Spiny Starfish (Marthasterias Glacialis)

Spiny starfish (Marthasterias Glacialis): Care, Diet, and Habitat

The spiny starfish is one of the most fascinating sea dwellers, famous for its unique defense mechanism. Spiny starfish facts provide interesting insights about these colorful creatures. These starfish are small, spiny, and often brightly colored.

Spiny starfish are the type of sea star that you’d normally find living in the wild. They have a natural defense mechanism that is embedded with very sharp spines that point towards the center of their body. That’s how they got their name- spiny! 

It is known by many common names, including the five-arm sea star, spiny starfish, and grey sea star. The scientific name for the spiny starfish is Marthasterias glacialis. “Marthasterias” roughly translates as “star of the seas” or “star of marshes”, whilst ‘glacialis’ means “icy” or “related to ice.”

Diet & Feeding Behaviour

Spiny starfish eat a wide range of foods, including molluscs, worms, small fish, and other echinoderms. They are also known to be scavengers, eating dead animals and plants. They have a ferocious appetite and can consume up to 40% of their own body weight in one day. They eat by extending their stomachs out of their bodies and over the prey. They then digest the soft parts and absorb them into the body. The indigestible leftovers are pushed out of the mouth again.

spiny starfish have been observed eating other spiny starfish! This cannibalism seems to occur when food is scarce or in crowded conditions (e.g., during breeding season). 

The Spiny Starfish( Marthasterias glacialis)  is a nocturnal feeder and will feed at night on live rock, macro-algae, micro-algae, and detritus. Spiny Starfish will not consume corals or any other animals. In order for the Spiny Starfish to thrive, it must be provided with a constant source of food like live rock and macro-algae. This will help prevent starvation and/or death.

Spiny starfish will also eat meaty foods such as Mysis shrimp and small pieces of fish. If fed correctly it should thrive well on commercially prepared food such as frozen foods. Feeding them should be easy as long as you make sure that there are no other large predators in the aquarium that might steal their food.

Natural Habitat of Spiny starfish

Spiny starfish can be found anywhere in the world where there are saltwater oceans. They live in shallow waters and all the way down to depths of 2,500 feet (800 meters). The largest spiny starfish, called sunflower starfish, can be found off the coast of Alaska and California. These starfish can grow to be as wide as 3 to 5 feet (1-1.5 meters) across!

The habitat of the spiny starfish( Marthasterias glacialis)  varies based on the species, but most like to be among rocks and coral reefs. These areas provide lots of hiding places from predators and lots of other sea creatures for them to eat.

These Sea stars are found in a wide range of habitats, from the intertidal zone to the abyssal zone. The greatest numbers occur in the subtidal zone below the low tide level, where they are often the top predators. Sea stars occur in all types of habitats, including estuaries, coral reefs, rocky shores, sandy beaches, and the open sea. Their versatility is indicated by the fact that they are found from the tropics to polar latitudes.

Appearance & Color Range

The spiny starfish can be found in a wide range of colors including red, brown, green, and blue, but their coloration is species-specific. The most common color for the crown of thorns starfish is brownish red with yellow tips on their spines. The spiny starfish derives its name from the spikes that protrude from its upper surface. The underside of the spiny starfish is smooth.

Spiny starfish are similar to most other sea stars. They have a central body from which five arms grow. Their bodies are flat, round, and covered by tough skin. The skin is bumpy and has spines that cover it. These spines help protect the starfish from other animals in the ocean. The arms are long and slender. Unlike most starfish, they do not have tube feet that are used for movement. Instead, they use their arms to slowly crawl along the seafloor. The backside of the arms is covered with small spines for protection.

The spiny starfish is a very small species of starfish. They are also known as the chocolate chip starfish and the chocolate chip sea star. They have a light to dark brown body with a mottled white pattern. Their underside is a lighter shade of brown but still covered in the same pattern as the top. This coloration makes them very difficult to see on their preferred substrate – sand, mud, or rock rubble. The color of a starfish is determined by the pigments in its body. They may also have other colors on their bodies that are not present in their skin cells. 

