Collector Urchin

Tripneustes gratilla, commonly known as the collector urchin, is a species of sea urchin that can be found at depths ranging from 2 to 30 meters in the waters of the Indo-Pacific, Hawaii (🇺🇸 United States), the 🌊 Red Sea, and The 🇧🇸 Bahamas. These urchins typically grow to a size of 10 to 15 centimeters.

Characterized by their dark bluish-purple color with white spines, collector urchins have white pedicles with a dark or black base. Some individuals found at Green Island exhibit orange-tipped spines, while others may have entirely orange or white spines. However, this distinctive coloration fades upon death or removal from the ocean, making it challenging to preserve. As their name suggests, debris tends to accumulate on these urchins due to their feeding habits.

Unlike some other sea urchin species, collector urchins graze continuously, both day and night. They primarily feed on algae, periphyton, and seagrass, with seagrass fronds being their main source of food. The impact of their grazing on the ecosystem varies depending on the season and the abundance of these urchins. During their peak feeding period between November and January, they can consume up to or even more than half of the seagrass production. However, on an annual basis, studies have shown that approximately 24% of seagrass production is consumed by collector urchins. The most commonly grazed seagrass species include Thalassodendron ciliatum and Syringodim isoetifolium, although other algae may also be consumed.

In terms of natural predators, collector urchins are preyed upon by puffer fish, octopuses, and humans.

Although widely distributed from 🇲🇿 Mozambique to the 🌊 Red Sea, as well as throughout the Indo-Pacific region and The 🇧🇸 Bahamas, collector urchins are particularly prevalent in areas such as Hawaii (🇺🇸 United States), Clarion Island, and Shark Bay in 🇦🇺 Australia. They have also been found in Governor's Harbor, Eleuthera Island, 🇧🇸 Bahamas. While mature collector urchins prefer open sea bottoms with some cover, younger individuals tend to seek rocky areas for concealment.

On an economic note, collector urchins hold significance in certain regions. They are edible and have been exploited by humans, leading to a decline in their population due to overexploitation over the past decade.