Abstract/Summary

Mites are the most abundant and diverse micro-arthropods in soils, on the surface or in deeper layers and form an important part of the grave fauna. They have been overlooked in death investigations of buried cadavers because of the lack of knowledge on their colonisation patterns. The results of this research found that cadaver decomposition in shallow graves attracts necrophagous, predatory and omnivorous species of soil and phoretic mites and the abundance and colonisation patterns vary in comparison to surface (control) cadavers. Cadaver decay caused an increase in soil alkalinity and an increase in mite abundance in both circumstances. Successional patterns of mite orders and families in relation to decay stages was observed. Mesostigmata were the most abundant and diverse mites colonising buried and surface cadavers, represented mainly by predatory Parasitidae and Macrochelidae and the Prostigmata family Tydeidae, was found to be an important marker of late decay. We found that there is a delayed colonisation of buried cadavers by Parasitidae mites, which first arrive during the bloated stage but are present from the fresh stage of surface cadavers. The composition of mite species was similar for both, however several different species were markers of decay stages and specific to decay in shallow graves. For buried cadavers, Cornigamasus lunaris was associated with the bloated stages, Gamasodes spiniger and Parasitus loricatus with active and advanced, Eugamasus sp. and Lorryia reticulata with advanced and Macrocheles matrius and Ramusella clavipectinata with dry. Trachygamasus sp. was associated with advanced decay of surface cadavers, Parasitus coleoptratorum with dry and Macrocheles mammifer and Tydeidae sp. with dry. In addition to one Mesostigmata (Pachylaelaps longisetis) a handful of Oribatida (soil-dwelling) species were significantly associated with control soils (bare) at a shallow depth and on the surface; Ramusella clavipectinata, Quadroppia michaeli, Schaeloribates laevigatus and Hoplophora anomla. Furthermore, investigation of the attractant and repellent effects of cadaveric volatile organic compounds decay (necromones) showed that combinations of necromones had a synergistic effect on attracting and repelling soil and phoretic mites. The results revealed that certain necromones may be key cues in attracting phoretic mites during stages of decomposition. In contrast, decay products such as components of adiopocere had a greater effect on soil-dwelling species. Case work conducted as part of this research demonstrated that mite species can be utilised in estimating time of death, in the form of a stage of decay and the habitat-specific nature of some mite species can indicate the origin of the corpse in cases of relocation. The findings of this research have critical value for time of death estimations such as the use of the abundance and succession of mite species as markers of stages of decay of buried and surface cadavers.