Thanks to Jaret Daniels, Isabella Plummer, Brett Scheffers, and Dan Hahn for input on the protocol as it was first developed. Additional gratitude to Jaime Haggard, Sebasti&#225;n Dur&#225;n, and Indiana Crist&#243;bal R&#243;is-M&#225;laver for implementing several iterations of this protocol and for input on key components. Thanks also to an anonymous reviewer for feedback on the manuscript as a whole. Support was provided by the McGuire Center for Lepidoptera and Biodiversity&#39;s publication fund, the College of Agricultural and Life Sciences, School of Natural Resources and Environment, and Wildlife Ecology and Conservation department at UF.&#160;

1. Identification of species of interest
<ol>
	<li>Identify species of interest to determine cold shock recovery time. Keep in mind that each group will differ in the time it takes to induce a chill coma (i.e., the point at which the insect is still alive, but is not moving and not responsive). Likewise, based on the organism and use of data, choose different cutoff points at which to stop the experiment if the focal individual(s) do not fly (see section 4). 
	&#8203;NOTE: This protocol was designed and developed for use on Lepidoptera. However, it is applicable to large, volant, terrestrial insects, in particular, those that can be stored flat in glassine envelopes restricting movement and damage (e.g., butterflies and dragonflies/damselflies).</li>
</ol>
2. Conducting a pretrial
<ol>
	<li>Conduct a pretrial on a small sample of individuals to determine the key parameters. Follow sections 3 through 5 of the protocol below with 5-10 individuals for a pretrial.
	<ol>
		<li>Test the time required on ice to induce a chill coma (not moving), but not kill the focal species by following step 5.1 using treatments of 30 min, 60 min, and 90 min. 
		NOTE: The time required to induce a chill coma will depend on the size, location, and natural history/behavior of the individuals.</li>
		<li>Based on results from steps 4.1-4.4 and using knowledge of the ecology of the focal insects, choose a time at which to conclude the trial if a given individual does not make a full recovery. Base this time cutoff on ecology of the species as well, keeping in mind that after many minutes of being incapable of flight, many insects are predated. 
		&#8203;NOTE: For example, if most preliminary trials end in flight after 15 min, one could decide to end trials after 25 min to ensure that even outliers have a chance to fully recover (i.e., fly). This protocol is based on a 30 min cutoff time (step 5.4).</li>
	</ol>
	</li>
	<li>Use parameters from pretrial data to inform data collection for the experiments. Modify the protocol described below based on the needs of the focal organisms, including time in the ice slurry, time at which to call trials to an end, and behaviors documented on the data sheet (e.g., shiver may be an inappropriate behavior for the insect of choice).
	<ol>
		<li>Define specific research questions to be answered with these data while refining the parameters. 
		&#8203;NOTE: For example, if the researcher is interested in the effect of prolonged exposure on recovery, the time in ice is a key variable to modify. If researchers are interested in differences in physiology between light and dark colored species, they can choose either two distinctly colored species or modify the insect&#39;s wing color to measure the effect of wing color on recovery time. Importantly, this method is highly customizable to the needs and research questions posed (see the discussion section).</li>
	</ol>
	</li>
</ol>
3. Collection of insects
<ol>
	<li>Collect insects using appropriate methods such as baited traps and entomological nets, (Supplementary Figure 1). Upon collection, place each individual in a separate glassine envelope with a unique ID.</li>
	<li>Store animals in a shaded, cool place after being captured and before exposure to the cold shock experiment. Always expose the animal to the experimental treatment within 24 h of being captured, and standardize this time as much as possible across trials.
	<ol>
		<li>Although storage conditions may vary, keep the insects out of direct sun. If possible, place them indoors in a cool, dark room.</li>
		<li>In the field, ensure that they will be shaded while stored and are protected from wind (blowing away) and other insect predators that may enter the envelopes.</li>
	</ol>
	</li>
</ol>
4. Set up the cold shock experiment
<ol>
	<li>Fill a cooler with ice and water. Ensure that there is sufficient ice to persist for at least one hour, and add ice periodically as needed with the goal to maintain the environment in the water at 0 &#176;C.</li>
	<li>Choose between 1 and 4 focal individuals for a round of experimentation, making sure that each individual is identifiable.
	<ol>
		<li>If using multiple species, use only one of each to avoid confusing individuals on the datasheet. If experimenting with only one species, only use individuals that can easily be distinguished, for example by a broken wing or distinct marking.</li>
		<li>If the goal of the experiment is unrelated with wing coloration, mark the wings with unique IDs (e.g., numbers) with a fine felt-tipped marker to distinguish individuals.</li>
		<li>If the experiments meet neither of the above criteria, conduct the experiment on one individual at a time.</li>
	</ol>
	</li>
	<li>Populate the rows of the data sheet with the information pertinent to each insect assayed including their unique ID and a useful identifier in the notes such as species name or distinguishing character (Supplementary Table 1).</li>
	<li>Place all focal individuals (still in their individually marked envelopes) in a sealed plastic bag with a weight (Table of Materials), and place the bag in ice water for 60 min (or until chill coma has been induced; see discussion) (Supplementary Figure 2).
	<ol>
		<li>Ensure the weight is heavy (e.g., large coins, large washers, or smooth rocks) and large enough to keep the bag of insects submerged in the ice water and perpendicular to the surface of the water. Use a weight that does not cause leaks in the sealed plastic bag. 
		&#8203;NOTE: While insects are still able to recover if they are exposed directly to the water while submerged, wet envelopes complicate removal of each individual. It is best to maintain the insects dry in their bag.</li>
	</ol>
	</li>
	<li>Record temperature and light data.
	<ol>
		<li>Use a data logger (see the Table of Materials) to record ambient temperature and light data using either step 5.1 or 5.2.
		<ol>
			<li>Program the data logger to collect temperature and light data at 10 s intervals, starting at the time that the insects will be released.</li>
			<li>Base the start time of the data logger on when the insects were placed in the ice water. Ensure that the data logger information (date, time) is synchronized so that data on ambient conditions may later be matched with each individual focal insect.</li>
		</ol>
		</li>
		<li>Use a simple thermometer to record temperature and light data at short intervals by hand (by a second researcher).
		<ol>
			<li>Decide on the experimental parameters to associate with recovery time that can be measured without a data logger. Use distinct treatments: shade/sun; twilight/mid-day.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Place a mesh cage for the insects in an appropriate location so that the temperature and light environments are as homogenous as possible within the cage, and so that the base of the cage is elevated and can be tapped by the observer.</li>
	<li>Place the data logger just outside of the cage, or inside the cage so that it will not be knocked over or otherwise affected by small movements inside the cage. If not using a data logger, position a thermometer appropriately and/or set up the cages in the appropriate configuration. 
	&#8203;NOTE: The data logger must be placed so that the ambient conditions recorded are as close as possible to those that the insect is experiencing.</li>
</ol>
5. Start cold shock experiment
<ol>
	<li>Remove the animals from the ice water bath after 60 min (or time determined appropriate; see above). Immediately remove the insects from the plastic bag, and remove each individual from its envelope as quickly as possible while minimizing handling (Supplementary Figure 3).</li>
	<li>Start the stopwatch as soon as the animals are in the mesh cages (see example data, Supplementary Table 1).</li>
	<li>Tap the base of the cage with a pencil to agitate the recovering insects. 
	NOTE: Providing stimuli during recovery ensures that the focal insects demonstrate recovery status and behaviors as soon as they are physiologically capable (Supplemental Video).
	<ol>
		<li>Tap frequently and strongly enough to ensure that an animal will respond if possible, but not cause a response. 
		&#8203;NOTE: For example, when tapping the cage, if an animal is catapulted into the air and lands upright, but does not move to stand on its own, that is not considered a &#34;stand&#34; behavior, as the organism did not indeed stand on its own.</li>
	</ol>
	</li>
	<li>Mark the trial as complete once an individual has flown (i.e., shown a full recover). End the trial and consider the insect to have achieved a full recovery if it does not move after 30 min.</li>
	<li>Remove the insects from the mesh cage, and place the individuals back into their labeled glassine envelopes. Liberate the animals or keep them for further data collection (e.g., individual traits of size, weight).</li>
	<li>If using a data logger, stop data logger data collection, and save the file of temperature and light data during the experiment with appropriate date/time information.</li>
</ol>
6. Data processing
<ol>
	<li>Enter the data presented from the datasheet into a spreadsheet (e.g., MS Excel).</li>
	<li>If using a data logger, add temperature and light data for each response of each individual assayed.
	<ol>
		<li>Calculate the mean and standard deviation of the temperature and light for each behavior of each individual. 
		&#8203;NOTE: As the data logger logs data every 10 s, if the stand behavior for one animal took 48 s to occur, use the first 5 entries from the data logger for that trial.</li>
		<li>Associate each recovery behavior of each individual with abiotic data recorded by the datalogger, rounding up or down to 10 s intervals as necessary.</li>
	</ol>
	</li>
	<li>Plot and analyze data. Figure 1, for example, visualizes the effect of temperature and light on cold shock recovery time.&#160;Compile other relevant data (species traits, regional habitat characteristics) to examine the ecological and evolutionary patterns in physiological traits of the groups tested. 
	NOTE: Figure 1 was plotted using the ggplot2 package in R. The level of detail of data on ambient conditions will differ based on the instruments used to measure ambient conditions. If a data logger is used, figures with detail comparable to Figure 2 can be generated. If a thermometer is used, the researcher will not be able to create a plot informed by ambient light. Likewise, if researchers use categories of light or temperature, these scatterplots can be modified into boxplots or another appropriate template to illustrate these phenomena.</li>
</ol>

