Molecular tuning of sea anemone stinging

Jellyfish and sea anemones fire single-use, venom-covered barbs to immobilize prey or predators. We previously showed that the anemoneNematostella vectensisuses a specialized voltage-gated calcium (Ca_V) channel to trigger stinging in response to synergistic prey-derived chemicals and touch (Weir et al., 2020). Here we use experiments and theory to find that stinging behavior is suited to distinct ecological niches. We find that the burrowing anemoneNematostellauses uniquely strong Ca_Vinactivation for precise control of predatory stinging. In contrast, the related anemoneExaiptasia diaphanainhabits exposed environments to support photosynthetic endosymbionts. Consistent with its niche,Exaiptasiaindiscriminately stings for defense and expresses a Ca_Vsplice variant that confers weak inactivation. Chimeric analyses reveal that Ca_Vβ subunit adaptations regulate inactivation, suggesting an evolutionary tuning mechanism for stinging behavior. These findings demonstrate how functional specialization of ion channel structure contributes to distinct organismal behavior.