Description and ecology of a new species of Edwardsia de Quatrefages, 1842 (Anthozoa, Actiniaria) from the St Lucia Estuary, South Africa

Abstract

A new species of the true anemone genus Edwardsia, E. isimangaliso sp. nov., is described from the St Lucia Estuary, Africa's largest estuarine lake. The species differs from its closest relatives in anatomy and cnidom and is the only species of the genus found in hypersaline waters. Its current distribution appears to be restricted to a narrow region in the middle reaches of the estuary (lower South Lake), where it has been recorded at salinity levels ranging from 21 to 55.6 psu. The species is also limited to substrata dominated by fine to very fine sand and does not occur in areas with either high silt or coarse sand content. Population densities appear to have decreased over time, with maxima over 1500 ind. m⁻² recorded in 2005, but only 20 ind. m⁻² in 2010. Prey items identified in its stomach include the snail Assiminea ovata and ostracods. However, stable isotope analysis showed that the main carbon sources for the anemone are the filamentous macroalga Cladophora sp. and benthic microalgae. The presence of zooxanthellae in tissues of E. isimangaliso sp. nov. suggests that the species may combine heterotrophic and autotrophic feeding modes in response to fluctuations in resource availability.

Keywords:

• Cnidaria
• sea anemone
• hypersaline waters
• iSimangaliso Wetland Park

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

The US National Science Foundation (NSF), the South African National Research Foundation (NRF, Pretoria), Marine & Coastal Management (MCM, Cape Town) and the World Wide Fund (WWF-SA, Stellenbosch) contributed grants towards the funding of this study. We are very grateful to the management and staff of Ezemvelo KZN Wildlife and the iSimangaliso Wetland Park for providing logistical support during the survey. Special thanks go to R. Taylor, C. Fox and the late A. Myeza for their invaluable assistance with field operations. N. Miranda, D. Pillay, S. Huripurshad, G. Kruger and N. Carrasco are also thanked for their assistance with data and sample collection and analysis. We are also grateful to N. Carrasco and A. McDonald for supervising the stable isotope and the DNA-PCR analyses, respectively.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark