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 anemone uses a specialized voltage-gated calcium (Ca) 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 anemone uses uniquely strong Ca inactivation for precise control of predatory stinging. In contrast, the related anemone inhabits exposed environments to support photosynthetic endosymbionts. Consistent with its niche, indiscriminately stings for defense and expresses a Ca splice variant that confers weak inactivation. Chimeric analyses reveal that Caβ 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.