Performance of single versus mixed coral species for transplantation to restore degraded reefs

Coral transplantation has become a potential tool for the restoration of coral cover in degraded reef habitats. Yet, very few investigations have attempted to determine whether there is an advantage for at least two species to be used together in coral transplantation. It is hypothesized that corals would perform better in terms of survival and growth when transplanted in mixed‐ than in single‐species plots. Single‐species plots were compared with combinations of two species at several reef sites, using three separate coral species, namely, Porites cylindrica, Pavona frondifera, and Hydnophora rigida. P. cylindrica performed consistently well in terms of survival whether alone or in the presence of another species. In a stressful environment with strong wave action, P. frondifera performed better when mixed with P. cylindrica than when alone. However, this difference was not evident where wave action was weak. The influence of mixing on the growth rates of H. rigida and P. frondifera transplants could not be examined completely because of high mortality because of predation by the starfish Acanthaster planci and the gastropod Drupella sp. Interestingly, the presence of P. cylindrica appeared to minimize the impact of predation on P. frondifera transplants. The setback caused by predation stresses the importance of other factors that influence the outcome of restoration interventions. Future initiatives should take into consideration management measures when selecting sites in relation to wave action and predators, control predator outbreaks, and use coral species, e.g. P. cylindrica that are less susceptible to predation.     

Development of microsatellite markers for the crown‐of‐thorns starfish Acanthaster planci

We isolated nine polymorphic microsatellites from the crown‐of‐thorns starfish, Acanthaster planci. These loci provide one class of highly variable genetic marker as the number of alleles ranged from three to 12 and the observed and expected heterozygosities ranged from 0.130 to 0.783 and from 0.163 to 0.862, respectively. We consider that these loci are potentially useful for detailing the genetic structure and gene flow among A. planci populations.     

Brown-band syndrome on feeding scars of the crown-of-thorn starfish Acanthaster?planci

Despite the growing impact of coral diseases on reef ecosystems, little is known about the role of coral predation in disease transmission. An experiment on the coral reefs of Derawan Island, Indonesia, revealed brown-band syndrome on Acropora cytherea coral colonies following predation by the crown-of-thorn starfish Acanthaster planci. To experimentally exclude predation, living coral tissue adjacent to feeding scars was enclosed using cages and monitored for 15 days. Compared with similarly caged but uninjured colonies, which showed no sign of disease or tissue loss, preyed upon colonies showed a higher incidence of the disease, coupled with further tissue mortality. This study provides preliminary evidence that A. planci might promote the transmission of some coral diseases.     

The detection of spatial variation in widespread marine species: methods and bias in the analysis of population structure in the crown of thorns starfish (Echinodermata: Asteroidea)

The basic assumptions that widespread marine species should show little spatial variation in genetic structure, given their high potential for dispersal on ocean currents, is being questioned. This has taken some time because there are few studies of widespread marine species over oceanic scales, few data sets that have the high density of sampling required for the detection of fine population structure, and there is little incentive to look further if initial analyses suggest the expected result. The interpretation of the population genetic structure of crown-of-thorns starfish (Acanthaster planci) has been found to vary considerably depending on the sample set included in the analyses and on the method of analysis used. Scatter plots of genetic distance or , and spatial autocorrelation approaches gave markedly different results ranging from no structure to isolation by distance. Only visual examination of maps of patterns of variation in allele variation first detected that crown-of-thorns starfish occupy large regions with little between population differentiation, but between which there are markedly higher levels of differentiation. These findings highlight the care required in interpreting population structure, particularly where there are few sample points. Many marine species may have population structures where sharp genetic disjunctions, not associated with any obvious environmental boundaries, separate regions of relative genetic homogeneity. Such population structures are very different from those traditionally assumed and are not yet understood. Further advances in understanding the genetic structure of marine species will demand an iterative approach where a greater number of samples are collected over particular regions identified by earlier interpretations.     

A gonad-stimulating peptide of the crown-of-thorns starfish,Acanthaster planci

The crown-of thorns starfish, Acanthaster planci, has been blamed for coral mortality in a large number of coral reef systems in the Indo-Pacific region. Because population outbreaks of A. planci are closely related to reproduction, it is important to examine the mechanism of reproductive control in this starfish. Previously, a relaxin-like gonad-stimulating peptide (RGP) in starfish Asterina pectinifera has been identified as the gonadotropin responsible for final gamete maturation. On the basis of homology research on RGP cDNAs from several species, this study was carried out to identify gonadotropin in A. planci. The cDNA sequence of RGP was determined using a RACE product of mRNA from the radial nerves of A. planci. The coding DNA sequence consisted of 351 base pairs with an open reading frame encoding a peptide of 116 amino acids (aa), including a signal peptide (29 aa), B-chain (19 aa), C-peptide (44 aa), and A-chain (24 aa). The chemical structure of A. planci RGP was exactly the same as that of A. pectinifera RGP. Furthermore, synthetic RGP could induce gamete spawning and oocyte maturation in the ovarian fragments of A. planci. This strongly suggested that the RGP is a gonadotropin in A. planci.     

