Would a 9 lb sapient spider producing 1/10 lb of silk a day suspend your disbelief?

[teviet]

Originally Posted by Ze'Manel Cunha

They cite 14,000 spiders to make 1 ounce of silk, or about 0.00007 oz per spider per day.

These golden orb spiders weigh maybe around 0.035 ounces, or about .002 of silk per ounce of spider.

You're scaling them up about 4,000 times to get to 9 lbs, so you should be ok with about an 8 oz max in a day for a 9 lbs spider.

No, that's 0.002oz silk per oz of spider, not per each 0.035oz spider. So a 9-pound spider is only a factor of 144 scale-up, giving us about 0.3oz of silk from the 9lb spider.

Originally Posted by Ze'Manel Cunha

Mind you, if you do milk the spider for all the silk it's worth you may need to give it time to replenish itself before milking it completely again.

http://www.wired.com/wiredscience/2009/09/spider-silk/
http://www.amnh.org/exhibitions/spidersilk/

The article said they could be re-milked every week, so divide everything by 7 to get a daily rate. The 9lb spider could produce 0.04oz of silk per day, or about 1/500 of a pound per day.

Spiders can spin silk at a much higher rate each day as they build their webs, but I think they usually eat their webs when they dismantle them so as to reuse the protein. Actually synthesizing the silk protein goes much slower.

TeV

[Johnny1A.2]

Better consider the oxygen factor, too. I'm not sure a 9-lbs spider could even get enough oxygen to function in our current atmosphere, and if its neural tissue is anything like mammalian neural tissue, a sapient spider is going to have a substantial oxygen demand to power whatever it uses for a brain, too.

(There were 'giant insects' and similar in the Carboniferous, but there is reason to to believe that global oxygen levels were substantially higher than today during that Period, as well.)

[Anthony]

Originally Posted by Johnny1A.2

Better consider the oxygen factor, too. I'm not sure a 9-lbs spider could even get enough oxygen to function in our current atmosphere.

Well, based on the crab it probably can, at least at the metabolic rate of a crab. Not much chance of being sapient at that metabolic rate, though (at least one order of magnitude too low, probably two).

[Flyndaran]

I should have written spider like creature. Of course it couldn't be just a scaled up version.
At the TL3 they live, if it looked like a spider that's what they would get called regardless of how far removed they may be genetically. Eight legged, silk producing, fanged, shelled critters would get the moniker whether they liked it or not.

[vierasmarius]

Originally Posted by Flyndaran

I should have written spider like creature. Of course it couldn't be just a scaled up version.
At the TL3 they live, if it looked like a spider that's what they would get called regardless of how far removed they may be genetically. Eight legged, silk producing, fanged, shelled critters would get the moniker whether they liked it or not.

I think the "shelled" part is what stretches it. That implies an exoskeleton instead of an internal skeleton, which severely limits their size under Earth's current conditions. Now, perhaps they are an aardvark-like animal with a bony shell but also a spine and internal structural support... that might increase their potential size.

[blacksmith]

Originally Posted by Johnny1A.2

Better consider the oxygen factor, too. I'm not sure a 9-lbs spider could even get enough oxygen to function in our current atmosphere, and if its neural tissue is anything like mammalian neural tissue, a sapient spider is going to have a substantial oxygen demand to power whatever it uses for a brain, too.

(There were 'giant insects' and similar in the Carboniferous, but there is reason to to believe that global oxygen levels were substantially higher than today during that Period, as well.)

Well it could have a better respiratory system and still say visually spider to people. They don't have anything like the nervous system needed to sentience either so why doesn't that bug you?

[blacksmith]

Originally Posted by vierasmarius

I think the "shelled" part is what stretches it. That implies an exoskeleton instead of an internal skeleton, which severely limits their size under Earth's current conditions. Now, perhaps they are an aardvark-like animal with a bony shell but also a spine and internal structural support... that might increase their potential size.

See the Carboniferous for big freaking bugs. The size mentioned is not a structural limit.

[Bruno]

Originally Posted by vierasmarius

I think the "shelled" part is what stretches it. That implies an exoskeleton instead of an internal skeleton, which severely limits their size under Earth's current conditions. Now, perhaps they are an aardvark-like animal with a bony shell but also a spine and internal structural support... that might increase their potential size.

As previously mentioned, coconut crabs, which actually have more primitive lungs than spiders do, get significantly larger, live entirely on line in adulthood (and will actually drown) and are fairly lively: climbing trees, tearing apart garbage cans, and yes, cracking coconuts.

And they are exoskeletal. Current Earth conditions have no more gravity than the conditions under which we supported nine foot long milipedes - the oxygen is less, but unsurprisingly the larger or more active arthropods have evolved better respiration in the past billion years in response to the reduction in oxygen. Many small arthropods still have very very primitive respiration, but for example tarantulas have quite good "book lungs" instead of spiracles.

[malloyd]

Another way to look at it, silk is energeticallly in the same general range as making new tissue. So you are looking at something that is effectively about the same as regenerating 1% of its body mass per day. That doesn't sound totally ridiculous, but is going to have a pretty substantial energy cost. It also must get the raw materials from somewhere, so it has to eat an extra 1/10 lb of protiens, over and above whatever it would normally need to live, in order to do that. Normally I'd expect an active 9 lb animal's basic metabolism to run at about 300 Calories, at about 4 Calories per gram for most protiens, the raw materials it needs to sustain this silk production add about the equivalent of another 180 Cal - over a third of its diet (of around 1/2 lb of meat per day) going into silk production may be *unlikely*, particularly for an evolved animal that's also using a bunch of extra energy for its brain, but isn't *totally* ridiculous, certainly no more than fitting enough processing power for sapience into something as small as 9 lbs.

Still, it's probably worth asking yourself what could the wild spiders possibly be using that much silk per day for which is so vital to their survival that evolution wouldn't have done something about that huge energy drain.

[LemmingLord]

Originally Posted by Flyndaran

I'm creating a non-physics violating species of sapient spider-like creatures.
But I can't for the life of me find out how much silk a spider produces let alone as a function of body mass.
So as a number pulled out of my spinnerets, does 1/10 lb for maximum output seem reasonable? Or would you say only 1/100 lb per day, etc.?

What do you mean - an African or European sapient spider-like creature?