Xin Zhan
I was born in a seaside city. Sea cucumber is a very famous dish in my country. There are many cooking methods – stew, stir-fry, cold, etc. In my impression, sea cucumbers are soft and lovely and have little taste or aggression. After learning more about invertebrates, I found that I still knew too little about sea cucumbers. Sea cucumbers, like all echinoderms, have an endoskeleton. They also have tentacles, tube feet, and mouth, surrounded by tentacles, and anus. Sea cucumbers belong to the Holothuroidea class and are long and worm-like in appearance. As shown in Figure 1, it still has the pentaradial symmetric look of Echinodermata. The figure is the ventral view of a sea cucumber, and you can see two distinct white lines. In the dorsal view, the lines are not as distinct as the ventral view, but it is the same shape. So, the body of a sea cucumber has five white lines around its central axis divided into five nearly identical parts. It has a separate anus and mouth at each end of its body. Sea cucumbers are not as defenseless as they look. They have some unique strategies to protect themselves. When facing predators, some sea cucumbers will erupt some white threads to protect themselves, called Cuvierian Tubules, used to stick to predators that they avoid or have time to escape by themselves (Flammang et al. 2002). In some cases, they blow out some sticky internal organs from their anus and use them to hit the predator, so that they have time to escape (Yazar, 2017).
I have been under the impression that people around me say that sea cucumber is good for people’s health, can supplement a lot of nutrition, and can prevent cancer. After learning of sea cucumbers, I know that sea cucumbers are not completely good for the human body. There are substances called holothurins in sea cucumbers, which are contained in Cuvier tubes and are used by sea cucumbers to defend themselves against other species (Ruppert et al. 2004). When sea cucumbers are used in large quantities, the human body may be harmed. But sea cucumbers in small amounts could help fight cancer. Holothurins have recently been found to help kill cancer cells in the body. Holothurins extracted from Holothuria leucospilota(Figure 2), H. Parva, and H. scabra(Figure 3), three sea cucumbers from the Persian Gulf, can kill cancer cells and inhibit the cancer cells’ growth (Mashjoor et al. 2019). In addition, sea cucumbers can control the cholesterol level of the human body – saponin Desulfated Holothurin A in Thelenota ananas is helpful in reducing low-density lipoprotein cholesterol (LDL-C) (Han et al. 2018). In addition, Han et al. show that it can block the synthesis of fatty acid synthase and promote the outflow of intracellular cholesterol (Han et al. 2018). So, sea cucumbers are really good for people.
In general, while holothurins are harmful to humans, they are only poisonous in large quantities. So, people can still eat a small amount of sea cucumber; a small amount of sea cucumber is good for the human body.
References
Flammang, P., et al. “Biomechanics of Adhesion in Sea Cucumber Cuvierian Tubules (Echinodermata, Holothuroidea).” Integrative and Comparative Biology, Vol. 42, no. 6, 2002, pp. 1107–1115
Han, Qi-an, et al. “Function of Thelenot’a Ananas Saponin Desulfated Holothurin A in Modulating Cholesterol Metabolism”. Sci Rep 8, 9506 (2018).
Mashjoor, S, and M Yousefzadi. “Cytotoxic effects of three Persian Gulf species of Holothurians.” Iranian journal of veterinary research vol. 20, no. 1, 2019, pp.19-26.
Ruppert, Edward E., et al. (2004). Invertebrate Zoology: A Functional Evolutionary Approach, 2004.
Yazar, Rumeysa. “Sea Cucumbers and Their Extraordinary Defense Systems.” The Fountain.
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