Special Issue "Biology, Ecology and Management of Crown-of-Thorns Starfish"

A special issue of Diversity (ISSN 1424-2818). This special issue belongs to the section "Marine Diversity".

Deadline for manuscript submissions: closed (30 November 2016)

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Guest Editor
Prof. Morgan Pratchett

ARC Centre of Excellence for Coral Reef Studies, James Cook University, QLD 4811, Townsville, Australia
Website | E-Mail
Interests: butterflyfishes; coral biology; crown-of-thorns starfish; coral reef management; dietary and habitat specialisation; disturbance ecology; ecology of reef fishes
Guest Editor
Dr. Sven Uthicke

Australian Institute of Marine Science, Townsville, Qld, Australia
Website | E-Mail
Interests: crown-of-thorns-seastar; climate change; ocean acidification; adaptation to stress; cumulative impacts; coral reef ecosystems

Special Issue Information

Dear Colleagues,

Outbreaks of crown-of-thorns starfish (Acanthaster spp.) are a major contributor to ongoing coral loss on reefs throughout the Indo-Pacific, thereby jeopardising productivity and biodiversity of these important marine ecosystems. Controlling outbreak populations of Acanthaster spp. is considered one of the most promising strategies to halt or reverse widespread declines in live coral cover (e.g., De’ath et al. 2012), which is critically important in improving the capacity of coral reef ecosystems to cope with inevitable threats caused by sustained and ongoing climate change, as well as other more direct anthropogenic disturbances. Effective management of crown-of-thorns starfish is, however, conditional on improved understanding of their biology and ecology. While crown-of-thorns starfish are arguably the most extensively studied of any single coral reef species, there remain considerable gaps in our knowledge of their basic biology and ecology. For example, there is little to no information on rates and causes of mortality for crown-of-thorns starfish. This Special Issue provides a platform to highlight new research and significant advances in understanding of crown-of-thorns starfish.

Prof. Morgan Pratchett
Dr. Sven Uthicke
Guest Editor

Manuscript Submission Information

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Keywords

  • Acanthaster spp.
  • Coral reefs
  • Disturbance
  • Ecology
  • Habitat loss
  • Management

Published Papers (18 papers)

