Pathogenesis in crown-of-thorns starfish (Acanthaster planci L): importance in outbreak dynamics and opportunities for controlling populations

Rivera Posada, Jairo, and Pratchett, Morgan (2012) Pathogenesis in crown-of-thorns starfish (Acanthaster planci L): importance in outbreak dynamics and opportunities for controlling populations. Report. NERP, Tropical Environmental Hub, Townsville, QLD, Australia.

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Outbreaks of the crown-of-thorns starfish, Acanthaster planci (L.), represent one of the most significant biological disturbances on coral reefs, contributing greatly to habitat degradation across the Indo-Pacific. While the cause(s) of outbreaks are still being debated, an equally important question is, what causes population declines at the end of outbreaks? Like all echinoderms, A. planci appear to be susceptible to disease, which may explain sudden declines in abundance that have been observed in the wild, as well as providing unique opportunities to potentially control starfish populations. Potentially pathogenic organisms normally associated with A. planci have been shown to cause rapid mortality following injection of Thiosulfatecitrate-bile-sucrose (TCBS). TCBS is a selective media culture that inhibits gram-positive organisms, suppresses coliforms, and allows selective growth of Vibrio bacteria. These bacteria constitute an important part of the bacterial microflora of numerous marine animals, and are also recognized as important pathogens of echinoderms and other marine animals. This study showed that injection of TCBS broth into A. planci organs induced disease, and all starfish then died within 24 hours. TCBS broth promoted an allergic reaction in the starfish, as well as promoting population growth of naturally occurring Vibrio spp., leading to an imbalance in natural symbiont communities. Most importantly, diseased starfish often infected seemingly healthy A. planci that were either in direct contact or in very close proximity.

In order to reverse sustained and ongoing degradation of coral reef habitats, increasing attention is being given to management and control of A. planci outbreaks. Previous control methods (e.g., hand collecting) are extremely labour intensive and often ineffective in either eradicating the coral-feeding starfish or preventing extensive coral loss. Controlled induction of disease would provide significant benefits over previous control methods, especially given that diseased starfish infect other starfishes in close proximity. The key issue however, is whether diseased A. planci could also infect other echinoderms, corals or other reef organisms.

As a first step towards testing the feasibility (and biosecurity) of using TCBS to eradicate A.planci, we exposed a range of echinoderms to diseased starfish within a closed environment. Vibrio rotiferianus, which was reported as a likely pathogen isolated from experimentally infected A. planci, was recovered from Linckia guildingi. Moreover, 80% of L. guildingi exhibited skin lesions after several days of direct contact with sick Acanthasther planci. However, unlike infected A. planci, which all died within 48 hrs, all L. guildingi starfish fully recovered after 53 days. Further studies need to be carried out to establish the possibility of disease transmission among species, but there are also several other important questions that must be addressed, before advocating disease induction as a method to control outbreak populations of A. planci.

Item ID: 34552
Item Type: Report (Report)
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Date Deposited: 25 Oct 2016 01:27
FoR Codes: 06 BIOLOGICAL SCIENCES > 0605 Microbiology > 060502 Infectious Agents @ 100%
SEO Codes: 96 ENVIRONMENT > 9604 Control of Pests, Diseases and Exotic Species > 960402 Control of Animal Pests, Diseases and Exotic Species in Coastal and Estuarine Environments @ 100%
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