Crocodile bulks of swallowed prey flesh and bone. Many large crocodilians swallow stones (called gastroliths or stomach stones), which may act as ballast to balance their bodies or assist in crushing food, similar to grit ingested by birds. Herodotus claimed that Nile crocodiles had a symbiotic relationship with certain birds, such as the Egyptian plover, which enter the crocodile's mouth and pick leeches feeding on the crocodile's blood; with no evidence of this interaction actually occurring in any crocodile species, it is most likely mythical or allegorical fiction. Since they feed by grabbing and holding onto their prey, they have evolved
Symbiotic binary term "symbiotic variable" or "symbiotic variable star" is sometimes also used synonymously, but more commonly is used only for Z Andromedae variable stars. Symbiotic binaries are often divided into two sub-types based on the nature of the continuum in their spectra. "S-type" systems have a stellar continuum since the giant component is not obscured. "D-type" systems are surrounded by optically thick dusty nebulosity and the star itself is not directly visible. D-type systems tend to contain a Mira variable or other long period variable star. Some symbiotic stars have jets which are a collimated outflow of material. These typically are