Ocean acidification (OA) has the potential to disrupt the behavior of marine organisms by altering the function of γ-aminobutyric acid type A (GABAA) receptors. In addition, OA can impair sensory performance by reducing the calcification of mineralized sensory structures. Some species of polyplacophoran mollusks (chitons) possess calcified visual organs (aragonitic lenses) that contribute to shadow defense responses triggered by sudden decreases in overhead illumination. Therefore, we hypothesized that OA affects this response by impairing GABAA-mediated signaling or lens calcification. To test this hypothesis, we exposed chitons to “control” or acidified seawater and examined their shadow defensive behavior with and without gabazine, a GABAA antagonist known to restore OA-induced GABAergic dysfunction. Although gabazine did not eliminate behavioral differences between the control and acidified groups, acidification reduced the response strength, suggesting that factors other than GABAA-mediated signaling may contribute to the observed behavioral impairment. Microscopic observations revealed clouding of aragonitic lenses under acidic conditions, suggesting reduced optical performance. Overall, our results indicate that OA-induced degradation of calcified lens structures is associated with impaired shadow defense responses and may contribute to behavioral dysfunction. To the best of our knowledge, this study provides the first evidence that acidification-induced physical and optical changes in the visual anatomy can alter behavioral performance in animals.
Matsumoto R., Takiyama N., & Kon K., 2026. Ocean acidification impairs the chiton shadow defensive response via degradation of aragonitic lenses. Marine Ecology 47(5): e70123. doi: 10.1111/maec.70123. Article.
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