Predicting the Weathering Time by the Empty Puparium of Sarcophaga peregrina (Diptera: Sarcophagidae) with the ANN Models

Abstract

Empty puparium are frequently collected at crime scenes and may provide valuable evidence in cases with a long postmortem interval (PMI). Here, we collected the puparium of Sarcophaga peregrina (Diptera: Sarcophagidae) (Robineau-Desvoidy, 1830) for 120 days at three temperatures (10 °C, 25 °C, and 40 °C) with the aim to estimate the weathering time of empty puparium. The CHC profiles were analyzed by gas chromatography-mass spectrometry (GC-MS). The partial least squares (PLS), support vector regression (SVR), and artificial neural network (ANN) models were used to estimate the weathering time. This identified 49 CHCs with a carbon chain length between 10 and 33 in empty puparium. The three models demonstrate that the variation tendency of hydrocarbon could be used to estimate the weathering time, while the ANN models show the best predictive ability among these three models. This work indicated that puparial hydrocarbon weathering has certain regularity with weathering time and can gain insight into estimating PMI in forensic investigations.

Genome-wide analysis of long noncoding RNAs and their association in regulating the metamorphosis of the Sarcophaga peregrina (Diptera: Sarcophagidae)

“…MSD ChemStation Data Analysis F.01.03 was used to integrate the peak height, and only compounds with a consistent peak height percentage above 0.5% were included. Hydrocarbons were identified using a library search (NIST14), the Kovats Index based on external standards, and literature [49].…”

Pupal Age Estimation of Sarcophaga peregrina (Diptera: Sarcophagidae) at Different Constant Temperatures Utilizing ATR-FTIR Spectroscopy and Cuticular Hydrocarbons

“…We found that the compound classes of hydrocarbons increased with the increases in temperature from 20 °C to 30 °C, and the percentage composition of long-chain hydrocarbons, such as C24, decreased regularly with the pupal development of S. peregrina . It might be that higher temperatures increased biodegradation and accelerated the weathering of the surface pupal cuticle, leading to an increase in the CHCs in pupae [ 31 ]. In addition, we found that the separation between the age classes from CHC analysis in Figure 3 is better with increasing temperatures from 20 °C to 30 °C and shows a clear separation at 30 °C.…”

“…A supervised statistical method of discriminant analysis was performed using orthogonal partial least squares discriminant analysis (OPLS-DA) [ 31 ]. Multivariate regression using partial least squares (PLS) is a common statistical technique [ 32 ].…”

“…The OPLS-DA and PLS modeling was conducted in SIMCA 14.1 software. The contribution of the factors to the model was evaluated by the variable importance of projection (VIP) value, the more significant a variable was to the model, the higher the VIP value for that variable would be [ 31 ]. In accordance with the OPLS-DA and PLS models, we selected spectroscopy with a VIP value > 1.0.…”

“…We cleaned the pupal tissue using ultrapure water and blotted it dry with filter paper. Then, one whole pupae tissue at each pupal development age (days) of S. peregrina at each constant temperature (20 °C, 25 °C, and 30 °C) was placed in a 2 mL glass vial with 1 mL of hexane and left at room temperature for 1 h [ 31 ]. The liquid was then transferred using a syringe filter with a nylon membrane with a 0.45 m aperture.…”