Tuesday, July 5, 2011
Swimming with Salps
At the Jersey Shore again today and when I plunge into the water I find myself in good company. Well, it's company anyways. There are swarms of small gelatinous creatures crowding the water. They are not jellies, but salps: a planktonic tunicate.
Tunicates are interesting in that they are in the phylum Chordata, and yet they don't have a backbone. As a biology teacher I had the interesting job of trying to clear up the misconception that all chordates have backbones. Technically a chordate simply has the following four characteristics at least at some point in their life:
1) a notochord
2) a hollow dorsal nerve cord
3) pharyngeal slits
4) a post-anal tail
At least this is what I was taught in school. In biology classification is an evolving field (pun intended) that is constantly causing us to shift how we categorize living things.
At any rate, as I scooped up my slimy companions from the water and studied them, I honestly couldn't discern any of the above structures. Of course these creatures are very small and transparent, and the features could have been present at a different stage in life, so who am I to judge. I suppose they are chordates, I'll have to take the word of the scientists out there who make these decisions.
I would really like to learn more about these little creatures. I know they are here because the pickings are good. Being planktonic they don't have a whole lot of say in where they go, but when there is lots of yummy phytoplankton around the salps go into asexual reproduction mode, consuming and budding off quickly to make lots of clones to profit from this feast. I guess the phytoplankton must be particularly abundant off the shore where I am staying right now for there to be so many salps.
Is the number of salp invasions increasing in frequency? I don't remember seeing salps a lot (or ever) as a kid, but now I seem to encounter them a lot. Any marine scientists out there able to speak to this? I better check the literature on salps. Is this an effect of global warming? Or pollution such as sewage or fertilizer run off in the oceans?
At any rate, the salps are harmless. Many swimmers find them a nuisance and complain, but I have to hand it to these tunicates, they are remarkably good at doing what they do. I try to think of them as little jelly gems in the ocean, and swim peacefully among them. After-all they do no harm, and these distant choradate relatives were probably on this Earth well before us cephalized bipedal primates decided to plan vacations along marine ecosystems that remind us of our evolutionary ancestral roots.