An investigation of the inter and intra post-mortem microstructural change seen in an experimental series of pigs exposed to a marine environment

Abstract

The identification of marine post-mortem microstructural change in human bone tissue is valuable in forensic casework as evidence of an individual's burial history. This study examined micro-tunneling in pig-bone tissue microstructure that had been submerged in a marine environment. The objective of the experiment was to assess total distribution of post-mortem microstructural change and degree of preservation within and between individual submerged pig skeletons. 14 juvenile pig carcasses were submerged in British Columbia at 92-300 m depths, between four to eight months. Seven pigs were individually submerged within caged platforms, seven were tied to open platforms. Six bones were selected from each carcass: first rib, radius, ulna, middle-rib, tibia, and femur. Two transverse thin sections were sampled at each bone mid-shaft (n = 148) and examined using circularly polarized transmitted light. The distribution of tunnels was assessed by measuring tunnel maximum ingress and diameter at 40 locations of the peripheral cortex. All element types were impacted by peripheral tunneling from the periosteum to the central cortex. Tunnels were observed as radiating, bifurcating with no remineralization boundary, isolated and in clusters. Tunnel diameters ranged between 2.00 μm and 12.8 μm, with a 3.7 μm mean. Ingress measurements ranged between 7.5 μm and 435.8 μm with a 93.0 μm mean. Distribution of post-mortem microstructural change across skeletal elements showed the averaged maximum ingress was deeper in the uncaged (99.6 μm), when compared to caged material (78.5 μm). The averaged tunnel ingress had statistically significant differences between uncaged and caged carcasses overall (p-value=0.02). Results of the study indicate microboring is present in marine submersed mammalian bone microstructure in as little as 134 days. This informs forensic investigators of the rate of skeletal destruction and of the narrow window for forensic recoveries, particularly in an enclosed environment. Furthermore, the presence of marine microboring in bone can assist forensic practitioners to histologically interpret the environmental history of a corpse.

Keywords: Bioerosion; Biological anthropology; Forensic anthropology; Marine decomposition; Marine taphonomy; Skeletal histology.