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<li>Perkins-Kirkpatrick, S. E., Gibson, P. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Changes+in+regional+heatwave+characteristics+as+a+function+of+increasing+global+temperature%5BTitle%5D)+AND+%22Scientific+Reports%22%5BJournal%5D)">Changes in regional heatwave characteristics as a function of increasing global temperature.</a> Scientific Reports. 7, 12256(2017).</li>
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<li>Nowakowski, A. J., Otero Jiménez, B., Allen, M., Diaz-Escobar, M., Donnelly, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Landscape+resistance+to+movement+of+the+poison+frog%2C+Oophaga+pumilio%2C+in+the+lowlands+of+northeastern+Costa+Rica%5BTitle%5D)+AND+%22Animal+Conservation%22%5BJournal%5D)">Landscape resistance to movement of the poison frog, Oophaga pumilio, in the lowlands of northeastern Costa Rica.</a> Animal Conservation. 16 (2), 188-197 (2013).</li>
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<li>Gotcha, N., Terblanche, J. S., Nyamukondiwa, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Plasticity+and+cross-tolerance+to+heterogeneous+environments%3A+divergent+stress+responses+co-evolved+in+an+African+fruit+fly%5BTitle%5D)+AND+%22Journal+of+Evolutionary+Biology%22%5BJournal%5D)">Plasticity and cross-tolerance to heterogeneous environments: divergent stress responses co-evolved in an African fruit fly.</a> Journal of Evolutionary Biology. 31 (1), 98-110 (2018).</li>
<li>Mutamiswa, R., Chidawanyika, F., Nyamukondiwa, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Superior+basal+and+plastic+thermal+responses+to+environmental+heterogeneity+in+invasive+exotic+stemborer+Chilo+partellus+Swinhoe+over+indigenous+Busseola+fusca+%28Fuller%29+and+Sesamia+calamistis+Hampson%5BTitle%5D)+AND+%22Physiological+Entomology%22%5BJournal%5D)">Superior basal and plastic thermal responses to environmental heterogeneity in invasive exotic stemborer Chilo partellus Swinhoe over indigenous Busseola fusca (Fuller) and Sesamia calamistis Hampson.</a> Physiological Entomology. 43 (2), 108-119 (2018).</li>
<li>de Jong, M. A., Saastamoinen, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Environmental+and+genetic+control+of+cold+tolerance+in+the+Glanville+fritillary+butterfly%5BTitle%5D)+AND+%22Journal+of+Evolutionary+Biology%22%5BJournal%5D)">Environmental and genetic control of cold tolerance in the Glanville fritillary butterfly.</a> Journal of Evolutionary Biology. 31 (5), 636-645 (2018).</li>
<li>DeVries, Z. C., Kells, S. A., Appel, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Estimating+the+critical+thermal+maximum+%28CTmax%29+of+bed+bugs%2C+Cimex+lectularius%3A+Comparing+thermolimit+respirometry+with+traditional+visual+methods%5BTitle%5D)+AND+%22Comparative+Biochemistry+and+Physiology.+Part+A%2C+Molecular+%26+Integrative+Physiology%22%5BJournal%5D)">Estimating the critical thermal maximum (CTmax) of bed bugs, Cimex lectularius: Comparing thermolimit respirometry with traditional visual methods.</a> Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology. 197, 52-57 (2016).</li>
<li>De Keyser, R., Breuker, C. J., Hails, R. S., Dennis, R. L. H., Shreeve, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Why+small+is+beautiful%3A+Wing+colour+is+free+from+thermoregulatory+constraint+in+the+small+lycaenid+butterfly%2C+Polyommatus+icarus%5BTitle%5D)+AND+%22PLoS+One%22%5BJournal%5D)">Why small is beautiful: Wing colour is free from thermoregulatory constraint in the small lycaenid butterfly, Polyommatus icarus.</a> PLoS One. 10 (4), 0122623(2015).</li>
<li>Nowakowski, A. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tropical+amphibians+in+shifting+thermal+landscapes+under+land-use+and+climate+change%5BTitle%5D)+AND+%22Conservation+Biology%22%5BJournal%5D)">Tropical amphibians in shifting thermal landscapes under land-use and climate change.</a> Conservation Biology. 31 (1), 96-105 (2017).</li>
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The author has no competing financial interests or other conflicts of interests.