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Research

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Open AccessFeature PaperArticle Age and Growth of An Outbreaking Acanthaster cf. solaris Population within the Great Barrier Reef
Diversity 2017, 9(1), 18; doi:10.3390/d9010018
Received: 20 December 2016 / Revised: 6 March 2017 / Accepted: 8 March 2017 / Published: 14 March 2017
Cited by 3 | PDF Full-text (2695 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Despite having been studied for more than 40 years, much about the basic life history of crown-of-thorns starfish (CoTS; Acanthaster spp.) remains poorly understood. Size at age—a key metric of productivity for any animal population—has yet to be clearly defined, primarily due to
[...] Read more.
Despite having been studied for more than 40 years, much about the basic life history of crown-of-thorns starfish (CoTS; Acanthaster spp.) remains poorly understood. Size at age—a key metric of productivity for any animal population—has yet to be clearly defined, primarily due to difficulties in obtaining validated ages and potentially indeterminate growth due to factors such as starvation; within-population variability is entirely unknown. Here we develop age and growth estimates for an outbreaking CoTS population in Australian waters by integrating prior information with data from CoTS collected from multiple outbreaking reefs. Age estimates were made from un-validated band counts of 2038 individual starfish. Results from our three-parameter von Bertalanffy Bayesian hierarchical model show that, under 2013–2014 outbreak conditions, CoTS on the GBR grew to a 349 (326, 380) mm (posterior median (95% uncertainty interval)) total diameter at a 0.54 (0.43, 0.66) intrinsic rate of increase. However, we also found substantial evidence (ΔDIC > 200) for inter-reef variability in both maximum size (SD 38 (19, 76)) and intrinsic rate of increase (SD 0.32 (0.20, 0.49)) within the CoTS outbreak initiation area. These results suggest that CoTS demography can vary widely with reef-scale environmental conditions, supporting location-based mechanisms for CoTS outbreaks generally. These findings should help improve population and metapopulation models of CoTS dynamics and better predict the potential damage they may cause in the future. Full article
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Open AccessArticle Microsatellites Reveal Genetic Homogeneity among Outbreak Populations of Crown-of-Thorns Starfish (Acanthaster cf. solaris) on Australia’s Great Barrier Reef
Diversity 2017, 9(1), 16; doi:10.3390/d9010016
Received: 30 November 2016 / Revised: 5 March 2017 / Accepted: 7 March 2017 / Published: 10 March 2017
Cited by 6 | PDF Full-text (804 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Specific patterns in the initiation and spread of reef-wide outbreaks of crown-of-thorns starfish are important, both to understand potential causes (or triggers) of outbreaks and to develop more effective and highly targeted management and containment responses. Using analyses of genetic diversity and structure
[...] Read more.
Specific patterns in the initiation and spread of reef-wide outbreaks of crown-of-thorns starfish are important, both to understand potential causes (or triggers) of outbreaks and to develop more effective and highly targeted management and containment responses. Using analyses of genetic diversity and structure (based on 17 microsatellite loci), this study attempted to resolve the specific origin for recent outbreaks of crown-of-thorns on Australia’s Great Barrier Reef (GBR). We assessed the genetic structure amongst 2705 starfish collected from 13 coral reefs in four regions that spanned ~1000 km of the GBR. Our results indicate that populations sampled across the full length of the GBR are genetically homogeneous (G’ST = −0.001; p = 0.948) with no apparent genetic structure between regions. Approximate Bayesian computational analyses suggest that all sampled populations had a common origin and that current outbreaking populations of crown-of-thorns starfish (CoTS) in the Swains are not independent of outbreak populations in the northern GBR. Despite hierarchical sampling and large numbers of CoTS genotyped from individual reefs and regions, limited genetic structure meant we were unable to determine a putative source population for the current outbreak of CoTS on the GBR. The very high genetic homogeneity of sampled populations and limited evidence of inbreeding indicate rapid expansion in population size from multiple, undifferentiated latent populations. Full article
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Open AccessArticle Interactive Effects of Endogenous and Exogenous Nutrition on Larval Development for Crown-Of-Thorns Starfish
Diversity 2017, 9(1), 15; doi:10.3390/d9010015
Received: 30 November 2016 / Revised: 22 February 2017 / Accepted: 27 February 2017 / Published: 4 March 2017
