Burrowing urchinEchinometra mathaei
Category
- Fringing Reef
General description
Echinometra mathaei, also known as the burrowing urchin, can be commonly found in shallow waters around the rocky shores of Mauritius and in Bel Ombre. This urchin belongs to the family of Echinometridae, recognized by their globe-shaped pedicellaria – the appendage common to sea urchins and sea stars. [1] Its oval-shaped test or shell is usually of a dark colour and its diameter can measure up to 9 centimeters. In the Western Indian Ocean, its spines usually measure up to 4 centimeters and are usually dark grey or light purple, with some greenish-grey varieties. The pale ring at the base of each spine distinguishes the burrowing urchin from other sea urchins.
[1] Natural History Museum. n.d. The Echinoid Directory. Accessed July 2018. http://www.nhm.ac.uk/our-science/data/echinoid-directory/taxa/taxon.jsp?id=1187
Habitat and ecology
The burrowing urchin can be found anywhere between the shallow eulittoral rocky shores to the deeper parts of the lagoon and reef.[1] The species uses its spines and teeth to burrow itself into basaltic and calcareous rock. Being a nocturnal animal, it emerges from its burrow at night to graze on coralline and other algae. Echinometra mathaei will breed like other urchins by releasing gametes into the water column, with fertilization occurring externally. The resulting larvae are planktonic until they settle on the seabed where they undergo metamorphosis into juvenile sea urchins. Because of its burrowing activities, Echinometra mathaei is a bio-eroder of coral reefs. The burrowing urchin’s predators include mainly finfish with some predation by brittle stars and gastropods.
Conservation status and threats
The IUCN status for this species is unknown. There are currently no known threats to Echinometra mathaei. Population outbreaks are often associated with the removal of fish predators due to overfishing. As a consequence of overfishing and their bio-erosion role, population outbreaks of the species lead to further degradation of the reef.
[1] Richmond, Matthew (ed.). 2011. A fieldguide to the seashores of Eastern Africa and the Western Indian Ocean islands. Sida/WIOMSA.
Did you know?
The mouth of sea urchins is commonly referred to as Aristotle’s lantern. The philosopher was among the first to write about the anatomy of the urchin. The comparison to a lantern is due to the fact that lanterns used at that time were horn lanterns which had five sides. This is a common feature of all echinoderms.