The study of thermal physiology incorporates measures of species and environmental traits to better understand the interactions between organisms and their surroundings that are key to survival and fitness. While always integral to understanding the natural history and ecology of plants and animals, thermal traits are of increasing importance in the face of landscape and climate change11,21. Several groups of ectothermic terrestrial insects, in particular, lepidoptera and odonatan, are relatively large and abundant, exhibit distinct behaviors, and are amenable to manipulation. Outlined here is an efficient and low-cost assay to effectively measure physiological responses of such insects. This protocol requires a source of healthy organisms to assay, whose handling time prior to the experiment is limited. While flexible in the number of organisms assayed at one time, the number of focal individuals per experiment will vary based on the purpose of data collection and/or number of observers. 
For example, this protocol was developed to collect detailed individual data on butterflies across entire communities. As such, the representative results illustrate an effort to maximize the data collection for individuals of as many species as possible and under a variety of conditions relevant to the local environment. Regardless of the number of focal species, it is crucial for the observer to be able to identify each individual in the cage experiencing the recovery. If the goal is to collect data from only one species, then only one or two individuals (if identifiable based on different wing wear or if individually marked) should be assayed at once. The study subjects must be chosen in accordance with a specific research question or plan of study. Based on the question posed and the purpose of data collection (research or classroom, for example), sample size and collection of other traits will differ.
To illustrate the fundamental components of physiology elucidated by this protocol (induction of chill coma, steps of recovery, role of ambient conditions), a classroom instructor may choose two distinct species or morphs of a single species. If the focal individuals differ only in one key trait (e.g., color), a smaller sample size will be necessary, and students can closely study the relationship of that trait and organismal physiology. Researchers interested in ecological physiology may use their experimental data to explore complex ecological and evolutionary questions. Researchers must be sure to carefully choose focal insects that directly address their questions (e.g., based on life stage, age, sex, location), and, based on the number of variables involved, determine the appropriate sample size. Sample sizes for complex models will be larger than those described above. 
While collecting behavioral recovery data, it is key that the cage rest above the ground because the observer must be able to tap the bottom of the cage to elicit recovery behaviors. This ensures that the organism responds (stands, flies) as soon as it is physiologically capable of doing so, and the terminal recovery behavior (flight) is documented. Recording ambient conditions during the cold shock recovery is integral to the study of thermal physiology, as this protocol is designed to study and disentangle the role of environment in organismal physiology. Data loggers (see the Table of Materials) are useful to record standardized measures of relevant conditions (e.g., temperature, light, and even humidity). However, if these tools are unavailable, relevant conditions can be measured in other ways like with a digital thermometer or by simplifying the variable of environmental conditions and using distinct environments such as shade and sun. This protocol gives the researcher options to measure the conditions during cold shock recovery based on the purpose and scope of the study.
Although this method can be modified to better suit specific taxonomic groups, it is recommended that large, volant insects be used. Flying insects that regain their ability to fly independently may be considered to have accomplished a full recovery. The method, as described, was successfully used on butterflies in the tropics and subtropics. Based on the thermal trends of a given area (i.e., the range of temperatures experienced at a site that will vary, thus influencing expectations based on elevation, latitude, canopy cover), an organism may require more or less than one hour in an ice water bath to enter a chill coma. The size of the organism may also affect the time necessary to enter a chill coma. It is key to find the time of cold exposure necessary to induce a chill coma (not moving), but not kill focal species. The time required to induce a chill coma will depend on the size, location, and natural history/behavior of the individuals. Based on results from the cold shock experiment described herein and using knowledge of the ecology of the focal insects, choose a time at which to conclude the trial if a given individual does not make a full recovery. 
Based on the specific questions of the researcher, this method can be employed either in the field or the laboratory to allow for both natural environmental variation and control for important variables, respectively. This assay is simple and inexpensive and helps to fill existing gaps in the field of thermal physiology. The ease of this protocol makes it accessible to employ for a diverse array of taxa, opening the field to more than lab-friendly organisms. The novelty of performing a standardized yet ambient thermal assay fills the gap between laboratory and field results22. Leveraging ambient conditions for organism recovery will help researchers partition the role of environmental and species factors in physiology14,22. Finally, because of its low cost and lack of required materials, this protocol can be used in remote locations in the field with little equipment-ideal for many field biologists-as well as in classrooms to allow young students a hands-on learning experience.

