# Today, a Sea Slug. Tomorrow, ... ? *The Urth list — 6 messages, 3 voices, 18 Jan 2010* > Exported from an unofficial mirror of a public mailing list. Copyright > in each message remains with the person who wrote it. > Email addresses are obscured as `user at host`, the form the original > archive published. This file was rebuilt from parsed fields rather than > retained headers, so it is faithful in content but not byte-exact. --- ### David Stockhoff *18 Jan 2010, 00:48* Severian's friend the Green Man always seemed quite plausible to me. I hadn't realized just how plausible. Apparently a sea slug has incorporate algae genes into its genome and produces and uses chlorophyll inside its body: http://www.sciencenews.org/view/generic/id/53496/title/Sea_slug_steals_genes_for_greens,_makes_chlorophyll_like_a_plan --- ### Jeff Wilson *18 Jan 2010, 02:44 · in reply to David Stockhoff* > Severian's friend the Green Man always seemed quite plausible to me. I > hadn't realized just how plausible. Apparently a sea slug has > incorporate algae genes into its genome and produces and uses > chlorophyll inside its body: > > http://www.sciencenews.org/view/generic/id/53496/title/Sea_slug_steals_genes_for_greens,_makes_chlorophyll_like_a_plan There's still a question of him being able to intercept enough sunlight to be more active than a slug. A man-sized silhouette in Earthly conditions intercepts less than 100 calories worth of sunlight a day. From the Green Man's sunny smile, his people apparently still have humanlike teeth, so presumably they can eat a variety of food to make up the deficit, but I'm not sure if reducing your food needs by 1/30 is worth the hassle. It might be that the chlorophyll isn't strictly for food, but for sensory purposes; can anyone think of an occasion when the Green Man would need to be able to feel a shadow falling on him, or would have to distinguish between bright lights of different character? --- ### Jerry Friedman *18 Jan 2010, 04:14 · in reply to Jeff Wilson* >> --- On Sun, 1/17/10, Jeff Wilson wrote: >> Severian's friend the Green Man >> always seemed quite plausible to me. I >> hadn't realized just how plausible. Apparently a sea >> slug has >> incorporate algae genes into its genome and produces >> and uses >> chlorophyll inside its body: >> >> http://www.sciencenews.org/view/generic/id/53496/title/Sea_slug_steals_genes_for_greens,_makes_chlorophyll_like_a_plan That's pretty amazing, if it's confirmed. > There's still a question of him being able to intercept > enough sunlight to > be more active than a slug. A man-sized silhouette in > Earthly conditions > intercepts less than 100 calories worth of sunlight a day. Is that with perfect efficiency? Gosh, are you seriously telling me to do the calculation? Half a square meter in sunbathing position, 1 kilowatt, 8 hours, that's 14,400 kJ or about 3400 big calories. You're assuming something like present photosynthetic efficiency. > From the Green > Man's sunny smile, his people apparently still have > humanlike teeth, so > presumably they can eat a variety of food to make up the > deficit, but I'm > not sure if reducing your food needs by 1/30 is worth the > hassle. The sun could be brighter in his time than ours, and genetic engineering could have improved the efficiency of photosynthesis and that of metabolism. > It might be that the chlorophyll isn't strictly for food, > but for sensory > purposes; can anyone think of an occasion when the Green > Man would need to > be able to feel a shadow falling on him, or would have to > distinguish > between bright lights of different character? I can't We do fine with vision. Though human color vision is rather klugy, I gather, and those same genetic engineers could probably improve it without any cost by making it more like birds'. Jerry Friedman --- ### Jeff Wilson *28 Jan 2010, 07:43 · in reply to Jerry Friedman* > On 1/17/2010 10:14 PM, Jerry Friedman wrote: > --- On Sun, 1/17/10, Jeff Wilson wrote: >>> Severian's friend the Green Man >>> always seemed quite plausible to me. I >>> hadn't realized just how plausible. Apparently a sea >>> slug has >>> incorporate algae genes into its genome and produces >>> and uses >>> chlorophyll inside its body: >>> >>> http://www.sciencenews.org/view/generic/id/53496/title/Sea_slug_steals_genes_for_greens,_makes_chlorophyll_like_a_plan > That's pretty amazing, if it's confirmed. Did you see the thing last year? A predator microbe that becomes photosynthetic if it eats this other microbe, then fissions into the original separate microbes again? >> There's still a question of him being able to intercept >> enough sunlight to >> be more active than a slug. A man-sized silhouette in >> Earthly conditions >> intercepts less than 100 calories worth of sunlight a day. > Is that with perfect efficiency? Gosh, are you seriously > telling me to do the calculation? Half a square meter in > sunbathing position, 1 kilowatt, 8 hours, that's 14,400 > kJ or about 3400 big calories. You're assuming something > like present photosynthetic efficiency. He said it was pond scum, so I presume it was something vaguely like pond scum. >> From the Green >> Man's sunny smile, his people apparently still have >> humanlike teeth, so >> presumably they can eat a variety of food to make up the >> deficit, but I'm >> not sure if reducing your food needs by 1/30 