Cited by 1 | PDF Full-text (1817 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Outbreaks of crown-of-thorns starfish are often attributed to step-changes in larval survivorship following anomalous increases in nutrients and food availability. However, larval growth and development is also influenced by the nutritional condition of spawning females, such that maternal provisioning may offset limitations imposed
[...] Read more.
Outbreaks of crown-of-thorns starfish are often attributed to step-changes in larval survivorship following anomalous increases in nutrients and food availability. However, larval growth and development is also influenced by the nutritional condition of spawning females, such that maternal provisioning may offset limitations imposed by limited access to exogenous sources of nutrients during the formative stages of larval development. This study examined the individual, additive, and interactive effects of endogenous (maternal diet: Acropora, Porites, mixed, and starved) and exogenous (larval diet: high concentration at 104 cells·mL−1, low concentration at 103 algal cells·mL−1, and starved) nutrition on the survival, growth, morphology, and development of larvae of the crown-of-thorns starfish. Female starfish on Acropora and mixed diet produced bigger oocytes compared to Porites-fed and starved treatments. Using oocyte size as a proxy for maternal provisioning, endogenous reserves in the oocyte had a strong influence on initial larval survival and development. This suggests that maternal reserves can delay the onset of obligate exogenous food acquisition and allow larvae to endure prolonged periods of poor environmental nutritive conditions or starvation. The influence of exogenous nutrition became more prominent in later stages, whereby none of the starved larvae reached the mid-to-late brachiolaria stage 16 days after the onset of the ability to feed. There was no significant difference in the survival, development, and competency of larvae between high and low food treatments. Under low algal food conditions, larvae compensate by increasing the length of ciliated feeding bands in relation to the maximum length and width, which improve food capture and feeding efficiency. However, the effects of endogenous nutrition persisted in the later developmental stages, as larvae from starved females were unable to develop larger feeding structures in response to food-limiting conditions. Phenotypic plasticity influenced by endogenous provisions and in response to exogenous food availability may be an important strategy in boosting the reproductive success of crown-of-thorns starfish, leading to population outbreaks. Full article
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Open AccessArticle The Effects of Salinity and pH on Fertilization, Early Development, and Hatching in the Crown-of-Thorns Seastar
Diversity 2017, 9(1), 13; doi:10.3390/d9010013
Received: 2 December 2016 / Revised: 4 February 2017 / Accepted: 10 February 2017 / Published: 22 February 2017
Cited by 1 | PDF Full-text (1340 KB) | HTML Full-text | XML Full-text
Abstract
Understanding the influence of environmental factors on the development and dispersal of crown-of-thorns seastars is critical to predicting when and where outbreaks of these coral-eating seastars will occur. Outbreaks of crown-of-thorns seastars are hypothesized to be driven by terrestrial runoff events that increase
[...] Read more.
Understanding the influence of environmental factors on the development and dispersal of crown-of-thorns seastars is critical to predicting when and where outbreaks of these coral-eating seastars will occur. Outbreaks of crown-of-thorns seastars are hypothesized to be driven by terrestrial runoff events that increase nutrients and the phytoplankton food for the larvae. In addition to increasing larval food supply, terrestrial runoff may also reduce salinity in the waters where seastars develop. We investigated the effects of reduced salinity on the fertilization and early development of seastars. We also tested the interactive effects of reduced salinity and reduced pH on the hatching of crown-of-thorns seastars. Overall, we found that reduced salinity has strong negative effects on fertilization and early development, as shown in other echinoderm species. We also found that reduced salinity delays hatching, but that reduced pH, in isolation or in combination with lower salinity, had no detectable effects on this developmental milestone. Models that assess the positive effects of terrestrial runoff on the development of crown-of-thorns seastars should also consider the strong negative effects of lower salinity on early development including lower levels of fertilization, increased frequency of abnormal development, and delayed time to hatching. Full article
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Open AccessArticle Variation in Incidence and Severity of Injuries among Crown-of-Thorns Starfish (Acanthaster cf. solaris) on Australia’s Great Barrier Reef
Diversity 2017, 9(1), 12; doi:10.3390/d9010012
Received: 8 December 2016 / Accepted: 10 February 2017 / Published: 21 February 2017
