Response of Tardigrades to Reactive Oxygen Species (ROS) Perturbation in the Presence of Exogenous Antioxidants

Overview

Tardigrades are eight legged microscopic invertebrates that are known for their ability to survive in extreme conditions by entering “tun” state, which is regulated by internal reactive oxygen species (ROS) signals. However, there have not been studies done to determine whether exogenous antioxidants positively or negatively affect internal ROS signaling and the redox dependent antioxidant system. My project investigates the effects of exogenous saffron-derived antioxidants on the locomotive performance and recovery of tardigrades post H₂O₂ (hydrogen peroxide) induced oxidative stress. I hypothesized that inducing saffron post-stress would enhance locomotor recovery because the antioxidants derived from saffron, specifically carotenoids, can neutralize and capture damaging free radicals generated by ROS. Tardigrade species Hypsibius exemplaris were exposed to 7.5 mM H₂O₂ with and without saffron treatment. Treatment includes adding two different concentrations of saffron at 1 hour after H₂O₂ perturbation, or pre incubating in saffron solution for 24 hours before perturbation. Locomotive performance in strides per min and percentage of active tardigrades were recorded before H₂O₂ perturbation and at four time points post exposure under microscope at 200×. All tardigrade samples exposed to H₂O₂ conditions showed decline in average stride rates and percentage active. Addition of saffron solution post perturbation accelerated drop in percentage active to 0%, but showed partial recovery in locomotive and active percentage after 13 hours. Recovery of locomotion by saffron was dependent on concentration. Interestingly, tardigrades that were pre-incubated in saffron solution did not show any recovery. By scavenging ROS in the surrounding after tun formation, saffron enhanced locomotive recovery when it was dosed post H₂O₂ perturbation. The effect allowed tardigrades to emerge after stressors were removed. Initial drop in percentage active was observed, possibly facilitating proper tun formation, because the antioxidants quenched excess ROS which otherwise overwhelmed the tardigrades’ internal defense system. Pre-incubation in saffron solution, in contrast, eliminated recovery because saffron-derived antioxidants disrupted essential ROS signaling when applied before stress onset. These results show that exogenous antioxidants can exert opposing effects on the ROS-signal dependent defense.

Competition history

• CSEF 2026 Zoology (Senior Division) · Entry S-20-10

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