Abstract
Crown-of-thorns starfish (CoTS; Acanthaster spp.) are among the most extensively studied coral reef taxa, largely owing to their devastating impacts on live coral cover during population outbreaks. Much of this research has however, been conducted in the western Pacific, although it is now apparent that there are several distinct species of Acanthaster spp. across the Indo-Pacific. The purpose of this study was to test for biogeographical variation in behaviour, comparing between Acanthaster planci at Lankanfushi Island in the Maldives and Acanthaster cf. solaris at Rib Reef on Australia’s Great Barrier Reef. The extent to which CoTS were exposed (cf. concealed within or beneath coral substrates) was substantially higher (63.14%) for A. planci at Lankanfushi Island, compared to 28.55% for A. cf. solaris at Rib Reef, regardless of time of day. More importantly, only 52% of individuals were exposed at night at Rib Reef compared to >97% at reefs around Lankanfushi Island. Biogeographic variation in the behaviour of Acanthaster spp. was independent of differences in the size structure of starfish and coral cover at specific study sites, but may be attributable to other environmental factors such as habitat complexity or prey availability. This is the first study to explicitly test for biogeographical differences in the biology and behaviour of Acanthaster spp., potentially linked to species-specific differences in the causes and explanations of population outbreaks. However, we did not find evidence at this stage of differences in behavior among regions, rather behavioural differences observed were most likely products of different environments.
Highlights
Crown-of-thorns starfishes (CoTS; Acanthaster spp.) have gained considerable notoriety over the last few decades following outbreaks throughout the Indo-Pacific [1,2,3,4,5,6,7,8]
Average densities of CoTS recorded at Rib Reef (6.29 starfish per 100m2 ±1.08 SE) were significantly higher than recorded at Lankanfushi Island, Maldives (2.65 starfish per 100m2 ±0.31 SE; F1,63 = 8.29, p
The average size of CoTS was significantly smaller at Rib Reef (31.01cm total diameter ±0.25 SE) compared to Lankanfushi Island (40.73cm total diameter ±0.43 SE), owing to the increased number of small starfish at Rib Reef (F1,967 = 269.3, p
Summary
Crown-of-thorns starfishes (CoTS; Acanthaster spp.) have gained considerable notoriety over the last few decades following outbreaks throughout the Indo-Pacific [1,2,3,4,5,6,7,8]. Along with anthropogenic climate change, outbreaks of CoTS are a major contributor to coral loss and reef degradation [9], causing extensive coral mortality [10] and shifts in the biological and physical structure of coral reef habitats [11,12,13,14]. CoTS are among the most extensively studied organisms from coral reef environments [2], though the majority of this. The funders did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.”
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