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Thümmel L, Tintner-Olifiers J, Amendt J. A methodological approach to age estimation of the intra-puparial period of the forensically relevant blow fly Calliphora vicina via Fourier transform infrared spectroscopy. MEDICAL AND VETERINARY ENTOMOLOGY 2024. [PMID: 39093723 DOI: 10.1111/mve.12748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2024] [Accepted: 07/19/2024] [Indexed: 08/04/2024]
Abstract
Estimating the age of immature blow flies is of great importance for forensic entomology. However, no gold-standard technique for an accurate determination of the intra-puparial age has yet been established. Fourier transform infrared (FTIR) spectroscopy is a method to (bio-)chemically characterise material based on the absorbance of electromagnetic energy by functional groups of molecules. In recent years, it also has become a powerful tool in forensic and life sciences, as it is a fast and cost-effective way to characterise all kinds of material and biological traces. This study is the first to collect developmental reference data on the changes in absorption spectra during the intra-puparial period of the forensically important blow fly Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae). Calliphora vicina was reared at constant 20°C and 25°C and specimens were killed every other day throughout their intra-puparial development. In order to investigate which part yields the highest detectable differences in absorption spectra throughout the intra-puparial development, each specimen was divided into two different subsamples: the pupal body and the former cuticle of the third instar, that is, the puparium. Absorption spectra were collected with a FTIR spectrometer coupled to an attenuated total reflection (ATR) unit. Classification accuracies of different wavenumber regions with two machine learning models, i.e., random forests (RF) and support vector machines (SVMs), were tested. The best age predictions for both temperature settings and machine learning models were obtained by using the full spectral range from 3700 to 600 cm-1. While SVMs resulted in better accuracies for C. vicina reared at 20°C, RFs performed almost as good as SVMs for data obtained from 25°C. In terms of sample type, the pupal body gave smoother spectra and usually better classification accuracies than the puparia. This study shows that FTIR spectroscopy is a promising technique in forensic entomology to support the estimation of the minimum post-mortem interval (PMImin), by estimating the age of a given insect specimen.
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Affiliation(s)
- Luise Thümmel
- Goethe-University Frankfurt, University Hospital, Institute of Legal Medicine, Frankfurt am Main, Germany
- Department of Aquatic Ecotoxicology, Faculty of Biological Sciences, Goethe University, Frankfurt am Main, Germany
| | | | - Jens Amendt
- Goethe-University Frankfurt, University Hospital, Institute of Legal Medicine, Frankfurt am Main, Germany
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Zhang X, Yang F, Xiao J, Qu H, Jocelin NF, Ren L, Guo Y. Analysis and comparison of machine learning methods for species identification utilizing ATR-FTIR spectroscopy. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2024; 308:123713. [PMID: 38056185 DOI: 10.1016/j.saa.2023.123713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 10/26/2023] [Accepted: 11/28/2023] [Indexed: 12/08/2023]
Abstract
Accurate identification of insect species holds paramount significance in diverse fields as it facilitates a comprehensive understanding of their ecological habits, distribution range, and impact on both the environment and humans. While morphological characteristics have traditionally been employed for species identification, the utilization of empty pupariums for this purpose remains relatively limited. In this study, ATR-FTIR was employed to acquire spectral information from empty pupariums of five fly species, subjecting the data to spectral pre-processing to obtain average spectra for preliminary analysis. Subsequently, PCA and OPLS-DA were utilized for clustering and classification. Notably, two wavebands (3000-2800 cm-1 and 1800-1300 cm-1) were found to be significant in distinguishing A. grahami. Further, we established three machine learning models, including SVM, KNN, and RF, to analyze spectra from different waveband groups. The biological fingerprint region (1800-1300 cm-1) demonstrated a substantial advantage in identifying empty puparium species. Remarkably, the SVM model exhibited an impressive accuracy of 100 % in identifying all five fly species. This study represents the first instance of employing infrared spectroscopy and machine learning methods for identifying insect species using empty pupariums, providing a robust research foundation for future investigations in this area.
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Affiliation(s)
- Xiangyan Zhang
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, Hunan, China
| | - Fengqin Yang
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, Hunan, China
| | - Jiao Xiao
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, Hunan, China
| | - Hongke Qu
- Key Laboratory of Carcinogenesis and Cancer Invasion of the Chinese Ministry of Education, Cancer Research Institute and School of Basic Medicine Sciences, Central South University, Changsha, Hunan, China
| | - Ngando Fernand Jocelin
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, Hunan, China
| | - Lipin Ren
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, Hunan, China.
| | - Yadong Guo
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, Hunan, China.
