Lyla Lindsey
Sea stars, commonly known as starfish, are echinoderms, which means spiny skin. They are not fish and do not have backbones, making them invertebrates. Sea stars are found in all the world's oceans, including in the waters of Australia, where they are very common and quick to breed. Sea stars have a unique feeding mechanism, ejecting their stomachs from their bodies to cover and partially digest prey before pulling it back into their mouths. They are predators with a varied diet, including molluscs, microalgae, sponges, bivalves, snails, crustaceans, worms, sea urchins, fish, and even other sea stars.
| Characteristics | Values |
|---|---|
| Common name | Starfish |
| Scientific name | Various, including: Pseudoreaster obtusangulus, Echinaster luzonicus, Mithrodia clavigera, Tosia australis, Petricia vernicina, Coscinasterias muricata, Uniophora granifera |
| Description | Spiny skin and five arms, though some species can have up to 50 arms |
| Habitat | All of the world's temperate and tropical seas, including tropical coral reefs, rocky shores, tidal pools, mud, sand, kelp forests, seagrass meadows, and the deep-sea floor |
| Diet | Most sea stars are scavengers or carnivores, preying on sponges, sea anemones, corals, snails, crustaceans, worms, sea urchins, bivalves (oysters, mussels, clams), fish, and even other sea stars. Some species are detritivores, eating decomposing organic matter and faecal matter. |
| Feeding mechanism | Sea stars use tiny tube feet with suckers on their underside to capture prey. They eject their stomach from their body and cover their prey to partially digest it before pulling it back into their body to complete digestion. |
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What You'll Learn
Sea stars are scavengers, carnivores, or detritivores
Sea stars, commonly known as starfish, are not actually fish. They are echinoderms, which means "spiny skin" in Greek. Echinoderms include animals such as sea urchins, sand dollars, and sea cucumbers. Sea stars are found in all the world's oceans, from tropical coral reefs to the deep sea floor, but they cannot live in freshwater habitats. They are capable of breeding very quickly if conditions are suitable.
Detritivorous sea stars, on the other hand, eat decomposing organic matter in suspension or deposited on the seabed. They consume tiny particles with their mouths and digest them in their stomachs. Some starfish species are suspension feeders, gathering phytoplankton, and are often found in association with sponges, benefiting from the water currents they produce.
In South Australia, the biscuit star (Tosia australis) is one of the most common sea stars. It is known for its variety of colours and patterns and is typically found on reefs and other hard surfaces, from the intertidal zone down to about 40 meters deep. Another species found in southern and southeastern Australia is the velvet sea star, which is also known as 'Patrick' from SpongeBob SquarePants.
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They prey on oysters, clams, and mussels
Sea stars, commonly known as starfish, are echinoderms, which means "spiny skin" in Greek. They are not fish and do not have backbones, making them invertebrates. They are found in all of the world's temperate and tropical seas, including the waters of Australia.
Sea stars prey on oysters, clams, and mussels, which are all types of bivalves or molluscs. Bivalves are marine animals with a shell made of two parts, and they can be challenging to open. Sea stars have developed an efficient technique to do this. They wrap their arms around the shell and use their suckers to pull the two parts of the shell apart, applying pressure. This forces the bivalve to open slightly to get oxygen, and when it does, the sea star inserts its stomach into the crack to start digestion. This unique feeding mechanism allows sea stars to feed on prey larger than their mouths can accommodate.
Sea stars use their tiny tube feet, located on their underside, to capture their prey. These tube feet have suckers that aid in movement and securing the sea star to rocks or other surfaces. Once they seize their prey with these suckers, they eject their stomach from their body, turning it inside out to cover and partially digest the food. This external digestion can take up to ten hours. After this, the partially digested food is pulled back into the sea star's body for final digestion.
In addition to oysters, clams, and mussels, sea stars also prey on other invertebrates and small animals. They are known to feed on snails, sponges, sea anemones, corals, crustaceans, worms, sea urchins, fish, and even other sea stars. Sea stars are generalist predators, and their diet can vary depending on the species and the availability of food in their habitat.
In Australia, sea stars can be found in various marine parks, such as the Montebello Islands Marine Park, which is home to 170 species of sea stars and other echinoderms. They are also commonly found in the waters of South Australia, with popular species including the biscuit star, the eleven-arm sea star, and the velvet sea star.
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They can also eat prey larger than their mouths
Sea stars, commonly known as starfish, are not fish but echinoderms, which means "spiny skin". They are invertebrates, meaning they do not have backbones. Sea stars have a wide distribution throughout all of the world's temperate and tropical seas, and numerous species are found in each of Western Australia's marine parks.
Sea stars are generalist predators, and their diet includes microalgae, sponges, bivalves, snails, and other small animals. They have tube feet with suckers on their underside, which they use to capture their prey. Once they seize their prey, they eject their stomach from their body and turn it inside out to cover and partially digest the food. This external digestion may take up to ten hours. This unique feeding mechanism enables sea stars to feed on prey larger than their mouths can eat.
