Thirty Years of Research on Crown-of-Thorns Starfish (1986–2016): Scientific Advances and Emerging Opportunities

Abstract

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 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.

Effects of larvae density and food concentration on Crown-of-Thorns seastar (Acanthaster cf. solaris) development in an automated flow-through system

“…solaris 6 , 7 . The GBR is presently experiencing its fourth outbreak since the 1960’s 4 , 8 , with the outbreak following previous patterns of starting in the Northern or Cairns section of the GBR and subsequently moving southwards 9 .…”

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

“…Our results suggest that not only are COTS larvae surviving (Wolfe et al 2015, Pratchett et al 2017 in areas of high chlorophyll concentration (1−2 µg chl a l −1 ), but they may actually multiply asexually. Recent metagenomic surveying of the surface waters of the GBR suggests that COTS larvae form a 'continuous cloud' over the GBR (Uthicke et al 2015), including areas where outbreaks are not occurring.…”

“…Asexual reproduction occurs in both the larval and adult life stages of echinoderms through a variety of methods and has been implicated in adjusting population densities with respect to available resources (Mladenov 1996, Lee et al 2008, Allen et al 2018. Descriptions of larval cloning exist across echinoderm classes, including the asteroids (Bosch et al 1989, Balser 1998, Vickery & McClintock 2000, Eaves & Palmer 2003, McDonald & Vaughn 2010, but despite being one of the most intensely studied starfish species on Earth (Pratchett et al 2017), cloning has not been assessed for COTS. We reared COTS to determine if larval cloning occurred, and then tested 2 factors to determine their role as potential inducers of larval cloning: larval density and algal food supply.…”

“…Recent work has not rendered a final decision on the role of predator removal versus nutrient enrichment in contributing to COTS outbreaks (Babcock et al 2016a). While the nutrientenrichment hypothesis has garnered wide support, both it and the predator-removal hypothesis invoked by Paine (1969) have been deemed 'largely unresolved' in a recent assessment of COTS biology (Pratchett et al 2017).…”

Dissolution: The Achilles’ Heel of the Triton Shell in an Acidifying Ocean

“…An altered competitive dynamic with other species, and the possible reduction in their top-down control, would likely disrupt their associated food web, and may alter ecosystem processes and derived services (Lemasson et al, 2017). For example, the giant triton (C. tritonis) plays an important role in the tropics as one of the very few natural predators of the coral-eating crown-of-thorns starfish (Acanthaster planci), which is a major contributor to ongoing coral loss on reefs across the Indo-Pacific (Pratchett et al, 2017).…”