The integration of thermal physiology and ecology in the late 1970s and early 1980s1,2 launched the field of ecological physiology. Extensive thermal studies conducted on ectotherms highlight ecological-physiological synergies across diverse eco-evolutionary contexts3,4,5. Research on thermal physiology of ectothermic organisms has regained attention recently in the face of climate change and altered thermal landscapes across the world6,7. In addition to informing studies in the academic field of ecological physiology, thermal physiology assays can be broadly accessible to researchers and can serve as a hands-on teaching approach for all levels. Components of thermal performance, including thermal limits and effects of temperature shocks, are fundamental to the ecology, behavior, and life history of animals8,9.
Specifically, ecototherms are used to address questions of physiology, as endothermy dictates an inextricable link between ambient and organismal temperature. The temperature range that organisms can withstand (their critical thermal minimum to maximum-thermal range) and the temperatures at which their behaviors and fitness are maximized (thermal optima) are often rooted in ecological and evolutionary processes. These physiological traits are of increasing importance as temperatures, both means and extremes, are increasing10. For example, the abiotic changes, including temperature increases, that accompany habitat destruction and fragmentation has affected communities of ectotherms, including anurans, limiting physiologically fragile species (with narrow thermal tolerance) to small remnant habitat patches11,12.
Assessing key components of thermal performance can be expensive both in terms of time and resources and traditionally requires laboratory equipment and standardized conditions. Moreover, conventional assays often do not reflect the breadth of ambient conditions experienced in nature by a given animal13 as temperature in similar physiology experiments is carefully controlled and often unrelated to ambient conditions experienced by an animal. This temperature control can diminish the understanding of variation in individual responses2,14. Physiologists have relied on laboratory-based heating and cooling experiments, using programmable water baths to steadily heat or cool an animal&#39;s environment to inform thermal performance curves15.
Typically, animals are placed in vials with a thermocouple, and their ambient temperature is changed steadily by controlling the temperature of the surrounding water bath. Researchers measure the time it takes to achieve an altered physiological state (e.g., chill coma, knockdown) and the temperature at which the status change occurred16,17. Starting at a minimum of USD $500, these tools are large, heavy, and require additional technical equipment (e.g., computer, thermocouples). Consequently, the basic tools to carry out classic methods of assessing thermal performance are 1) not economically accessible to all, 2) not suitable for assaying animals too large to be contained in customary vials used for small dipterans, and 3) not portable for use in remote field settings. Adherence to common practice has resulted in limited representation across taxonomy and experimental conditions18,19,20.
While complete thermal performance curves can inform species distribution, life history traits, and behavior, among other traits, the quantification of fewer and simpler thermal metrics can be more efficient and still extremely informative. Physiological assays, measuring chill coma onset and subsequent cold shock recovery, cold-hardening, and righting behavior, are effective and executable proxies for the critical thermal minimum of an organism8. Described here is a cold shock assay useful for eliciting physiological data from large terrestrial ectothermic insects. The assay is affordable, accessible, and easy to execute under field conditions or in the classroom. Data on cold shock recovery generated by this protocol can be coupled with species or individual-level trait data to pursue questions regarding ecological physiology and/or used to teach students about physiological principles.

<table><tbody><tr><td>24 x 24 x 36&quot; Popup Rearing &amp;amp; Observation Cage</td><td>Bioquip</td><td>1466PB</td><td>Ensure that the cage is slightly elevated from the ground to be able to tap the floor of the cage during experiments.</td></tr><tr><td>Cooler</td><td>Any</td><td>NA</td><td></td></tr><tr><td>Glassine envelopes</td><td>Bioquip</td><td>1130B</td><td></td></tr><tr><td>HOBO Pendant Temperature/Light 8K Data Logger</td><td>Onset</td><td>UA-002-08</td><td>If a datalogger is not accessible, researchers may choose to use a digital thermometer to record ambient temperatures at regular intervals. See protocol step 4.5 for additional information.</td></tr><tr><td>HOBO Optic USB Base Station</td><td>Onset</td><td>Base-U-1</td><td></td></tr><tr><td>Ice water</td><td>NA</td><td>NA</td><td></td></tr><tr><td>Insects (focal taxa)</td><td>NA</td><td>Any</td><td>Collect sufficient samples to test, ensuring replication of experimental groups (e.g. species, sampling location)</td></tr><tr><td>PVC T-joint</td><td>Any</td><td>Any</td><td></td></tr><tr><td>Sealable plastic bag</td><td>Any</td><td>NA</td><td></td></tr><tr><td>Stopwatch/timer</td><td>Any</td><td>NA</td><td></td></tr><tr><td>Weight</td><td>Any</td><td>NA</td><td>Large coins or small rocks to weigh down the plastic bags will ensure that specimens are submerged in ice water. A standardized weight is ideal.</td></tr></tbody></table>

field-based thermal physiology assay: cold shock recovery under ambient conditions

Ecological physiology, particularly of ectotherms, is increasingly important in this changing world as it uses measures of species and environmental traits to explore the interactions between organisms and their surroundings to better understand their survival and fitness. Traditional thermal assays are costly in terms of time, money, and equipment and are therefore often limited to small sample sizes and few species. Presented here is a novel protocol that generates detailed data on individual behavior and physiology of large, volant, terrestrial insects, using the example of butterflies. This paper describes the methods of a cold shock recovery assay that can be performed in the field under ambient environmental conditions and does not require costly laboratory equipment. This method has been used to understand the response and recovery strategy to cold shock of tropical butterflies, generating individual level data across entire butterfly communities. These methods can be employed in both remote field settings and classrooms and can be used to generate ecologically relevant physiological data and as a teaching tool.

