live in the deep water of the ocean. While many species live in tropical areas, sea stars can also be found in cold areas—even the polar regions.
While many people are most familiar with the five-armed species of sea stars, not all sea stars have just five arms. Some species have many more, such as the sun star, which can have up to 40 arms.
Amazingly, sea stars can regenerate lost arms, which is useful if a sea star is injured by a predator. It can lose an arm, escape, and grow a new arm later. Sea stars house most of their vital organs in their arms. This means that some species can even regenerate an entirely new sea star from just one arm and a portion of the star's central disc. T...
Depending on the species, a sea star's skin may feel leathery or slightly prickly. Sea stars have a tough covering on their upper side, which is made up of plates of calcium carbonate with tiny spines on their surface. A sea star's spines are used for protection from predators, which include birds, fish, and sea otters. One very spiny sea star is t...
Instead of blood, sea stars have a circulatory system made up primarily of seawater. Seawater is pumped into the animal's water vascular system through its sieve plate. This is a sort of trap door called a madreporite, often visible as a light-colored spot on the top of the starfish. From the madreporite, seawater moves into the sea star's tube fee...
Sea stars move using hundreds of tube feet located on their underside. The tube feet are filled with seawater, which the sea star brings in through the madreporite on its top side. Sea stars can move quicker than you might expect. If you get a chance, visit a tide poolor aquarium and take a moment to watch a sea star moving around. It is one of the...
Sea stars prey on bivalveslike mussels and clams as well as small fish, snails, and barnacles. If you've ever tried to pry the shell of a clam or mussel open, you know how difficult it is. However, sea stars have a unique way of eating these creatures. A sea star's mouth is on its underside. When it catches its food, the sea star will wrap its arms...
Many people are surprised to learn that starfish have eyes. It's true. The eyes are there—just not in the place you would expect. Sea stars have an eye spot at the end of each arm. This means that a five-armed sea star has five eyes, while the 40-armed sun star has 40 eyes. Each sea star eye is very simple and looks like a red spot. It doesn't see ...
Learn about starfish, also known as sea stars, which are not fish but echinoderms related to sea urchins and sand dollars. Discover their amazing features, such as regeneration, tube feet, eyes, and stomachs inside-out.
Starfish provides calendar management, appointment scheduling, and documentation of appointment outcomes for college employees and student services. Students can arrange scheduled appointments with their instructors, advisors, and other support services.
Learn about the starfish, also known as sea star, an echinoderm with no brain but amazing abilities to regenerate and feed. See stunning images of different species and habitats of these marine animals.
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Aug 22, 2024 · examine a variety of echinoderm species such as starfish, basket star, sand dollar, and sea cucumber Echinoderms exhibit a variety of body plans. The starfishes are also called sea stars. Although they commonly have five arms, some can have many more. Basket stars have branched and coiling arms.
- The Editors of Encyclopaedia Britannica
There are around 1,600 different species of starfish living in the world’s oceans, where they occupy every type of habitat including tidal pools, rocky shores, sea grass, kelp beds and coral reefs. Some kinds of starfish are even found on sandy seabeds 9,000 metres deep!
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Learn about starfish, also known as sea stars, their appearance, behavior, diet, habitat, reproduction, and threats. Find out how starfish are related to other echinoderms, how they can grow back limbs, and why some are keystone species.
