Assessing the Effect of Prolonged Saltwater Exposure on DNA Recovery in Submerged Skeletal Remains from Sus scrofa domesticus (Erxleben, 1777)

Abstract

Both water-related and mass disasters occurring over or in water (e.g., boating disasters, commercial plane crashes, and natural disasters) result in multiple deaths every year. Due to the ocean\u27s vastness and lack of equipment, remains may not be recovered for some time, resulting in soft tissue decomposition, leaving bone as the last repository of recoverable DNA for identification purposes. Skeletal remains\u27 physical and chemical components protect them from environmental deterioration and biological attack and preserve DNA well. Therefore, identifying an individual may depend on DNA obtained from skeletal remains. However, there is limited research on how long DNA can be preserved in skeletal remains, especially within water. Hence, this research study focused on observing the effect of prolonged saltwater exposure on DNA recovery in submerged skeletal femurs from the species Sus scrofa domesticus (Erxleben, 1777), or domestic pig, over six months. Two silica-based DNA extraction methods were also studied to optimize the most efficient technique for DNA recovery from the skeletal samples. Silica-based methods were chosen for this study to find a replacement for organic extraction, a time­ consuming procedure that poses health hazards. With the help of a local butcher, a total of eight juvenile domestic pig femurs with the tissue removed were used for this experiment, with 6/8 submerged in a 75-liter fish tank in room-temperature saltwater over six months, 1/8 in a secured dry fume hood as a control, and 1/8 used in a preliminary experiment. One femur was removed from the tank monthly for DNA extraction and quantification using the two silica-based extraction techniques. Samples were taken from each wet and dry femur monthly for six months and quantified using Quantstudio™ 5, a real-time PCR instrument. Based on the quantitative and qualitative analysis of the DNA yield recovered from the femurs in both environmental conditions and extraction techniques, it was concluded that the modified method used in the dry condition significantly yielded more DNA than other combinations. These findings suggest that dry conditions preserve DNA in skeletal remains more than wet conditions; however, the modified silica-based extraction method may improve DNA yield regardless of such conditions