A threat to coral reefs multiplied? Four species of crown-of-thorns starfish

In the face of ever-increasing threats to coral reef ecosystems, it is essential to understand the impact of natural predators in order to devise appropriate management strategies. Destructive population explosions of the crown-of-thorns starfish Acanthaster planci have devastated coral reefs throughout the Indo-Pacific for decades. But despite extensive research, the causes of outbreaks are still unclear. An important consideration in this research is that A. planci has been regarded as a single taxonomic entity. Using molecular data from its entire distribution, we find that A. planci is in fact a species complex. This discovery has important consequences for future coral reef research, and might prove critical for successful reef conservation management.     

Genomic organization of Hox and ParaHox clusters in the echinoderm,Acanthaster planci

The organization of echinoderm Hox clusters is of interest due to the role that Hox genes play in deuterostome development and body plan organization, and the unique gene order of the Hox complex in the sea urchin Strongylocentrotus purpuratus, which has been linked to the unique development of the axial region. Here, it has been reported that the Hox and ParaHox clusters of Acanthaster planci, a corallivorous starfish found in the Pacific and Indian oceans, generally resembles the chordate and hemichordate clusters. The A. planci Hox cluster shared with sea urchins the loss of one of the medial Hox genes, even‐skipped (Evx) at the anterior of the cluster, as well as organization of the posterior Hox genes. genesis 52:952–958, 2014. © 2014 Wiley Periodicals, Inc.     

Specialization in habitat use by coral reef damselfishes and their susceptibility to habitat loss

While it is generally assumed that specialist species are more vulnerable to disturbance compared with generalist counterparts, this has rarely been tested in coastal marine ecosystems, which are increasingly subject to a wide range of natural and anthropogenic disturbances. Habitat specialists are expected to be more vulnerable to habitat loss because habitat availability exerts a greater limitation on population size, but it is also possible that specialist species may escape effects of disturbance if they use habitats that are generally resilient to disturbance. This study quantified specificity in use of different coral species by six coral‐dwelling damselfishes (Chromis viridis, C. atripectoralis, Dascyllus aruanus, D. reticulatus, Pomacentrus moluccensis, and P. amboinensis) and related habitat specialization to proportional declines in their abundance following habitat degradation caused by outbreaks of the coral eating starfish, Acanthaster planci. The coral species preferred by most coral‐dwelling damselfishes (e.g., Pocillopora damicornis) were frequently consumed by coral eating crown‐of‐thorns starfish, such that highly specialized damselfishes were disproportionately affected by coral depletion, despite using a narrower range of different coral species. Vulnerability of damselfishes to this disturbance was strongly correlated with both their reliance on corals and their degree of habitat specialization. Ongoing disturbances to coral reef ecosystems are expected, therefore, to lead to fundamental shifts in the community structure of fish communities where generalists are favored over highly specialist species.     

Declines in the abundance of Chaetodon butterflyfishes following extensive coral depletion

This study documented temporal variation in the abundance of butterflyfishes (Chaetodontidae) at Trunk Reef, on the central Great Barrier Reef, Australia, from May 2000 to March 2005. During this period, live coral cover declined by >90%, mostly due to severe coral bleaching. There were no short-term changes (within 4 months) in the abundance of butterflyfishes following initial declines in live coral cover. Surveys conducted in 2005, however, revealed significant declines in the abundance of Chaetodon baronessa , Chaetodon lunulatus , Chaetodon trifascialis, Chaetodon plebeius and Chaetodon rainfordi , all of which are obligate hard-coral feeders. In contrast, there was no significant change in the abundance of Chaetodon auriga , Chaetodon aureofasciatus , Chaetodon citrinellus , Chaetodon melannotus or Chaetodon vagabundus , which are much less reliant on scleractinian coral for food. Clearly, extensive coral depletion, such as that caused by severe coral bleaching, can have a major effect on the abundance of butterflyfishes. Specific responses of butterflyfishes varied according to their reliance on hard corals for food and their ability to utilize alternate prey types.