Clannish coral:
Coral is once more in the news.  (Coral in Love, Rebecca Coffey SCIENTIFIC AMERICAN vol. 304 no. 5 May 20ll page 18)  Usually new news is bad.  They are threatened by ocean acidification.  That means the increased CO2 in the atmosphere is combining with water in the ocean to produce carbonic acid, which is a weak acid, but it depletes bicarb and slowly shifts the ocean’s acid base balance.  The result is things that depend on a hard exoskeleton, like coral, loose their shells.  You don’t hear as much about it as about the greenhouse effect.  Maybe that’s because they think we can spell greenhouse.

The news is that they have found the signal that synchronizes the release of eggs and sperm into the ocean.  It has something to do with the color of the light at sunset on the full moon.  At the right moment the whole reef will have a party.  The gametes combine and, assuming the environment hasn’t been too badly trashed, little corals will be on the way.

The thing they do not make much of is the fact that different reefs will choose different night for the mating call.  That mechanism thus is population specific.

It also serves a purpose that the researchers don’t even guess at.  If different reefs mate on different days, then there is a greatly reduced chance of eggs and sperm from different micro populations getting mixed with the inevitable reduction in fertility that this would entail. 

This principle gets into everything.

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