Brittle Star

Brittle Star (Ophiura leutkeni)

Brittle Stars have long, flexible arms
 
Brittle Stars can clone themselves!!

Brittle Stars are echinoderms so they are related to sea stars but they have many important differences. Sea stars use tube feet for locomotion and have broad arms to capture bigger prey, whereas, brittle stars have long, narrow, and fragile arms for fast mobility (most mobile of all echinoderms!) and they mainly feed on small food particles. These creatures are from the order Ophiurida, from the Greek root ophis meaning “snake,” because of the serpent-like movement of its arms. They grow to 27 cm across, have a small central disc which contains their organs, and most have five arms although some species have as many as nine. This creature is unique, because even though it is a radilly-symmetrical animal, it moves in a bi-lateral direction like a human! It points one of its arms in the direction it wants to head, and then the remaining arms either row like a sea turtle, or grab on to objects to pull it forward!
Brittle stars are an adaptable, invasive species because they have evolved to thrive in diverse conditions and habitats. They are non-fussy eaters, can reproduce rapidly, and are extremely good at evading predators. Many are filter feeders, and they strain food particles from the water including dead and dying animals, or they ingest food within detritus. They use their tube feet as suction cups to collect food, and then pass it from one tube foot to the next, until it reaches their mouth.
Brittle stars are extremely proficient at evading predators which include crabs, fish,, birds, and sea stars. They remain dormant during the day and only feed at nights to avoid capture. Some species rely on colours and colour patterns to confuse predators, and large colonies of brittle stars will use colour variation to blur the shape of individuals so that they are difficult to distinguish. The coolest evasive method every species uses is called self-amputation, fragmentation, or arm-dropping! To confuse predators, they will drop one or more arms, and the autotomized arm will then continue to wriggle to distract the predator until the brittle star can escape. Some predators enjoy a constant food supply, so they only target the dropped arm instead of killing the entire food source!! It takes a couple of weeks to months for the arms to grow back, and it is most likely that when you see a brittle star in the ocean, it will be in the process of regenerating one or more limbs.
Another cool feature is that brittle stars can reproduce both sexually and asexually. They can reproduce asexually through fission (otherwise known as creating a Clone Army), where their central disc separates into two, and then both segments regrow the missing arms and organs. This allows the organism to reproduce rapidly, and results in massive clonal colonies. They can also repoduce sexually, and some stars are a single sex and some are both. Some species can actualy change the type of reproduction depending on environmental conditions, and when numbers are low, they favour the cloning method.
Brittle stars can be found in all oceans of the world, from the tropics to the poles, and can live in all types of habitats from shallow sand and mud, to intertidal, to living on surfaces like ships, to deep sea. Their tube feet allow them to stick to substrates or burrow into deep sand. They have become an invasive species, and have travelled from the Pacific Ocean to the Atlantic, by hitchhiking on drifting seaweed or debris, or by adhering to ships!

http://marinelife.about.com/od/Starfish/fl/Brittle-Stars.htm
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