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Ngando FJ, Zhang X, Qu H, Zhang C, Yang F, Feng Y, Shang Y, Chen S, Ren L, Guo Y. Analysis of the Influence of Changing and Fixed Temperatures on the Growth and Pteridine Content in the Head of Adults Sarcophaga crassipalpis (Diptera: Sarcophagidae). Animals (Basel) 2023; 13:2402. [PMID: 37570212 PMCID: PMC10417853 DOI: 10.3390/ani13152402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 07/15/2023] [Accepted: 07/21/2023] [Indexed: 08/13/2023] Open
Abstract
Flesh flies (Diptera: Sarcophagidae) are regarded as significant in medical and veterinary entomology, and their development models can be utilized as considerable markers to ascertain the minimum postmortem interval (PMImin). In this research, we explored the growth cycle and larval body length of Sarcophaga crassipalpis Macquart 1839 (Diptera: Sarcophagidae) reared under variable temperatures ranging from 15.7 to 31.1 °C, with an average of 24.55 °C and relative humidity ranges from 31.4 to 82.8% and at six fixed temperatures of 15, 20, 25, 30, 32, and then 35 °C. Moreover, pteridine from the head was used to assess adult age grading. Our results allowed us to provide three development models: the isomorphen chart, the isomegalen chart, and the thermal summation models. The time taken for S. crassipalpis to complete its development from larviposition to adult emergence at constant temperatures of 15, 20, 25, 30, 32, and 35 °C was 1256.3 ± 124.2, 698.6 ± 15.1, 481.8 ± 35.7, 366.0 ± 13.5, and 295.8 ± 20.5 h, respectively, except 35 °C, where all pupae were unable to attain adulthood. They lasted 485.8 ± 5.4 h under variable temperatures. The minimum developmental limit (D0) temperature and the thermal summation constant (K) of S. crassipalpis were 9.31 ± 0.55 °C and 7290.0 ± 388.4 degree hours, respectively. The increase in pteridine content exhibited variations across different temperatures. There was quite a considerable distinction in the pteridine contents of male and female S. crassipalpis at 15 °C (p = 0.0075) and 25 °C (p = 0.0213). At 32 °C and variable temperatures, the pteridine content between female and male S. crassipalpis was not statistically divergent. However, temperature and gender remain the main factors influencing the pteridine content in the head of S. crassipalpis. We aim to provide detailed developmental data on S. crassipalpis that can be used as a valuable resource for future research and PMI estimation.
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Affiliation(s)
- Fernand Jocelin Ngando
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, China; (F.J.N.); (X.Z.); (C.Z.); (F.Y.); (Y.F.); (Y.S.); (S.C.)
| | - Xiangyan Zhang
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, China; (F.J.N.); (X.Z.); (C.Z.); (F.Y.); (Y.F.); (Y.S.); (S.C.)
| | - Hongke Qu
- Cancer Research Institute, School of Basic Medical Sciences, Central South University, Changsha 410013, China;
| | - Changquan Zhang
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, China; (F.J.N.); (X.Z.); (C.Z.); (F.Y.); (Y.F.); (Y.S.); (S.C.)
| | - Fengqin Yang
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, China; (F.J.N.); (X.Z.); (C.Z.); (F.Y.); (Y.F.); (Y.S.); (S.C.)
| | - Yakai Feng
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, China; (F.J.N.); (X.Z.); (C.Z.); (F.Y.); (Y.F.); (Y.S.); (S.C.)
| | - Yanjie Shang
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, China; (F.J.N.); (X.Z.); (C.Z.); (F.Y.); (Y.F.); (Y.S.); (S.C.)
| | - Sile Chen
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, China; (F.J.N.); (X.Z.); (C.Z.); (F.Y.); (Y.F.); (Y.S.); (S.C.)
| | - Lipin Ren
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, China; (F.J.N.); (X.Z.); (C.Z.); (F.Y.); (Y.F.); (Y.S.); (S.C.)
| | - Yadong Guo
- Department of Forensic Science, School of Basic Medical Sciences, Central South University, Changsha 410013, China; (F.J.N.); (X.Z.); (C.Z.); (F.Y.); (Y.F.); (Y.S.); (S.C.)
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