I'm hoping this story'll be readable without any out-of-story exposition, but in case it isn't-- or in case like me, you just love the heck out of annotations--there's some explanation of the terms and biology at play here over on the blog, over at http://carapace.insanejournal.com/.
Also. still, anyone who comments on the comic for the rest of the month still gets a free sketch.
Mailed, even. And comments on the blog count.