BY ALPER ÖZKAN (MSN/PhD)
d_ozkan@ug.bilkent.edu.tr
First things first—let me say that those who attempted the contest in my previous column (all three of you) probably had difficulties sending their e-mails to me. This is because I can no longer access the address provided in my last column—it is a remnant from my undergraduate days, and Bilkent thoughtfully deletes these addresses before their unread e-mails reach critical mass and collapse into a technological singularity. So please resend your answers to alper.ozkan@bilkent.edu.tr, which is the address that I now use. Also, you get a bonus question for this week: There are many fish, amphibians, reptiles and insects that give birth to live offspring by retaining their eggs within their bodies until they hatch (if you haven’t yet seen a tsetse fly give birth, you really should). There is also a well-known plant that does something very similar, releasing its progeny as saplings instead of seeds—can you name it?
That was the error. And now for the bell—let’s talk about jellies.
Nature may abhor a vacuum, but it sure loves crabs—in fact, it loves crabs so much that it tries to turn other animals into crabs, a process called carcinisation (this leads to a large proportion of crustaceans being called crabs, despite not being crabs: none of the king crabs, hermit crabs, porcelain crabs and mole crabs, or the coconut crab, are truly crabs, although they are closely related to true crabs—and I think I’ve just used my yearly quota for the word “crabs”). Perhaps the same could be said of jellies—transparent, floating, non-nutritious lumps of goo would seem to be a winning combination in nature, and many distantly related animals adopt this configuration to eke out a living in the depths (their venom helps, too—even the juveniles of certain squid will imitate siphonophores to look dangerous or unpalatable, their disguise enhanced by a long “tail” that resembles a chain of zooids).
One particularly divergent group of jellies are the ctenophores—genome sequencing places these little beasts at the very base of the animal family tree, more distantly related to us than sponges. I’m not so sure that I buy into this just yet, but if true, then, well, evolution sure works in mysterious ways (I could take the “birds diverged from maniraptorans, ergo they are dinosaurs” bit, but I’m still recovering from the shock of the “insects diverged from remipedes, ergo they are crustaceans” discovery). In any case, ctenophores are distinguished by eight rows of cilia that run across their bodies; these bands give the group their name (“comb jellies”), and shine with the colors of the rainbow as the animal swims.
Most are, as usual, vicious predators—where a conventional jellyfish packs a nasty sting, the tentacles of a ctenophore bear a strong adhesive that is no less effective in securing prey (although incapable of producing nematocysts themselves, ctenophores may also gain the capacity to sting after eating true jellyfish, an ability that they share with nudibranchs). Two groups of ctenophores diverge from this state of affairs: lobates have repurposed their tentacles and combs for filter feeding, while beroids have abandoned tentacles altogether to become floating mouths—they feed on other comb jellies, which they either engulf whole into their greatly expanded pharynx or, if their prey is too large or ornery, bite into more manageable chunks with their teeth (also repurposed cilia). I saw quite a few of this latter group during my trip to Samsun, which was good news—the ctenophore Mnemiopsis had pretty much taken over the Black Sea since the 1980s, wreaking havoc on the native fish populations in the process, and attempts were made to control it by introducing beroids into the region (why, the only way to fight invasive ctenophores is with more invasive ctenophores). This seems to have worked, somewhat, as evidenced by the beroid population hanging around on the coast.
Another gelatinous staple of ocean life are the salps, the life cycle of which involves two phases: they are mostly seen as blastozooids, long chains of clonal animals, which exchange gametes along the length of the chain and produce the next stage, the oozoid—which in turn buds off into a new blastozooid chain. This whole process happens extremely rapidly, which allows salps to capitalize on plankton blooms like no other animal can—a salp can grow around 20 percent in length per hour, under the right circumstances (if I ever run a D&D campaign, it’s going to be inside a giant salp that, for reasons unknown, never stopped growing at this pace, and now expands at the speed of light). As you might remember, salps are also tunicates, meaning that they’re fairly close to us—they’re also closely related to pyrosomes, which are the combining super-robot versions of salps (think a few hundred zooids or so, embedded in a roughly Dalek-shaped capsule).
And then there are cnidarians, which include the genuine jellyfish (well, genuine jellyfish and hydrozoans, plus siphonophores, box jellyfish, stalked jellyfish and possibly these bizarre floating anemones, depending on how far you’re willing to stretch the word “jellyfish”). But those will be the topic of the next column.
…And now I’ve finally gotten to make my Lafcadio Hearn pun—I originally intended to do this with the Maya hero twins column, which was titled “Of a Mirror and a Ball,” but I later changed my mind because that legend didn’t really have Tezcatlipoca in it. You are very much recommended to read the original story, which by the way also forms the basis for the Pokemon Bronzor and Bronzong.