The relationship between size and metabolic rate of juvenile crown of thorns starfish

Abstract

Despite the notoriety of the corallivorous crown of thorns starfish (COTS, Acanthaster sp.), with population outbreaks that decimate reefs throughout the Indo‐Pacific, the physiology of the juvenile stage remains poorly understood. We determined the feeding rate and metabolic rate of juvenile COTS during their initial algae‐eating stage. The metabolic rate of juveniles after their ontogenetic diet transition from a diet of coralline algae to coral was also investigated. We found that the weight‐specific metabolic rate of both the herbivorous (mean = 0.052 mg O2 g−1 h−1) and corallivorous (mean = 0.034 mg O2 g−1 h−1) juveniles increased exponentially with juvenile size. Juveniles consumed ~4 mm2 of algae (Amphiroa sp.) in 1 day, and consumption rate also increased with juvenile size. Juveniles may impact the distribution of coralline algae for other herbivores on coral reefs and the settlement habitat for many invertebrate larvae. Increased metabolism of both herbivorous and corallivorous juveniles with size is indicative of their increasing ecological impact as they grow, highlighting the importance of understanding the juvenile physiology of influential species such as COTS.

Juvenile waiting stage crown‐of‐thorns sea stars are resilient in heatwave conditions that bleach and kill corals

“…The faster righting time and higher metabolic rate of the juveniles in the warmest treatment (30°C) are similar to that seen in other studies where a gradual increase in temperature was undertaken in an acclimation approach with echinoderms (Christensen et al, 2023;Harianto et al, 2018). The metabolic rate determined here for the juveniles maintained in the 27°C controls is similar to that obtained previously (Deaker & Byrne, 2022b). In adult COTS, the righting time of acclimated individuals was not affected by increased temperature (to 32°C), but metabolic rate was higher at 30°C and decreased at 32°C (Lang et al, 2022).…”

“…Competent larvae (16-day postfertilisation) were transferred into Petri dishes (10 mm diameter) with 1.0 μm FSW (26-27°C) and a settlement inducer, a small piece of the coralline alga, Amphiroa sp. This alga is also a good food source for the juveniles (Deaker & Byrne, 2022b). The juveniles were fed fresh Amphiroa sp.…”