is worth the >> hassle. > The sun could be brighter in his time than ours, and genetic > engineering could have improved the efficiency of > photosynthesis and that of metabolism. maybe, but 30x as efficient? ``` Jeff Wilson - jwilson at io.com IEEE Student Chapter Blog at < http://ieeetamut.org > ``` --- ### Jerry Friedman *29 Jan 2010, 01:52 · in reply to Jeff Wilson* > --- On Thu, 1/28/10, Jeff Wilson wrote: > On 1/17/2010 10:14 PM, Jerry Friedman > wrote: >> --- On Sun, 1/17/10, Jeff Wilson? > wrote: >>>> Severian's friend the Green Man >>>> always seemed quite plausible to me. I >>>> hadn't realized just how plausible. Apparently >>>> a sea slug has >>>> incorporate algae genes into its genome and >>>> produces and uses >>>> chlorophyll inside its body: >>>> >>>> http://www.sciencenews.org/view/generic/id/53496/title/Sea_slug_steals_genes_for_greens,_makes_chlorophyll_like_a_plan >> That's pretty amazing, if it's confirmed. > Did you see the thing last year? A predator microbe that > becomes > photosynthetic if it eats this other microbe, then fissions > into the original separate microbes again? Missed that one. >>> There's still a question of him being able to >>> intercept enough sunlight to >>> be more active than a slug. A man-sized silhouette >>> in Earthly conditions >>> intercepts less than 100 calories worth of >>> sunlight a day. >> Is that with perfect efficiency? Gosh, are you >> seriously >> telling me to do the calculation? Half a square >> meter in >> sunbathing position, 1 kilowatt, 8 hours, that's >> 14,400 >> kJ or about 3400 big calories. You're assuming >> something >> like present photosynthetic efficiency. > He said it was pond scum, so I presume it was something > vaguely like pond scum. Sure. I just wanted to know what you were presuming. >>> ? From the Green >>> Man's sunny smile, his people apparently still >>> have humanlike teeth, so >>> presumably they can eat a variety of food to make >>> up the deficit, but I'm >>> not sure if reducing your food needs by 1/30 is >>> worth the hassle. >> The sun could be brighter in his time than ours, and >> genetic >> engineering could have improved the efficiency of >> photosynthesis and that of metabolism. > maybe, but 30x as efficient? As you said, he probably still needs to eat. If between more sunlight and more efficient photosynthesis and metabolism he gets ten times as much as we would, it would reduce his need for food by about 1/3, which seems worth some hassle. Jerry Friedman --- ### David Stockhoff *29 Jan 2010, 23:22 · follows Jerry Friedman* Furthermore, if those calculations are based on American calorie intake, you could cut the Green Man's food energy needs by up to 50% just by changing that assumption to a level more typical of the rest of humanity. > ------------------------------ > > Message: 4 > Date: Thu, 28 Jan 2010 17:52:02 -0800 (PST) > From: Jerry Friedman > To: The Urth Mailing List > Subject: Re: (urth) Today, a Sea Slug. Tomorrow, ... — > Message-ID: <378986.85096.qm at web50706.mail.re2.yahoo.com> > Content-Type: text/plain; charset=iso-8859-1 > > --- On Thu, 1/28/10, Jeff Wilson wrote: > > On 1/17/2010 10:14 PM, Jerry Friedman > wrote: > >> --- On Sun, 1/17/10, Jeff Wilson? >> > wrote: > >>>> Severian's friend the Green Man >>>> >>> always seemed quite plausible to me. I >>> >>>> hadn't realized just how plausible. Apparently >>>> > a sea slug has > >>>> incorporate algae genes into its genome and >>>> > produces and uses > >>>> chlorophyll inside its body: >>>> >>>> http://www.sciencenews.org/view/generic/id/53496/title/Sea_slug_steals_genes_for_greens,_makes_chlorophyll_like_a_plan >>>> >> That's pretty amazing, if it's confirmed. >> > Did you see the thing last year? A predator microbe that > becomes > photosynthetic if it eats this other microbe, then fissions > into the original separate microbes again? > > > Missed that one. >>> There's still a question of him being able to >>> > intercept enough sunlight to > >>> be more active than a slug. A man-sized silhouette >>> > in Earthly conditions > >>> intercepts less than 100 calories worth of >>> > sunlight a day. > >> Is that with perfect efficiency? Gosh, are you >> > seriously > >> telling me to do the calculation? Half a square >> > meter in > >> sunbathing position, 1 kilowatt, 8 hours, that's >> > 14,400 > >> kJ or about 3400 big calories. You're assuming >> > something > >> like present photosynthetic efficiency. >> > He said it was pond scum, so I presume it was something > vaguely like pond scum. > > > Sure. I just wanted to know what you were presuming. >>> ? From the Green >>> Man's sunny smile, his people apparently still >>> > have humanlike teeth, so > >>> presumably they can eat a variety of food to make >>> > up the deficit, but I'm > >>> not sure if reducing your food needs by 1/30 is >>> > worth the hassle. > >> The sun could be brighter in his time than ours, and >> > genetic > >> engineering could have improved the efficiency of >> photosynthesis and that of metabolism. >> > maybe, but 30x as efficient? > > > As you said, he probably still needs to eat. If between > more sunlight and more efficient photosynthesis and > metabolism he gets ten times as much as we would, it > would reduce his need for food by about 1/3, which seems > worth some hassle. > > Jerry Friedman > > > > > > ------------------------------ ---