Facts: The Collector Urchin

Collector urchins are short-spined urchins that get their common name from the fact that they pile everything from trash to seaweed and rocks on their bodies. They hold the collection there with their tube feet. Scientists believe that they exhibit this behavior because of their aversion to bright light. The debris can be used as a shield from ultraviolet radiation. They may also use their collection for camouflage. Collector urchins can be found primarily in different habitats throughout the tropical seas of the Indo-Pacific, such as seagrass meadows, algae forests, sand with coral rubble, and coral reefs. They are most commonly found in very shallow water, but they can be observed down to a depth of around 250 ft. Their densities vary over time and location. Collector urchins graze on seagrass and algae during the day or at night. Five rasping teeth are used to feed. The body is round and enclosed within a hard shell called a test that consists of unified plates. The body surface has colorful, short spines and tube feet. Both can be used for defense and locomotion. Five double rows of tube feet radiate from the center, interspersed with bands of spines. The tube feet can extend well beyond the body. Nestled among the spikes are tiny biting appendages. The pincer-like heads of the appendages bite attacking predators, releasing venom as they do so. When threatened, the urchins can release these biting heads en masse, creating a cloud of biting defenders. Collector urchins have separate males and females. Females release eggs into the water column where they are fertilized. Urchin larvae are free swimming and they feed on phytoplankton. For three weeks, the larvae go through a variety of growth stages. Then the larvae settle and take the shape of a true urchin. In four to five months, they reach the size of a quarter. They can grow to about 5 in across. Collector urchins are economically important and eaten in some countries. They support small scale fisheries and commercial trade. Collector urchins contain bioactive compounds useful for pharmaceutical research. They are also important ecologically. In Hawaii, they are an important tool in fighting invasive seaweeds. So much so that they are raised in captivity and released into the wild to keep the invading seaweed under control so the coral can thrive. For more marine facts, click the SUBSCRIBE button!!