The data collected in this protocol allow for examination and partitioning of variables important to organismal physiology. For example, both temperature and light conditions contribute to the recovery of butterflies from cold shock (Figure 1). The plot is intended to explore the interaction between ambient conditions and cold shock recover. Using wild-caught butterflies from both traps and netting, 181 species of butterflies demonstrated distinct recovery from chill coma induced by cold shock (Figure 2). Data presented in Figure 2 were collected by three observers over approximately five months (January, February, May-July 2020) in the Colombian Andes. Experiments were always conducted on the morning after butterfly collection. At maximum efficiency, it was possible for two observers to simultaneously observe four butterflies each, repeated seven times (minimum 7.37 hours), resulting in the testing of 56 individuals on a single morning. This allowed for a great deal of data collection across entire butterfly communities while including and considering data on individual variation. As assays can occur under ambient environmental conditions, recovery conditions are representative of their habitats and reflect the natural variation experienced by organisms in nature. Figure 3 illustrates the overlap between temperature and light conditions of the cold shock recovery experiment and conditions in a pasture from which some tested butterflies were collected.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/62218/62218fig01.jpg" /> 
Figure 1:&#160;Scatterplots of recovery time (in seconds) of butterflies after cold shock. (A) Mean temperature and (B) mean LUX (light intensity) during their recovery. Species are organized and colored by Family. Overall, as light and temperature increase, cold shock recovery time decreases, showing variability across taxa. <a href="https://www.jove.com/files/ftp_upload/62218/62218fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/62218/62218fig02.jpg" /> 
Figure 2: Example of results from the cold shock recovery assay on 181 species of butterfly from the Colombian Andes. The data represent the number of seconds that elapsed from removing the butterfly from cold and when it was able to fly. Species are organized and colored by Family. This figure demonstrates the taxonomic breadth across which this experiment can be successfully applied, and the variety of cold shock recovery responses across species. <a href="https://www.jove.com/files/ftp_upload/62218/62218fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/62218/62218fig03.jpg" /> 
Figure 3: Ambient temperature and LUX during cold shock recovery trials. Plot of ambient temperature (blue) and LUX (light intensity, red) as recorded by data loggers placed in the pastures where butterfly collection took place (light colors, conditions span entire day) and conditions during cold shock recovery trials (dark colors, only morning hours). The ambient field conditions and experimental conditions plotted show the range of and average conditions experienced by butterflies over one week of field sampling and experimentation. Experiments were only conducted in early hours (07:00-13:00 h), while the dataloggers were deployed in the field for one week (daylight hours, 06:00-18:00 h shown). Shown here is the overlap between experimental conditions and ambient conditions experienced by butterflies, demonstrating the ecological relevancy of conducting physiology assays under ambient conditions. <a href="https://www.jove.com/files/ftp_upload/62218/62218fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Supplementary Figure 1:&#160;Procedure for collecting focal insects-in this case, butterflies-using baited Van-Someren traps and active netting. Traps were baited with both rotting fish and rotting fruit baits. Trap (without bait) in background, in the foreground is a specimen in its unique envelope against a blue plastic collection box. <a href="https://www.jove.com/files/ftp_upload/62218/Jove supplement fig 1.jpg" target="_blank">Please click here to download this File.</a>
Supplementary Figure 2: Bags with up to four individual butterflies submerged in ice water in a cooler. Plastic bags were marked with the time they were placed in the ice water, so that cold shock experiments could be staggered through the morning. Plastic bags should be sealed to prevent specimens from getting wet; however, flooding of the bags and envelope in this case had no measurable effect on the recovery of the butterflies. <a href="https://www.jove.com/files/ftp_upload/62218/jove supp fig 2.jpg" target="_blank">Please click here to download this File.</a>
Supplementary Figure 3: Two observers collect data in the field. Each mesh cage contains four unique butterflies recovering from cold shock. The polyvinyl chloride T-joint in the cage houses the data logger to prevent direct sun or rain exposure. Each observer has a stopwatch that was started immediately upon butterfly release into the cage. The cages are elevated by benches, permitting observers to agitate the base of the cage to ensure that the butterflies responded behaviorally as quickly as physiologically possible. <a href="https://www.jove.com/files/ftp_upload/62218/jove sup fig 3.jpg" target="_blank">Please click here to download this File.</a>
Supplementary Table 1: Example data sheet. The sheet shows each butterfly&#39;s unique ID as assigned in the field and distinguishing characters (species name, key colors) in notes. Also recorded is the dominant position of the butterfly (i.e., which side of the wing was exposed to the sun) during the recovery period, noted as D (dorsal) or V (ventral). <a href="https://www.jove.com/files/ftp_upload/62218/62218_R1_Supp-table 1.xlsx" target="_blank">Please click here to download this Table.</a>
Supplemental Video 1:&#160;Tapping of the cage for cold shock recovery. As butterflies recover, the observer taps the base of the cage gently to induce behaviors as soon as the butterflies are capable. <a href="https://www.jove.com/files/ftp_upload/62218/IMG_1712.MOV" target="_blank">Please click here to download this Video.</a>

Watch this Scientific Journal Video about Field-Based Thermal Physiology Assay: Cold Shock Recovery under Ambient Conditions at JoVE.com

Field-Based Thermal Physiology Assay: Cold Shock Recovery under Ambient Conditions

Here, a low-cost, accessible protocol is described to evaluate cold shock recovery of butterflies under ambient environmental conditions.

