A starfish, also called a sea star, is a star-shaped echinoderm that lives in ocean environments. It has five arms radiating out from a central core; each arm has a number of tiny suction cups that it uses to move around and to get food. Starfish eat by sucking their prey into their mouth and then digesting it with the help of their stomach acids.
The starfish is a very hardy animal, they can live for many years without being affected by pollution or other environmental hazards. They are also able to regenerate lost limbs, which makes them a perfect example of how plasticity helps animals survive in harsh conditions.
The Diversity Of Starfish Species
Starfish are a diverse group of sea creatures that belong to the echinoderm phylum. These animals live in both shallow and deep seas, but they can be found on every continent except Antarctica.
There are many types of starfish. Some have more than five arms – the Brisingida family can have up to 16 arms. Technically, brittle stars and basket stars belong to the class Ophiuroidea, which is closely related to starfish’s class (Asteroidea).
Starfish are divided into 7 major groups, or orders, comprising around 1,900 individual identified species.
Oreasteridae Order Types of Starfish
1. Red Cushion Sea Star
All cushion sea stars are born male, and only when they grow to be a certain size do some of them develop into females. They are what zoologists call protandrous hermaphrodites,
The red cushion sea star (scientific name Oreaster reticulatus), also known as the West Indian sea star, is found in shallow waters of the western Atlantic Ocean and the Caribbean Sea. The red cushion star is an omnivore, and likes to eat algae, sponges, and small invertebrates that it comes across on the sea floor.
Size: up to about 50 centimeters (20 in) in diameter
Arms: 5
Habitat: sandy sea bottoms and coral rubble (adults), seagrass meadows (juveniles)
2. Granulated Sea Star
The granulated sea star (scientific name Choriaster granulatus), also called Cushion Sea Star, and the Doughboy star is a chubby (thus the name Doughboy) Oreasteridae that is found in the waters of the Pacific Ocean. It has also been seen in parts of the Indian Ocean, Red Sea, and around the Great Barrier Reef.
It is a carnivore, feeding on small crustaceans and other invertebrates. It does not have any natural predators and it has been seen to be able to regenerate lost limbs.
Size: up to about 27 centimeters (10 in) in diameter
Arms: 5
Habitat: shallow waters, sandy sea floor
3. Arabian Cushion Star
The Arabian cushion starfish is another pin cushion type of starfish. Its scientific name is Culcita coriacea.
It lives in the Arabian region, particularly the Red Sea and around Oman. It has a leathery surface and looks puffy as if someone inflated it with a bicycle pump. Culcita coriacea varies in color, often having a darker background with small colored patches.
It prefers to eat organic detritus and micro-organisms growing on algae and sea grasses.
Size: up to about 25 centimeters (9 1/2 in) in diameter
Arms: 5
Habitat: coral and reef plateaus, sand, rubble, lagoons, and slopes
Brisingida Order
All Brisingids are deep-sea dwellers. They feature between 6 to 18 long, attenuated arms which they use for suspension feeding.
4. Astrolirus patricki
Astrolirus patricki is a recently discovered species of the family Brisingidae. The name references Patrick Star, the cartoon starfish from SpongeBob SquarePants.
Why Patrick Star? In the animated series, he is best friends with the title character, a talking underwater sponge. All known specimens of the species were seen to be attached to hexactinellid sponges, suggesting a close, possibly symbiotic, relationship between the two.
This deep-sea species was first discovered in 2013 and described in 2020, so information about it is still scarce.
Size: up to about 25 centimeters (9 1/2 in) in diameter
Arms: 7
Habitat: deep-sea seamounts (1,458–2,125 m depth)
5. Velcro Sea Star
The Velcro Sea Star (Novodinia antillensis) inhabits the deep sea in the tropical and subtropical western Atlantic. It has peculiar large eyespots on the tips of its long tapering arms.
Brisingids use their clawed spines to act like velcro to capture their miniature prey – miniature crustaceans that happen to be drifting by.
Spines cover both the disc and arms of Novodinia antillensis, and each spine is armed with tiny claw-shaped organs called pedicellariae.
Arms: 10-14
Habitat: deep-sea coral mounds
Forcipulatida Order
Includes 49 types of starfish, among them some well-known species, such as the common starfish, Asterias rubens.
6. Common Starfish
In the northeast Atlantic ocean, there is no starfish more frequent than the sugar starfish (Asterias rubens) also known as the common sea star or common starfish. They are typically the familiar orange, brick red, or brown colour, sometimes purple. Those found in deeper waters are paler.
There are rows of small tube feet on the undersides of the arms, which they use to crawl around with and in eating. Common starfish feed on bivalve molluscs, polychaete worms, barnacles, gastropod molluscs, other echinoderms and even the decaying flesh of mammals or fish.
The common starfish can make a bitter organic chemical for repelling predators, which causes a reaction in whelks (Buccinum undatum), a common prey species.
