DOI: 10.5061/dryad.83bk3jb6t
title: Data from: Surviving in the mountains: Temperature and elevation have contrasting physiological effects and no effect on morphology of the hoverfly <em>Eristalis tenax</em> in the Himalayas

description: Insect populations are experiencing a global decline due to a variety of
 human-linked environmental changes. Among these changes, the potential
 impact on insect physiology of predicted upslope migration due to climate
 change is unknown. Being ectotherms, insect physiology is influenced by
 abiotic factors such as ambient temperature, which changes with elevation.
 Here, we performed in situ experiments to assess the sensory and cardiac
 physiology of an important generalist pollinating hoverfly Eristalis tenax
 (Diptera: Syrphidae), across different elevations in the eco-sensitive and
 biodiverse Himalayan mountains. We built a portable physiology setup and
 measured hoverfly antennal responses towards common floral volatiles at
 3600 masl and 4200 masl. We also recorded their heart rate at 3000 masl,
 3500 masl, and 4000 masl. We also performed tissue morphometric
 measurements on wild-caught E. tenax using micro-CT. To our knowledge, we
 report the first in situ physiology experiments performed in the
 high-altitude Himalayas and the first measurements of internal structures
 of wild-caught E. tenax. Our results show a contrasting impact of
 elevation and temperature on the sensory and cardiac physiology of
 hoverflies, with antennal olfactory sensitivity decreasing with increasing
 elevation, while average heart rate increased with temperature,
 independent of elevation. However, elevation did not show an impact on
 morphometric parameters like body size and flight musculature. With
 upslope migration and climate warming, consequent sensory mismatches and
 potential cardiac stress could have deleterious effects on the health of
 both hoverflies and the vulnerable Himalayan ecosystem.
description: # Data from: Surviving in the mountains: Temperature and elevation have
 contrasting physiological effects and no effect on morphology of the
 hoverfly *Eristalis tenax* in the Himalayas Dataset DOI:
 [10.5061/dryad.83bk3jb6t](https://doi.org/10.5061/dryad.83bk3jb6t) ##
 Description of the data and file structure Measurement of antennal
 olfactory sensitivity and threshold for stimulus detection: We
 standardized a portable electrophysiology (pEAG) rig to perform
 electroantennograms to measure the antennal response towards the given
 olfactory stimuli at each site. Measurement of heart rate: We performed
 dissections to record the heart rate at each site using a modified
 protocol. Wild-caught individuals of Eristalis tenax were used for all
 experiments.  1. Whole insect preparation was used to perform
 electroantennograms at different elevations (3600 and 4200 masl) in the
 Himalayas and the lab in Bengaluru (900 masl). 2. Individuals were
 dissected to reveal the beating heart, which was video recorded for 5
 minutes, at different elevations (3000, 3500, 3600, 4000, 4200 masl) in
 the Himalayas and the lab in Bengaluru (900 masl). ### Files and variables
 #### File: eag_data_zipped_.zip **Description:** The EAG, ASC and CSV
 files of electroantennograms of *E. tenax* at all sites #### File:
 heartrate_videos.zip **Description:** The video files of heartrate
 recordings of E. tenax at all sites ## Code/software ####
 eag_data_zipped_.zip Each recording for EAG has three files: (1) .eag
 files - can be opened using EAG2000 software; (2) .asc files - can be
 opened using Notepad and similar programs/software and (3) .csv files -
 can be opened using MS Excel and similar programs/software. ####
 heartrate_videos.zip The heartrate files (extension .mp4) can be opened
 with any media player. **Some notes about extracting data for the
 electroantennogram (EAG) recordings:** For each EAG recording, there are 3
 files: (1) EAG file – open using EAG2000 software (though proprietary one
 but the data are also available in the following ASC and CSV files) (2)
 ASC file – open using Notepad (3) CSV file – open using MS Excel Procedure
 to extract data: 1.    Open CSV file using MS Excel. There are four
 sheets: ‘data’ ‘chemicals’, ‘sorting’ and ‘max deflections’. 2.    In
 ‘data’ sheet, values in column B are the values of electric potential
 measured at that time in that recording. These data have to be extracted.
 The numbers “1, 2, 3…” in column A indicate the stimulus number. These
 demarcate different stimuli given. 3.    First, in a new sheet
 (‘chemicals’ in this Excel document), copy and paste each stimulus and
 corresponding electric potential values. There should be one column with
 the potential values for each stimulus presented (henceforth called ‘mV
 column’). Each such column corresponds to one chemical stimulus, whose
 name should be written above the columns. 4.    Next, insert two columns
 before the mV column. In first of those columns, write the serial numbers
 from 1, 2, 3 .. until the last entry in the mV column (henceforth ‘S. no.
 column). There should be between 250 to 256 entries for each stimulus.
 5.    Next, in the second column, we will calculate the time of stimulus
 presentation. The entire recording last for 10 seconds. That means the
 electric potential in mV column have been recorded over 10 seconds. In
 order to calculate the exact time for each entry in mV column, we will use
 the formula – 10/(value in serial number column). These values should be
 calculated and inserted in the second column, in front of each of the mV
 column; this column will be henceforth called ‘Time column’. This last
 entry in this column should be ‘10’, indicating the value of electric
 potential at the 10-second time point for each presented stimulus. 6.   
 Next, we make a copy of this sheet, called ‘sorting’ in this Excel
 document. Here, we will consider values only until 4 seconds, which is
 when the stimulus is presented. Hence, only retain the values until
 4-second timepoint and discard the rest. Repeat for each presented
 stimulus. 7.    In the retained dataset, sort the values in mV column from
 lowest to highest. The lowest value will be the value of maximum
 deflection for each presented stimulus. 8.    Take this value for each
 stimulus and tabulate it for each recording. This is represented in the
 sheet ‘max deflections’ in the document. 9.    Repeat for each individual
 recording (which in our case, is from one individual). Compile the maximum
 deflection values for each stimulus for each individual and proceed for
 further analyses. ***Legend:*** (i) mV = milliVolts; (ii) CHA =
 cis-3-hexenyl-acetate; (iii) cym = p-cymene; (iv) pin = alpha-pinene; (v)
 PF = 2-pentylfuran; (vi) 10 ^-1^, 10 ^-2^, 10 ^-3^, 10 ^-4^, 10 ^-5^ = 
 serial dilutions of the chemical stimulus (percent volume/volume)
 representing 0.1, 0.001, 0.0001, 0.00001 and 0.00001 times (respectively)
 the concentration of the pure chemical stimulus; (vii) MO = mineral oil
 (solvent control); (viii) SKP = Sikkim Positive stimulus (positive control
 stimulus obtained from Mishra et al. (2025)*.*