Temperature effects Mormon cricket Anabrus simplex embryo development, hatching and nymphal growth: Thermal performance curves change with ontogeny

Authors: Srygley, Robert

Submitted to: Journal of Thermal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2022
Publication Date: 10/7/2022
Citation: Srygley, R.B. 2022. Temperature effects Mormon cricket Anabrus simplex embryo development, hatching and nymphal growth: Thermal performance curves change with ontogeny. Journal of Thermal Biology. 110. Article 103356. https://doi.org/10.1016/j.jtherbio.2022.103356.
DOI: https://doi.org/10.1016/j.jtherbio.2022.103356

Interpretive Summary: Temperature affects all biological processes. Mormon crickets are a pest of rangeland and crops in the western United States, and yet little is known about the effect of temperature on development of Mormon cricket life stages. To fill this gap, the effects of temperature on development of Mormon cricket embryos, and hatching and development of nymphs were measured on a population from the Bighorn Mountains of Wyoming. Temperature has a unique non-linear relationship with development in each Mormon cricket life stage, and within the egg stage, the peak temperature for development was found to change. Until the embryos were half-sized, development was fastest at 26.9°C (80.4°F), but the embryos typically arrested development at temperatures above 26°C (78.8°F). The latter half of embryonic development was fastest at 24.1°C (75.4°F). Nymphs hatched fastest at 21.8°C (71.2°F), but developed fastest at 35.7°C (96.3°F). Other differences, such as the breadth of the thermal window for development in each stage, are discussed. This study provides the first complete set of curves relating development through the life stages of this important economic pest. The curves are a more precise measure than degree-days to predict egg development and hatching and improve models of population growth. In addition, pest managers can more accurately predict hatch and nymphal growth to better time management operations, which are less effective on adults.

Technical Abstract: Thermal performance curves for development are an essential tool for population modeling and pest management. More broadly, they characterize how selection on thermal limits or maximum rates change with life stage. The effects of temperature on development of Mormon cricket embryos, and hatching and development of nymphs were measured on a population from the Bighorn Mountains of Wyoming and modeled with four non-linear equations. Taylor’s Gaussian curve characterized embryonic development, which was most rapid at 26.9°C. However, half-grown embryos aestivated at high temperatures, resulting in a significant shift in the optimum temperature to complete embryonic development to 24.1°C and a reduction in the breadth of the performance curve (thermal breadth). Fully grown embryos hatched fastest at relatively low temperatures (21.8°C), whereas nymphal development was maximized at relatively high temperatures (35.7°C). Thermal breadths for nymphal hatching and development were also significantly broader than that for embryonic development. Differences in optimum temperature and thermal breadth of each life stage should be taken into consideration in population modeling, comparisons among populations, and epigenetic studies of acclimation.