Clusters of sticky tubules, located at the base of the respiratory tree, which may be discharged by some sea cucumbers (holothurians) when mechanically stimulate, as for example, when being threatened by a predator. Their great adhesivity, combined with their high tensile strength, allows the Cuvierian tubules to entangle and immobilise potential predators with which they come into contact. After expulsion, the lost tubules are readily regenerated, making them a formidable defence mechanism.