Time-dependent Changes in Shrimp Armor and Escape Kinematics under Ocean Acidification and Warming

Pandalid shrimp use morphological and behavioral defenses against their numerous fish and invertebrate predators. Their rapid tail-flip escape and rigid exoskeleton armor may be sensitive to changes in ocean temperature and carbon chemistry in ways that alter their efficacy and impact mortality. Here we tested the hypothesis that ocean warming and acidification conditions affect the antipredator defenses of Pandalus gurneyi. To test this hypothesis, we exposed shrimp to a combination of pH (8.0, 7.7, 7.5) and temperature (13°C, 17°C) treatments and assessed their tail-flip escape and exoskeleton armor after short-term (2 weeks) and medium-term (3 months) exposure. Results revealed complex effects on escape kinematics, with changes in different variables explained by either pH, temperature, and/or their interaction; decreased pH, for instance, primarily explains reduced acceleration while cold temperature explains increased flexion duration. Carapace mineral content (Ca and Mg) was unaffected, but warmer temperatures primarily drove enhanced mechanical properties (increased hardness and stiffness). No effects were observed in the stiffness and strength of the rostrum. Furthermore, most of the observed effects were temporary, as they occurred after short-term exposure (2 weeks), but disappeared after longer exposure (3 months). This demonstrates that P. gurneyi defenses are affected by short-term exposure to temperature and pH variations; however, they can acclimate to these conditions over time. Nonetheless, changes in the tail-flip escape kinematics may be disadvantageous when trying to flee predators and the enhanced exoskeleton armor could make them more resistant to predation during short periods of environmental change.