Multimethod combination for age estimation of Sarcophaga peregrina (Diptera: Sarcophagidae) with implications for estimation of the postmortem interval.

Abstract

Sarcophaga peregrina (Robineau-Desvoidy, 1830) (Diptera: Sarcophagidae) is a forensically important flesh fly with potential value for estimating the minimum postmortem interval (PMImin). Here, the developmental patterns of S. peregrina were investigated at 5 constant temperatures (15-35°C). Morphological changes at different developmental stages of the pupa were observed at 4 constant temperatures (15-30°C) by removing the puparium and staining the pupa with hematoxylin and eosin. Furthermore, differentially expressed genes (DEGs) were analyzed at 25°C in the intrapuparial period to estimate the age of S. peregrina during the intrapuparial stage. S. peregrina completed development from larviposition to adult eclosion at 15°C, 20°C, 25°C, and 30°C; the developmental durations were 1090.3 ± 30.6h, 566.6 ± 21.9h, 404.6 ± 13.01h, and 280.3 ± 4.5h, respectively, while the development could not be completed at 35°C. The intrapuparial period of S. peregrina was divided into 12 sub-stages on the basis of the overall external morphological changes; 6 sub-stages on the basis of individual morphological structures such as the compound eyes, antennae, thorax, legs, wings, and abdomen; and 10 sub-stages on the basis of internal morphological changes detected using histological analysis. The period of each sub-stage or structure that appeared was determined. Moreover, we found that 6 genes (NDUFS2, CPAMD8, NDUFV2, Hsp27, Hsp23, and TPP) with differential expression can be used for the precise age estimation of S. peregrina during the intrapuparial period. This study provided basic developmental data for the use of S. peregrina in PMImin estimation, and we successfully estimated PMImin in a real forensic case by using a multimethod combination.