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Sunday, December 15, 2013


An intriguing scaleworm on a Giant Sea Star (Pisaster giganteus):

I think the worm might be a Ruffled Scaleworm (Arctonoe fragilis).  This species of scaleworm is often associated with sea stars.  

I was struck by how closely it matched the colors and patterns of the sea star especially how the white spots along the sides of the worm matched the white tubercles (short rounded spines) of the sea star.

When the worm turned sideways along the side of an arm, you could see it if you knew where to look, but it was amazingly well camouflaged (see below).

Here are two more close-ups of the worm.  I'm not sure if the "ruffles" visible in the next picture led to the common name, Ruffled Scaleworm?

Below, the worm's white head with its pointed, transparent appendages is facing left.  It was fun to think about the scaleworm crawling among the sea star's spines like a maze.


John W. Wall said...

I wouldn't have noticed it if you hadn't pointed it out. Are your Pisasters having a disaster? I've read that many of them are dying due to unknown causes.

Jackie Sones said...

Hi, John,

Some of the sea stars in the Bodega Bay area have been affected by wasting disease, but not as many as further south at sites near Santa Cruz. Researchers at UC Santa Cruz are mapping the extent of the disease and working with other scientists to try to identify the cause. There's more information here: