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Lately I've been slowly making my way though "How the Leopard changed its spots" by Brian Goodwin. It's an anti-reductionist book, showing how organisms cannot be reduced to mere containers of their genes (pace Dawkins). Interesting but rather dense, I've been reading it a few pages at a time.

The point of this post, however, is one of the really neat organisms that Goodwin picks as an example:

Meet Acetabularia acetabulum, a species of sexually reproducing single celled algae found in the Mediterranean.

That's right, single celled, sexually reproductive -- each of those little parasols is a single cell, consisting of a "root" base that attaches to the rock, a stalk 3 to 5 centimeters long, and a parasol about half a centimeter in diameter. The parasol is the reproductive part, which releases hundreds of flagellum-bearing haploid gametes. A patch of Acetabularia will release their gametes all at once; when two gametes meet up in the water, they fuse into a diploid zygote, attach to a rock, and grow a new stalk and parasol.

It turns out A. Acetabulum is not the biggest species of acetabularia; A. major, found in the waters around Hawaii, grows 10 centimeters long.

Acetabularia have been around for almost 500 million years, but today they're not very common because multicellular seaweed is able to outcompete them in most marine habitats. That's because a good designer would never have tried to make a macroscopic, 5 or 10 centimeter long plant out of a single celled organism. Fortunately for lovers of the unusual and wonderful, life on earth was not designed but rather evolved, scattershot and happenstance, with half-assed rube goldberg designs like panda's thumbs and giant single celled algae.

In closing, another picture:

These acetabularia are growing in an aquarium. They look greener because the water is softer; they're whitish in the first picture due to calcium buildup.


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October 2017


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