The thermal tolerance of crown-of-thorns (Acanthaster planci) embryos and bipinnaria larvae: implications for spatial and temporal variation in adult populations

Abstract

To understand the role of sea temperature on the population biology of the crown-of-thorns sea star Acanthaster planci, the thermal window for embryonic and larval development was investigated. In two experiments, the response of embryos and larvae across 12 temperatures from 19.4 to 36.5°C was quantified as the percentage of individuals reaching cleavage stage embryos, blastula, gastrula, early-bipinnaria, late-bipinnaria larvae or abnormal. Measurements were made at 7 times up to 72 h postfertilisation, with the morphometrics of larvae measured in the 72-h sample. Acanthaster planci developed at temperatures between 19.4 and 33.2°C, with a thermal window for development to the late-bipinnaria stage between 25.6 and 31.6°C. Development rate, normal development and larval size were optimal at 28.7°C, with development rates remaining relatively constant up to 31.6°C. Rates of abnormality increased steadily (early embryonic stages) above 28.7°C and was 100 % at temperatures approaching 33°C. These experiments provide a more detailed insight into the response of A. planci developmental stages to temperature. The present day distribution of the species in eastern Australia overlap with the optimal thermal window for development to the late-bipinnaria stage (&25-32°C), implying a role of temperature in controlling population distributions and abundances. Despite this, short-or longterm temperature increases may not be a major modulator of the crown-of-thorns recruitment success, population dynamics and distribution in the future as no significant change in development rates, larval survival and growth occurred within this thermal window. Therefore, moderate (1-2°C) increases in sea temperatures caused by El Niño or near-future ocean warming may not drive an increase in developmental and settlement success. Indeed, without any acclimation to warmer temperatures expected under nearfuture warming (?2 to 4°C), climate change could ultimately reduce larval survival due to elevated mortality above the optimal development temperature.

Interactive effects of near-future temperature increase and ocean acidification on physiology and gonad development in adult Pacific sea urchin, Echinometra sp. A

“…In situ temperature increased in comparison with our control temperature during the course of the experiment. Longterm water temperatures for this region are available (at: http://data.aims.gov.au/aimsrtds/latestreadings.xhtml, see also Collier et al 2012;Lamare et al 2014) from a 4-m deep station at Davies Reef (18°49.8 0 S, 147°37.8°E), a similar midshelf reef to Rib Reef.…”

Visual orientation by the crown-of-thorns starfish (Acanthaster planci)

“…Because of the ecological and economic importance of coral reefs, interest in the crown-of-thorns starfish has been increasing in an effort to discover potential mitigation avenues against them. The vast majority of research has focused on the ecology of the crown-of-thorns starfish, the dynamics of population outbreaks, life history (Henderson and Lucas 1971;Zann et al 1987;Keesing and Lucas 1992;Lamare et al 2014;Uthicke et al 2015), larval dispersal and survival (Fabricius et al 2010;Wooldridge and Brodie 2015), effective culling methods Rivera-Posada et al 2014) and, to a lesser extent, investigations into their toxicity (Lee et al 2014). However, the sensory biology of the crown-of-thorns starfish remains mostly unstudied.…”

30 Years of Research on Crown-of-thorns Starfish (1986-2016): Scientific Advances and Emerging Opportunities

“…has received a great deal of attention (e.g., Lucas 1982;Olson and Olson 1989) and there has been a recent resurgence in research on the environmental tolerances of CoTS larvae aimed at establishing the vulnerability of Acanthaster spp. to ocean warming and acidification (Uthicke et al 2013;Kamya et al 2014;Lamare et al 2014;Caballes et al 2017b). Temperature is widely regarded as the foremost abiotic factor influencing development rates and survivorship of planktonic larvae (Byrne 2011), and Acanthaster spp.…”

“…are sensitive to extreme temperatures at all stages of their lifecycle (Yamaguchi 1973;Caballes et al 2017b). Performance and fitness of CoTS is generally highest at 26-30 °C (Lamare et al 2014;Caballes et al 2017b). There is increasing evidence that CoTS are adversely affected when exposed to temperatures ≥30 °C (Kamya et al 2014), suggesting that ocean warming suppress population outbreaks at low latitudes.…”

“…However, projected changes in ocean temperatures and seawater chemistry are also expected to have direct effects on Acanthaster spp. (Uthicke et al 2013(Uthicke et al , 2015bKamya et al 2014;Lamare et al 2014;Sparks et al 2016;Allen et al 2017;Caballes et al 2017b) and juveniles (Uthicke et al 2013;Kamya et al 2016Kamya et al , 2017 especially during early life-history stages.The optimal temperatures for embryonic and larval development of A. cf. solaris (28-29 °C), reflects ambient temperatures currently experienced during the reproductive season in the northern GBR (Lamare et al 2014;Caballes et al 2017b).…”