The effect of nandrolone decanoate on the development rate of Chrysomya putoria (Fabricius) (Diptera: Calliphoridae), a fly of forensic importance in Brazil

Necrophagous insects are important tools in criminal investigations because they provide information about causes and circumstances of death. The presence of drugs in decomposing tissues can affect the insect development rate of necrophagous insects, potentially altering the estimate of the postmortem interval (PMI). This study aimed at determining the effect of nandrolone decanoate on Chrysomya putoria (Diptera: Calliphoridae) developmental rate. Nandrolone decanoate, commercially known as Deca-Durabolin®, is an androgenic anabolic steroid used in the treatment of osteoporosis and breast carcinoma, and is used by bodybuilders to induce muscular gain. Larvae obtained from lab colonies of Chrysomya putoria were placed in plastic vials containing an artificial rearing diet. Four experimental groups were used: 3 of them contained the following nandrolone decanoate concentrations: 4.5mg/kg, 22.5mg/kg and 45mg/kg; The control group was reared in substrate without the drug. The treatment and the control groups were replicated 6 times. Individual weights were recorded for groups of 10 larvae at 12h intervals until the larvae reached the pupae stage. A one-way ANOVA was used to compare the effect of the treatments on larval weight. Differences were not observed on total time of larval development (132h) and on the weights recorded at post-feeding larval stage (approximately 32mg) in all groups. However, the larval weight at 48h was significantly different among the treated groups and control (F=2627.4; p<0.0001). In this age, a 6h overestimation of the PMI could occur when larvae are exposed to the nandrolone decanoate. The survival rate ranged from 76 to 87% and from 60 to 84% for larval and pupae stages, respectively.