Effects of preservatives and killing methods on morphological features of a forensic fly, Chrysomya megacephala (Fabricius, 1794) larva

摘要

Preservation of larvae retrieved from cadavers is important in ensuring the qualityand integrity of entomological specimens used for the estimation of post-mortem interval(PMI). The process of killing and preserving larvae could distort the larvae leading to inaccurateestimation of PMI. In this study, the effects of killing Chrysomya megacephala larvae withhot water at different temperatures and subsequent maintenance in various preservativeswere determined. Larvae not killed by hot water but preserved directly were used as control.The types of preservative used were 10% formalin, 70% ethanol and Kahle’s solution. Themorphological features examined were length, turgidity, curvature and coloration of larvae.Larvae killed in 80oC hot water have shorter mean length (12.47 ± 2.86mm) compared tothose in 60oC hot water (12.95 ± 2.69mm). Increasing the duration of preservation in all typesof preservative caused elongations of larvae treated or untreated with hot water. There wereno significant changes in larval turgidity preserved in Kahle’s solution compared to other twopreservatives and were unaffected by the duration of storage. Larvae preserved in Kahle’ssolution experienced the least changes in coloration and shape compared to other preservedlarvae in 70% ethanol or 10% formalin. Larvae directly immersed alive in 70% ethanolexperienced the most changes in curvature, coloration and turgidity. This study suggestedthat killing larvae with hot water at 80oC and preservation in Kahle’s solution is the optimummethod resulting in least changes in morphological features of Ch. megacephala larvae.