Minimum postmortem interval estimation using the development and gene expression patterns of Hemipyrellia ligurriens...

The developmental patterns of the oldest developing flies are commonly used by forensic entomologists to estimate the minimum postmortem interval (PMImin). Hemipyrellia ligurriens (Wiedemann, 1830) (Diptera: Calliphoridae) are widely distributed in the Australian and Palearctic regions and are closely associated with human corpses. Here, the developmental pattern of H. ligurriens was studied under laboratory conditions at 7 different constant temperatures between 16 and 34 °C. Five models were established for the study of H. ligurriens, including an isomorphen diagram, an isomegalen diagram, a linear thermal summation model, a nonlinear SSI model, and a logistic model. The lower developmental threshold and thermal summation constant of H. ligurriens evaluated by the linear thermal summation models were 8.99 °C and 4,967.35 degree hours, respectively. The lower developmental threshold, intrinsic optimum temperature, and upper lethal developmental threshold obtained by Optim SSI models were 12.56, 19.91, and 33.21 °C, respectively. The expression levels of 5 genes (Hsp83, Hsp60, USP, wg, and amKI) were analyzed at sequential developmental time points to estimate the pupal formation time of H. ligurriens under constant temperatures of 16 and 25 °C, and to verify the temporal regularity of this process. This study provides a foundation for forensic entomologists to accurately estimate the PMImin using H. ligurriens in future death investigations.