When most people clean a fish, they throw away the guts, but a team of biologists would rather take a close look at them.
To understand the roles of the many microbes that live naturally within mammalian intestines, Jeffrey I. Gordon of Washington University School of Medicine in St. Louis has long studied mice born and raised germfree (SN: 5/31/03, p. 344: Gut Check). Now, he and his colleagues are pursuing similar studies with zebra fish.
While these small vertebrates don't possess a stomach, much of the rest of their intestinal tract resembles the mammalian system. Equally important, zebra fish larvae are transparent, enabling the scientists to easily observe gut development.