Cuvierian tubules

Threatened or wounded sea cucumber Holothuraided) will contract its body exposing the small skeletal bones that make up the body wall, which can act as hooks to the mouths of predators. For most species, the connective tissue that makes up the greater part of the body wall is the primary deterrent to predators.The contracted body not only makes a more compact body to bite, but increases the stiffness of the body wall. The sea cucumber also has a very unusual defense mechanism. Many species use the Cuvierian tubules, which are located in the digestive system of the animal to confuse... 

Mollusks are not the only invertebrates to produce bioadhesives the same is true for sedentary Polychaetes such as Phragmatopoma califomica, which live in tubes impregnated with grains of sand (see Chapter 21), as well as for most sea cucumbers that use their Cuvierian tubules to defend themselves against predators (Jensen and Morse, 1988 Waite, Jensen, and Morse, 1992 Deming, 1999 Stewart et al, 2004 Flammang, 2003). Lastly, bioadhesives produced by the sea urchin Paracentrotus lividus to inhabit wave-swept shores are constituted by protein-carbohydrate complexes and are devoid of dopa (Santos et al, 2009). 

Isemura, M., Zahn, R. K., and Schmid, K., 1973, A new neuraminic acid derivative and three types of glycopeptides isolated from the cuvierian tubules of the sea cucumber Holothuria forskali, Biochem. J. 131 509. 

A previously unknown sialic acid was found in two glycopeptide fractions isolated from the Cuvierian tubules of the sea cucumber, Holothuria forskali. It is resistant to enzymic cleavage by neuraminidase, even after mild alkaline hydrolysis for the removal of O-acyl residues however it is readily released by mild acid hydrolysis. Its chromatographic properties differ from other known sialic acids, but presumably the new species possesses neuraminic acid as its basic structure (Isemura a/., 1973). See Chapter 1. 

---