Brittle Star Facts: These Species Have One of a Kind Movement

While the oceans hold a multitude of captivating creatures, few can match the enigmatic allure of the brittle star. This species will impress you with its mesmerizing movements and mind-boggling adaptations. Get ready to be spellbound as we lift the veil on these enigmatic beings and delve into their interesting facts.

Brittle star
Phylum: Echinodermata
Class: Ophiuroidea

1. They’re not starfish

Brittle stars or serpent stars, belonging to the Ophiurida class of echinoderms, are intriguing marine organisms with a close kinship to sea stars. They share a family with sand dollars, sea urchins, sea cucumbers, and sea stars.

Brittle stars are not sea stars, although they are both echinoderms and have radial symmetry. The differences between sea stars and brittle stars are quite clear. They belong to different classes, while starfish are a member of the class Asteroidea, serpent stars belong to the class Ophiurida.

In contrast to sea stars, brittle sea stars possess arms and central discs that are notably more distinct from each other. Their central discs encasing all their internal organs are made up of a calcium carbonate skeleton. These arms are supported by vertebral ossicles made of calcium carbonate plates and are capable of twisting and coiling to facilitate locomotion.

These species are divided into 2 big groups: basket stars (Euryalida) and brittle stars (Ophirudia). With over 2,000 recognized species, these stars come in different shapes, colors, and sizes. The discs of brittle stars generally vary in size, spanning from 0.1 to 3 inches, while their arms have the impressive ability to grow up to 20 times the diameter of the disk. Among the known brittle starfish, the largest one is Ophiopsammus maculata, measuring an impressive 24 inches in length.

The red brittle star

Certain brittle star species possess blunt spines that are neither poisonous nor venomous. Consequently, these creatures are harmless and cannot hurt you.

They commonly display shades of grey, green, yellow, pink, orange, or brownish-red, though coloration may vary across species, giving rise to additional variations. Remarkably, certain species even showcase mesmerizing bioluminescent properties, producing green or blue wavelengths.

These marine stars may not possess brains or eyes, but they boast a substantial stomach, powerful muscles, and genitals. Their mouths located on the underside of their disc are equipped with five jaws, which also function as their anus. To breathe, move, and manage the transportation of food and waste, they rely on a sophisticated water vascular system.

The green brittle star
This species is kept a lot in reef tank

While many species lack traditional eyes or specialized sense organs, they possess a diverse array of sensitive nerve endings throughout their epidermis. This unique adaptation allows them to perceive the environment through various means, such as detecting the light and chemicals in the water or responding to touch.

Fun fact:
They derive their name from two origins: the New Latin term ‘ophiurus’ (referring to brittle star) and the Greek words ‘ophis,’ meaning serpent, and ‘oupa,’ denoting tail. Consequently, they are aptly named serpent stars or brittle stars, owing to their arms resembling a serpent’s tail. 

2. Habitat

Brittle stars exhibit a remarkable diversity, boasting more than 2,000 identified species distributed across the world. Some of them are Savigny’s or little brittle star, harlequin serpent starfish, black serpent star, Alexander’s spiny or banded brittle star, crevice or daisy brittle star, fancy brittle sea star, or common European brittle star.

These species inhabit a wide range of environments, spanning from the depths of the sea (11,000 feet below the surface) to shallow waters and from polar regions to tropical waters.

Serpent stars in the coral reef

Their preferred to live in transfixed creatures like coral reefs and sponges on the sea bed. They coexist with a diverse array of animals here. Nevertheless, they can also be found alone in deeper waters.

Interestingly, certain locations boast significant aggregations of brittle stars, like the phenomenon observed in “Brittle Star City” near Antarctica, where tens of millions of these creatures densely cluster together.

The Indo-Pacific region stands out for its remarkable species diversity of brittle stars, boasting a total of 825 recorded species across all depths. On the other end of the spectrum, the Arctic exhibits the lowest species count with only 73 species identified. Most species in this area thrive in shallower waters of the ocean shelf.

