Red Sea Urchins

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Distinctive Features The red sea urchin is the largest of all sea urchin species in the world. Their colors usually vary among shades of light pink to burgundy red to black (*Rogers-Bennett, 2007). Their outer skeletons, called “tests”, can reach diameters of more than 19 cm and are made of ten fused plates that are covered by spines (Bartholomew and Hursrkey, 2014*). These spine lengths can reach around 8 cm (Bartholomew and Hursrkey, 2014*) and are used by this species to move across the sea floor. These spines also function as the sea urchin’s first line of protection against predators because their sharp spikes can penetrate or hurt possible predators. The species has slow growth rates that tend to decrease as their size and age increases (Rogers-Bennet et al., 2003), however, they can grow to be older than 100 years old (Ebert and Southon, 2003).
Strongylocentrotus franciscanus possess a unique “defense mechanism” in which the juvenile sea urchins will hide under adult sea urchin spine "canopies" as a way to hide and avoid predation (Breen et al., 1985*). These sea urchins are also keystone species because their absence or presence in the benthic shallow water communities can cause tremendous effects on the …show more content…
Red sea urchins have a mouth structure called “Aristotle’s Lantern” which is made of five calcareous plates that are used to scrape algae or kelp off of rocks (Kato and Schroeter, 1985). The foraging behavior of sea urchins depends largely on its location and distance from nearby kelp forests. For the most part, when sea urchins are near kelp forests, they become selective in the type of kelp they eat and barely move around. However, when they are relatively far from kelp forests, there will be a noticeable increase in sea urchin movement as well as less food selectivity (Mattison et al.,

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