The palatability of stonefish (Synanceia spp.) ichthyocrinotoxins to potential predators

Numerous fish species are known to utilise ichthyocrinotoxins to defend themselves against predators, often by deterring the predator from feeding on them. This study investigated whether stonefish ichthyocrinotoxins act as antifeedants by assessing its effect on the feeding behaviours of two potential predators of stonefish: lionfish and morays. Food laced with either Synanceia horrida (Estuarine Stonefish) or Synanceia verrucosa (Reef Stonefish) ichthyocrinotoxin were highly palatable (>85% food acceptance) to both predator types, demonstrating similar acceptance rates as untreated food (>95% food acceptance). In contrast, food coated in Diploprion bifasciatum (Barred Soapfish) ichthyocrinotoxin, a known antifeedant used experimentally as a positive control, prompted high rejection rates (<10% food acceptance). These results suggest that stonefish ichthyocrinotoxins may not play a significant role in antifeedant defence. Stonefish ichthyocrinotoxins also exhibited a greater adhesion to prawn fillets (>45% retention), compared to soapfish ichthyocrinotoxin (27% retention), which may reflect differences in their ecological functions and/or application mechanisms. The findings of this study have expanded our understanding of stonefish toxin ecology.