Cited by 3 | PDF Full-text (1884 KB) | HTML Full-text | XML Full-text
Abstract
Despite the presence of numerous sharp poisonous spines, adult crown-of-thorns starfish (CoTS) are vulnerable to predation, though the importance and rates of predation are generally unknown. This study explores variation in the incidence and severity of injuries for Acanthaster cf. solaris from Australia’s
[...] Read more.
Despite the presence of numerous sharp poisonous spines, adult crown-of-thorns starfish (CoTS) are vulnerable to predation, though the importance and rates of predation are generally unknown. This study explores variation in the incidence and severity of injuries for Acanthaster cf. solaris from Australia’s Great Barrier Reef. The major cause of such injuries is presumed to be sub-lethal predation such that the incidence of injuries may provide a proxy for overall predation and mortality rates. A total of 3846 Acanthaster cf. solaris were sampled across 19 reefs, of which 1955 (50.83%) were injured. Both the incidence and severity of injuries decreased with increasing body size. For small CoTS (<125 mm total diameter) >60% of individuals had injuries, and a mean 20.7% of arms (±2.9 SE) were affected. By comparison, <30% of large (>450 mm total diameter) CoTS had injuries, and, among those, only 8.3% of arms (±1.7 SE) were injured. The incidence of injuries varied greatly among reefs but was unaffected by the regulations of local fisheries. Full article
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Open AccessArticle Environmental Tipping Points for Sperm Motility, Fertilization, and Embryonic Development in the Crown-of-Thorns Starfish
Diversity 2017, 9(1), 10; doi:10.3390/d9010010
Received: 30 November 2016 / Revised: 25 January 2017 / Accepted: 10 February 2017 / Published: 15 February 2017
Cited by 3 | PDF Full-text (1339 KB) | HTML Full-text | XML Full-text
Abstract
For broadcast spawning invertebrates such as the crown-of-thorns starfish, early life history stages (from spawning to settlement) may be exposed to a wide range of environmental conditions, and could have a major bearing on reproductive success and population replenishment. Arrested development in response
[...] Read more.
For broadcast spawning invertebrates such as the crown-of-thorns starfish, early life history stages (from spawning to settlement) may be exposed to a wide range of environmental conditions, and could have a major bearing on reproductive success and population replenishment. Arrested development in response to multiple environmental stressors at the earliest stages can be used to define lower and upper limits for normal development. Here, we compared sperm swimming speeds and proportion of motile sperm and rates of fertilization and early development under a range of environmental variables (temperature: 20–36 °C, salinity: 20–34 psu, and pH: 7.4–8.2) to identify environmental tipping points and thresholds for reproductive success. We also tested the effects of water-soluble compounds, derived from eggs, on sperm activity. Our results demonstrate that gametes, fertilization, and embryonic development are robust to a wide range of temperature, salinity, and pH levels that are outside the range found at the geographical limits of adult distribution and can tolerate environmental conditions that exceed expected anomalies as a result of climate change. Water-soluble compounds derived from eggs also enhanced sperm activity, particularly in environmental conditions where sperm motility was initially limited. These findings suggest that fertilization and embryonic development of crown-of-thorns starfish are tolerant to a wide range of environmental conditions, though environmental constraints on recruitment success may occur at later ontogenic stages. Full article
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Open AccessArticle Selective Feeding and Microalgal Consumption Rates by Crown-Of-Thorns Seastar (Acanthaster cf. solaris) Larvae
Diversity 2017, 9(1), 8; doi:10.3390/d9010008
Received: 24 November 2016 / Revised: 25 January 2017 / Accepted: 30 January 2017 / Published: 7 February 2017
Cited by 3 | PDF Full-text (1978 KB) | HTML Full-text | XML Full-text
Abstract
Outbreaks of the crown-of-thorns seastar (CoTS) represent a major cause of coral loss on the Great Barrier Reef. Outbreaks can be explained by enhanced larval survival supported by higher phytoplankton availability after flood events, yet little is known about CoTS larvae feeding behaviour,
[...] Read more.
