Marine & Environmental Sciences Faculty Articles

Non-native brittle star interactions with native octocoral epizoites: an endemic benthic ctenophore in peril?


0000-0002-6003-9324, 0000-0002-2945-6576

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Marine Biology



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Widespread and large populations of the non-native eastern Pacific ophiuroid brittle star Ophiothela mirabilis now occur in southeastern Florida, extending the range of this recently introduced species from southern Brazil northward to the eastern Caribbean Sea and Florida. The Florida brittle stars, representing two lineages, are epibionts on shallow (3–18 m depth), tropical/subtropical plexaurid (e.g., Eunicea spp., Muricea spp.) and gorgoniid (Antillogorgia spp.) octocorals. The scope of this study includes recent distributional records of O. mirabilis in south Florida, feld abundances in relation to the cohabiting endemic ctenophore Coeloplana waltoni, behavioral observations of the ophiuroid, ctenophore and the predatory amphipod Caprella penantis, as well as a laboratory experiment testing the efects of the non-native ophiuroid on the native ctenophore. Individuals of O. mirabilis have been collected near St. Lucie Inlet, extending its northern-most range by about 110 km since 2019. Two years of feld sampling have demonstrated signifcant declines of the native, benthic ctenophore with increasing abundances of the non-native ophiuroid. Evidence suggests that the ophiuroid is negatively afecting the abundances of the ctenophore through interference competition, greatly aided by its abrasive armature of calcareous spines, plates and hooks. This detrimental efect justifes considering O. mirabilis as an invasive species in south Florida. Sporadic and intense predation by a caprellid amphipod also probably contributes to the ctenophore’s decline, but to a lesser extent than that caused by the ophiuroid. Adding to the risk of extinction of C. waltoni is its narrow requirement of living octocorals as hosts and restricted distribution in southeast Florida and the Bahamas.








Thanks are due W. L. Bullock (Landis), B. Enright, R. L. Ionata, and the South Florida Beach Divers Meetup Group for help with obtaining collections, and to Markus Niemeyer for the report and specifc location data on O. mirabilis at Blue Heron Bridge. A special thanks to Julie Gross for sundry laboratory tasks and enlightening discussions. R. C. Brusca, D. Cadien, D. Drumm, and Lea–Anne Henry ofered literature sources, helpful discussions, and contacts with systematists for species identifcations. J. M. Guerra–García kindly identifed Caprella penantis, and Dale R. Calder a hydrozoan. We are grateful for the details on the Bunaken caprellid infestations provided by Carlo Cerrano. The Ophiothela collection at Blue Heron Bridge was under FWC Special Activity License SAL-20-2267-SR.

All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. Experiments and observations involving the invertebrates were approved by the IACUC committees at UM and NSU. The Ophiothela collection at Blue Heron Bridge was under FWC Special Activity License SAL20–2267-SR.

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