I have written a short article for EKOMAR-UKM on the above title, below is the writeup for all whom interested to know more about sea urchins :D.Sea urchins or locally known as ‘landak laut’ is the most conspicuous marine organism in our waters. It is also one of the most feared organisms by many tourists. When one is asked why they fear them, I often get answers, such as, “Its spines looks scary!”, “Afraid it will poke me!”, “Very painful!”, “It is dangerous!”
I agree that the spines of sea urchins could be very painful if one was misfortuned enough to get poked by it, but everybody needs to understand that sea urchins do not actively attack people, or intentionally hurt anyone. One could get hurt only by applying force onto its spine, which is sharp enough to pierce the skin and yet fragile enough to be broken easily. In other words, we can get hurt by sea urchin only if we were not careful enough to get poked by it.
One of the most common species in the reef and intertidal area is Diadema setosum. It is best be distinguished by its long and thin black spines. It also has an eye-like feature with an orange ring, which is actually its anus, and five white-spots on top. I would like to stress that sea urchins DO NOT HAVE EYES, but this is what most people would describe it when they saw one. It is actually the anus, as mentioned earlier. The reason why one felt pain when accidentally touched or stepped onto them is the fact that a sea urchins has a toxin sac at the end of its thin black spine, which is fragile and easily broken off. When a person’s skin is pierced by the spine, the toxin sac is released and would deliver a painful sensation. The level of irritation depends on the sensitivity of an individual, some people feel numbness at the pierced area and some won’t even feel a thing. The broken spine, which is left in the skin will slowly disappear, so there is no need to make an appointment with a surgeon! The immediate remedy for a painful stinging sensation from sea urchins is to pour vinegar on it. If the injury worsened due to allergic reaction, one must seek medical attention as soon as possible to avoid more serious after effect.
Sea urchins are viewed as pests by most people, but it is one of the most important citizens of the reef ecosystem. It helps the reef to counter-check populations of the fast-growing of algaes. Algaes are like weed, they grow very fast and if they keep on going, they could overgrow the entire reef and transform the coral reef ecosystem into an algae ecosystem. Sea urchins are herbivores, and their main diet is actually algaes, and they are active grazers. They graze all the time, everywhere! From the shallow waters of rocky areas to the pillars of a jetty. They are the gardeners of the reef and with the help of other herbivore reef fishes, keep the algaes at bay.
All medicines are good for the health if consumed in appropriately small quantity, but could turn poisonous and detrimental to the body if consumed in large quantities. This statement can also be used for sea urchins. If its population size is under control, there would not be any population outbreak, and they become the reef’s best friend, but if they became overwhelmingly plenty in a reef area, they could bring bring negative impact. Sea urchins are active grazers by nature and they graze on almost everything. They have a mouth structure, which is called ‘Aristotle lanterns’, which can break coral skeletons. When food source in an area, which is the algaes is scarce, they tend to feed on coral polyps. The structure of their jaws allows them to break the calcareous skeletons of coral and feeds on the polyps. Although their feeding on corals do not cause as much damage as that made by their relative, the Crown-of-torns (C.O.T) or its species name Acanthaster planci, this kind of feeding could weaken the coral structure, which would leave the corals susceptible to the monsoon. Finally, the next time you saw a sea urchin, please remember not to underestimate its presence and importance to the ecology of a reef ecosystem. One thing for sure, sea urchins do not form a legion to “Attack the humans!!!”
Close-up of the Diadema setosum
Another species of the sea urchins which can also be found in the reef.
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