Developmental Indicators of Chrysomya nigripes Aubertin under Different Constant Temperature Conditions and an Application Case for Estimating the PMI(min)

SIMPLE SUMMARY: As ectotherms, the growth and development of sarcosaprophagous insects at different temperatures can be useful to estimate the minimum postmortem interval. Blow flies are the most common indicator insects for estimating the minimum postmortem interval. Chrysomya nigripes Aubertin, 1932, in the family Calliphoridae, shows later colonization and longer durations on carcasses than those of other species in this family. This species can be used to estimate the minimum postmortem interval over shorter periods and can be applied to highly decomposed bodies and those in the skeletonized stage. In the present study, we characterized the development of C. nigripes at eight constant temperatures between 16 °C and 37 °C and constructed various models to describe patterns of development. Chrysomya nigripes completed the entire developmental process at 19–37 °C. The overall duration of development (±SD) decreased steadily as the temperature increased from 644.9 ± 36.8 h at 19 °C to 191.5 ± 3.8 h at 34 °C and then remained stable with values of 191.8 ± 2.0 h at 37 °C. This study provides comprehensive developmental data for estimating the minimum postmortem interval using C. nigripes. ABSTRACT: Chrysomya nigripes Aubertin, 1932, is a Calliphoridae species that colonize the carcass after the bloat phase and remains for long periods. Some early sarcosaprophagous insects complete one generation of development and are no longer associated with the corpse and surrounding environment, while C. nigripes larvae and pupae remain, providing a basis for the estimation of the minimum postmortem interval (PMI(min)) for highly decomposed or skeletonized carcasses. However, data on the growth and development of this species are not yet complete. As a result, we studied the developmental patterns of C. nigripes at eight constant temperatures ranging from 16–37 °C and constructed various developmental models, including the isomorphen diagram, isomegalen diagram, linear thermal summation model, nonlinear thermodynamic Optim SSI model, and logistic regression model. Chrysomya nigripes could not complete the entire developmental process at 16 °C, although it could be completed at other temperatures. The mean developmental times (±SD) of C. nigripes from egg to adult at 19 °C, 22 °C, 25 °C, 28 °C, 31 °C, 34 °C, and 37 °C were 644.9 ± 36.8 h, 422.9 ± 20.1 h, 323.1 ± 13.9 h, 246.6 ± 11.2 h, 202.5 ± 1.8 h, 191.5 ± 3.8 h, and 191.8 ± 2.0 h, respectively. The thermal summation constant (K) and lower critical thermal threshold (T(L)) derived from the linear thermal summation models were 4083.00 ± 293.39 degree hours and 12.52 ± 0.83 °C, respectively. In addition, T(L), intrinsic optimum temperature (T(Φ)), and upper critical thermal threshold (T(H)) estimated by the optimized nonlinear thermodynamic Optim SSI model were 15.76 °C, 24.88 °C, and 38.15 °C, respectively. This study provides more comprehensive developmental data of C. nigripes for PMI(min) estimation.