Continuity of chronic predation risk determines changes in prey physiology

Abstract

Prey reconfigure their physiology to avoid costs of prolonged predator pressure. However, these changes might not occur under periodic predation risk, with repeating acute phases. To test the effect of predation risk continuity on changes in prey physiology, we exposed amphipods: Dikerogammarus villosus and Gammarus jazdzewskii to periodic and constant predation cue. After one week, we measured: cellular defence systems: total antioxidant status (TAS), heat shock proteins (Hsp70); intracellular damage marker: lipid peroxidation (TBARS); condition index: glycogen concentration. Predator presence reduced TAS level in G. jazdzewskii independent of its continuity and in D. villosus after periodic exposure. Amphipods showed downregulation of Hsp70 when exposed to periodic (D. villosus) or constant (G. jazdzewskii) predation risk. Exposure to predators reduced TBARS level in D. villosus (irrespective of the continuity) and G. jazdzewskii (periodic exposure). Glycogen concentration in both species was not affected by predator presence. Thus, the continuity of the predator cue shaped prey physiology reconfiguration, optimizing costs of physiological adjustments under challenging conditions. Nevertheless, the lack of negative consequences of the prolonged exposure to the predator cue, whether constant or periodic, shows that amphipods can thrive under chronic predation risk, which is a constant part of the wild environment.

Living with predators at the larval stage has differential long-lasting effects on adult life history and physiological traits in two anopheline mosquito species

“…Our results show a decrease in the total antioxidant capacity in the two sexes of the two mosquito species exposed to predation risk. Such a decrease or absence of variation in antioxidant capacity during chronic stress was already observed in damselflies (Slos & Stoks, 2008;Janssens & Stoks, 2013), Corixids (Trekels, Van de Meutter, Bervoets & Stoks, 2012) and amphipods (Jermacz et al, 2020a;Jermacz, Nowakowska, Kletkiewicz & Kobak, 2020b), and was described as a mechanism to reduce the cost of production of antioxidant response which cannot be sustained for long. Three scenarios could explain these results.…”

“…Three scenarios could explain these results. In the first, larvae could reduce their metabolic rate due to the habituation to predation threat cues (Ferrari, Elvidge, Jackson, Chivers & Brown, 2010;Roux et al, 2014) and/or to reduce costs due to the production of reactive oxygen species (ROS) and antioxidant molecules (Jermacz et al, 2020a). Late instar larvae which reset their activity would be more vulnerable to predator attacks unless their larger sizes dissuaded predators.…”

“…Late instar larvae which reset their activity would be more vulnerable to predator attacks unless their larger sizes dissuaded predators. In the second scenario, larvae could reconfigure their physiology to conserve both an increased metabolism and their ability to develop a fight-or-flight response, while reducing costs related to a higher ROS level (Jermacz et al, 2020a;Jermacz et al, 2020b). In the third scenario, individuals could adjust their levels of defense to maintain a certain level of damages (Janssens & Stoks, 2013).…”

Warming and predation risk only weakly shape size-mediated priority effects in a cannibalistic damselfly

“…There is accumulating evidence that changes in phenological events such as relative hatching dates increase the magnitude of SMPE due to larger variation in relative body size of interacting animals (Murillo-Rincón et al 2017; Sniegula et al 2019a). Although the theoretical background of priority effects in a warming world is well understood (Yang and Rudolf 2010;Fukami 2015), to our knowledge there have been few empirical approaches that linked life history with physiology in the context of SMPE caused by temperature-mediated hatching dates (Jermacz et al 2020;Raczyński et al 2021).…”

Feeding strategy trade-off and selection of marine nocturnal gastropods under predation risk

“…In addition, prey may experience chronic stress under long-term risk, and a delay in the stress response may have adverse consequences, such as retarded growth, the consumption of stored energy, and accumulation of toxic compounds. As a result, prey may readjust its physiological functions and utilize physiological compensation mechanisms (e.g., improving assimilation efficiency) to avoid the losses due to a long-term predation stress (Thaler et al, 2012;Jermacz et al, 2020). For example, the energy cost may increase if a high metabolic rate is maintained.…”