The effect of different water types on the survival and eclosion rate of submerged Lucilia sericata pupae
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Blowflies (Diptera: Calliphoridae) are main colonizers of decomposing remains and any information on the influences of their lifecycle of growth and development are important to forensic entomologists when estimating postmortem interval during a medicolegal death investigation. Pupal survival of blowfly species, Lucilia sericata were studied at different developmental stages following pupation, white (0-12 hrs), young (24 hrs), medium (5 days), old (9 days) were submerged at various immersion intervals ranging from 1 hr to 120 hr (5 days) in different water types (fresh, salt, polluted, and drinking water). Control group (N= 100) were white pupae that were not submerged were also observed in order to compare the survival and eclosion rate. Two trials of the submergence process were conducted to observe the pupae survival. Data were analyzed using multiple logistic regressions in a 3-way interaction to determine if significant differences were seen between the water, time in water, and pupal stage. Dissolved inorganic nitrogen (DIN) of NH4+, NO2-, NO3-, and oP or DIP were analyzed to examine to determine if a correlation between the water types could be seen. DIN analyses exhibited similar NO2- + NO3- and NO3- in polluted and fresh water. The results show that as the pupae developmental age progressed, the pupae generally survived longer immersion intervals. The survival of white pupae decreased with the increase of submergence for all four water types, exhibiting a 100%mortality rate with pupae submerged longer than 24-36 hours. While pupae immersed in polluted water had similar survival rates in the white stage, the survival rate declined as the developmental age increased for pupae immersed in polluted water. Pupae immersed in salt and polluted water had earlier eclosion times when compared to other water groups, emerging at 36 hours from when the control group first emerged at day 12. Understanding the survival rate of submerged Lucilia sericata (Diperta: Calliphoridae) pupae will be potentially useful for criminal investigations by providing a better understanding of the survival of pupae submerged in different aquatic environments.