Epizoic Ophiothela brittle stars have invaded the Atlantic
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KeywordsSponge Coral Reef Asexual Reproduction Molecular Phylogenetic Analysis Environmental Requirement
It was thought that ophiuroids of the genus Ophiothela are confined to Pacific waters (Clark 1976). However, animals provisionally identified as Ophiothela mirabilis have founded emergent populations in the Atlantic. Further expansion of the range of Ophiothela could alter the appearance and the ecology of Atlantic coral reef habitats because ophiothelas, in multitudes, densely colonize gorgonians and sponges on Indo-West central Pacific and on tropical eastern Pacific reefs.
Proliferation of the small, 6-armed species is enhanced by its capacity for fissiparous, asexual reproduction, a process producing cloned progeny with regenerating arms (Fig. 1a, d). Low host specificity of O. mirabilis (already associated with at least 20 Atlantic host species) may also help it colonize new territory (Fig. 1b–d). Unfortunately, too little is known of the species’ biology to predict its potential impact on Atlantic reef communities. Sexual reproduction, larval and post-larval dispersal, feeding habits, environmental requirements, and interactions of Ophiothela species with their hosts, predators, and parasites have not been studied. Taxonomy and identification of ophiothelas is complicated by the morphological plasticity of their regenerating structures. A molecular phylogenetic analysis of the 10 named species of 6-armed Ophiothela is required to establish whether they comprise one species (as suggested by Clark 1976) and possibly identify the source of colonization.
We are grateful to Ray Haberman for photographs and information on Vincentian Ophiothela, Raymond Ryan (Chief Fisheries Officer, St. Vincent) for governmental assistance, Any Wilk for field observations, Stephen Cairns and Odalisca Breedy for gorgonian identifications, David Pawson and the late Cynthia Ahearn for loan of specimens, and Harilaos Lessios for reviewing a draft manuscript.
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