Sea Cucumbers

I never enjoy getting sick, especially if it’s a sickness like the flu in which vomiting is a normal occurrence.  It is one of the most unpleasant feelings I think I’ve experienced. If I could never vomit again I would be one of the happiest people alive. It’s easy to understand why I would hate to be a sea cucumber, which basically vomits as defence mechanism.The sea cucumber Holothuria forskali will expel Cuvierian tubules when they are irritated. These tubules will then lengthen, become sticky and immobilize organisms (Vandenspiegel et al., 2000) by entangling the predator. These tubules are connected to the small and large intestines in the posterior part of the animal. Not only do they entangle the predators but they are also toxic which is effective against non-specialist predators (Dyck et al., 2011).

Normally when an organism loses an organ it is unlikely to survive. However, after the sea cucumber expels these tubules they will regenerate. Regeneration occurs immediately when many tubules have been expelled, but if only a few tubules were expelled there is a short period before regeneration occurs. Even though the tubules are regenerated it takes five weeks for them to be totally regenerated (Vandenspiegel et al., 2000). This brings up the question as to whether or not it is worthwhile to expel these tubules. In most cases when an organism is being preyed upon there is a flight or fight response. In the case of the sea cucumber it can’t run away very quickly but it doesn’t have a traditional method of fighting either. It doesn’t have to expel all of its tubules at one moment and as long as it has some tubules to expel, the sea cucumber has a method of fighting predators. Since the tubules do regenerate it isn’t losing its ability to fight either.

Here's a video about the sea cucumber:

References:

Dyck, SV, Caulier, G, Todesco, M, Gerbaux, P, Fournier, I, Wisztorski, M & Flammang, P 2011, ‘The triterpene glycosides of Holothuria forskali: usefulness and efficiency as a chemical defense mechanism against predatory fish’, Journal of Experimental Biology, vol. 214, pp. 1347-1356, doi:10.1242/jeb.050930.

Vandenspiegel, D, Jangoux, M & Flammang, P 2000, ‘Maintaining the line of defense: regeneration of cuvierian tubules in the sea cucumber Holothuria forskali (Echinodermata, Holothuroidea)’, The Biological Bulletin, vol. 198, no. 1, pp. 34-49, < http://www.biolbull.org/content/198/1/34.short>.