The common brittle star sometimes congregates offshore in vast numbers and as many as two thousand individuals have been recorded in a single square metre.
Higher up the shore it normally lives a solitary existence under seaweed or pebbles or in crevices.
It moves by jerking a pair of limbs forward and pulling itself along.

The common brittle star is a scavenger, feeding on dead organisms.
It is also a suspension feeder, raising an arm and extending the tube feet in order to catch particles floating by.
It then passes the food to the mouth with its arms.
Its abundance varies according to environmental conditions including temperature and the availability of food.
After mild winters, it has been found in very large numbers in the Oosterschelde estuary in the Netherlands.

The common brittle star is itself eaten by other species and can be found among the stomach contents of most common predators.
However its glassy spicules may make it unpalatable, it lives in concealed places and is well camouflaged so that it blends in with its surroundings which combine to reduce predation.
A study of skeletal bands suggests that it may live for as many as ten years.

Like some other brittle stars, Ophiothrix fragilis has symbiotic bacteria under its cuticle.
The host-bacteria association can be upset by acute stress, and changes in levels of bacteria present can be used as an indicator of stress.

This brittle star usually spawns between May and January.
Each individual is thought to spawn just once during each breeding season.
A week after spawning, the planktonic larvae appear in the water column.
They metamorphose into young brittle stars which drift in the plankton for about three weeks before settling.
The smallest brittle stars found have just two segments per arm and a disc diameter of two millimetres.
The common brittle star sometimes congregates offshore in vast numbers and as many as two thousand individuals have been recorded in a single square metre. Higher up the shore it normally lives a solitary existence under seaweed or pebbles or in crevices. It moves by jerking a pair of limbs forward and pulling itself along.
The common brittle star is a scavenger, feeding on dead organisms. It is also a suspension feeder, raising an arm and extending the tube feet in order to catch particles floating by. It then passes the food to the mouth with its arms. Its abundance varies according to environmental conditions including temperature and the availability of food. After mild winters, it has been found in very large numbers in the Oosterschelde estuary in the Netherlands.
The common brittle star is itself eaten by other species and can be found among the stomach contents of most common predators. However its glassy spicules may make it unpalatable, it lives in concealed places and is well camouflaged so that it blends in with its surroundings which combine to reduce predation. A study of skeletal bands suggests that it may live for as many as ten years.
Like some other brittle stars, Ophiothrix fragilis has symbiotic bacteria under its cuticle. The host-bacteria association can be upset by acute stress, and changes in levels of bacteria present can be used as an indicator of stress.
This brittle star usually spawns between May and January. Each individual is thought to spawn just once during each breeding season. A week after spawning, the planktonic larvae appear in the water column. They metamorphose into young brittle stars which drift in the plankton for about three weeks before settling. The smallest brittle stars found have just two segments per arm and a disc diameter of two millimetres.
Ophiothrix fragilis