Nile crocodile stability and additional weight to sink in water, this bearing great probability over the theories that they assist in digestion and staving off hunger. However, Alderton (1998) stated that a study using radiology found that gastroliths were seen to internally aid the grinding of food during digestion for a small Nile crocodile. Herodotus claimed that Nile crocodiles have a symbiotic relationship with certain birds, such as the Egyptian plover ("Pluvianus aegyptius"), which enter the crocodile's mouth and pick leeches feeding on the crocodile's blood, but no evidence of this interaction actually occurring in any crocodile species has been found, and
Symbiotic binary binaries show brightness changes and are classified as variable stars. The star Z Andromedae is often considered the prototype of the symbiotic binary class of stars. More commonly it is considered as the prototype of only a subset of symbiotic stars with irregular variations up to about 4 magnitudes in amplitude. Even the Z Andromedae variable stars are thought to be an inhomogeneous group. The so-called symbiotic novae are a closely related class of symbiotic binaries, more formally known as type NC novae. They appear similar to classical novae but have extremely slow outbursts that can remain near maximum brightness