Astropyga is a genus of tropical sea urchins.
These echinoids are found in shallow waters throughout all the tropics, as well in the Atlantic (A. magnifica) as in the Indian (A. radiata) and Pacific oceans (A. pulvinata). They usually live at snorkelling depths in coral ecosystems, but can be found at more than 30m deep ; they can be very common in seagrass beds. They are mainly algae grazers, but can eat a wide variety of foods.
These species all share a distinctive shape, with a flattened test and rather long, hollow and slender spines. They all wear bright colors, usually bright red and white (sometimes black), with a distinctive star-shaped naked pattern on the aboral surface, around the anus ("astro-pyga" means "star-shaped anus"), ponctuated by iridophores (lines of bright blue dots). The anal papilla is rather big and rounded. Young specimens have banded spines, but some mature specimens can still be so.
Some of their spines are venomous and painful, but not really dangerous.
