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Echinometra mathaei, the burrowing urchin, is a species of sea urchin in the family Echinometridae. It occurs in shallow waters in the Indo-Pacific region. The type locality is Mauritius.

Description
Echinometra mathaei grows to a test diameter of about 5 cm. The colour is quite variable with the test being a dark colour and the spines being green and purple with a pale base and purple tips, or entirely green with purple tips. It can be distinguished from other species by the pale ring at the base of each spine.

Distribution
Echinometra mathaei is found on reefs in tropical parts of the Indo-Pacific Ocean. Its range extends from Madagascar, the East African coast and the Red Sea to Hawaii.

Biology
Echinometra mathaei uses its teeth (part of the mouthparts known as Aristotle's lantern) and spines to dig itself into the calcareous rock where it lives. It emerges at night to feed by grazing on algae. As with other sea urchins, breeding involves releasing gametes into the water column. Fertilisation is external and the echinopluteus larvae are planktonic. When these settle on the seabed, they undergo metamorphosis into juvenile sea urchins. In the Gulf of Suez, in the most northerly part of its range, it spawns in the summer and autumn but in warmer waters, breeding takes place all year long.

Because of its burrowing activities, Echinometra mathaei causes bioerosion of coral reefs. Its natural predators are mostly finfish but there is also some predation by brittle stars and gastropod molluscs. It has been found that in areas where heavy fishing takes place, the number of urchins is increased because their natural predators are less abundant and as a consequence, greater damage to the reef takes place.

A commensal shrimp, Athanas areteformi, lives among its spines. Its appearance is mimicked by the mantis shrimp Echinosquilla guerinii which conceals itself in a hole in the rock with only its spiny telson visible.