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Journal of Marine Biology
Volume 2014 (2014), Article ID 769356, 11 pages
http://dx.doi.org/10.1155/2014/769356
Research Article

The Immune Response of Acanthaster planci to Oxbile Injections and Antibiotic Treatment

1School of Marine and Tropical Biology, James Cook University, Townsville, QLD 4811, Australia
2ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia
3Australian Institute of Marine Science, PMB No. 3, Townsville, QLD 4810, Australia

Received 16 December 2013; Accepted 10 March 2014; Published 9 April 2014

Academic Editor: Norman Ying Shiu Woo

Copyright © 2014 Alexandra Grand et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Bile salts have been recently identified as a rapid and effective method for killing A. planci. However the mechanistic basis of this new control method is poorly understood. This study explored the immune response(s) of A. planci and/or pathogenesis resulting from the injection of bile salts. To account for the possible role of pathogenesis in causing high rates of mortality, A. planci was treated with antibiotics to minimise the incidence and severity of bacterial infections. No significant difference in the time to death between groups with and without antibiotic treatment was reported, suggesting a limited bacterial effect on the induction of disease and death of injected sea stars. The number of circulating coelomocytes increased significantly after injection confirming the induction of a strong immune response. Five types of circulating cells were identified: (1) phagocytes, (2) small hyaline cells, (3) colourless spherule cells, (4) red spherule cells, and (5) fusiform cells. Histological analysis of A. planci tissues showed that the mechanism leading to rapid mortality is related to necrosis and/or apoptosis, rather than transmissible disease. Therefore, bile salts are an effective and safe method for killing crown-of-thorns sea star in situ.