Outbreaks of the crown-of-thorns seastar (CoTS) represent a major cause of coral loss on the Great Barrier Reef. Outbreaks can be explained by enhanced larval survival supported by higher phytoplankton availability after flood events, yet little is known about CoTS larvae feeding behaviour, in particular their potential for selective feeding. Here, single- and mixed-species feeding experiment were conducted on CoTS larvae using five algae (Phaeodactylum tricornutum, Pavlova lutheri, Tisochrysis lutea, Dunaliella sp. and Chaetoceros sp.) and two algal concentrations (1000 and 2500 algae·mL−1). Cell counts using flow-cytometry at the beginning and end of each incubation experiment allowed us to calculate the filtration and ingestion rates of each species by CoTS larvae. In line with previous studies, CoTS larvae ingested more algae when the initial algal concentration was higher. We found evidence for the selective ingestion of some species (Chaetoceros sp., Dunaliella sp.) over others (P. lutheri, P. tricornutum). The preferred algal species had the highest energy content, suggesting that CoTS selectively ingested the most energetic algae. Ultimately, combining these results with spatio-temporal patterns in phytoplankton communities will help elucidate the role of larval feeding behaviour in determining the frequency and magnitude of CoTS outbreaks. Full article
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Open AccessCommunication Larval Survivorship and Settlement of Crown-of-Thorns Starfish (Acanthaster cf. solaris) at Varying Algal Cell Densities
Diversity 2017, 9(1), 2; doi:10.3390/d9010002
Received: 14 November 2016 / Revised: 2 January 2017 / Accepted: 4 January 2017 / Published: 10 January 2017
Cited by 5 | PDF Full-text (589 KB) | HTML Full-text | XML Full-text
Abstract
The dispersal potential of crown-of-thorns starfish (CoTS) larvae is important in understanding both the initiation and spread of population outbreaks, and is fundamentally dependent upon how long larvae can persist while still retaining the capacity to settle. This study quantified variation in larval
[...] Read more.
The dispersal potential of crown-of-thorns starfish (CoTS) larvae is important in understanding both the initiation and spread of population outbreaks, and is fundamentally dependent upon how long larvae can persist while still retaining the capacity to settle. This study quantified variation in larval survivorship and settlement rates for CoTS maintained at three different densities of a single-celled flagellate phytoplankton, Proteomonas sulcata (1 × 103, 1 × 104, and 1 × 105 cells/mL). Based on the larval starvation hypothesis, we expected that low to moderate levels of phytoplankton prey would significantly constrain both survival and settlement. CoTS larvae were successfully maintained for up to 50 days post-fertilization, but larval survival differed significantly between treatments. Survival was greatest at intermediate food levels (1 × 104 cells/mL), and lowest at high (1 × 105 cells/mL) food levels. Rates of settlement were also highest at intermediate food levels and peaked at 22 days post-fertilization. Peak settlement was delayed at low food levels, probably reflective of delayed development, but there was no evidence of accelerated development at high chlorophyll concentrations. CoTS larvae were recorded to settle 17–43 days post-fertilization, but under optimum conditions with intermediate algal cell densities, peak settlement occurred at 22 days post-fertilization. Natural fluctuations in nutrient concentrations and food availability may affect the number of CoTS that effectively settle, but seem unlikely to influence dispersal dynamics. Full article
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Open AccessArticle Modelling Growth of Juvenile Crown-of-Thorns Starfish on the Northern Great Barrier Reef
Diversity 2017, 9(1), 1; doi:10.3390/d9010001
Received: 18 November 2016 / Revised: 23 December 2016 / Accepted: 26 December 2016 / Published: 29 December 2016
Cited by 3 | PDF Full-text (3135 KB) | HTML Full-text | XML Full-text
Abstract
The corallivorous crown-of-thorns starfish (Acanthaster spp.) is a major cause of coral mortality on Indo-Pacific reefs. Despite considerable research into the biology of crown-of-thorns starfish, our understanding of the early post-settlement life stage has been hindered by the small size and cryptic
[...] Read more.
The corallivorous crown-of-thorns starfish (Acanthaster spp.) is a major cause of coral mortality on Indo-Pacific reefs. Despite considerable research into the biology of crown-of-thorns starfish, our understanding of the early post-settlement life stage has been hindered by the small size and cryptic nature of recently settled individuals. Most growth rates are derived from either laboratory studies or field studies conducted in Fiji and Japan. The Great Barrier Reef (GBR) is currently experiencing its fourth recorded outbreak and population models to inform the progression of outbreaks lack critical growth rates of early life history stages. High numbers of 0+ year juveniles (n = 3532) were measured during extensive surveys of 64 reefs on the northern GBR between May and December 2015. An exponential growth model was fitted to the size measurement data to estimate monthly ranges of growth rates for 0+ year juveniles. Estimated growth rates varied considerably and increased with age (e.g., 0.028–0.041 mm·day−1 for one-month-old juveniles versus 0.108–0.216 mm·day−1 for twelve-month-old juveniles). This pioneering study of 0+ year juveniles on the GBR will inform population models and form the basis for more rigorous ongoing research to understand the fate of newly settled Acanthaster spp. Full article