Reproduction and Breeding Cycle for the Spiny Starfish

Like all starfish, the spiny starfish has a unique way of reproducing. It is a simultaneous hermaphrodite, meaning that it possesses both male and female reproductive organs in its body. The spiny starfish will typically spawn during the night, once or twice a year.

The breeding cycle for the Spiny Starfish( Marthasterias glacialis) is not clearly understood in detail. The breeding season varies depending on the species and geographic location. The breeding season usually begins during the spring months and extends until late summer or fall.

Spiny Starfish Reproduction and Growth
Spiny Starfish Reproduction and Growth

Most species spawn externally, meaning that they release eggs and sperm into the water at the same time. Some species are hermaphroditic, meaning that they are able to produce both eggs and sperm, while other species are gonochoristic (containing animals with distinctly female or male sexual organs).

The eggs produced by the Spiny Starfish are fertilized externally by sperm from another starfish of the same or a related species. Once fertilized, the eggs then develop into microscopic larvae known as bipinnaria. Once born, these larvae float in open water as plankton for about two weeks until they reach their second stage of larval development, called brachiolaria.

At this stage, each larva develops tiny structures that resemble small arms called brachioles which enable them to attach themselves to rocks or other objects on the seafloor. They also develop a small mouth and digestive system during this time. After four to six weeks as brachiolaria, they eventually settle down as adult starfish.

Predators and Threats to Marthasterias Glacialis

The spiny starfish has plenty of natural predators. Larger fish, sea birds, and marine mammals such as sea lions, dolphins, and whales will all happily eat the spiny starfish if it is available. However, the biggest threat to the spiny starfish is human activity. Seals are also their common predator. Birds are also part of the list, but not in large numbers. Another predator is the sunflower sea star. It has a very strong stomach and can digest spiny starfish with no trouble at all.

Pollution of its habitat can kill off large numbers of this species, as can overfishing and the use of destructive fishing practices. When the spiny starfish is in danger and being pursued by a predator, it can detach its arms, and regrow them later.

The spiny starfish is also threatened by human activities, including pollution, habitat destruction, fishing, coastal development, and climate change. Overfishing can also be a threat because it causes an imbalance in the ecosystem, which often leads to other problems down the line.

Spiny starfish or Marthasterias glacialis are not as vulnerable to predators as other invertebrates due to their spines, which act as a strong defense mechanism against predators.

Aquarium care for Spiny sea star

The spiny sea star (also called the spiny starfish or Prickly starfish) is a lovely animal to have in your saltwater aquarium.It is not only a beautiful sight but quite useful as well. The spiny sea star will pick at algae and detritus, which keeps the tank clean. It is very peaceful and doesn’t bother any corals or fish.

Tank size

This type of starfish is not very mobile and will spend most of its time settled on a rock or other surface. The spiny sea star is a slow swimmer and cannot catch prey, so it needs to be placed in an environment where food is easily reachable. In the wild, these invertebrates eat mussels and oysters, so your tank should have plenty of hiding places for these animals to find food.

Spiny Sea Star
Spiny Sea Star


Since spiny sea stars live at the bottom of the ocean, they are used to dim lighting conditions and do not need bright lights. They also prefer to be kept in a tank with low lighting because they don’t like being disturbed by people passing by or other fish moving around them while they eat. In addition, these creatures are sensitive to changes in light intensity so keep them away from windows or direct sunlight as much as possible.

Water conditions

As far as water conditions go, this starfish doesn’t demand anything special. The pH in their tank should be between 8.0 and 9.0, and the temperature should be between 65 and 80 degrees Fahrenheit (18 to 27 Celsius). The Spiny Starfish also prefers low-moderate flow, so it can catch and eat food easily.


Spiny sea stars need plenty of space for swimming. They can grow up to about 10 inches across, so a very large aquarium is required. The recommended minimum tank size is 75 gallons. The aquarium should have a sandy substrate and plenty of live rock with caves and crevices for hiding places. The lighting can be moderate to strong, but the water movement should not be too strong because this species does not do well with the intense current. This species does not bother corals and other invertebrates, but it will eat clams, small crabs, snails, and other small animals.


