Echinometra mathaei Breeding Guide

How the rock-boring urchin Echinometra mathaei reproduces by releasing gametes into the water column, producing planktonic echinopluteus larvae that are not raised in home aquaria.

Overview

Echinometra mathaei is a small urchin of tropical Indo-Pacific reefs, ranging from Madagascar, the East African coast and the Red Sea to Hawaii. It uses its spines and the teeth of its Aristotle's lantern to bore into basaltic and calcareous rock, emerging from these hollows at night to graze on algae. Its test reaches about 5 centimetres in diameter.

Reproductive Mode

As with other sea urchins, breeding involves releasing gametes into the water column, so the species is a broadcast spawner with separate sexes and external fertilisation. In the Gulf of Suez it spawns in summer and autumn, but in warmer waters breeding can take place at any time of year.

Sexual Reproduction

Fertilisation in open water gives rise to echinopluteus larvae that are planktonic. When these settle on the seabed they undergo metamorphosis into juvenile sea urchins. The long planktonic phase ties recruitment to open-ocean conditions rather than to the parent's immediate habitat.

Common Challenges

The planktonic larval stage demands months of suspended culture on microalgae, which cannot be reproduced in a display reef tank. Spawning events may occur in captivity, but the larvae are not raised and no juveniles are recovered.