3. Brittle star Diet

Brittle stars mainly eat small organisms and detritus such as small mollusks, algae, plankton, snails, and even shrimp, squids, or fish. These omnivores acquire their food through two main methods: filter feeding and actively capturing prey.

To catch prey, serpent stars employ various techniques. One such method involves raising themselves on their arms, creating an elevated position. From this vantage point, they skillfully ensnare fish that venture too nearby wrapping them in a spiral and subsequently consuming them.

Some use their tube feet to catch minuscule food particles by lifting their arms. These tube feet are covered in mucous strands that help trap the food, which is then carried to their mouth. Once in their mouth, the food particles are crushed by 5 jaws before continuing their journey through the esophagus and into the stomach. The stomach, situated within the central disk, consists of ten pouches where the digestion of the prey takes place. As there is no anus, the brittle stars will expel food through their mouth.

The animals have to face threats from many predators, including starfish, various fish, crabs, and other sea creatures. To avoid predators, they resort to hiding beneath shells, and rocks, and even seeking shelter among larger animals.

Another defense mechanism at their disposal is autotomy, or self-amputation, as seen in sea stars. When ensnared by a predator, they drop their arms to distract the enemies and take the opportunity to escape. The wound left behind undergoes healing, and over the course of several weeks to months, depending on the species, the lost arm regenerates into a new one.

4. They’re seafloor ecosystem engineers 

Brittle stars are nocturnal animals, being most active during the night when they emerge to forage for food. In contrast, they tend to seek shelter and remain hidden during the day, likely as a survival strategy to decrease their exposure to potential predators.

These mesmerizing beings play a vital role in altering sediment patterns on the ocean floor, profoundly influencing the distribution of other seafloor species. Serpent stars can do this just by the way they move.

The brittle star is walking

In contrast to starfish and urchins, these creatures don’t use tube feet to move. Instead, they propel themselves across the sea floor by twisting, wriggling, and coiling their arms. They have earned the reputation of being the swiftest among echinoderms.

When moving, they use one arm as a guiding pointer, indicating the direction of their movement. The adjacent arms on either side then synchronize in a graceful “rowing” fashion, propelling the star forward. Thanks to this synchronized rowing action, the creatures can walk with remarkable speed and cover significant distances.

When they need to change direction, all they need to do is choose a new pointer arm to take charge and guide the way. This amazing adaption allows them to maneuver through their environment effortlessly.

5. Life cycle

Certain brittle star species exhibit different reproductive methods, encompassing sexual and asexual modes, while specific species are versatile and can employ both strategies.

In the case of sexual reproduction, males and females release their respective eggs and sperm into the surrounding water. These species are known for breeding consistently throughout the year, with most activity observed from May to July.

During external fertilization, the formation of ophiopluteus, free-swimming larvae, occurs. These larvae remain suspended in the water until they eventually settle on the seafloor. Over a few months, they transform into juvenile serpent stars and usually attain maturity after 2 – 3 years. These fascinating creatures are hermaphroditic, which means they can change their sex at different stages of their lifetime. 

The ruby brittle star

In certain species, their reproductive process varies significantly. Take the small brittle star Amphipholis squamata, for instance, where the young are brooded. The eggs are kept in specialized sacs known as bursae, located near the base of each arm. Fertilization occurs when released sperm come into contact with the eggs. Subsequently, the embryos undergo development within these protective sacs until they are ready to hatch and emerge into the environment.

For asexual reproduction, these unique creatures create offspring via fission. Through this process, they divide their central disk into two parts. Each half is genetically identical to its parents and eventually develops into a new serpent star.

The average lifespan of brittle stars ranges from 5 to 10 years.

6. Threats

With more than 2,000 known species all over the world ocean, serpent stars are stable species. However, they’re still threatened by global warming, pollution, and habitat loss.



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