Aliens Amongst Us

I was thinking about the biological dogma that cephalisation can only occur
within bilaterally symmetric animals (Bilateria). It seems to me that a bilateral
symmetry would put evolutionary pressure on such animals to evolve
cephalization (and hence eyes/sensors and response cells) because they
are on “rails”, but that the evolution of a rapid, focussed
stimulus-response within a radially symmetric animal would be less
likely, but would still happen, given enough time and stimulus. Therefore *more* bilateria should exhibit cephalisation and developed brains (and in fact that is overwhelmingly true!) but that development of complex environmental processing adaptations analogous to brains could still evolve within Radiata. Of course, the proportion of radially symmetric animals that develop advanced mentation will be less than bilaterally symmetric animals, but it’s still happen. Maybe there *are* massive intelligent medusae on Jupiter?

Then I found the box jellies, Cubozoa. These things are cool. They are a class of “hunting” Cnidaria (jellyfish!) that have evolved complex eyes and rapid, directed locomotion (sometimes lunging up to 6 feet in a second to sting prey).

There’s is a close-up of these multi-eyed predators:

Rhopalium Box Jelly

Here’s the mystery. The box jellies manage to use complex eyes (corneas, lenses, retinas), and directed hunting tactics, yet have no discernable brain or, indeed, a nervous column. They have a ring of nerve cells around their periphery and this seems to be sufficient to build models of their environment.

And along the way, I did find out where Cameron got his idea for the Abyss aliens: the comb jellies, or Ctenophora. They are free-swimming, aggressive predators, with a curiously streamlined radial symmetry:

Red Line Bolinopsid -- 15cm
Red Line Bolinopsid -- 15cm

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.