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Red sea urchin

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Red sea urchin
Scientific Classification
Binomial Name

Strongylocentrotus Franciscanus

A close-up of the urchin's test.

Red sea urchins are a species from the phylum Echinodermata (meaning spiny-skinned), which is quite evident when one is looking at a sea urchin.[1] Their sharp spines which measure to be about 5 inches long,[2] have a few different uses. One is that they are used as stilts for walking along on the bottom sea. These urchins have both significant and slight differences from other sea urchins. For example, they have a life span that is known to live up to 200 years and they are the largest of all the sea urchins. The Red Sea Urchin can be found in the Pacific Ocean lining the low tide lines of British Columbia amongst the rocky ground. [3]


A close-up of the Red Sea Urchin's spines.

The Red Sea urchin is the largest of all sea urchins.[4] Going back to it's name, the Red Sea Urchin's colors can range all the way from its original bright red to dark burgundy. While the urchins are in their larval stage, their body goes through a transitional stage from bilateral to radial symmetry. The red sea urchin outer skeleton can have a diameter of more than 18 cm. But even some of the oldest urchins have found to be 19 cm. [5] In order to move across the ocean floor, they use their spiny legs as if they were stilts. [6] The biggest their spine length can grow to is 8 cm. Their outer skeleton is also called a "test." [7] The urchin's test is made up of 10 fused plates. The urchins have other sections that have holes so that the urchin will be able to extend it's tube feet in order to move. [8] The urchins have a water vascular system that fully controls the tube feet. They are able to extend and contract their tube feet by adjusting the amount of water in their sections.


Almost all urchins are notorious for being huge spawners, which means that the urchins release their gametes into the water and the fertilization cycle occurs within the water column. The spawning season tends to be highest from around July to September. The larvae will remain in the water column for around a month before they reach the bottom. Once they reach the bottom, they undergo metamorphosis and become young urchins. [9]

These young urchins have chemicals that are able to track and locate adult urchins. Once they find these adults, they crawl and live under them until they have reached their adult size. Adult size is usually a test diameter of around 40 mm. Many of the urchins that are found under the older urchins, have no relation whatsoever, they are just living under them and feeding with them until they've reached their adult size. [10] In order to repopulate, other Red Sea Urchins will join and try help repopulate that local area.[11]


The Red Sea Urchin have different styles of feeding to match their age and the stage of their life they are in. While the urchin is still in its larval stage, it collects food from the water column through bands of cilia. At the same time, they are capable of absorbing amino acids straight from the seawater. [12]The urchins have unique jaws that consist of 5 teeth that are used to chew up mostly plant material. One would be able to locate their mouths identified on their ventral surface.[13] In order to save themselves from floating away with the current, while they're eating, they use their tube feet to hold on to the bottom. Their favored diet consists of different kinds of seaweed, kelp, and algae. [14]


Red Slate Pencil Sea Urchin (Heterocentrotus mammillatus) on the urchin's preference of rocky ground.

Red Sea Urchins are the delight of every predator's diet. Even certain kinds of fish would eat them in a second such as the wolf eel, sea stars, and crabs. [15] The younger urchins are targeted the most for their smaller size. Although large urchins tend to make sea otters quite happy, since these are almost the only animals that are able to get them open, by cracking them upon rocks. [16]

Red Sea Urchins, are located in the Pacific Ocean along the rocky low-tidal grounds, approximately 90m in British Columbia. These urchins reside right under the low tide line where all the seaweed and kelp are. The urchins have a preference for rocky ground, just because this is where the seaweed and kelp grow. Although they like rocky ground, they try and stay away from rocky areas with high tidal action. These creatures want to avoid a lot of big waves and any areas that consist of mud, gravel, and sand. [17]

Immortal Urchins?

These sea urchins are generally known to live past the age of 30 years. But a recent article from Oregon State University found that these urchins are able to grow and live to be 100 years old. [18]Some may even be able to live up to 200 years, with hardly any signs of aging or difference. For a while, scientists believed that these urchins were immortal and would never come to find an end to their lifespan. [19] Studies show that even the oldest urchins were able to reproduce the exact same way, without showing any difference to the reproduction of an extremely younger urchin.[20] There would be many more urchins, but since the urchins are so fragile and delicate and prone to damage, not many survive up to the reproduction stage in their life; which explains why not very many make it to the old ages. [21]


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