Résumé
Objective To explore the effect of morphine hydrochloride on growth accumulated degree hour(ADH)and cephalopharyngeal skeleton of larvae of Parasarcophaga crassipalpis under natural condition, and to prove the feasibility of predicting the postmortem interval(PMI)using ADH and the shape indexes of cephalopharyngeal skeleton. Methods The larvae of Parasarcophaga crassipalpis were fed under natural condition with rabbit meat injected with morphine hydrochloride before death. The larvae were collected at 12 h intervals until the end of the stage(the larvae did not eat any more). The larvae were fixed in boiling water and were stored as specimen. The average daily temperature during the experiment was calculated for ADH. Then the cephalopharyngeal skeletons were isolated, observed, and then photographed under light mircoscope. Finally the morphology of the cephalopharyngeal skeleton was analyzed by digital image processing system. Results (1)Under natural conditions, the ADH was changed by morphine hydrochloride to a certain degree.(2)The area of the cephalopharyngeal skeleton maintained at a certain level when entered the third instar. The sclerotized area and the average optical density of the cephalopharyngeal skeleton were increased with the increase of ADH till the end of the third instar. The ADH that the sclerotized area and the average optical density reached the maximum was obviously higher than the one that the area of the cephalopharyngeal skeleton reached the maximum. Conclusion Morphine hydrochloride can obviously change the growth ADH of larvae of Parasarcophaga crassipalpis under natural conditions. The sclerotized areas and the average optical densities of the pharyngeal sclerite of the larvae show a good linearity with ADH till the end of the third instar, which can deduce PMI when combined together.
Résumé
Objective: To study the effects of morphine hydrochloride and temperature on the cephalopharyngeal skeleton of the larvae of Parasarcophaga crassipalpis in Shijiazhuan, Hebei, so as to provide evidence for forensic toxicologic entomology of sarcosaphagous flies and inference of the postmortem interval(PMI) in Shijiazhuang. Methods: Adult Parasarcophaga crassipalpis were collected. Four domestic rabbits were used in this experiment, with one receiving normal saline (control) and the others receiving morphine hydrochloride (0. 5,1. 0 and 2. 0 folds of lethal doses) via ear vein injection. Then the rabbits were hit on the head and the muscle was marked with M0, M1, M2 and M3, then the larvae were transferred to the muscle sites at 24°C, 28°C and 32°C. When larvae were laid, 10 of them were randomly sampled from each group at 12 h intervals until the beginning of the prepuparial stage. The larvae were collected every 12 h, fixed with boiling water, and stored as specimen. The scolex of the larvae was sparated and then the cephalopharyngeal skeleton was separated symmetrically, observed and photographed. Finally the indices, including the areas of different parts of cephalopharyngeal skeleton, sclerotized area, and average optical density were determined using digital image processing equipment. Results: (1) The larvae of Parasarcophaga crassipalpis grew faster with the increase of morphine hydrochloride concentration and the temperature. (2)The color of the cephalophargngeal skeleton of the larvae changed from yellow to dark brown as time went by. Meanwhile, the degree and range of chitinazation were increased, accompanied by increase of the sclerotized area. The attached larval mouth (shaped like a dot) could be observed during the third age. (3) The areas of the larval mouth hook and the larval pharyngeal sclerite increased with time. Especially, remarkable changes were observed during the fold period, and the changes reached their maximum in the third age, and then remained basically unchanged. (4) The sclerotized areas and the average optical densities of the cephalopharyngeal skeleton kept an increasing tendency till the end of the third age. The periods needed for reaching the maximal optical density and sclerotized area were greatly longer than that needed for reaching the maximal area of the cephalopharyngeal skeleton. Conclusion: The sclerotized area and the average optical density of the mouth hook and the pharyngeal sclerite of the larvae of Parasarcophaga crassipalpis keep increasing till the end of the third stage, and they are ideal indices for deducing PMI.