Ecological physiology, particularly of ectotherms, is increasingly important in this changing world as it uses measures of species and environmental ...

field-based-thermal-physiology-assay-cold-shock-recovery-under

Research

JoVE Journal

Biology

2.9K Views.  University of Florida. Here, a low-cost, accessible protocol is described to evaluate cold shock recovery of butterflies under ambient environmental conditions. 

Video: Field-Based Thermal Physiology Assay: Cold Shock Recovery under Ambient Conditions

Standardized Methods for Measuring Induction of the Heat Shock Response in Caenorhabditis elegans

The heat shock response (HSR) is a cellular stress response induced by cytosolic protein misfolding that functions to restore protein folding homeostasis, or proteostasis. Caenorhabditis elegans occupies a unique and powerful niche for HSR research because the HSR can be assessed at the molecular, cellular, and organismal levels. Therefore, changes at the molecular level can be visualized at the cellular level and their impacts on physiology can be quantitated at the organismal level. While assays for measuring the HSR are straightforward, variations in the timing, temperature, and methodology described in the literature make it challenging to compare results across studies. Furthermore, these issues act as a barrier for anyone seeking to incorporate HSR analysis into their research. Here, a series of protocols is&#160;presented for measuring induction of the HSR in a robust and reproducible manner with RT-qPCR, fluorescent reporters, and an organismal thermorecovery assay. Additionally, we show that a widely used thermotolerance assay is not dependent on the well-established master regulator of the HSR, HSF-1, and therefore should not be used for HSR research. Finally, variations in these assays found in the literature are discussed and best practices are proposed to help standardize results across the field, ultimately facilitating neurodegenerative disease, aging, and HSR research.

Standardized Methods for Measuring Induction of the Heat Shock Response in Caenorhabditis elegans

Here, standardized protocols are presented to assess induction of the heat shock response (HSR) in Caenorhabditis elegans using RT-qPCR at the molecular level, fluorescent reporters at the cellular level, and thermorecovery at the organismal level.

The heat shock response (HSR) is a cellular stress response induced by cytosolic protein misfolding that functions to restore protein folding homeostasis, ...

Environment

A Simple and Inexpensive Method for Determining Cold Sensitivity and Adaptation in Mice

Cold hypersensitivity is a serious clinical problem, affecting a broad subset of patients and causing significant decreases in quality of life. The cold plantar assay allows the objective and inexpensive assessment of cold sensitivity in mice, and can quantify both analgesia and hypersensitivity. Mice are acclimated on a glass plate, and a compressed dry ice pellet is held against the glass surface underneath the hindpaw. The latency to withdrawal from the cooling glass is used as a measure of cold sensitivity.
Cold sensation is also important for survival in regions with seasonal temperature shifts, and in order to maintain sensitivity animals must be able to adjust their thermal response thresholds to match the ambient temperature. The Cold Plantar Assay (CPA) also allows the study of adaptation to changes in ambient temperature by testing the cold sensitivity of mice at temperatures ranging from 30 &#176;C to 5 &#176;C. Mice are acclimated as described above, but the glass plate is cooled to the desired starting temperature using aluminum boxes (or aluminum foil packets) filled with hot water, wet ice, or dry ice. The temperature of the plate is measured at the center using a filament T-type thermocouple probe. Once the plate has reached the desired starting temperature, the animals are tested as described above.
This assay allows testing of mice at temperatures ranging from innocuous to noxious. The CPA yields unambiguous and consistent behavioral responses in uninjured mice and can be used to quantify both hypersensitivity and analgesia. This protocol describes how to use the CPA to measure cold hypersensitivity, analgesia, and adaptation in mice.

The Cold Plantar Assay (CPA) measures cold responsiveness between 30 &#176;C and 5 &#176;C, and can also measure cold adaptation. This protocol describes how to use the CPA to measure cold hypersensitivity, analgesia, and adaptation in mice.

Cold hypersensitivity is a serious clinical problem, affecting a broad subset of patients and causing significant decreases in quality of life.  The cold ...

Neuroscience

Thermal Imaging to Study Stress Non-invasively in Unrestrained Birds

Stress, a central concept in biology, describes a suite of emergency responses to challenges. Among other responses, stress leads to a change in blood flow that results in a net influx of blood to key organs and an increase in core temperature. This stress-induced hyperthermia is used to assess stress. However, measuring core temperature is invasive. As blood flow is redirected to the core, the periphery of the body can cool. This paper describes a protocol where peripheral body temperature is measured non-invasively in wild blue tits (Cyanistes caeruleus) using infrared thermography. In the field we created a set-up bringing the birds to an ideal position in front of the camera by using a baited box. The camera takes a short thermal video recording of the undisturbed bird before applying a mild stressor (closing the box and therefore capturing the bird), and the bird&#8217;s response to being trapped is recorded. The bare skin of the eye-region is the warmest area in the image. This allows an automated extraction of the maximum eye-region temperature from each image frame, followed by further steps of manual data filtering removing the most common sources of errors (motion blur, blinking). This protocol provides a time series of eye-region temperature with a fine temporal resolution that allows us to study the dynamics of the stress response non-invasively. Further work needs to demonstrate the usefulness of the method to assess stress, for instance to investigate whether eye-region temperature response is proportional to the strength of the stressor. If this can be confirmed, it will provide a valuable alternative method of stress assessment in animals and will be useful to a wide range of researchers from ecologists, conservation biologists, physiologists to animal welfare researchers.

There is a need for a non-invasive assessment of stress. This paper describes a simple protocol using thermal imaging to detect a significant response in eye-region temperature in wild blue tits to a mild acute stressor.

Stress, a central concept in biology, describes a suite of emergency responses to challenges. Among other responses, stress leads to a change in blood ...

