This morning I was doing some routine cleaning of animal-containing dishes at the marine lab when I noticed a little blob of snot on the outside of the bowl I was working on. Normally I just wipe off blobs like that, but something about this one caught my attention in a different way and I paused to take a closer look at it. What I saw made me glad I hadn't given it the old Kim-Wipe™ treatment.
It was this:
This little 3mm blob of cuteness is the tiniest Melibe I've ever seen. Melibe is one of my favorite creatures of all time. It's an entertaining animal that has unfathomable amounts of charm. Unlike most other nudibranchs, which prey on other animals (typically cnidarians, sponges, or bryozoans), Melibe is a filter feeder. It sweeps its large oral hood, visible to the right, through the water to capture plankton. The flat large-ish structures projecting from the animal's back like wings are cerata, of which there will eventually 4-5 pairs when the slug reaches adult size. The cerata function as gas exchange surfaces; they also contain extensions of the digestive system. When a Melibe is mishandled or stressed, it drops cerata, which can then be regenerated.
Melibe is the most animated of slugs. I dropped a few brine shrimp nauplii on this little guy to see if it would be able to catch them. Unfortunately it looked more like the nauplii were ganging up on the Melibe than the other way around. However, I know from experience that even larger Melibe take a while to figure out how to eat brine shrimp.
But isn't that the cutest slug you've ever seen? It has tiny bright blue dots on its body! Those two little flaps on the top surface of the oral hood are rhinophores. I know they look like ears, but they are chemosensory rather than auditory organs.
And look how fast this little nudibranch can crawl! Remember, it's only 3mm long, and it's making pretty good progress getting to the corner of the bowl.
When dislodged from whatever it's crawling on, Melibe can swim. I thought this one would attach itself to the underside of the surface tension, as they often do, but it thrashed for quite a while before sort of accidentally finding the bottom of the dish again.
And do you know what the best thing about Melibe is? It smells like watermelon. I kid you not. If you touch a Melibe, your finger will smell like watermelon Jolly Ranchers. How could an animal possibly be any cooler than that?