Brittle stars, also known as ophiuroids or serpent stars, are marine invertebrates belonging to the class Ophiuroidea. They are closely related to sea stars, sea urchins, and sea cucumbers, all part of the phylum Echinodermata. Brittle stars are characterized by a distinct central disc and five slender, flexible arms that can be smooth or covered in spines. These arms, which can sometimes reach up to 60 cm in length, enable them to move across the seafloor.
Over 2,000 species of brittle stars inhabit marine environments worldwide. They are found in diverse habitats, ranging from shallow coastal waters and coral reefs to the deepest parts of the ocean, including abyssal plains and hydrothermal vents. Many species prefer to hide under rocks, in crevices, or within other organisms during the day, emerging at night to feed.
Threats to Humans
Brittle stars are considered harmless to humans. They do not possess venom, stingers, or specialized mechanisms to inflict significant bites.
While their arms are often covered with fine spines, direct contact might cause minor skin irritation or a rough sensation. This irritation is superficial and does not lead to serious harm or toxicity. Discomfort from handling a brittle star is comparable to a minor scrape, and severe reactions are not expected.
Physical harm from a brittle star is unlikely due to their lack of offensive capabilities. Their primary defense mechanism involves crawling away quickly or, if threatened, shedding an arm, which they can later regenerate.
Ecological and Aquarium Impact
Brittle stars play an important role in marine ecosystems as scavengers and detritivores. They consume decaying organic matter, uneaten food, and small organisms, helping to keep the seafloor clean. Some species also filter feed, using their arms to capture food particles suspended in the water column.
They are recognized as “seafloor ecosystem engineers” because their movements and digging activities can reshape sediment, influencing the distribution of other marine life. This continuous activity contributes to nutrient recycling on the seafloor.
In an aquarium setting, most brittle stars are considered beneficial members of the “clean-up crew.” They help maintain tank cleanliness by consuming leftover food and detritus that might otherwise accumulate. Their nocturnal habits mean they often emerge at night to forage, contributing to the tank’s overall health.
While peaceful, some larger brittle star species can be opportunistic predators. They may prey on small, compromised invertebrates and fish, especially if not adequately fed. For instance, the Green Brittle Star (Ophiarachna incrassata) has been observed to hunt fish in aquariums, particularly when underfed. However, many species are considered reef-safe and do not pose a threat to healthy corals or other aquarium inhabitants.