|Other names:||Chydrus, Cydro, Idres, Ydre, Ydrus|
The enemy of the crocodile, which it kills from the inside
The hydrus is an animal that lives in the Nile River. It is the enemy of the crocodile. When it sees a crocodile sleeping with its mouth open, the hydrus first rolls in mud to make itself slippery, then enters the crocodile's mouth and is swallowed. It then eats its way out of the crocodile's belly, killing it.
There is considerable confusion in applying the name hydrus and its variations to beasts. The root of the word itself refers to water, and this led to several beasts, mostly serpents, being so labelled. Isidore of Seville lists the hydros, a water snake that causes those bitten to swell up, the cure for which is the dung of an ox. The hydrus was also confused with the hydra of the Hercules legend, some texts saying that it was a many-headed water dragon, living it the swamp of Lerna, that could grow new heads; the legend actually refers to a water fountain that sprouted new outlets when one was blocked.
The crocodile signifies hell, and the hydrus Christ, who descended into hell to recover imprisoned souls.