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

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.