Brittle star

Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They inhabit all oceans of the world and live in a variety of sea floor habitats, from coral reefs to the deep sea. Brittle stars are characterized by their slender, flexible arms which allow for rapid movement and their ability to break off arms as a defense mechanism, hence the name "brittle star".

Brittle starfish in kona

Ophiopetra_lithographica_aboral_larger

Asteriacites Utah

Greenbrittlestar

Flickr library

Anatomy and Physiology

Brittle stars have a central disk-shaped body from which five (occasionally more in some species) slender, whip-like arms extend. The arms are covered with scales and spines, which serve as protection and aid in feeding. The skeleton of a brittle star is made up of calcareous plates and ossicles. Unlike starfish, their arms are distinct from the central disk, and their tube feet lack suction cups. Brittle stars do not use their tube feet for locomotion but for feeding and respiration. They move by wriggling their arms which propels them along the seabed.

The central nervous system of brittle stars is simple, consisting of a nerve ring that surrounds the mouth and branches into each arm. They have light-sensitive cells on their arms that detect changes in light, aiding in their escape from predators. Brittle stars have no true eyes, but these light-sensitive cells can detect shadows and movements, helping them to avoid threats.

Brittle stars are omnivores, feeding on plankton, small mollusks, and detritus. They capture food using their arms and move it towards their mouth located on the underside of their disk. Some species are also known to be suspension feeders, using the mucus on their arms to trap food particles from the water.

Reproduction

Brittle stars reproduce both sexually and asexually. In sexual reproduction, they release sperm and eggs into the water, where fertilization occurs. The larvae are planktonic and undergo several stages of development before settling on the seabed and transforming into adults. Asexually, some species can regenerate lost arms, and in certain cases, a new individual can grow from a severed arm.

Ecology

Brittle stars play a significant role in the marine ecosystem. They are important detritivores, helping to break down and recycle organic matter. Additionally, they serve as prey for a variety of marine predators, including fish, crabs, and other starfish.

Brittle stars exhibit a wide range of colors and patterns, which can serve as camouflage or warning signals to predators. Their ability to rapidly regenerate lost arms is a remarkable adaptation that allows them to escape predation and survive in the competitive marine environment.

Conservation

While brittle stars are widespread and not currently considered endangered, they face threats from ocean acidification, habitat destruction, and overfishing of their predators and prey. Conservation efforts are focused on protecting marine habitats and ensuring sustainable fishing practices to preserve brittle star populations and the broader marine ecosystem.

Gallery

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  Brittlestar
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  Haeckel Ophiodea
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  Haeckel_Ophiodea
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  Ophioderma (Charleston, South Carolina)
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  Tu - Asteronyx loveni
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  Asteroschematidae Hawaii

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