Variable heritability of Cochliomyia macellaria (Diptera: Calliphoridae) development time with and without thermal shock.

The relative effect size of additive genetic action, often studied as heritability, on informative phenotypes is rarely considered in forensic entomology. In addition, while extended thermal exposures are known to have an impact on the growth and development of blow flies throughout their life cycle less is known about the effects of acute exposure to high or low temperatures, which can also potentially impact phenotypes. The objective of this study was to estimate the heritability of development time and determine if the estimate is impacted by acute thermal shock. Development times of offspring were compared to parental development times under control conditions (25 °C), and when dams/grand dams were exposed to heat (25 °C with brief exposure to 42 °C) or cold (25 °C with brief exposure to 2 °C). Heritability values were calculated for all groups. A moderate (h2=0.510) contribution of parental phenotype was determined for the control condition. When dams or grand dams were exposed to thermal shock, this value could change considerably (h2=0 to 0.907) depending on the nature of the thermal shock and the generation exposed to the shock. These results indicate that blow fly development times may be influenced by maternal effects and the possibility of epigenetic impacts on development. Short term exposure to thermal spikes is likely to coincide with changing seasons and further work is needed to explore the potential for seasonal effects on the genetic impact of temperature on blow fly developmental variation.