In yesterday's post, I provided a brief overview of how the process of digestion works in Terran animals. There are so many different ways of digesting food that it's hard to think of ways to improve the process--or at least provide useful alternatives. I've come up with a couple of ideas, though some of them may be twists on what some animals already do.
WARNING: Although I'm not trying to be gross, this post isn't for the squeamish.
OK, now that that's out of the way, here are my ideas, along with thoughts on how they might actually work in a real fictional creature:
Internal Cooking--If humans cook food before we eat it, perhaps other species, either aliens or fantasy creatures, might do the same. Of course, fire-breathing dragons could do this, but my idea is to have a stomach with a temperature higher than the rest of the body. It couldn't be too much higher (a 350ºF oven in a 98.6ºF body would cook the rest of the body, unless there was some excellent thermal insulation), but a stomach just a few degrees warmer might help break down the food. More importantly, enzymes are generally more active at higher temperatures, though they they tend to be less stable. Perhaps the stomach could also act as an internal heat source, warming the rest of the body.
How could an animal or alien have a stomach warmer than the rest of the body? The way I see it, the stomach would have to have a high concentration of energy-producing cells/tissue. Perhaps these cells would have high concentrations of mitochondria, organelles that produce energy by breaking certain chemical bonds. Alternatively, the stomach muscles could be designed in such a way to give off excess heat.
A Series of Stomachs/Different Solvents--Eric's original suggestion to me was to talk about how several stomachs, like in cows, might work in aliens. Cows have four stomachs with different functions; two are devoted to forming the cud and breaking down fibers, one is devoted to absorbing water and minerals, and the final one is where proteins are broken down (similar to our own stomach). Perhaps in aliens with several stomachs, this specialization could be extended. Perhaps each stomach could be at a slightly different pH and have different enzymes, so each stomach digests a different type of food. Or instead of just mixing the food with water (or strong acid, as in our stomachs), one stomach might be more saline, another might have an oil-water emulsion, and so on.
Pre-Digestion--Some animals, such as spiders, inject their digestive enzymes into their food before they actually eat it. What if aliens had other methods of pre-digesting their food? Maybe they would domesticate animals that could predigest food and then milk it out (or use harsher methods) to get their "soup." Let's imagine an alien race that had done this for so long their digestive system had atrophied. Perhaps instead of a stomach, all they may have left are the intestines for absorbing micronutrients. What would be the advantage of this? One idea that I came up with is allowing more room for other organs or perhaps reducing the alien's weight to make it easier for it to fly. The alien wouldn't have to spend energy on digesting food and could divert it to other activities. The downside is that I think aliens with such limited digestive systems might be more prone to starvation if they're separated from their traditional food supply.
If you were going to design an alien race, what kind of foods would it eat, and how would it digest them? What would you do for really exotic aliens, those with completely different metabolisms? Tune in tomorrow to find out!