Although the blob was only ~2 mm long, Eric's eyes are good enough that he wondered if it might be a very young Scarlet Sea Cucumber (Lissothuria nutriens). I looked with a hand lens and I thought I could see tube feet, which meant that sea cucumber was a definite possibility. Then we thought — since Lissothuria broods its young, if the blob is a tiny sea cucumber perhaps the mother is nearby. You've heard that old expression, "The cucumber never falls far from the tree..."? [Instead of growing up in the plankton, the embryos develop on the mother's back and then the juvenile sea cucumbers walk away from the mother as smaller versions of her.]
We looked more closely and there she was! Here's a zoomed out view. Although Scarlet Sea Cucumbers are red, they hold small bits of seaweed and other debris on their backs, so they can be very hard to see at first. In the photo below, there's one adult sea cucumber and five juveniles. This will be tricky, but can you spot them all?
Below the sea cucumbers are circled, mom in blue and juveniles in orange:
Since this is one of the species we're tracking, we documented them with some microscope photos and yes, a video!
These are beautiful little sea cucumbers, so it's a treat to see them up close:
With a ruler for scale (marks are in millimeters):
At this stage, the sea cucumbers are almost transparent, so it's a wonderful view of their ossicles. Look for the shiny plates in the body wall and the tentacles. (For more info about ossicles, see the post called "Scarlet fire" on 12 February 2017.)
And as if those pictures weren't enough, Eric captured some amazing video. Check it out! [If you can't see the video player in your e-mail, click on the title of the post to go directly to the website.]
That is the most adorable sea cucumber video I have ever seen. Thank you Jackie and Eric!
ReplyDelete(I will say, in the first few seconds of viewing, my brain jumped to a dancing pineapple who was the star of a French Canadian kids TV show I watched in my youth... Though these guys are of course more endearing!)
I find it interesting that these cukes are intensely colored but then make an effort to camouflage. (Mom was hard to find!) Has me wondering about how often we see bright coloration paired with "behavioral" camouflage. Also wondering about how important visual detection might be for potential predators (versus detection by smell, etc.).
Great post!
May be covering to prevent drying out and sun protection at low tide, not camouflage at all. Many sea cucumbers are distasteful. Only thing I ever found eating them was Pycnopodia helianthoides
ReplyDeleteThat video!!
ReplyDeleteThis post was great fun!
Hi, everyone!
ReplyDeleteThanks so much for the comments and thoughts. We've also had questions about the gathering-debris behavior for little while now. It's incredibly consistent -- somehow, they tend to gather the same types of debris, so the visual effect is similar among individual cucumbers. It would be interesting to know more about what the debris actually is. And when we saw this individual with the young cucumbers nearby, I wondered how the debris interacts with brooding, as the embryos are apparently brooded on the backs of the adults. So many questions!
Jackie