Data from: How temperature shifts affect parasite production: testing the roles of thermal stress and acclimation

1. Changes in the magnitude and frequency of temperature shifts with climate change will influence species interactions if species have differential acclimation responses. For example, if parasites acclimate to temperature shifts faster than their hosts, as might be expected due to their smaller sizes and faster metabolisms, temperature variability could lead to increased infection. However, this assumption might not hold if benefits of acclimation are counteracted by energetic costs or thermal stress, underscoring the need for empirical efforts to assess how temperature variability will influence host-parasite interactions. 2. We used an array of replicate incubators to test how temperature shifts from five acclimation temperatures (13-25°C) to five performance temperatures (16-28°C) influenced release of infective stages by the trematode parasite, Ribeiroia ondatrae, from its snail intermediate host (Helisoma trivolvis) at four time points after a temperature shift. 3. Initially, parasite release was higher at warm temperatures and increased temporarily after infected snails were shifted to higher temperatures, particularly for hosts acclimated to cooler temperatures. However, these effects were transient, such that parasite release at warm temperatures declined steadily over the seven days following the shift. Warmer temperatures also increased snail mortality. 4. Parasite release was strongly influenced not only by ambient temperature but also by the thermal history of the host. Prior acclimation to warm temperatures reduced parasite release at warm performance temperatures, contrary to the beneficial acclimation hypothesis. Rather, the observed pattern was likely driven by: (1) energetic costs of prolonged exposure to high temperatures (“thermal stress”) or (2) parasites’ capacity to “store” infectious stages at cooler temperatures. 5. The time-dependent nature of thermal effects on parasite performance highlights the importance of considering the amplitude and frequency of temperature variability for understanding future changes to disease dynamics

SnailShedDataforDryad

Laboratory-raised Helisoma trivolvis snails were held at one of 5 acclimation temperatures (13-25 deg C) for 11 days prior to being moved to one of 5 performance temperatures (16-28 deg C) for 7 days. Some snails were exposed in the laboratory to Ribeiroia ondatrae, and parasite release was measured at several time-points before and after the temperature shift. Please see paper methods for more details

Data from: Host and parasite thermal acclimation responses depend on the stage of infection

1. Global climate change is expected to alter patterns of temperature variability, which could influence species interactions including parasitism. Species interactions can be difficult to predict in variable-temperature environments because of thermal acclimation responses, i.e. physiological changes that allow organisms to adjust to a new temperature following a temperature shift. 2. The goal of this study was to determine how thermal acclimation influences host resistance to infection and to test for parasite acclimation responses, which might differ from host responses in important ways. 3. We tested predictions of three, non-mutually exclusive hypotheses regarding thermal acclimation effects on infection of green frog tadpoles (Lithobates clamitans) by the trematode parasite Ribeiroia ondatrae with fully replicated controlled-temperature experiments. Trematodes or tadpoles were independently acclimated to a range of ‘acclimation temperatures’ prior to shifting them to new ‘performance temperatures’ for experimental infections. 4. Trematodes that were acclimated to intermediate temperatures (19–22 °C) had greater encystment success across temperatures than either cold- or warm-acclimated trematodes. However, host acclimation responses varied depending on the stage of infection (encystment vs. clearance): warm- (22–28 °C) and cold-acclimated (13–19 °C) tadpoles had fewer parasites encyst at warm and cold performance temperatures, respectively, whereas intermediate-acclimated tadpoles (19–25 °C) cleared the greatest proportion of parasites in the week following exposure. 5. These results suggest that tadpoles use different immune mechanisms to resist different stages of trematode infection, and that each set of mechanisms has unique responses to temperature variability. Our results highlight the importance of considering thermal responses of both parasites and hosts when predicting disease patterns in variable-temperature environments

Altman et al. 2016 JAE trematode acclimation data

Data from the trematode acclimation experimen

Altman et al. 2016 JAE tadpole acclimation data

Data from the tadpole acclimation experimen