Different cadaver astigmatan mites (Arthropoda: Acari) are designed to bite flesh differently

Abstract

How dead bodies decay is useful forensically. Necrophagous astigmatan mites (Acari: Sarcoptiformes) commonly attacking cadavers change from protein-seeking Type 1 surface feeding omnivores to interstitial Type 2 fragmentary feeding obligate fungivore / microbiovores as human body decomposition progresses after death. An analytical occlusive method shows that at each forensic decay stage the chelae of the astigmatans are designed to bite foodstuff differently. Fixed chelal digits are more ‘toothy’ than moveable digits in such sarcoptiform mites. Variation in fixed digit design is all about the size and pattern of peaks (‘peakiness’) for biting, while astigmatan moveable digit variation is mainly about the size and pattern of valleys (’gullet-ness’) for the ‘scooping’ of decaying material. Foodstuff caught on the moveable digit is thus masticated against the fixed digit like an ‘excavation-bucket’ machine used for handling aggregates in building construction. Lardoglyphus zacheri has a distinct chela suitable to slice flesh and grip myofibrils. Acarus siro through Sancassania berlesei to Tyrophagus putrescentiae show a cline in digit design from a dry material ‘demolition crusher’ with rough surface digits, through a wet chunk and slice feeder, to a specialist multifunctional saprophage. Sancassania berlesei is unlikely to actively burrow into flesh. Trophic niche width increases from stage 2 (bloated putrefaction) as soft food specialist species invade. Niche width markedly widens at stage 5 (mummified dry desiccated bones and remains), as incorporation into a soil with diverse saprophagous mites is coming to completion.