One Variety of Sea Slugs Cuts Out the Energy Middleman

dragonturtle69 writes with this story, short on details but interesting: "These sea slugs, Elysia chlorotica, have evolved the ability to gain energy via photosynthesis. Forget about genetic modifications for sports enhancements. I want to be able to never need to eat again — or do I?"

Comments

eating

[mcgrew]

I want to be able to never need to eat again -- or do I?

I'l like the ability to never HAVE to eat again, but I wouldn't want to lose the ability to eat at all. Eating is enjoyable. One would hope that you could control the photosynthesis to keep from getting too fat, though.

Re:eating

[Attila Dimedici]

Yeah, but how would this help? Instead of eating you would have to go out into the sun (you know, that big, bright, yellowish thing on the eastern horizon when you go to bed).

Re:eating

[characterZer0]

whoosh.

The sun rises on the eastern horizon just as you are going to bed after sitting at your computer all night.

Re:eating

[confused one]

Slugs aren't very energetic. It's doubtful that photosynthesis alone will provide the energy necessary to power your body and that meat based computer in your head. You would still need to ingest a fair amount of food, in order to extract the concentrated energy contained in it.

Re:eating

[clone53421]

New rule: You’re only allowed to intentionally miss the point of a joke if the joke you’re making is funnier than the one you’re ignoring.

Re:eating

[sarahbau]

I just did a few quick calculations. Assuming humans have 2 square meters of skin, and stood naked in direct sunlight in the best conditions for 8 hours per day, and assuming 5% efficiency for photosynthesis, we would only get enough energy to provide for 11 hours of sleep (250 BTU/hr), 7 hours of sitting still (400 BTU), 4 hours of light work (650 BTU) or 1 hour of heavy work (2400 BTU). We'd still probably need to consume 2/3 or so of our normal caloric intake from food.

Sources:
http://www.solarexpert.com/Heat-theory.html
http://hypertextbook.com/facts/2001/IgorFridman.shtml
http://www.answerbag.com/q_view/514275
http://www.ccmr.cornell.edu/education/ask/index.html?quid=1021

Re:eating

[Kompressor]

Perhaps the GP planned to unzip his skin down the back, peel it forward, and present his entire "surface area" to the sun?

** shudder **

Re:eating

[mea37]

The point I think you (and GP, and the submitter, and many others) are missing is, photosynthesis does not remove the need to eat. Energy isn't the only thing you get from food. If you had vitamin pills so effective that you could live on them, plus sugar, plus water - and nothing else - then you could replace the sugar with the ability to perform photosynthesis. Such pills do not exist.

In case you're wondering, plants do indeed "eat". That's why they need roots in fertile soil.

I want the reverse.

[jeffb (2.718)]

I want to be able to consume as many extra calories as I like, and then radiate the excess as visible light, with radiant area, spectrum and direction under my conscious control.

Or, at least, I'd like to be able to metabolize my food and store excess energy as electric charge, easily transferred to whatever devices are handy.

Re:I want the reverse.

[ArsonSmith]

This would be awesome. having a + and - poll could give men's nipples a purpose.

Re:I want the reverse.

[Kratisto]

If you can make that light coherent and focused, you can be some sort of super hero. Laser Pointer Assisted Presentation Man! Is it a CEO? Is it a college professor? No! It's Laser Pointer Man! Boring wrongdoers into soporific oblivion at the speed of light! Taunting cats in his free time...

Re:Nitpick

[kmcarr]

No, the statement is essentially correct. The slugs harvest (i.e. gain) energy via trapping photons with chlorophyll. They store that energy as chemical bonds in sugar molecules. They then release the energy as needed by metabolizing the sugar. Photosynthesis is the coupled capturing and storing of energy so saying that it "gains" energy via photosynthesis is a reasonable simplification.

Sea Slugs and nematocysts

[Guppy]

Some species of Sea Slugs have another similar interesting ability -- to adsorb and host nematocysts (stinging cells) from jellyfish and hydrozoans they've eaten, and use them for their own defense. The mechanism is substantially different (foreign cells are sequestered in specialized sacs, compared to the intracellular hosting of an organelle) though.

http://en.wikipedia.org/wiki/Glaucus_atlanticus

Re:Exactly, eating like a plant

[clone53421]

I’d say, “hi, did you realise that you’re standing in the toilet?”

Re:been a while since bio class

[reverseengineer]

Chloroplasts, just as with mitochondria, have a small DNA genome of their own. Due to the endosymbiotic relationship that has formed between chloroplasts and their photosynthetic hosts, chloroplasts have found it convenient to offload the majority of their genes to the nucleus. It is estimated that about 90% of the genes necessary for photosynthesis are nuclear, with the rest in chloroplasts, so these sea slugs appear to have acquired the nuclear genes, but not the chloroplast genes.

Chlorophyll itself is made in the cytoplasm, and actually requires relatively few new genes for an animal to be able to produce it, since the complicated steps of its biosynthesis are identical to the heme structures it is already able to make. The real difficulty, and one that this sea slug seems to have been able to surmount according to the Wikipedia page, is the production of the "oxygen-evolving complex," a metalloenzyme with a manganese-calcium core which transfers absorbed energy to a bound water molecule to break it into electrons, protons, and molecular oxygen. Heterotrophic organisms don't produce anything like it.