Cobalt blue

I haven't posted much about sponges.  That's primarily because they can be a little more challenging to identify.  The species featured tonight, however, is quite distinctive.

Sponges are animals and have skeletons comprised of elements called spicules.  Some species have spicules made of calcium carbonate, but most have spicules made of silicon dioxide.  The spicules are wrapped in elastic fibers that together make up the wall of the sponge.

As with the ossicles of sea cucumbers (featured previously), sponge spicules come in a diversity of sizes and shapes.  The characteristics of the spicules can often be used to identify the species.

This particular sponge can basically be identified by its color alone, but we also checked the spicules to confirm the identification.

Many encrusting animals in the low intertidal zone are variations of yellow, red, orange, pink, and sometimes purple, brown, gray, or white.  This one stands out because it's brilliant cobalt blue:

 

Meet the Cobalt Sponge (Acanthancora cyanocrypta)!

We noticed this sponge under a rock overhang in the low intertidal zone in Monterey County.  It's primarily a southern species (distributed from Monterey south), but has also been reported in British Columbia.  We haven't seen it in northern California.

Note the species name — "cyanocrypta."  This sponge has symbiotic cyanobacteria (which apparently contributes to the amazing blue color).  Crypta means hidden, so I'm guessing cyanocrypta refers to the cyanobacteria living within the sponge.

Now for the spicules.  Here's an example of the types of spicules in Acanthancora cyanocrypta:

 

Figures modified from The Sponges of California: A guide and key to the marine sponges of California (Lee, Elvin, and Reiswig, 2007).

 

Note the different shapes — the long, simple tornotes; the club-like and spiky acanthostyles; and the barbell-like amphiasters.

Eric took some nice photos of the spicules so you can compare.  Remember, the spicules are microscopic.  In the images below, they are magnified 400x.  See if you can find all three types of spicules in the next three pictures:

 

 

 

There are over 250 species of marine sponges in California, so perhaps we'll be able to feature a few other species in future posts.