43 Oceanography and Marine Biology: An Annual Review, 2011, 49, 43–104 © R. N. Gibson, R. J. A. Atkinson, J. D. M. Gordon, I. P. Smith and D. J. Hughes, Editors Taylor & Francis CORAL-ASSOCIATED INVERTEBRATES: DIVERSITY, ECOLOGICAL IMPORTANCE AND VULNERABILITY TO DISTURBANCE JESSICA S. STELLA 1,2,3 , MORGAN S. PRATCHETT 2 , PAT A. HUTCHINGS 4 & GEOFFREY P. JONES 1,2 1 School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia E-mail: Jessica.Stella@my.jcu.edu.au (corresponding author) 2 ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia 3 Climate Adaptation Flagship, CSIRO, Hobart, Tasmania 7001, Australia 4 The Australian Museum, Sydney, New South Wales 2010, Australia Abstract The biodiversity of coral reefs is dominated by invertebrates. Many of these invertebrates live in close association with scleractinian corals, relying on corals for food, habitat or settlement cues. Given their strong dependence on corals, it is of great concern that our knowledge of coral- associated invertebrates is so limited, especially in light of severe and ongoing degradation of coral reef habitats and the potential for species extinctions. This review examines the taxonomic extent of coral-associated invertebrates, the levels of dependence on coral hosts, the nature of associations between invertebrates and corals, and the factors that threaten coral-associated invertebrates now and in the future. There are at least 860 invertebrate species that have been described as coral asso- ciated, of which 310 are decapod crustaceans. Over half of coral-associated invertebrates appear to have an obligate dependence on live corals. Many exhibit a high degree of preference for one or two coral species, with species in the genera Pocillopora, Acropora and Stylophora commonly pre- ferred. This level of habitat specialization may place coral-associated invertebrates at a great risk of extinction, particularly because preferred coral genera are those most susceptible to coral bleaching and mortality. In turn, many corals are also reliant on the services of particular invertebrates, lead- ing to strong feedbacks between abundance of corals and their associated invertebrates. The loss of even a few preferred coral taxa could lead to a substantial decline in invertebrate biodiversity and have far-reaching effects on coral reef ecosystem function. A full appreciation of the consequences of further coral reef degradation for invertebrate biodiversity awaits a more complete description of the diversity of coral-associated invertebrates, the roles they play in coral reef ecosystems, their contribution to reef resilience and their conservation needs. Introduction Coral reefs are complex and productive ecosystems that encompass the highest biodiversity of any marine ecosystem (Sebens 1994, Gray 1997, Hoegh-Guldberg 1999, Veron 2000). Estimates of the number of species found on coral reefs range from 172,000 to over 9 million (Reaka-Kudla 1997,