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Open AccessArticle Citric Acid Injections: An Accessible and Efficient Method for Controlling Outbreaks of the Crown-of-Thorns Starfish Acanthaster cf. solaris
Diversity 2016, 8(4), 28; doi:10.3390/d8040028
Received: 10 October 2016 / Revised: 29 November 2016 / Accepted: 3 December 2016 / Published: 10 December 2016
Cited by 2 | PDF Full-text (1491 KB) | HTML Full-text | XML Full-text
Abstract
Outbreaks of the crown-of-thorns starfish (Acanthaster cf. solaris, COTS) are one of the primary causes of coral decline in the Indo-Pacific region. Effective methods to control COTS outbreaks may therefore be one of the most direct and immediate ways to reduce
[...] Read more.
Outbreaks of the crown-of-thorns starfish (Acanthaster cf. solaris, COTS) are one of the primary causes of coral decline in the Indo-Pacific region. Effective methods to control COTS outbreaks may therefore be one of the most direct and immediate ways to reduce coral loss. However, the cost and logistical challenges associated with current control methods have undermined the effectiveness of many control efforts. In this study, we tested the feasibility of using powdered citric acid, which is widely available and low-cost, as an injection chemical for COTS control. We tested what combination of concentration, number of injections, volume, and water type were most efficient at killing COTS. All COTS injected in two or four sites died, irrespectively of the concentration of citric acid used, while single injections failed at reaching 100% mortality. The fastest combination was the injection of 150 g·L−1 citric acid solution in four injection sites (5 mL per site), which killed the starfish in 26.4 ± 4 h. These results suggest that injections of powdered citric acid are an effective, economical, and widely available alternative to current COTS control methods. Full article
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Open AccessArticle Benthic Predators Influence Microhabitat Preferences and Settlement Success of Crown-of-Thorns Starfish (Acanthaster cf. solaris)
Diversity 2016, 8(4), 27; doi:10.3390/d8040027
Received: 28 October 2016 / Revised: 4 December 2016 / Accepted: 6 December 2016 / Published: 9 December 2016
Cited by 3 | PDF Full-text (1018 KB) | HTML Full-text | XML Full-text
Abstract
Like most coral reef organisms, crown-of-thorns starfish (Acanthaster spp.) are expected to be highly vulnerable to predation as they transition from a planktonic larval phase to settling among reef habitats. Accordingly, crown-of-thorns starfish might be expected to exhibit behavioural adaptations which moderate
[...] Read more.
Like most coral reef organisms, crown-of-thorns starfish (Acanthaster spp.) are expected to be highly vulnerable to predation as they transition from a planktonic larval phase to settling among reef habitats. Accordingly, crown-of-thorns starfish might be expected to exhibit behavioural adaptations which moderate exposure to predation at this critical stage in their life history. Using pairwise choice experiments and settlement assays, we explored the ability of competent larvae of Acanthaster cf. solaris to first detect and then actively avoid benthic predators during settlement. Pairwise choice experiments revealed that late stage brachiolaria larvae are able to detect predators in the substrate and where possible, will preferentially settle in microhabitats without predators. Settlement assays (without choices) revealed that larvae do not necessarily delay settlement in the presence of predators, but high levels of predation on settling larvae by benthic predators significantly reduce the number of larvae that settle successfully. Taken together, these results show that crown-of-thorns starfish are highly vulnerable to benthic predators during settlement, and that variation in the abundance of benthic predators may exert a significant influence on patterns of settlement for crown-of-thorns starfish. Full article
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Open AccessArticle The Influence of Water Currents on Movement Patterns on Sand in the Crown-of-Thorns Seastar (Acanthaster cf. solaris)
Diversity 2016, 8(4), 25; doi:10.3390/d8040025
Received: 9 October 2016 / Revised: 16 November 2016 / Accepted: 17 November 2016 / Published: 25 November 2016
Cited by 3 | PDF Full-text (1667 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Outbreaks of the coral-eating crown-of-thorns seastar (Acanthaster cf. solaris) threaten coral reefs of the Indo-Pacific. Movement patterns may play an important role in the spread of outbreak populations, but studies investigating adult movement behavior are scarce. It remains unknown if Acanthaster
[...] Read more.
