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Sunday, December 18, 2016

Crystal connections

Brrrr!  It was a chilly 30°F in Cotati this morninga brisk morning in this part of the world.  Here are some frost crystals that were on my car in the front yard:

When we were looking at the frost this morning, we were struck by the similarities to something quite different:

Although they resemble sparkling frost crystals, these are the calcareous spines of a Glass-spined Brittle Star (Ophiothrix spiculata). You might recall an earlier post (from 9 November 2014) when I described how these brittle stars feedby wiping their spines with their tubefeet to pick up small organic particles stuck on the sharp points and then transferring the particles to their mouth (on the underside of the central disc).

Recently, Eric captured some footage of this behavior.  First, here's another still image.  If you look carefully, you can see a long flexible tubefoot being drawn along one of the spines:

And, for an outstanding view of this feeding behavior in action, here's a video clip.  There are some general views of the brittle star crawling, and then watch for the feeding behavior between ~16-40 seconds. [If you can't see the video in the e-mail, click on the title of this post to go to the web page.]

Pretty amazing!  

Thanks to Eric for sharing these photos and the video clip.

P.S.  Stay warm, everyone!


Hollis said...

Thanks so much for sharing these with us, Jackie. The magnified stills are always amazing but seeing the movement of these animals reveals how they do what they do and truly brings them to life

Alice Chan said...

I love the comparison between these two so-unrelated items. Thank you!

Jackie Sones said...

Hi, Hollis and Alice,

I agree! The video makes a difference in understanding the brittle star's behavior.

And -- I'm glad you appreciated *both* the frost crystals and the brittle star spines! We liked comparing them and putting those images together in one post. It's fun to see connections between things that might not necessarily seem similar at first!