For example, sea stars can pry open bivalves such as oysters, mussels, and clams. They wrap their arms around the shell and use their suckers to pull the two parts of the shell apart, forcing the mollusc to open its valves slightly to get oxygen. When the bivalve opens, even by a fraction of a millimetre, the sea star inserts its stomach into the crack to begin digestion.
Sea stars are also known to prey on other invertebrates, such as crustaceans and worms, as well as sea urchins, fish, and even other sea stars. They can be quite adaptable in their feeding habits, making them formidable predators in their marine environments.
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They are common in Western Australia's marine parks
Sea stars, formerly known as starfish, are echinoderms, which means "spiny skin" in Greek. They are closely related to sea urchins, and both are found in Western Australia's marine parks. Sea stars are common in these parks, with numerous species present. For example, the Montebello Islands Marine Park is home to 170 species of sea stars, sand dollars, heart urchins, and sea cucumbers. They are also found in other marine parks in Western Australia, such as the Dampier Archipelago Marine Park and the Jurien Bay Marine Park.
Sea stars are native to Western Australia and have a wide range of habitats, from tropical coral reefs to rocky shores, tidal pools, and even the deep-sea floor. They can survive in a variety of depths, from the intertidal zone down to 6,000 meters under the sea. This adaptability contributes to their common presence in Western Australia's marine parks.
Sea stars are carnivores, scavengers, or detritivores, and their diet includes a variety of prey. They are known for their unique feeding mechanism, where they capture prey with tube feet and then eject their stomach to cover and partially digest the food before ingesting it. This allows them to feed on prey larger than their mouths. Sea stars prey on bivalves such as oysters, mussels, and clams, as well as sponges, sea anemones, corals, snails, crustaceans, worms, sea urchins, fish, and even other sea stars.
While sea stars are common in Western Australia's marine parks, they have not been extensively surveyed. Many of the species found in these parks are yet to be described and studied by scientists. This highlights the need for further research and conservation efforts to protect these fascinating creatures and their ecosystems.
In summary, sea stars are common in Western Australia's marine parks due to their adaptability to a range of habitats and their ability to quickly breed in suitable conditions. They play an important role in the ecosystem, and their presence contributes to the diverse marine life found in Western Australia.
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They are also known as starfish
Sea stars, also known as starfish, are echinoderms, which means "spiny skin" in Greek. They are invertebrates, meaning they do not have backbones. Starfish are found in all the world's oceans, including in Western Australia's marine parks, and inhabit a range of habitats from tropical coral reefs to the deep-sea floor. They can be found in both temperate and tropical waters, and some species even live in frigid polar waters under ice floes.
Starfish have a unique feeding mechanism. They use tiny tube feet with suckers on their underside to capture prey and secure themselves to rocks. Once they seize their prey, they eject their stomachs from their bodies, turning them inside out to cover and partially digest the food before pulling it back into their body to complete digestion. This allows them to feed on prey larger than their mouths. Starfish are generalist predators, and their diet includes molluscs like clams, oysters, and snails, as well as microalgae, sponges, bivalves, and other small animals. Some species are detritivores, feeding on decomposing organic matter, while a few are suspension feeders, gathering phytoplankton.
The ochre sea star (Pisaster ochraceus) and the reef sea star (Stichaster australis) are examples of keystone species in ecology. The crown-of-thorns starfish (Acanthaster planci) is a voracious predator of coral in the Indo-Pacific region. Starfish have an ancient fossil record dating back 450 million years, but their remains are hard to locate as they tend to disintegrate after death.
In South Australia, you can find the biscuit star (Tosia australis), a pretty, five-pointed star with colourful patterns, often found near sponges and sea squirts, which are their preferred food. The eleven-arm sea star (Coscinasterias muricata) is another species found in southern Australia, and it can drop and regrow arms when stressed. The velvet sea star (Petricia vernicina) is found across southern and southeastern Australia, and the granular sea star (Uniophora granifera) can also be spotted in South Australia.
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Frequently asked questions
Sea stars, commonly known as starfish, are echinoderms, which means 'spiny skin'. They are not fish and do not have backbones, making them invertebrates. They have a wide distribution throughout all of the world's temperate and tropical seas.
Sea stars are scavengers or carnivores, preying on sponges, sea anemones, corals, snails, crustaceans, worms, sea urchins, bivalves, fish, or even other sea stars. They use tiny tube feet with suckers on their underside to capture their prey. Once they seize their prey, they eject their stomachs from their bodies to cover and partially digest the food before pulling it back into their body to complete digestion.
There are numerous species of sea stars found in Australia, including the biscuit star, velvet sea star, and eleven-arm sea star. Western Australia's Montebello Islands Marine Park is home to 170 species of sea stars.