Non-invasive Assessments of Subjective and Objective Recovery Characteristics Following an Exhaustive Jump Protocol

Fast recovery after strenuous exercise is important in sports and is often studied via cryotherapy applications. Cryotherapy has a significant vasoconstrictive effect, which seems to be the leading factor in its effectiveness. The resulting enhanced recovery can be measured by using both objective and subjective parameters. Two commonly measured subjective characteristics of recovery are delayed-onset muscle soreness (DOMS) and ratings of perceived exertion (RPE). Two important objective recovery characteristics are countermovement jump (CMJ) performance and peak power output (PPO). Here, we provide a detailed protocol to induce muscular exhaustion of the frontal thighs with a self-paced, 3 x 30 countermovement jump protocol (30-s rest between each set). This randomized controlled trial protocol explains how to perform local cryotherapy cuff application (+ 8 &#176;C for 20 min) and thermoneutral cuff application (+ 32 &#176;C for 20 min) on both thighs as two possible post-exercise recovery modalities. Finally, we provide a non-invasive protocol to measure the effects of these two recovery modalities on subjective (i.e., DOMS of both frontal thighs and RPE) and objective recovery (i.e., CMJ and PPO) characteristics 24, 48, and 72 h post-application. The advantage of this method is that it provides a tool for researchers or coaches to induce muscular exhaustion, without using any expensive devices; to implement local cooling strategies; and to measure both subjective and objective recovery, without using invasive methods. Limitations of this protocol are that the 30 s rest period between sets is very short, and the cardiovascular demand is very high. Future studies may find the assessment of maximum voluntary contractions to be a more sensitive assessment of muscular exhaustion compared to CMJs.

This protocol describes the procedure for non-invasive recovery assessments during a 72 h recovery period. This protocol induces muscular exhaustion of the frontal thighs using countermovement jumps and uses either local cold-cuff or thermoneutral-cuff application as a recovery modality.

Fast recovery after strenuous exercise is important in sports and is often studied via cryotherapy applications. Cryotherapy has a significant ...

Medicine

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the function and regulation of protein folding was studied in vitro, in isolated tissue culture cells and in unicellular organisms. Recent studies have uncovered links between protein homeostasis (proteostasis), metabolism, development, aging, and temperature-sensing. These findings have led to the development of new tools for monitoring protein folding in the model metazoan organism Caenorhabditis elegans. In our laboratory, we combine behavioral assays, imaging and biochemical approaches using temperature-sensitive or naturally occurring metastable proteins as sensors of the folding environment to monitor protein misfolding. Behavioral assays that are associated with the misfolding of a specific protein provide a simple and powerful readout for protein folding, allowing for the fast screening of genes and conditions that modulate folding. Likewise, such misfolding can be associated with protein mislocalization in the cell. Monitoring protein localization can, therefore, highlight changes in cellular folding capacity occurring in different tissues, at various stages of development and in the face of changing conditions. Finally, using biochemical tools ex vivo, we can directly monitor protein stability and conformation. Thus, by combining behavioral assays, imaging and biochemical techniques, we are able to monitor protein misfolding at the resolution of the organism, the cell, and the protein, respectively.

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

To study the relationship between protein homeostasis, stress and aging, we monitored changes in protein folding by following protein dysfunction, protein localization in the cell and protein stability at the organismal, cellular and protein levels, using the genetically tractable metazoan Caenorhabditis elegans as a model system.

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the ...

In vitro Assessment of Myocardial Protection following Hypothermia-Preconditioning in a Human Cardiac Myocytes Model

Ischemia/reperfusion-derived myocardial dysfunction is a common clinical scenario in patients after cardiac surgery. In particular, the sensitivity of cardiomyocytes to ischemic injury is higher than that of other cell populations. At present, hypothermia affords considerable protection against an expected ischemic insult. However, investigations into complex hypothermia-induced molecular changes remain limited. Therefore, it is essential to identify a culture condition similar to in vivo conditions that can induce damage similar to that observed in the clinical condition in a reproducible manner. To mimic ischemia-like conditions in vitro, the cells in these models were treated by oxygen/glucose deprivation (OGD). In addition, we applied a standard time-temperature protocol used during cardiac surgery. Furthermore, we propose an approach to use a simple but comprehensive method for the quantitative analysis of myocardial injury. Apoptosis and expression levels of apoptosis-associated proteins were assessed by flow cytometry and using an ELISA kit. In this model, we tested a hypothesis regarding the effects of different temperature conditions on cardiomyocyte apoptosis in vitro. The reliability of this model depends on strict temperature control, controllable experimental procedures, and stable experimental results. Additionally, this model can be used to study the molecular mechanism of hypothermic cardioprotection, which may have important implications for the development of complementary therapies for use with hypothermia.

The distinct effects of different degrees of hypothermia on myocardial protection have not been thoroughly evaluated. The goal of the present study was to quantify the levels of cell death following different hypothermia treatments in a human cardiomyocyte-based model, laying the foundation for future in-depth molecular research.

Ischemia/reperfusion-derived myocardial dysfunction is a common clinical scenario in patients after cardiac surgery. In particular, the sensitivity of ...

A Preclinical Model of Exertional Heat Stroke in Mice

Heat stroke is the most severe manifestation of heat-related illnesses. Classic heat stroke (CHS), also known as passive heat stroke, occurs at rest, whereas exertional heat stroke (EHS) occurs during physical activity. EHS differs from CHS in etiology, clinical presentation, and sequelae of multi-organ dysfunction. Until recently, only models of CHS have been well established. This protocol aims to provide guidelines for a refined preclinical mouse model of EHS that is free from major limiting factors such as the use of anesthesia, restraint, rectal probes, or electric shock. Male and female C57Bl/6 mice, instrumented with core temperature (Tc) telemetric probes were utilized in this model. For familiarization with the running mode, mice undergo 3 weeks of training using both voluntary and forced running wheels. Thereafter, mice run on a forced wheel inside a climatic chamber set at 37.5 &#176;C and 40%-50% relative humidity (RH) until displaying symptom limitation (e.g., loss of consciousness) at Tc of 42.1-42.5 &#176;C, although suitable results can be obtained at chamber temperatures between 34.5-39.5 &#176;C and humidity between 30%-90%. Depending on the desired severity, mice are removed from the chamber immediately for recovery in ambient temperature or remain in the heated chamber for a longer duration, inducing a more severe exposure and a higher incidence of mortality. Results are compared with sham-matched exercise controls (EXC) and/or na&#239;ve controls (NC). The model mirrors many of the pathophysiological outcomes observed in human EHS, including loss of consciousness, severe hyperthermia, multi-organ damage as well as inflammatory cytokine release, and acute phase responses of the immune system. This model is ideal for hypothesis-driven research to test preventative and therapeutic strategies that may delay the onset of EHS or reduce the multi-organ damage that characterizes this manifestation.

