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Avatar’s Bioluminescence

October 28, 2012

This week for Biology in Science Fiction, my students came up with testable hypothesis for why bioluminescence evolved in the plants and animals of Avatar. Here are some of the more fascinating proposals.

Since the luminescence is activated by touch [Jake shows, while chasing Neytiri back to Hometree], it may be a warning signal. It is possible the plants are poisonous and they light up to warn others away.

Some lab animals may have to take one for the team. First, we must gather some Pandorian herbivores. One group would be presented with normal food as a control. Another group would be presented with bioluminescent plants to eat. If they are scared away by the luminescence, it might be possible to infer that the luminescence is in fact a warning device.

Well, I hope Cameron’s listening for the sequel; perhaps we’ll find out.

But #1 was just one of many diverse ideas. Here are three more:

Bioluminescence increases a plant’s fitness by alerting nocturnal animals to its presence—animals like the fan lizard will feed on bioluminescent plants as a result and, after plant-matter passes through their digestive tract, the plants’ seeds will be dispersed elsewhere.

I propose the hypothesis that luminescent animals are favored because it is a characteristic that helps them attract mates. I predict that this hypothesis will be correct, because luminescence is an impressive trait in organisms that displays health, and I predict organisms will find that attractive in potential mates.

Suppose the luminescence in pandoran creatures is caused by bacteria or some other  microorganism that forms a mutualisic  relationship with its host. The bacteria release light, but the light is only visible when a large colony of the light producing microorganism are gathered together. The chemical reaction that produces the light may be a way that the microorganisms communicate with each other.

The 4th is my favorite, for obvious reasons.
Readers, what do you think? Can you come up with more?

  1. Alex Tolley permalink
    October 28, 2012 9:08 pm

    Or maybe the bioluminescence is used by the host organism to communicate.
    Or maybe the bioluminescence is just a byproduct of toxic bacteria, that the animal uses to signal that they have good genes to prospective mates.
    Or maybe the Pandoreans are the result of ancient biotech that had GFPs inserted for aesthetic or research reasons.
    Or maybe it isn’t bioluminescence, but some sort of phosphorescence, the intensity managed by occlusion.

  2. October 28, 2012 9:42 pm

    Pandora is rather obviously an engineered ecosystem; that’s clear from the way the Na’vi are able to plug in to other species to control them. I suspect that the actual civilization are a bunch of uploads living in a giant network spread through the soil and occasionally surfacing interface points with those big Trees of Souls, and the embodied Na’vi are the few holdouts who would rather be living as hunter-gatherers in the physical world rather than being part of the information environment.

    So when theorizing about Pandora, we only need to worry about “how does it function?” rather than “how could it have possibly developed that way?” So very likely, the bioluminescence is part of the signaling in the planetary ecosystem maintenance.

    (In my opinion, the obvious sequel to Avatar is where Jake points out that kicking the company off the planet isn’t going to stop them from coming back with a few big light-sails to freeze out the atmosphere and kill all life on the planet so they can mine unobtainium without interruptions, so the elders make him go to a Tree of Souls and explain this to the uploaded civilization. The planet then grows a bunch of biotech seeder starships that the Na’vi hop into and fly to Earth to fix the wrecked biosphere there…)

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