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Tuesday, February 19, 2013

Will a serpent suffice?

Do you recognize the animal in the photo above?  
(It's a close-up, so it's only a small portion of the animal.)

Last weekend Eric and I checked a few kelp holdfasts that had washed ashore on Salmon Creek Beach.  One of the animals seems an appropriate follow-up to the recent discussion about the Year of the Snake.

Here are two pictures, the first showing the upper surface and the second with the mouth-side up.  The entire animal was ~6 cm across from arm tip to arm tip.

This is a brittle star, so called because they sometimes drop parts of their arms when disturbed or threatened (they can regenerate the lost parts later).  They're also called serpent stars because of the snake-like appearance and movements of the arms.

This particular species is a Daisy Brittle Star, or Ophiopholis kennerlyi (formerly Ophiopholis aculeata).  [Alternative common names include Painted Brittle Star and Painted Serpent Star.]  The scientific name is informative, especially for the topic of this post.  Ophio means snake or serpent and pholis means scaly.

Brittle stars (formally known as ophiuroids) are echinoderms, related to sea stars, sea urchins, sand dollars, sea cucumbers, and crinoids.  They have a star-shaped central disc covered with short spines (see below).

Five long arms radiate away from the central disc.  When you look at the arms, you'll see flattened plates on the upper surface, projecting spines along the sides, and flexible tubefeet underneath.

In this species, the large plates on the upper (dorsal) surface are surrounded by smaller accessory plates arranged in a mosaic-like pattern.

The tubefeet look quite different than the tubefeet of most sea stars and sea urchins in that they lack suckers at the tips.  Daisy Brittle Stars are suspension feeders — they extend their arms up into the water to catch food particles with their tubefeet and then pass a ball of mucus-coated food particles towards the mouth.

What do you think — Does a brittle star, or serpent star, qualify as a highlight for the Year of the Snake?

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