Dynamics of insects, microorganisms and muscle mRNA on pig carcasses and their significances in estimating PMI

The accurate estimate of the postmortem interval (PMI) is of vital significance in the investigation of ho-micide cases. In this study, three pig carcasses were placed in the field to study the pattern of insect suc-cession, the change of microorganisms and the degradation of muscle tissue RNA during the decomposition process. The results showed that insects could quickly colonize the carcasses and still exist on them until the end of the experiment (41 days). Their development and succession patterns are useful indicators for PMI estimation. The diversity of rectal microorganisms decreased with the decomposition time. In different decomposition periods, significant differences in the rectal and soil microbial composition and relative abundance were found, which could be used to estimate the PMI with an accuracy of 3-4 days. The RNA of muscle tissue was found to have a time-dependent relationship with the PMI. Ppia and Gapdh showed a linear upward trend within 10 h after the death, followed by a gradual downward trend from 10 to 240 h. The expression of beta-actin gene showed a gradual downward trend during 0-240 h. This is the first study in China to analyze the changes of insects, muscle RNA and microorganisms on pig carcasses in the same natural environment, which provide basic data for the PMI estimation. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study found that the development and succession patterns of insects, changes in microbial composition, and degradation of muscle tissue RNA during decomposition can be used as indicators for estimating postmortem interval (PMI) with an accuracy of 3-4 days. This research provides basic data for PMI estimation by analyzing the changes of insects, muscle RNA, and microorganisms on pig carcasses in the same natural environment in China.