The protocol describes the development of a standardized, repeatable, preclinical model of exertional heat stroke (EHS) in mice free from adverse external stimuli such as electric shock. The model provides a platform for mechanistic, preventative, and therapeutic studies.

Heat stroke is the most severe manifestation of heat-related illnesses. Classic heat stroke (CHS), also known as passive heat stroke, occurs at rest, ...

Measurements of Physiological Stress Responses in C. Elegans

Organisms are often exposed to fluctuating environments and changes in intracellular homeostasis, which can have detrimental effects on their proteome and physiology. Thus, organisms have evolved targeted and specific stress responses dedicated to repair damage and maintain homeostasis. These mechanisms include the unfolded protein response of the endoplasmic reticulum (UPRER), the unfolded protein response of the mitochondria (UPRMT), the heat shock response (HSR), and the oxidative stress response (OxSR). The protocols presented here describe methods to detect and characterize the activation of these pathways and their physiological consequences in the nematode, C. elegans. First, the use of pathway-specific fluorescent transcriptional reporters is described for rapid cellular characterization, drug screening, or large-scale genetic screening (e.g., RNAi or mutant libraries). In addition, complementary, robust physiological assays are described, which can be used to directly assess sensitivity of animals to specific stressors, serving as functional validation of the transcriptional reporters. Together, these methods allow for rapid characterization of the cellular and physiological effects of internal and external proteotoxic perturbations.

Measurements of Physiological Stress Responses in C. Elegans

Here, we characterize cellular proteotoxic stress responses in the nematode C. elegans by measuring the activation of fluorescent transcriptional reporters and assaying sensitivity to physiological stress.

Organisms are often exposed to fluctuating environments and changes in intracellular homeostasis, which can have detrimental effects on their proteome and ...

High-Throughput Assays of Critical Thermal Limits in Insects

Upper and lower thermal limits of plants and animals are important predictors of their performance, survival, and geographic distributions, and are essential for predicting responses to climate change. This work describes two high-throughput protocols for measuring insect thermal limits: one for assessing critical thermal minima (CTmin), and the other for assessing heat knock down time (KDT) in response to a static heat stressor. In the CTmin assay, individuals are placed in an acrylic-jacketed column, subjected to a decreasing temperature ramp, and counted as they fall from their perches using an infrared sensor. In the heat KDT assay, individuals are contained in a 96 well plate, placed in an incubator set to a stressful, hot temperature, and video recorded to determine the time at which they can no longer remain upright and move. These protocols offer advantages over commonly used techniques. Both assays are low cost and can be completed relatively quickly (~2 h). The CTmin assay reduces experimenter error and can measure a large number of individuals at once. The heat KDT protocol generates a video record of each assay and thus removes experimenter bias and the need to continuously monitor individuals in real time.

Thermal limits can predict the environments organisms tolerate, which is valuable information in the face of rapid climate change. Described here are high-throughput protocols to assess critical thermal minima and heat knockdown time in insects. Both protocols maximize the throughput and minimize the cost of the assays.

Upper and lower thermal limits of plants and animals are important predictors of their performance, survival, and geographic distributions, and are ...

Optimized RNA Extraction for qRT-PCR in Individual Tardigrades

Single-Animal, Single-Tube RNA Extraction for Comparison of Relative Transcript Levels via qRT-PCR in the Tardigrade Hypsibius exemplaris

The tardigrade Hypsibius exemplaris is an emerging model organism renowned for its ability to survive environmental extremes. To explore the molecular mechanisms and genetic basis of such extremotolerance, many studies rely on RNA-sequencing (RNA-seq), which can be performed on populations ranging from large cohorts to individual animals. Reverse transcription polymerase chain reaction (RT-PCR) and RNA interference (RNAi) are subsequently used to confirm RNA-seq findings and assess the genetic requirements for candidate genes, respectively. Such studies require an efficient, accurate, and affordable method for RNA extraction and measurement of relative transcript levels by quantitative RT-PCR (qRT-PCR). This work presents an efficient single-tardigrade, single-tube RNA extraction method (STST) that not only reliably isolates RNA from individual tardigrades but also reduces the required time and cost for each extraction. This RNA extraction method yields quantities of cDNA that can be used to amplify and detect multiple transcripts by quantitative PCR (qRT-PCR). The method is validated by analyzing dynamic changes in the expression of genes encoding two heat-shock-regulated proteins, Heat-Shock Protein 70 &#946;2 (HSP70 &#946;2) and Heat-Shock Protein 90&#945; (HSP90&#945;), making it possible to assess their relative expression levels in heat-exposed individuals using qRT-PCR. STST effectively complements existing bulk and single tardigrade RNA extraction methods, permitting rapid and affordable examination of individual tardigrade transcriptional levels by qRT-PCR.

This work presents a rapid RNA extraction and transcript level comparison method for analyzing gene expression in the tardigrade Hypsibius exemplaris. Using physical lysis, this high-throughput method requires a single tardigrade as the starting material and results in robust production of cDNA for quantitative reverse transcription polymerase chain reaction (qRT-PCR).

The tardigrade Hypsibius exemplaris is an emerging model organism renowned for its ability to survive environmental extremes. To explore the molecular ...

Field-Based Thermal Physiology Assay: Cold Shock Recovery under Ambient Conditions

Summary

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