I watched a video of my colleagues at FreethoughtBlogs, Matt Herron of Fierce Roller and PZ Myers of Tentacly Overlord infamy, discussing some very cool science-y stuff about the evolution of multicellularity. One of the most interesting takeaways for me is that it had long been thought that evolving multicellularity would be an exceedingly rare and difficult jump to make. But it has been discovered, only in the last five to ten years, that this is actually relatively easy and common:
Matt (@3:51): I think there’s been sort of a natural assumption that it has to be difficult. And maybe it is difficult to evolve a complex multicellular organism, with lots and lots of cell types and tissues and maybe even organs, because that hasn’t happened very many times. But Rick Grossberg has a paper where he argues basically what we’ve found, which is that at least the initial steps towards a multicellular lifestyle really aren’t that difficult. It’s happened lots of times that we know of, at least a couple of dozen times, and probably more because in a lot of cases these things don’t leave any fossil record. It is surprising, compared to what people thought five or ten years ago, that multicellularity evolves so easily, but now we’ve seen it in several of these experiments. And in a lot of cases it happens within just a few hundred generations.
OMG cool, right?
Then they touch on the intersection of philosophy and biology, and specifically the question of what exactly constitutes an individual organism, as opposed to, say, a colony of creatures that appear to function as one. I don’t know about you, but this kind of stuff really gets my beanie spinning. I am reminded of my unfortunate encounter with a species known as Physalia physalis, a.k.a. the “floating terror,” a.k.a. the Atlantic Portuguese man o’ war, which I would henceforth (and forevermore) refer to as a “sea squirrel.” Despite its similarity in appearance to the common jellyfish—an individual multicellular organism that will also sting the everloving shit out of you if given a chance—it turns out that the Sea Squirrel™ is actually something very different:
[T]he Portuguese man o’ war is not a jellyfish but a siphonophore, which, unlike jellyfish, is not actually a single multicellular organism, but a colonial organism made up of specialized individual animals called zooids or polyps. These polyps are attached to one another and physiologically integrated to the extent that they are unable to survive independently, and therefore have to work together and function like a so-called individual animal.
These weird little fuckers are carnivorous, wielding their wickedly venomous tentacles to paralyze prey (e.g. small fish), and to inflict upon barefoot beachwalkers excruciating pain even after they are long dead (the sea squirrels, not the beachwalkers).
Detached tentacles and dead specimens (including those that wash up on shore) can sting just as painfully as the live organism in the water and may remain potent for hours or even days after the death of the organism or the detachment of the tentacle.
And I would be remiss if I did not mention an interesting cephalopod angle here. Blanket octopuses are immune to sea squirrel venom, which is an amazing enough trick to evolve. But these cephalopods go waaaaaay beyond that: they rip the venomous tentacles right off of those critters (hopefully while mocking them mercilessly), and then they carry the tentacles around with them to wield as weapons for defensive (and possibly offensive) purposes. Now that is some serious next level shit, blanket octopuses! I mean, can you just picture that? Because I sure can!
Octopus Wielding Sea Squirrel™ Tentacles Against Douchefish.
©Iris Vander Pluym
8′ x 11′
(oil on canvas)
But! I digress. As beanie-spinning as all of this clearly is (as evidenced by the foregoing blather), it has absolutely nothing to do with the subject of this post. Continue reading