Drifting by the dock

We've returned to California, but I can't help showing another fascinating invertebrate from San Juan Island.  And this one could be found in California, too, so it's relevant to the Bodega Head area.

One of the funnest things about the Friday Harbor Laboratories is all of the planktonic animals drifting by the dock.  It's easy to spend hours on your stomach staring at the various gelatinous creatures swimming along just below the surface, magically appearing and disappearing from view.

Eric and I brought a jar so we could gently scoop up anything interesting for photographs.  I was excited when this animal emerged from the depths.  It was ~6 cm long.

 

This is a colonial animal called a siphonophore.  (I've mentioned siphonophores on this blog twice before — once in January 2012 and again in April 2013.  You can check out those posts for more information about them.)  I think it's a species of Nanomia, perhaps Nanomia bijuga.  But I don't have much experience identifying siphonophores, so please correct me if you think this is something different.

This siphonophore has a gas-filled float at the top (see below for a close-up).  The float is somewhat similar to a Portuguese Man O' War float, but in this case the float is much smaller and has ruby red pigment.

In the next image you can also see the swimming bells that the siphonophore uses to propel itself.  When it contracts the bells, the siphonophore can move very quickly!

 

The lower portion of the siphonophore is very complex.  I don't claim to understand everything down there.  But it's made up of both reproductive and feeding structures.  In the following image, you can see some of the feeding structures.

Look for the orange coils — those are called cnidobands.  And in the lower left corner, you can see a long thread-like structure trailing downward.  This might be a filament extending down from a cnidoband.  Stefan Siebert shared a neat description of these structures (and better photos) at the CreatureCast website.  (Remember that siphonophores are cnidarians so these feeding structures have stinging cells like jellyfish.)

 

I wish I could share more about these amazing animals, but for now it's just fun to know that they're out there.