Size: 10–30 cm (4-12 in) across
Arms: 5
Habitat: rocky and gravelly substrates
7. Sun Star
The sun star (Heliaster helianthus), as you might expect, looks like a drawing of the sun, with multiple arms radiating out from a large central disc. It is found living in the waters off South American tropical, subtropical and temperate west coast regions.
Unusual in this kind of starfish, they are able to continue foraging for food when out of the water at low tides. The inner parts of their arms are connected to adjacent arms by weblike tissue, so the range of motion of the arms is somewhat limited.
The upper surfaces of the sun star are brown with reddish tubercles and the lower side is coloured white or yellowish-white.
Size: 6-8 inches in diameter
Arms: 28 to 39
Habitat: shallow water with a rocky bottom, kelp forests
8. Sunflower Sea Star
Sunflower sea stars, scientific name Pycnopodia helianthoides, are one of the world’s largest starfish. They can grow up to 1 meter from arm tip to arm tip, or 3.3 feet, and weigh up to 10 pounds. In case you were wondering, the only starfish larger than the sunflower is the little-known Midgardia xandaros, a deep water sea star that can measure 53 inches across (but it doesn‘t weigh as much as the sunflower does).
Colours can vary, with some being reddish-orange, some yellow, violet brown, or purplish. The suctions cups on their underside are so strong that if you try to pull a sunflower sea star off of a rock, the suction cups can break loose from the sea star and stay stuck on the rock.
Sunflower sea stars at one time not too long ago were common throughout waters of the pacific northwest coastline from Alaska to southern California. Unfortunately, they have joined the ranks of critically endangered species, due to sea star wasting disease, and abnormally high water temperatures probably caused by global climate change.
Size: up to 40 in. diameter
Arms: 28 to 39
Habitat: shallow water with a rocky bottom, kelp forests
Paxillosida Order
Paxillosida are one of the largest orders, having 372 different kinds of starfish.
9. The Magnificent Star
The magnificent star (Luidia magnifica), is found in the Pacific Ocean around Hawaii and the Philippines. Despite its large size, the magnificent can move quickly, gliding around the ocean floor.
Small umbrella-like spine structures called paxillae protect the upper surface as well as parts of the underside, giving them a grainy texture. Arms can regenerate if they are damaged or detached by a predator.
The magnificent starfish are known as voracious predators. Unlike other types of sea stars, which extend their stomach to feed externally, those in the order Paxillosida swallow food whole. Magnificent‘s fare includes bivalve molluscs and other echinoids, digested in their two stomachs.
Size: up to 33 in. diameter
Arms: 10
Habitat: sandy seabeds
10. Nine-armed Sea Star
A tropical starfish found in the Atlantic Ocean, the nine-armed sea star (Luidia senegalensis) might not be the only sea star with nine arms, nevertheless, it is commonly called that, and the name has stuck.
You can see this sea star around the coasts of the Gulf of Mexico, Florida, the Caribbean, and along the eastern coast of South America as far south as southern Brazil. It is both a predator and a scavenger, with a diet consisting of mollusks, small crustaceans and polychaete worms (small, bristly segmented worms that crawl along and burrow in the sea floor).
In waters that are polluted, the nine-armed sea star has been found with concentrated heavy metals in its tissues, so they would not be something you would want to eat. Zinc, and to a lesser extent nickel, lead, cadmium and silver accumulate in their body and arms.
Size: 12-16 in. diameter
Arms: 4 (just kidding- 9 of course)
Habitat: sandy, muddy or shelly seabeds
11. Royal Starfish
The Royal Starfish (Astropacten Articulatus) is a bold-coloured sea star found in the west of the Atlantic Ocean, especially in the Caribbean. It has a royal purple disc and arms. They are arms fringed in orange with white spines.
They are carnivores, feeding on mollusks and oysters, but consuming more organisms than a typical starfish species. In a study investigating the stomach contents of 124 Royal Starfishes, scientists found that on average, each sea star has 12 organisms in its stomach, with the highest number of organisms recorded being 54.
Predators that like to eat royal starfish include the Monkfish and the Cancer Pagurus crab. If a seagull finds one washed up on the beach it will make a meal out of it. If you find one washed up on the beach though, please help it back into the water. Starfish aren’t actually fish but they do have to breathe to live, just as we do. They can only do it underwater. Please be careful moving them back into the water- starfish are delicate and can easily be damaged by human touch.
Size: 8 in. diameter
Arms: 5
Habitat: sandy, muddy or shelly seabeds
12. Crown Of Thorns Sea Star
The Crown of Thorns sea star (Acanthaster planci) can be found in many colours, with an average size of 4 inches. They feed on coral and other invertebrates and have been known to cause significant damage to reefs. One individual sea star can eat as much as 65 sq ft of living coral reef per year.
