| Part I:The development of Hemipyrellia ligurriens and the application in estimation of postmortem intervalObjective In order to provide methods to estimate the postmortem interval, a systematic study was undertaken to explore the development of H. ligurriens under constant temperature. The models of estimating postmortem interval were set up, to provide the basis for forensic investigation.Methods H. ligurriens is studied at 7 constant temperatures (16,19, 22,25,28,31, and 34℃). This study explored the growth curves of larval H. ligurriens at 7 constant temperatures. The time to the developmental events (first ecdysis, second ecdysis, wandering, pupation, or eclosion) is observed. The isomegalen diagram, isomorphen diagram were established according to larval length or developmental events. The times of the different developmental stages(egg,1st instar,2nd instar,3rd instar, wandering- period, pupation) under the 7 temperatures were used to calculate the values of the developmental threshold temperature t and thermal summation constant K, using the linear regression formula to establish thermal summation model.Results The growth curve displayed the typical shape with two periods:increasing first and then decreasing. As temperatures decreased from 34 to 16℃, the larval period increased. As temperatures increased, the times for first ecdysis, second ecdysis, or wandering of H. ligurriens decreased gradually. Similarly, the times for pupation and eclosion gradually decreased as temperatures increased from 16 to 28℃. However, the time for pupation at 31℃ or 34℃ increased relative to the time for pupation at 28℃. Isomegalen and isomorphen diagrams were successfully constructed, depicting the time of larval length or developmental event, respectively, at different temperatures. A thermal summation model was also constructed via regression analysis, by estimating the developmental threshold temperature t and thermal summation constant K. The thermal summation model indicated that t at 8.28±0.22℃ and K at 5747.45± 110.25degree-hours (℃h) are required for complete development from oviposition to eclosion,Conclusion This study reports for the first time the developmental time for H. ligurriens under constant temperatures.Three temperature-dependent developmental models were constructed and are ready for application to estimate the PMImin. Temperatures 31℃ or above are likely non-optimal conditions, and caution should be paid.Part Ⅱ:Influence of fluctuating temperature on the development of Hemipyrellia ligurriensObjective Development of larvae of H. ligurriens under daily fluctuating temperatures as well as constant temperatures in a climatic chamber was investigated and compared. Influence of fluctuating temperature on the development of H. ligurriens will be discussed in order that the data in the constant temperature can be used in fluctuating temperature(natural environment).Methods 3 daily fluctuating temperatures including (14-24)℃, (20～30)℃, (26～36)℃ were simulated in a climatic chamber according to the environmental temperature, and which is corresponding to the average temperature 19℃,25℃,31℃ respectively. H. ligurriens is studied at 3 daily fluctuating temperatures. The growth curves of H. ligurriens larvae under 3 daily fluctuating temperatures was studied. The time to the developmental events is observed. At last, the development of H, ligurriens under between daily fluctuating temperatures and constant temperatures was compared.Results Results gained in this study shows that the growth curves under daily fluctuating temperatures were consistent with the growth curves under the corresponding constant temperature in general. But some difference exist in the local details. There was the difference within 6 h between daily fluctuating temperatures and constant temperatures in estimation of postmortem interval. Developmental time shows no difference under between daily fluctuating temperatures (20～30)℃ and the corresponding constant temperature 25℃. However, developmental time under daily fluctuating temperatures (14～24)℃ was a short 51.96h than the corresponding constant temperature 19℃, and there is a short 20.04h under daily fluctuating temperatures (26～36)℃ than the corresponding constant temperature 31℃.Conclusion The growth curves under daily fluctuating temperatures is different in the local details with the growth curves under the corresponding constant temperature, but the difference is very little.The data in the constant temperature can be used in daily fluctuating temperature (natural environment). Developmental time show no difference under between daily fluctuating temperatures (14～24)℃ and the corresponding constant temperature 19℃. But when the temperature is too low or too high, the developmental time shorten in a certain extent under daily fluctuating temperatures than the corresponding constant temperatures.Part Ⅲ:Influence of forced postfeeding on the development of Hemipyrellia ligurriensObjective Influence of forced postfeeding on the development of H. Ligurriens was observed. Refeeding on larvae with forced postfeeding was also studied to investigate the time of pupation and the time of eclosion of H. ligurriens, in order that the influence of forced postfeeding on estimation of postmortem interval was explored.Methods H. ligurriens is forced to postfeed in different developmental time(8h,20h,32h,44h,56h,68h). Subsequently, the larvae with forced postfeeding was refeed at a specific time(3h,6h,12h, and so on, after forced postfeeding). And the study observe the reaction of the larvae and the influence of forced postfeeding on the development of H.ligurriens.Results The first and second instar larvae with forced postfeeding will stop developing until death. The third instar larvae with forced postfeeding can continue to develop and pupate. In the first and second instar larvae with forced postfeeding, the longer the developmental time is, and the longer the survival time is. Before death, if larvae was refeed, they can continue to feed and develop. But the longer the interval of the larvae being refeeded is, the longer the time of pupation and the time of eclosion are. And the time of pupation and the time of eclosion can reach the biggest extension of 89.76 h,88.02 h respectively. The immature third instar larvae with forced postfeeding can come into postfeeding period and pupate, when the time interval of forced postfeeding reaches a certain time, and the pupae is small than normal pupae. The time of pupation and the time of eclosion can reach biggest short 28.61 h,28.61 h respectively than normal control group. In the same temperature, the period of pupal stage is only related to the pupal weight. The smaller the pupal weight is, the shorter the period of pupal stage is, and there is a short below 23.95 h compared with normal control group.Conclusion The forced postfeeding is an important influence factor to H. ligurriens. The first and second instar larvae with forced postfeeding will stop to develop until death. The immature third instar larvae with forced postfeeding can continue to develop and pupate, and the pupae is small than normal pupal weight. The refeeding on larvae with forced postfeeding is also an important influence factor to the time of pupation and the time of eclosion. Different time of forced postfeeding and refeeding all can lead to different developmental time. |
