Glowing green

When the winds let up during the summer, sometimes you can find gelatinous animals washed up on the beach — e.g., jellyfish, hydromedusae, siphonophores, ctenophores (also known as comb jellies), and salps.  (I'll show some examples of these animals during the next week.)  

Several days ago I noticed quite a few gelatinous animals, and I was especially curious about some of the comb jellies.  This particular comb jelly (Beroe sp.) doesn't look like much once it ends up on the beach.  It could even just look like a thin patch of slime with a pinkish hue:

 

But if you look closely, you can see long parallel lines running from one end to the other — that's your first clue that it's a comb jelly (rather than a jellyfish).

I was looking at these lines (called comb rows) when I thought I saw some green coloration:

 

In my experience, it's unusual for the comb rows to appear green, so I zoomed in for a closer view:

 

Definitely green!  So what's going on?

Most (but not all) species of comb jellies are bioluminescent.  That means they can emit light via an internal chemical reaction.  Bioluminescence is often more visible in the dark, so I was a little confused about what I was seeing...and I still am.

On this web page about bioluminescence, I read that "there are strong antioxidant properties to luminescent reactions (i.e., they mop up oxygen radicals) so there may be light produced internally during protective reactions."

Could this be what has happening with the comb jellies washed up on the beach?  I'll have to ask around, but I thought you might like to see the photos, and perhaps you have some ideas about the green color in these comb jellies:

 

P.S.  Several years ago I showed pictures of this species of comb jelly swimming.  If you'd like to see those pictures, check out the post called "The Pink Predator — Part 2" from 3 November 2014.

 

The Pink Predator -- Part 2

Last fall I showed you a large pink blob on the beach and told you it was a comb jelly, or ctenophore, called Beroe (review that post here).

Well, at that time I didn't have a chance to show you Beroe in its element — when suspended in the water.

Tonight I noticed at least a dozen Beroe washed up on the beach.  Here's one:

 

In mid-September I found a smaller individual so recently stranded that when I placed it in a bowl of seawater, it immediately started swimming around.  Here's a look at this comb jelly looking more like itself (rather than a deflated mass of jelly on the sand!):

 

Above, you can see the long rows of "combs" (made of fused cilia) that Beroe uses to swim.  There are a total of eight comb rows (not all of them are visible in the picture).  [Comb rows are one of the main features that distinguish comb jellies from jellyfish.]  Below is a close-up of those "combs" as they beat from one end of the comb jelly to the other:

 

Beroe has a very large mouth (remember that it's an active predator that often eats other comb jellies).  The mouth is open on the right side in the image below:

 

Now I can feel better that you've seen the true form of this Pink Predator!