But something didn't feel right about it, so we kept wondering about it in the back of our minds. Here's a view from above:
And then we found another one that looked just like it. Hmmmphh. Puzzling. Another small reddish-orange tunicate?
While continuing our survey, I thought to myself, "Well, if it's a tunicate, it should be attached, so if we find another one, I'll push it a little and see what happens."
We did find a third individual, and as soon as I touched the little mystery lump, it just slid away from where it had been.
Okay, it wasn't attached, so it probably wasn't a tunicate...but then what was it? We were distracted by something else for several seconds, and when I looked back, the little orange mystery animal was moving! It had started crawling away. When we looked closely, we could see a snail-like foot underneath.
Now I was confused. It looked so much like a tunicate! Was it possible that a tunicate was growing on top of a snail or a limpet? But all three of the little mystery animals looked exactly the same...same shape, same color, same patterning, same texture. (An aside: The interesting angles that are visible from the side and the coloration reminded me of a pomegranate seed, so that's what I started calling them.)
We decided to look at it under water and with a microscope, and here's what we saw:
Aha! Two tentacles, a long foot trailing behind, and a rolled-up siphon (visible between the tentacles). It had to be a snail...but which species?
We worked on this for a little while and finally identified it as Hainotis sharonae (formerly Marseniopsis sharonae). They feed on tunicates, and they have evolved incredibly effective camouflage to look just like them.
Here's another view, this one from below. The snail is upside down, looking up. In this position you can see how much it looks like a snail, but return to the first picture of this post and I'm guessing that snail is not the first thing you think of!
There's always something new to learn!
5 comments:
This reminds me of a similair mystery I found in Alaska. Marsenina stearnsii, another cryptic tunicate predator.
I love your blog! I found these in Monterey Harbor on Wednesday and knew exactly what I was looking at thanks to this post!
Hi, Lynn and Laura,
I might have some Marsenina photos to share soon! ;)
And Laura -- so cool that the blog post helped identify a Hainotis that you found in Monterey. It's definitely a species where a photo taken in the field is helpful. If a taxonomic key only provides information about the internal shell, that's not that useful with a live animal in the field. I'm glad the post was useful!
Jackie
Fascinating! I am not sure what I am seeing here. Does the foot wrap up over the top of the shell, or does the shell just look translucent and fleshy? Thanks, as always, for aharing!
Hi, Marni!
The shell is internal, so not visible when the animal is alive. The shell itself looks like a tiny moon snail shell and is apparently quite fragile (I've only seen pictures of it.) It's the mantle that is covering the shell. The snail can pull its head and foot into the little pocket formed by the mantle on the underside, so the mantle is almost serving like an external shell. It appears that instead of depending on a hard shell for protection, this species has evolved a different strategy depending on the mantle for camouflage.
Jackie
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