This demonstrates what happens when you try to catch up on your science reading; you discover all the neat things that scientists have figured out recently, and this is really the neatest thing about being part of science, there are always new things to learn, figure out, and understand. The previous blog mentioned green sea slugs, a organism introduced to me decades ago by a former colleague who went West. Sea slugs eat algae, harvest the chloroplasts and keep them in body cavities where they continue to photosynthesize providing food to the slug. Now it turns out this symbiosis has been going on so long the slug has acquired enough of the chloroplast genes that it can synthesize chlorophyll! Apparently this replenishes the chlorophyll in the captured chloroplasts so that they can function longer. While chloroplasts used to be independent organisms, they long ago lost some genes to the host cell nucleus that were necessary for synthesizing chlorophyll, which makes the symbiosis permanent, except for green sea slugs. Evolution is pretty nifty because biological weirdness makes no sense otherwise. The other thing to note is that green sea slugs actually look sort of leaf-like, now they almost are; they just need a bit of cellulose.