Outbreaks of the coral-eating crown-of-thorns seastar (Acanthaster cf. solaris) threaten coral reefs of the Indo-Pacific. Movement patterns may play an important role in the spread of outbreak populations, but studies investigating adult movement behavior are scarce. It remains unknown if Acanthaster cf. solaris orientates in inter-reef areas using chemical, visual, or mechanical cues (e.g., water currents) or which trigger is used for the onset of movement. We investigated the movement patterns of adult starved, fed, and blinded A. cf. solaris on sand at two sites with different unidirectional water current strengths. We found that the movement direction of the seastars in strong currents was downstream, whereas movement in weaker currents was random and independent from the current direction. However, the directionality of movement was consistently high, independent of the nutritional state, its visual abilities, or current strength. Starved A. cf. solaris started to move significantly faster compared to fed individuals. Therefore, starvation might trigger the onset of movement. Our findings indicate that navigation of A. cf. solaris in inter-reef areas is inefficient. Movements between reefs may be random or current-dependent and finding a new reef from a distance subject to chance, unless it is only few meters away. Full article
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Open AccessArticle Using Long-Term Removal Data to Manage a Crown-of-Thorns Starfish Population
Diversity 2016, 8(4), 24; doi:10.3390/d8040024
Received: 21 September 2016 / Revised: 11 November 2016 / Accepted: 14 November 2016 / Published: 18 November 2016
Cited by 3 | PDF Full-text (1062 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Background: Removal programs are effective strategies for short-term management of Crown-of-Thorns Starfish (Acanthaster spp.) populations, especially on a small scale. However, management programs are costly, and, in order to be effective, they must be based on local Acanthaster spp. population dynamics. We
[...] Read more.
Background: Removal programs are effective strategies for short-term management of Crown-of-Thorns Starfish (Acanthaster spp.) populations, especially on a small scale. However, management programs are costly, and, in order to be effective, they must be based on local Acanthaster spp. population dynamics. We have developed simple models to predict the annual number of removable A. cf. solaris along the Onna coast of western central Okinawa Island, where chronic outbreaks have continued for several decades. Methods: The Onna coastal area was divided into five sectors, and annual abundance of small A. cf. solaris individuals was used to predict the total number of removable individuals of a cohort in each sector. Three models were developed, based on size class data collected by the Onna Village Fisheries Cooperative (OVFC) for 2003–2015, according to possible patterns of recruitment and adult occurrence. Using the best-fit models selected for each of the five sectors, the number of individuals that potentially escaped removal was calculated. Results: Best-fit models were likely to differ among the five sectors instead of small differences in the coefficients of determination. The models predict differences in the number of residual starfish among sectors; the northernmost sector was predicted to have a high number of residuals and the potential density of A. cf. solaris in the sector exceeded the outbreak criterion. Conclusions: These results suggest how to allocate resources to reduce the population of A. cf. solaris along the Onna coast in 2016. The OVFC implemented a control program for A. cf. solaris based on three model predictions. Full article
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Open AccessCommunication Crown-of-Thorns Starfish Larvae Can Feed on Organic Matter Released from Corals
Diversity 2016, 8(4), 18; doi:10.3390/d8040018
Received: 10 August 2016 / Accepted: 28 September 2016 / Published: 6 October 2016
Cited by 6 | PDF Full-text (451 KB) | HTML Full-text | XML Full-text
Abstract
Previous studies have suggested that Crown-of-Thorns starfish (COTS) larvae may be able to survive in the absence of abundant phytoplankton resources suggesting that they may be able to utilize alternative food sources. Here, we tested the hypothesis that COTS larvae are able to
[...] Read more.
Previous studies have suggested that Crown-of-Thorns starfish (COTS) larvae may be able to survive in the absence of abundant phytoplankton resources suggesting that they may be able to utilize alternative food sources. Here, we tested the hypothesis that COTS larvae are able to feed on coral-derived organic matter using labeled stable isotope tracers (13C and 15N). Our results show that coral-derived organic matter (coral mucus and associated microorganisms) can be assimilated by COTS larvae and may be an important alternative or additional food resource for COTS larvae through periods of low phytoplankton biomass. This additional food resource could potentially facilitate COTS outbreaks by reducing resource limitation. Full article
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Review

