Thermal tolerance data

Description

Research hypothesis We first hypothesized that acclimation improves tolerance to heat and cold in the life stage of T. batrachopa and that the response to acclimation differs for each life stage. Secondly, we hypothesized that pre-exposure to cold and warm temperatures improves the survival of each T. batrachopa life stage, and survival differs among life stages. Notable findings The life stages of T. batrachopa showed significant variation in their thermal tolerance. The acclimation ability of T. batrachopa varied with acclimation temperatures and life stages, and the results were pronounced for larval stages. The larval stages had higher CTmin and CTmax than adult moths across all acclimation temperatures. Instar 4 larvae were the most heat and cold-tolerant after acclimation in all temperatures. Pre-exposure for 2h and exposure for 2h didn’t significantly improve each life stage's survival. However, the adult moths had a higher %survival than larval stages after RHH and RCH. Our data was collected to determine the T. batrachopa's ability to adapt and survive unfavourable temperatures. The thermal tolerance assay were performed on larval and adult moths stages of this pests since they are key or damaging life stages. The data can be interpreted by understanding the impact that acclimation temperatures, and pre-exposure temperatures have on survival of T. batrachopa. Temperature has a great influence on development and survival of insect species. Our study addressed the influence of temperature variations on T. batrachopa life stages. This will help to understand how T. batrachopa survives temperatures variations in the natural habitat due to climated change.

Steps to reproduce

Acclimation data was obtained through running critical limits assay of larvae and adult moths. Critical thermal limits (CTLs) Different life stages were put individually in 10ml plastic vials. The vials were then put into ‘organ pipes’ joined to the programmable water bath (Grant, SG8 6GB; Grant instruments, Cambridge Ltd, UK). The water bath had water: propylene glycol (1:1) to allow flow regulation at freezing temperatures. The larvae and adult moths were allowed to first equilibrate to the ambient temperature for 10 minutes before ramping up the temperature to determine CTmax or down to determine CTmin at 0.25 °C min-1 rate. Two Thermochron ibutton loggers (Semiconductor Corporation, Dallas/Maxin TX and USA) were placed in one of the chambers to verify the temperature at 1-minute intervals. The CTLs were defined as the temperature at which individuals lost coordinated muscle function (Nyamukondiwa and Terblanche 2009). Lethal assay data The measured larvae and adult moths were put individually inside 6 ml vacutest tubes, placed in labeled plastic zip lock bags, and plunged into a programmable water bath with water and 1:1 propylene glycol ratio inside. The larvae were plunged for 1, 2, and 3h to acute temperatures varying from 40°C to 45°C for upper lethal temperature (ULT), and from 0 to -14°C for lower lethal temperature (LLT). However, adult moths were plunged for 2h to acute temperatures varying from 37 to 42°C for ULT and 0 to -8 for LLT. Two ibutton loggers were placed inside one of the ziplock bags to record the temperature every minute. The plunged larvae and adult moths were taken to the rearing room and kept at 25 ± 1°C, 60-75 %RH, 16L:8D. The plunged larvae were provided with fresh macadamia husks as a source of food, and the adult moths with 10% sucrose solution. Survival was recorded after 24h for T. batrachopa individuals that responded to prodded stimuli made with a paintbrush after 24h. The discriminating temperature (DT) was the temperature that caused 80% mortality of the larvae and adult moths. Rapid hardening The larvae and adult moths were put individually in 6ml vacutest tubes and pre-exposed for 2h at 35°C for heat and 10°C for cold hardening pre-treatment. In the control treatment, the larvae and adult moths were not pre-exposed and were taken directly from the rearing room. The pre-exposure temperatures used in our study were also used for rapid hardening assays (e.g.,Ceratitis capitata and Ceratitis rosa, Nyamukondiwa et al., 2010, and B. distincta, Muluvhahothe et al., 2023). The larvae were then plunged into a programable water bath with water and 1:1 propylene glycol ratio inside for 2h at the DTs of 43°C for RHH and -11°C for RCH. Adult moths were plunged at the DTs of 40°C for RHH and -5°C for RCH. Hardening was recorded as % survival after 24h at 25°C, which is defined as a coordinated reaction to stimulation.

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