Appearance
Gracilechinus acutus usually grow up to 150 mm in diameter in their adult stage. They appear commonly in a reddish to brown-red color with occasional urchins having a green color. There are vertical white stripes on the ambulacral plates. The Gracilechinus acutus have two types of spines, primary and secondary. Its primary spines are long and tapered while secondary spines are more short and thin. The spines act as a defense mechanism against predators. The area around the mouth does not contain spines, but instead have pedicellariae.

