Michael Gago
Echinodermata in Greek means “Spiny Skin,” but not all of the phylum shares this external defensive system. Holothuroidea, which is the class that includes sea cucumbers, have a soft exterior unlike most other echinoderms. Sea cucumbers do not need to have these external spines because they have a unique type of defense called evisceration. Evisceration is a type of autonomy which involves releasing internal organs from the anus and then regenerating those organs. Some members of Holothuroidea, such as Holothuria Forskali, have the unique ability to release Cuvierian tubules that contain toxins which immobilize predators in a form evisceration (VandenSpiegel et al., 2000). Cuvierian tubules are a part of the respiratory tree, which when expelled instantly lengthen and become sticky (VandenSpiegel et al., 2000). The respiratory tree is also unique to sea cucumbers and is used for gas exchange unlike other echinoderms which use their water vascular system and tube feet for respiration.
Though giving up the ability to breathe to escape a predator might seem counterproductive, sea cucumbers can regenerate these Cuvierian tubules quickly. The Cuvierian tubules regenerate at different rates depending on how many are expelled. For example, H. Forskali usually have at least 200 tubules and can have up to 600 tubules. When H. Forskali is gently irritated it will only release a small amount of the tubules, approximately 15, and won’t start regeneration of those tubules for up to 3 weeks since it should still have most of its tubules left for respiration. In contrast, when H. Forskali is strongly irritated it will release a very large amount of its tubules, up to 300, which is instantly followed by the regeneration process. This regeneration process is done in 10-day long waves which regenerate 10 to 30 tubules at a time (VandenSpiegel et al., 2000). This system is especially advantageous because it allows for the sea cucumber to split up the high energy cost of regenerating organs.
These tubules are extremely unique and could have a lot of different uses for humans. They have a very high tensile strength and very strong adhesive property to them which allows them to stick to almost anything they touch, all while underwater! When released they come out as long white filaments like glue (DeMoor et al., 2003). As of now it is known that Cuvierian Tubules of H. Forskali, are about 60% protein but only made of 10 different types of proteins and 40% carbohydrates which is unique when compared to other marine invertebrate adhesive secretions (DeMoor et al., 2003). If further research is done on these Cuvierian tubules, then it is very likely that we will be able to isolate the adhesive property from the toxins and possibly recreate them in a lab.
References
DeMoor, S., Waite, H. J., Jangoux, M. J., & Flammang, P. J. (2003). Characterization of the adhesive from Cuvierian tubules of the sea cucumber Holothuria Forskali (echinodermata, holothuroidea). Marine Biotechnology, 5(1), 45-57. doi:10.1007/s10126-002-0049-2
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, 198(1), 34-49. doi:10.2307/1542802
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