When Nature Coast Marine Group took part in ‘What’s Under Narooma Wharf’ in January, the collectors brought up some unusual creatures that they had not seen there in past years. They were two very beautiful dark brown feather stars.
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Many people photographed them but unfortunately we did not get the contact details of the photographers. The photo here, taken by Jen Thompson, is of a similar tropical species.
Feather stars belong to the Phylum of spiny skinned animals – the Echinoderms. They are Crinoids but unlike their fossil ancestors, they do not have a stalk.
Their delicate arms (called pinnules) have sticky feathery fringes which wave in the water and collect microorganisms. The food is passed along central grooves to the mouth which is on top of their body, unlike sea stars or urchins. Also unlike seastars, feather stars do not have stomachs. The food breaks down inside their bodies and the nutrients just circulate in waves through their whole body and arms.
On their under surface they have a bunch of cirri. These grasping “legs” allow them to cling onto something hard like rock or coral so they can extend their arms high up in the water currents.
They can use their feathery arms to crawl along. If they want to move faster, they use their arms to swim through the water. YouTube has some fantastic videos of them in action. Since they do not have brain but only a nervous system and sensory organs, it is amazing to see how they co-ordinate all their arms to swim so gracefully.
Feather Stars are either male or female and have to be close enough to each other and time their release of eggs and sperm accurately to reproduce successfully. The young develop through a larval stage and a free-swimming stage before reaching the adult form with pinnules.
The Nature Coast Marine Group has an extensive program of activities where members can have fun learning about our marine environment.
New members are always welcome. To find out more about the Group and to see other stories in this series, visit the website www.ncmg.org.au or search for Nature Coast Marine Group on Facebook and follow us there.