The utility of acorn barnacles (Crustacea: Cirripedia: Sessilia) in forensic investigations in marine environment
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Estimating the minimum time since death (minimum Post Mortem Interval, minPMI) is a necessary part of a forensic investigation. Besides the coroner’s assessment of the typical signs of death, minPMI can be estimated using forensic entomology, the scientific discipline that considers insects and other arthropods that colonize the remains. In an aquatic environment, insects, as well as crustaceans, have the potential to provide data regarding the time spent in water of the remains (FT, floating time and PMSI, Post Mortem Submersion Interval), and this can also assist in determining the minPMI. Barnacles (Crustacea: Cirripedia) are common crustaceans that colonize hard substrates in marine environments and they can often be found in association with human and animal remains floating in the sea. The scientific literature reports that barnacles are typically found colonizing shoes. Barnacles can colonize both floating remains and submerged remains and their growth rate is dependent on the water temperature. Despite their potential to be indicative of the FT and/or PMSI, at present research is deplete and only a few case studies have considered it for this purpose. The present research is focused on the barnacle colonization of different type of shoes (sport vs patent leather) placed in the sea (Boston Harbor, Boston, Massachusetts). The objectives of this study are 1) identification of the species of barnacles that colonize shoes; 2) identification of the settlement preferences of the barnacles associated with the shoes; 3) determination of the growth rate of the barnacles associated with the shoes. This research as initially conducted in early March 2016, with 64 sport and 64 patent leather shoes placed in the Boston Harbor at -8/-10 meters below the sea level. Four of each shoe type were collected every two weeks from April 2016 to November 2016 inclusive. Each shoe was photographed and the barnacles and other sea life colonization was documented. Individual barnacles from each shoe were sampled and measured to determine species, age as well as the overall colonization density and settlement preference. Data loggers were placed with the shoes to record temperature throughout the course of the study. Results show that Amphibalanus improvisus (Darwin) (Crustacea: Cirripedia: Sessilia) colonized the vast majority of shoes. Colonization occurred quickly and continued throughout the study period. A significant difference in colonization densities was found between the sport and patent leather shoes, with the patent leather seeing higher densities. Barnacles also showed preferential colonization of specific sections on both shoe types. Overall, higher quantities of barnacles were found on the exterior and bottom of shoes and low quantities of colonization on the inside, tongue, and laces. Barnacle growth was found to be significantly affected by water temperature. Statistical analysis of the effect of water temperature, time in the water, and shoe type on the size of the largest barnacle revealed a highly significant effect of temperature and shoe type but no significant effect of time. As well, time and shoe type had a highly significant effect on the total number of barnacles per shoe, whereas water temperature did not.