Thursday, October 04, 2018

The Wonders of Jellyfish

If possible, pick up a copy of the October NATIONAL GEOGRAPHIC and contemplate the dazzling photos in the article on jellyfish. Typical jellyfish (not all of which are related to each other; the general name is popularly applied to different groups of creatures) have a complicated life cycle. The adult stage, the parachute-like shape with tentacles that we're most familiar with, is called a medusa. Medusae reproduce sexually, releasing eggs and sperm into the water. The larval stage, known as planula, anchors itself on a rock or the sea bottom, where it becomes a polyp. Polyps reproduce asexually, budding off multiple clones called ephyra, which grow into new medusae.

The highly toxic Portuguese man-of-war illustrates a transitional phase between a colony of separate organisms and their union into a larger, more complex creature. What looks like an individual is "technically a colony that developed from the same embryo."

The oral arms—the tendrils that sweep food into the mouth—of some jellyfish have mouths on the streamers themselves, a feature that sounds like a model for a Lovecraftian eldritch monster.

One species has a unique, almost unbelievable ability to revert to the polyp stage and start life over when confronted by environmental stress such as near-starvation or severe injury, sort of like reincarnation. By producing clones of itself that become medusae, which in turn transform back into polyps, and repeating the cycle, it effectively never dies (at least from "natural causes") or grows old.

The Immortal Jellyfish

Understanding this process of "cell recycling," called "transdifferentiation," could make a vital contribution to stem cell research.

If an intelligent species with an alternating sexual-asexual and mobile-stationary life cycle existed on some alien planet, it would surely have a social structure very different from ours, especially if it followed the jellyfish pattern of producing myriads of offspring with every instance of sexual reproduction. Of course, such alien sapient beings couldn't be jellyfish as we know them, which have no brains. It's also hard to imagine an r-selected species, one that engenders huge numbers of fast-maturing young in hopes that some may survive, evolving intelligence. It wouldn't have the long childhood and parental care that we assume to be essential to intelligence as we know it. What about intelligence not-as-we-know-it, though? Could animals similar to jellyfish, given some sort of neural network, develop a hive mind? After all, in one phase of their life cycle, they're clones, so they might conceivably have a shared consciousness. Genetically identical "immortal jellyfish" have been discovered in widely scattered parts of the Earth. Might similar organisms on another planet belong to a worldwide group mind? If so, what would they think of us as solitary individuals?

Margaret L. Carter

Carter's Crypt

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