The spiny sea star can live with similar-sized fish and peaceful invertebrates in a reef tank. It won’t attack other fish unless it feels threatened (or if they are getting too close to its food). Fish that may not do well with this species include angelfish, butterflyfish, and triggerfish, as they may nip at the starfish.

Aquarium care for Spiny sea stars includes providing enough water flow, ensuring good filtration, and maintaining optimal temperature and pH levels in the aquarium water.

Interesting facts about Spiny starfish

  • Spiny starfish are small and have a flat, round body with arms that radiate from the center. 
  • The spiny starfish derives its name from the five spines located on the top of its body. These spikes are triangular in shape and are generally smaller in size compared to other parts of their bodies.
  • Spiny starfish make great aquarium pets. Their size, color, and lower demand for care make them a suitable and interesting addition to any fish tank.
  • The spiny starfish is a land-dwelling starfish that can live for a long time without water. They prefer to live in low salinity water, but most of the time they are found in waters that are heavily polluted.
  • Some people call this sea star the “Sawtooth Sea Star” or the “Velcro Star” because of its bristles. 
  • It is also known as the crown-of-thorns starfish due to the venomous thorn-like spines that cover its upper surface, and the chocolate chip starfish due to the brownish, chocolaty appearance of its upper surface.
  • A rarer variation of the Spiny starfish is a spotted specimen, which is considered less aggressive than other species and is highly prized by collectors.
  • The spiny starfish has a small central mouth surrounded by hundreds of tiny tube feet. Its body is dotted with light-sensitive eyespots.
  • They do not have any gills, lungs, or kidneys and rely on diffusion for gas exchange and osmosis for waste removal. They also lack an anus and can not eliminate waste through the digestive system like other species can.
  • The spiny starfish has a very wide distribution range and can be found in almost all areas of the world’s oceans. 

Spiny  Starfish- Related FAQs

Q1. What do Spiny sea stars look like?

The spiny starfish has bright orange or red arms scattered with white spines. They often have a beautiful and unique appearance. The way that their spines branch out from their bodies is similar to the branches of a tree. These arms have a knobbly texture and are quite long, measuring up to 15 cm in length. It is usually found on sandy or muddy seabeds rather than on rocky reefs.

The spiny starfish is a very unique-looking starfish. Their bodies are round and flat, but they have many spines that are long and pointy. These spines cover their entire bodies except for the underside.

Q2. How long do Spiny starfish live?

Spiny starfish can live for several years in the tank is provided with the proper care. They are considered to be one of the most long-lived species of starfish in the aquarium. The spiny starfish has a very interesting lifespan. It doesn’t die from old age; instead, its life ends when it is eaten by a predator like a sea otter or a bird.

Spiny starfish have an average lifespan of about 5 years, and some species can live for more than ten years. The lifespan of a spiny starfishh will depend on its species, where it lives, and the availability of food.

Q3. How many eyes does a spiny starfish have?

They have five eyes, but they can’t see well. Instead, they use their feet to feel for prey. They are nocturnal and hunt at night. Many starfish species send out long tendrils from their bodies to help them find food.

Q4. Are spiny starfish poisonous?

Spiny starfish are not poisonous. They don’t have any toxins like the poisonous fish do. They are slower than most predators, so it is safe to keep them with other species. It is better to keep them in the tank along with fish that are of similar size or bigger. Smaller or similar-sized fish may be attacked by them.


Spiny starfish are not only aesthetically pleasing to many aquarists, but they are also easy to keep and relatively low maintenance. Spiny starfish are a great addition to any marine aquarium because of their interesting appearance, care level, and habits. With the right information and planning, you can be one of the successful hobbyists who has a healthy, long-lived spiny starfish in their aquarium for years to come.

They are solitary animals that feed mainly on benthic invertebrates. Marthasterias glacialis or spiny starfish, has a very important ecological role as it helps control populations of benthic invertebrates that would otherwise grow out of control!

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