They live most commonly around Australia but can be seen in tropical and subtropical latitudes from the Red Sea and the East African coast across the Indian Ocean, and across the Pacific Ocean to the west coast of Central America. Basically, anywhere coral reefs are.
Crown of Thorns has noxious substances known as asterosaponins in their tissues. Touching their body or their long spines that resemble thorns can result in severe stinging pain and nausea plus swelling that lasts for hours or days.
Size: 10 to 14 in
Arms: up to 21
Habitat: coral reefs
Valvatida Order
This order contains 695 species, divided into 17 different families.
13. Cushion Starfish
The cushion sea star (Culcita novaeguineae) is an inflated-looking underwater creature that resembles a five-sided pincushion. The babies of this species look nothing like a pincushion, resembling a flat uncooked cookie shaped like a star.
In fact, this juvenile form has been mistaken by many hobbyists for a separate type of starfish and even marine biologists called it by a different name like Goniodiscus sebae or Randasia granulata until they were identified as simply different developmental stages of the same sea star.
The cushion star is variable in colour, ranging between darker and lighter shades of fawn, brown, orange, yellow and green. It lives in tropical waters in the Indo-Pacific Ocean. Its name novaeguineae means New Guinea, where it is commonly found.
Size: 7 -10 in diameter
Arms: 5
Habitat: sandy seabeds, coral reefs
14. Aquilonastra conandae
This species of starfish lives in the Indian Ocean off Réunion Island and elsewhere in the Mascarene Islands. It is named after the French marine biologist Chantal Conand, who first collected it.
Aquilonastra conandae is small, less than 2 cm, and being well camouflaged, is difficult to see. It is not surprising that it was only identified in 2006. Some specimens are hermaphrodites, and it reproduces both asexually, by separation of the body into two new bodies, and by sexual reproduction.
Each of its eight arms measures 5 mm (0.20 in) in length, and the sea star has multiple openings used to filter water into its water-based vascular system. The water vascular system of a sea star is a series of seawater-filled ducts that have functions in its locomotion, feeding and respiration.
Size: 3/4 in diameter
Arms: 8
Habitat: coral reefs
15. Bat Star
The bat starfish (Patiria miniata), also called the sea bat, webbed star, or the broad-disk starfish, has a center disk much broader than its stubby arms. It is an omnivorous scavenger, feeding mostly on surf grass, but also on moss animals, algae, sponges, and biofilms on rocks.
The species’ name comes from the webbing between its arms, which somewhat resembles a bat’s wings. Bat stars can be seen in many colours, including green, purple, red, orange, yellow and brown, both mottled and solid.
Patiria miniata lives in the Pacific Ocean from Sitka, Alaska to Baja California, but is most abundant along the coast of Central California and in Monterey Bay. It does not have the pedicellariae or pincers that most starfish have for cleaning debris from their skin surface, but its small, moving cilia may make enough current in the water to keep the surface of its skin clean.
Size: up to 8 in diameter
Arms: 5
Habitat: rocky intertidal bottoms, near surfgrass, algae, sponges
Velatida Order
16. Striking Sea Star
The striking sea star (Euretaster insignis), is found in tropical shallow waters of the western central Pacific Ocean.
Its upper surface appears inflated due to it being covered by a canopy-like supradorsal membrane. Bundles of spinelets sprouting from flat plates arranged in a mosaic pattern on the cuticle below. support this membrane. There is a water-filled cavity between, filled with gill-like structures for respiration.
During reproduction, the brood of developing embryos resides in the supradorsal cavity, where they receive nourishment from the mother in the form of a secretion from the cuticle. The larvae remain there until they grow to about 1 cm diameter when they are released into the sea as juvenile starfish.
Arms: 5
Habitat: coral reefs, intertidal rocky, sandy and muddy seabeds
17. Slime Star
The slime starfish (Pteraster tesselatus) is named for its defence mechanism of exuding large amounts of clear slimy mucous when attacked by a predator or when stressed. The mucous is toxic to other invertebrates immersed in it.
A thick, raised, fleshy membrane covers its upper surface, giving the slime star a puffy or inflated appearance. Colours vary, including pale brown, grey, red, or orange.
The slime star is found in waters off the west coast of North America, from central California up northwards to the Bering Sea.
P. tesselatus feeds on invertebrates living on and near the ocean floor, such as scallops, clams, sponges, and sea squirts, as well as biofilms growing on mussel shells.
Size: up to 6 in diameter
Arms: 5, sometimes 6 or 7
Habitat: rocky seabeds
The starfish is known for its ability to regenerate its limbs, which can grow back if lost or damaged. This unique characteristic makes it a favourite for many scientists studying sea creatures’ life cycles.
But just about everyone has a fascination with starfish. They are beautiful and come in various colours and shapes, inspiring painters, poets and novelists. Let us hope they continue to thrive and advocate for the conservation of endangered sea star species.