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Open AccessReview Thirty Years of Research on Crown-of-Thorns Starfish (1986–2016): Scientific Advances and Emerging Opportunities
Diversity 2017, 9(4), 41; doi:10.3390/d9040041
Received: 22 August 2017 / Revised: 14 September 2017 / Accepted: 14 September 2017 / Published: 21 September 2017
Cited by 1 | PDF Full-text (3328 KB) | HTML Full-text | XML Full-text
Abstract
Research on the coral-eating crown-of-thorns starfish (CoTS) has waxed and waned over the last few decades, mostly in response to population outbreaks at specific locations. This review considers advances in our understanding of the biology and ecology of CoTS based on the resurgence
[...] Read more.
Research on the coral-eating crown-of-thorns starfish (CoTS) has waxed and waned over the last few decades, mostly in response to population outbreaks at specific locations. This review considers advances in our understanding of the biology and ecology of CoTS based on the resurgence of research interest, which culminated in this current special issue on the Biology, Ecology and Management of Crown-of-Thorns Starfish. More specifically, this review considers progress in addressing 41 specific research questions posed in a seminal review by P. Moran 30 years ago, as well as exploring new directions for CoTS research. Despite the plethora of research on CoTS (>1200 research articles), there are persistent knowledge gaps that constrain effective management of outbreaks. Although directly addressing some of these questions will be extremely difficult, there have been considerable advances in understanding the biology of CoTS, if not the proximate and ultimate cause(s) of outbreaks. Moving forward, researchers need to embrace new technologies and opportunities to advance our understanding of CoTS biology and behavior, focusing on key questions that will improve effectiveness of management in reducing the frequency and likelihood of outbreaks, if not preventing them altogether. Full article
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Open AccessReview Potential Enhanced Survivorship of Crown of Thorns Starfish Larvae due to Near-Annual Nutrient Enrichment during Secondary Outbreaks on the Central Mid-Shelf of the Great Barrier Reef, Australia
Diversity 2017, 9(1), 17; doi:10.3390/d9010017
Received: 7 December 2016 / Revised: 6 March 2017 / Accepted: 7 March 2017 / Published: 12 March 2017
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Abstract
The Great Barrier Reef (GBR) is currently experiencing widespread crown of thorns starfish (CoTS) outbreaks, as part of the fourth wave of outbreaks since 1962. It is believed that these outbreaks have become more frequent on the GBR and elsewhere in the Indo-Pacific
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The Great Barrier Reef (GBR) is currently experiencing widespread crown of thorns starfish (CoTS) outbreaks, as part of the fourth wave of outbreaks since 1962. It is believed that these outbreaks have become more frequent on the GBR and elsewhere in the Indo-Pacific and are associated with anthropogenic causes. The two widely accepted potential causes are (1) anthropogenic nutrient enrichment leading to the increased biomass of phytoplankton, the food of the planktonic stage of larval CoTS; and (2) the overfishing of predators in the juvenile to adult stages of CoTS, for example, commercially fished species such as coral trout. In this study, we show that the evidence for the nutrient enrichment causation hypothesis is strongly based on a large number of recent studies in the GBR. We also hypothesise that secondary outbreaks in the region between Cairns and Townsville can also be enhanced by nutrient enriched conditions associated with the annual nutrient discharge from Wet Tropics rivers. Full article
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Open AccessReview Known Predators of Crown-of-Thorns Starfish (Acanthaster spp.) and Their Role in Mitigating, If Not Preventing, Population Outbreaks
Diversity 2017, 9(1), 7; doi:10.3390/d9010007
Received: 20 November 2016 / Revised: 3 January 2017 / Accepted: 17 January 2017 / Published: 22 January 2017
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Abstract
Predatory release has long been considered a potential contributor to population outbreaks of crown-of-thorns starfish (CoTS; Acanthaster spp.). This has initiated extensive searches for potentially important predators that can consume large numbers of CoTS at high rates, which are also vulnerable to over-fishing
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Predatory release has long been considered a potential contributor to population outbreaks of crown-of-thorns starfish (CoTS; Acanthaster spp.). This has initiated extensive searches for potentially important predators that can consume large numbers of CoTS at high rates, which are also vulnerable to over-fishing or reef degradation. Herein, we review reported predators of CoTS and assess the potential for these organisms to exert significant mortality, and thereby prevent and/or moderate CoTS outbreaks. In all, 80 species of coral reef organisms (including fishes, and motile and sessile invertebrates) are reported to predate on CoTS gametes (three species), larvae (17 species), juveniles (15 species), adults (18 species) and/or opportunistically feed on injured (10 species) or moribund (42 species) individuals within reef habitats. It is clear however, that predation on early life-history stages has been understudied, and there are likely to be many more species of reef fishes and/or sessile invertebrates that readily consume CoTS gametes and/or larvae. Given the number and diversity of coral reef species that consume Acanthaster spp., most of which (e.g., Arothron pufferfishes) are not explicitly targeted by reef-based fisheries, links between overfishing and CoTS outbreaks remain equivocal. There is also no single species that appears to have a disproportionate role in regulating CoTS populations. Rather, the collective consumption of CoTS by multiple different species and at different life-history stages is likely to suppress the local abundance of CoTS, and thereby mediate the severity of outbreaks. It is possible therefore, that general degradation of reef ecosystems and corresponding declines in biodiversity and productivity, may contribute to increasing incidence or severity of outbreaks of Acanthaster spp. However, it seems unlikely that predatory release in and of itself could account for initial onset of CoTS outbreaks. In conclusion, reducing anthropogenic stressors that reduce the abundance and/or diversity of potential predatory species represents a “no regrets” management strategy, but will need to be used in conjunction with other management strategies to prevent, or reduce the occurrence, of CoTS outbreaks. Full article
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Open AccessOpinion Persistent Gaps of Knowledge for Naming and Distinguishing Multiple Species of Crown-of-Thorns-Seastar in the Acanthaster planci Species Complex
Diversity 2017, 9(2), 22; doi:10.3390/d9020022
Received: 19 September 2016 / Revised: 18 April 2017 / Accepted: 9 May 2017 / Published: 12 May 2017
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Abstract
Nearly a decade ago, DNA barcoding (partial mitochondrial COI gene sequences) showed that there are at least four species in the Indo-Pacific within what was previously conceived to be a single Crown-of-Thorns-Seastar (COTS) species, Acanthaster planci. Two of these species—A. planci
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Nearly a decade ago, DNA barcoding (partial mitochondrial COI gene sequences) showed that there are at least four species in the Indo-Pacific within what was previously conceived to be a single Crown-of-Thorns-Seastar (COTS) species, Acanthaster planci. Two of these species—A. planci Linnaeus, 1758, distributed in the North Indian Ocean, and A. mauritiensis de Loriol, 1885, distributed in the South Indian Ocean—have been already unequivocally named. In contrast, the Pacific COTS (proposed name: A. solaris (Schreber, 1795) and the COTS from the Red Sea (still to be named) require further taxonomic work. COI barcoding sequences and Barcode Identification Numbers (BINs) are available for all four COTS species in the global Barcode of Life Database (BOLD). We recommend depositing voucher specimens or tissue samples suitable for DNA analyses when studying any aspect of COTS, and use BINs to identify species, to ensure that no information is lost on species allocation until unequivocal Linnean names are available for the Pacific and Red Sea species as well. We also review the differences between COTS species with respect to morphology, ecology, and toxicity. Future studies should widen the current biogeographic coverage of the different COTS species by strategically sampling neglected areas, especially at the geographic distribution limits of each species, to enhance our understanding of the diversity of this reef coral predator. Full article
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