Structural and mechanical properties of the decapod exoskeleton affect foraging, defense, and locomotion, making the ability of decapods to maintain their calcified exoskeleton a crucial physiological process. Ocean acidification (OA) poses a threat to marine biomes and their inhabitants, particularly calcifying organisms. Vulnerability of the snow crab, Chionecetes opilio, a commercially important, high-latitude species, to OA has not been explored. Although all oceans are experiencing acidification, abiotic factors in high-latitude areas increase the rate of acidification. We examined the effect of long-term (2-year) exposure to decreased seawater pH (7.8 and 7.5) on exoskeletal properties in post-terminal-molt female C. opilio. Since the effects of OA vary among body regions in decapods, exoskeletal properties (microhardness, thickness, and elemental composition) were measured in five body regions: the carapace, both claws, and both third-walking legs. Overall, the C. opilio exoskeleton was robust to OA in all body regions. Decreased pH had no effect on microhardness or thickness of the exoskeleton, despite a slight (~6%) reduction in calcium content in crabs held at pH 7.5. In contrast, exoskeletal properties varied dramatically among body regions regardless of pH. The exoskeleton of the claws was harder, thicker, and contained more calcium but less magnesium than that of other body regions. Exoskeleton of the legs was thinner than that of other body regions and contained significantly greater levels of magnesium (~2.5 times higher than the claws). Maintenance of exoskeletal properties after long-term OA exposure in C. opilio suggests that wild populations may tolerate future ocean pH conditions.

Structural and mechanical properties of the decapod exoskeleton affect foraging, defense, and locomotion, making the ability of decapods to maintain their calci ed exoskeleton a crucial physiological process. Ocean acidi cation (OA) poses a threat to marine biomes and their inhabitants, particularly calcifying organisms. Vulnerability of the snow crab, Chionecetes opilio, a commercially important, highlatitude species, to OA has not been explored. Although all oceans are experiencing acidi cation, abiotic factors in high-latitude areas increase the rate of acidi cation. We examined the effect of long-term (2year) exposure to decreased seawater pH (7.8 and 7.5) on exoskeletal properties in post-terminal-molt female C. opilio. Since the effects of OA vary among body regions in decapods, exoskeletal properties (microhardness, thickness, and elemental composition) were measured in ve body regions: the carapace, both claws, and both third-walking legs. Overall, the C. opilio exoskeleton was robust to OA in all body regions. Decreased pH had no effect on microhardness or thickness of the exoskeleton, despite a slight (~6%) reduction in calcium content in crabs held at pH 7.5. In contrast, exoskeletal properties varied dramatically among body regions regardless of pH. The exoskeleton of the claws was harder, thicker, and contained more calcium but less magnesium than that of other body regions. Exoskeleton of the legs was thinner than that of other body regions and contained signi cantly greater levels of magnesium (~2.5 times higher than the claws). Maintenance of exoskeletal properties after long-term OA exposure in C. opilio suggests that wild populations may tolerate future ocean pH conditions.