Burrowing Urchin

Echinometra mathaei, commonly known as the burrowing urchin, is a species of sea urchin in the Echinometridae family. It is primarily found in the shallow waters of the Indo-Pacific region, with its type locality being 🇲🇺 Mauritius.

Measuring approximately 5 centimeters (2.0 in) in test diameter, Echinometra mathaei displays a variable coloration, typically appearing dark. Its spines can be green and purple with purple tips, or entirely green with purple tips. However, what sets this sea urchin apart from other species is the distinct pale ring at the base of each spine.

This species typically inhabits reefs in tropical areas of the 🌊 Indo-Pacific Ocean, at depths as deep as 139 meters (456 ft). Its range spans from 🇲🇬 Madagascar, the East African coast, and the 🌊 Red Sea to Hawaii.

Echinometra mathaei utilizes its spines and teeth, part of the mouthparts known as Aristotle's lantern, to burrow into basaltic and calcareous rocks where it makes its home. At night, it emerges from these hollows to feed on algae. Breeding in Echinometra mathaei involves the release of gametes into the water column, with external fertilization. The resulting larvae, known as echinopluteus, are planktonic. Upon settling on the seabed, they undergo metamorphosis, developing into juvenile sea urchins. While in the Gulf of Suez, its most northerly habitat, breeding occurs during the summer and autumn, warmer waters allow for breeding to occur year-round.

Due to its burrowing behavior, Echinometra mathaei has the capacity to cause bioerosion in coral reefs. Its natural predators mainly consist of finfish, although brittle stars and gastropod molluscs also engage in predation. It has been observed that in areas with intensive fishing activities, the abundance of urchins can increase due to a decrease in their natural predators. Consequently, this can lead to greater damage to the reef ecosystem. Interestingly, a commensal shrimp, Athanas areteformi, resides among the spines of this sea urchin, and its appearance is mimicked by the mantis shrimp, Echinosquilla guerinii, which conceals itself in a rock crevice, exposing only its spiny telson.