Larval cloning in the crown-of-thorns sea star, a keystone coral predator

Allen, Jonathan D.; Richardson, Emily L.; Deaker, Dione J.; Agüera, Antonio; Byrne, Maria

doi:10.3354/meps12843

Cited by 31 publications

(21 citation statements)

References 30 publications

(51 reference statements)

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“…The resilience of the herbivorous juvenile COTS to coral scarcity adds to the suite of remarkable traits that may contribute to its boom-bust dynamics. Larval plasticity is seen in cloning and body form and potential nutritive augmentation from a phototropic microbiome to dissolved organic matter [29][30][31][32], and some adults may be hermaphrodites [33]. That the herbivorous phase has the potential to accumulate in the reef infrastructure for years to seed an outbreak should be considered alongside the current larva-centric model of COTS outbreaks.…”

Section: Discussionmentioning

confidence: 99%

The hidden army: corallivorous crown-of-thorns seastars can spend years as herbivorous juveniles

et al. 2020

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Crown-of-thorns seastar (COTS) outbreaks are a major threat to coral reefs. Although the herbivorous juveniles and their switch to corallivory are key to seeding outbreaks, they remain a black box in our understanding of COTS. We investigated the impact of a delay in diet transition due to coral scarcity in cohorts reared on crustose coralline algae for 10 months and 6.5 years before being offered coral. Both cohorts achieved an asymptotic size (16-18 mm diameter) on algae and had similar exponential growth on coral. After 6.5 years of herbivory, COTS were competent coral predators. This trophic and growth plasticity results in a marked age-size disconnect adding unappreciated complexity to COTS boom-bust dynamics. The potential that herbivorous juveniles accumulate in the reef infrastructure to seed outbreaks when favourable conditions arise has implications for management of COTS populations.

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Section: Discussionmentioning

confidence: 99%

The hidden army: corallivorous crown-of-thorns seastars can spend years as herbivorous juveniles

et al. 2020

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“…If hermaphrodites are more common than expected and if such individuals are self‐fertile, then reproductive assurance through self‐fertilization (Jarne & Auld, ) in COTS could be added to the growing list of life history traits (e.g., larval cloning; Allen, Richardson, Deaker, Aguera, & Byrne, ) that are likely to facilitate high reproductive success, and the boom‐and‐bust nature of the population outbreaks that decimate coral reefs. The interpretation of facultative hermaphroditism in COTS as a potential adaptation depends on the phylogenetic context: in taxa such as sea stars in which most species are gonochoric outcrossers, the occurrence of facultative hermaphrodites is evolutionarily derived and might be considered an adaptation.…”

Section: Discussionmentioning

confidence: 99%

Nonspecific expression of fertilization genes in the crown‐of‐thorns Acanthaster cf. solaris: Unexpected evidence of hermaphroditism in a coral reef predator

et al. 2020

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The characterization of gene expression in gametes has advanced our understanding of the molecular basis for ecological variation in reproductive success and the evolution of reproductive isolation. These advances are especially significant for ecologically important keystone predators such as the coral‐eating crown‐of‐thorns sea stars (COTS, Acanthaster) which are the most influential predator species in Indo‐Pacific coral reef ecosystems and the focus of intensive management efforts. We used RNA‐seq and transcriptome assemblies to characterize the expression of genes in mature COTS gonads. We described the sequence and domain organization of eight genes with sex‐specific expression and well known functions in fertilization in other echinoderms. We found unexpected expression of genes in one ovary transcriptome that are characteristic of males and sperm, including genes that encode the sperm‐specific guanylate cyclase receptor for an egg pheromone, and the sperm acrosomal protein bindin. In a reassembly of previously published RNA‐seq data from COTS testes, we found a complementary pattern: strong expression of four genes that are otherwise well known to encode egg‐specific fertilization proteins, including the egg receptor for bindin (EBR1) and the acrosome reaction‐inducing substance in the egg coat (ARIS1, ARIS2, ARIS3). We also found histological evidence of both eggs and sperm developing in the same gonad in several COTS individuals from a parallel study. These results suggest the occurrence of hermaphrodites, and the potential for reproductive assurance via self‐fertilization. Our findings have implications for management of COTS populations, especially in consideration of the large size and massive fecundity of these sea stars.

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“…An interesting observation was that one juvenile split in half through the central disk, reminiscent of fissiparity in other sea stars [61] and cloning in COTS larvae [62]. One half perished and the surviving half regenerated to a normal juvenile with 16 arms, four more than it had initially.…”

Section: Plos Onementioning

confidence: 98%

Diet flexibility and growth of the early herbivorous juvenile crown-of-thorns sea star, implications for its boom-bust population dynamics

et al. 2020

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The ecology of the early herbivorous juvenile stage of the crown-of-thorns sea star (COTS, Acanthaster spp.) is poorly understood, yet the success of this life stage is key to generating population outbreaks that devastate coral reefs. Crustose coralline algae (CCA) has been considered to be the main diet of herbivorous juveniles. In this study, we show that COTS can avail of a range of algal food. Juveniles were reared on CCA, Amphiroa sp., and biofilm, and survived for 10 months on all three diets. The juveniles fed CCA and Amphiroa sp. reached 15-16.5 mm diameter at~6 months and maintained this size for the rest the experiment (an additional~4 months). Juveniles fed biofilm grew more slowly and to a smaller maximum size (~3 mm diameter). However, when juveniles were switched from biofilm to CCA they resumed growth to a new asymptotic size (~13.5 mm, 13-20 months). In diet choice experiments, juveniles did not show a preference between Amphiroa sp. and CCA, but generally avoided biofilm. Our results show that juvenile COTS grew equally well on CCA and Amphiroa sp. and can subsist on biofilm for months. Some juveniles, mostly from the biofilm diet treatment, decreased in size for a time and this was followed by recovery. Flexibility in diet, growth, and prolonged maintenance of asymptotic size indicates capacity for growth plasticity in herbivorous juvenile COTS. There is potential for juvenile COTS to persist for longer than anticipated and increase in number as they wait for the opportunity to avail of coral prey. These findings complicate our ability to predict recruitment to the corallivorous stage and population outbreaks following larval settlement and the ability to understand the age structure of COTS populations.

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Larval cloning in the crown-of-thorns sea star, a keystone coral predator

Cited by 31 publications

References 30 publications

The hidden army: corallivorous crown-of-thorns seastars can spend years as herbivorous juveniles

The hidden army: corallivorous crown-of-thorns seastars can spend years as herbivorous juveniles

Nonspecific expression of fertilization genes in the crown‐of‐thorns Acanthaster cf. solaris: Unexpected evidence of hermaphroditism in a coral reef predator

Diet flexibility and growth of the early herbivorous juvenile crown-of-thorns sea star, implications for its boom-bust population dynamics

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