THE BOREHOLES OF THE SEA-URCHIN GENUS ECHINOMETRA (ECHINODERMATA, ECHINOIDEA, ECHINOMETRIDAE) AS A MICROHABITAT IN TROPICAL SOUTH-AMERICA

Members of the genus Echinometra (Echinoidea: Echinometridae) inhabit hard substrata in shallow waters where they live in self-excavated dwe llings. Boring by Echinometra spp. causes a secondary structure of the surface, thus forming additional microhabitats. In this study the eff ects of boring activities of Echinometra lucunter (L.) along the Carib bean coast of Colombia and of Echinometra vanbrunti A. AGASSIZ in the Colombian Pacific is examined. Several species inhabit the boreholes o ccupied by these urchins. The associates live underneath the echinoid on the bottom of the borehole, where they find shelter from exposure a nd predators. The co-inhabitants of E. lucunter include the porcellani d Clastotoechus vanderhorsti (SCHMITT), the recently described brittle star Ophiothrix synoecina (SCHOPPE), and the clingfish Acyrtus rubigin osus (POEY). The species co-occurring with E. vanbrunti include the po rcellanid crab Clastotoechus gorgonensis WERDING & HAIG and the clingf ish Arcos decoris BRIGGS. With the exception of A. decoris, all of the se species are obligatorily associated with the Echinometra host.