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Wednesday, April 3, 2013

Swimming bells

A couple of nights ago I promised to show a few more gelatinous marine animals that have appeared on local beaches during the past month.  Here's one of them:

In March we discovered these washing up on Salmon Creek Beach.  You can see they were somewhat rigid (they held their shape instead of collapsing).  Each was about 1-1.5 cm long. 

As we walked along the beach, and the sun glinted off of them, they looked like little diamonds in the swash zone.

I brought a few back to look for more clues under the microscope.  Now you'll see that there were very strong ridges and some internal structures and organs.

I needed some help identifying these, so sent a few images to experts.  I'm very thankful to Claudia Mills and Phil Pugh for their assistance with the identification! 

Now for some fancy terminology to impress all of your friends.  This is the anterior nectophore of a calycophoran siphonophore called Chelophyes appendiculata (try pointing that out to your friends the next time you find one of these while walking the beach!).

So what does all of that mean?  A siphonophore is a type of cnidarian, related to jellyfish, sea anemones, and hydroids.  Of those groups, siphonophores are most closely related to hydroids.  Most of them are planktonic, spending all of their time swimming in the open ocean.  The most famous siphonophore is the Portuguese Man O' War, but that's misleading because most siphonophores live below the surface and most of them lack such large floats (and some, like the one in this post, don't have any floats at all.  That's what "calycophoran" refers to; it's just a group of siphonophores that lacks floats).

So what's an anterior nectophore?  Anterior means front, and nectophore means swimming bell.  This type of siphonophore has two basic body regions: a nectosome made up of two nectophores, or swimming bells, one anterior and one posterior; and a siphosome, made up of a long siphosomal stem that has structures designed for feeding and reproduction.

Here's a diagram that illustrates the basic body plan of this type of siphonophore:

Modified from Siphonophores and Velellids by Kirkpatrick and Pugh (1984)

And these drawings show the species we found on Salmon Creek Beach, Chelophyes appendiculata.  Note the claw-like shape of the hydroecium which is a distinctive feature of this species.  (I'm not sure what a hydroecium is, but you can see that the siphosomal stem can be drawn up into it.) 

Modified from Siphonophores and Velellids by Kirkpatrick and Pugh (1984) 

The genus, Chelophyes, means "clawed structure."  I'm wondering if it refers to the shape of the hydroecium?

Siphonophores are active carnivores.  They extend their stinging tentacles into the water column to catch crustaceans or small fish.

It was great fun to find out that these diamond-like gelatinous structures were siphonophore swimming bells.  You never know what's going to wash up on the beach!

P.S.  For a great introduction to siphonophores, check out siphonophores.org by Casey Dunn.

1 comment:

Anonymous said...

I would comment but my tongue (and brain) are tangled !! c