Attachment & locomotion
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Research study 1

photograph of feather star Florometra serratissima close view of cirridrawing of ossicle construction of cirrus of feather star Florometra serratissima courtesy Holland & Grimmer 1981 Cell Tissue Res 214: 207Stalkless crinoids such as Florometra serratissima anchor to the substratum using flexible cirri.  The cirri are jointed and can slowly bend and straighten. An individual can slowly move about its habitat by crawling on its cirri. There are several theories on how the cirri contract, including use of muscles, hydrostatics, ligament elasticity, and ligament contractility. No muscle cells are visible with a light microscope and there is no strong evidence to support the other ideas.  However, electron-microscopical studies in southern California on Florometra and other stalkless species (from Japan and Europe) suggest that the bending may owe to contraction of nano-filaments in the cytoplasm of epidermal cells surrounding each cirrus.  The contraction is thought to be antagonised by ligaments joining adjacent ossicles, and it is the elastic energy in these that is thought to straighten the cirrus. The authors conjecture that a cirrus is able to be locked in a rigid state by neurosecretory changes in the protein rubber of the ligaments.  Holland & Grimmer 1981 Cell Tissue Res 214: 207.

NOTE  of roughly 650 extant crinoids, about 570 (88%) are stalkless


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Research study 2


photograph of feather star Florometra serratissima ready to swimFlorometra serratissima is the only swimming species of crinoid on the west coast of North America.  It swims by graceful undulation of its arms in 2 sets of five, each set moving alternately.  While half the arms effect the power stroke, the other half are in recovery.  During the power stroke the arms extend out maximally for greatest frictional resistance, while during the recovery stroke they bend inwards to minimise resistance.



Florometra ready to swim 0.3X



Florometra just after take-off 1X

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CLICK HERE to see a video of a Florometra serratissima swimming.

NOTE the video replays automatically

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