Acclimation capacity and rate change through life in the zooplankton Daphnia

Abstract

When a change in the environment occurs, organisms can maintain an optimal phenotypic state via plastic, reversible changes to their phenotypes. These adjustments, when occurring within a generation, are described as the process of acclimation. While acclimation has been studied for more than half a century, global environmental change has stimulated renewed interest in quantifying variation in the rate and capacity with which this process occurs, particularly among ectothermic organisms. Yet, despite the likely ecological importance of acclimation capacity and rate, how these traits change throughout life among members of the same species is largely unstudied. Here we investigate these relationships by measuring the acute heat tolerance of the clonally reproducing zooplankter Daphnia magna of different size/age and acclimation status. The heat tolerance of individuals completely acclimated to relatively warm (28°C) or cool (17°C) temperatures diverged during development, indicating that older, larger individuals had a greater capacity to increase heat tolerance. However, when cool acclimated individuals were briefly exposed to the warm temperature (i.e. were ‘heat-hardened'), it was younger, smaller animals with less capacity to acclimate that were able to do so more rapidly because they obtained or came closer to obtaining complete acclimation of heat tolerance. Our results illustrate that within a species, individuals can differ substantially in how rapidly and by how much they can respond to environmental change. We urge greater investigation of the intraspecific relationship between acclimation and development along with further consideration of the factors that might contribute to these enigmatic patterns of phenotypic variation.

Prior selection affects phenotypic and transcriptional response to hypoxia

“…However, the hormesis principle (Mattson 2007; Maynard 2011; Berry & López-Martínez 2020), should not be taken for granted (Axelrod et al 2004). For example, in Daphnia, while adaptive effects of moderate heat acclimation have been well established (Yampolsky et al 2014; Burton et al 2020), the present study does not show a similar effect for moderate hypoxia. To the contrary, Daphnia reared in mild intermittent hypoxia showed lower survival in acute trials.…”

Breaking Free from Thermodynamic Constraints: Thermal Acclimation and Metabolic Compensation in a freshwater zooplankton species

“…longer survival at a constant sublethal temperature or higher temperature tolerance limit). Beneficial thermal acclimation has been convincingly demonstrated in a variety of ectotherms (Fry, 1971;Angilletta, 2009), including Daphnia (Armitage and Lei, 1979;McKee, 1995;Lamkemeyer et al, 2003;Zeis et al, 2004;Williams et al, 2012;Yampolsky et al, 2014a,b;Coggins et al, 2017;Martin-Creuzburg et al, 2019;Burton et al, 2020), but details of the physiological mechanisms are largely unknown. Two lines of evidence suggest that this mechanism may be tightly linked to changes in respiration and/or metabolic demands for oxygen.…”

Variation in the rate of phenotypic plasticity among ectotherms

“…This pattern may be explained by the general relationship that exists between developmental rate and body temperature in ectotherms, which is driven by the positive effect of temperature on biochemical reactions and metabolic rate (Brown et al 2004). It may also explain the observation that within a species, acclimation to high temperature is achieved faster than acclimation to low temperature (Burton et al 2020). A relationship between metabolic rate and the rate of plasticity was previously hypothesized and addressed by Rohr et al (2018), but in a less direct manner.…”