Macrocheles species (Acari: Macrochelidae) associated with human corpses in Europe

Estimating the postmortem interval: applications of forensic acarology, palynology, and taphonomy

Determination of the minimum postmortem interval remains an important factor in the investigation of deaths, especially homicides. It is important for near-accurate reconstruction of the fatal event, especially after putrefaction has commenced. It helps to weigh the alibi of suspects, and to include or exclude these individuals. The science of forensic entomology, acarology, palynology and taphonomy have been applied with varying degree of accuracy depending on a plethora of biotic and abiotic factors. Each of these specialties is most useful at specific times during decomposition and depending on local environmental factors. As decomposition progresses, the estimation of the PMI becomes more difficult. Here, we review how different forensic techniques are most appropriate for estimating the postmortem interval at different times since death. Ultimately, the determination of the interval is a difficult task requiring a multidisciplinary approach comprising many forensic specialists.

Biomechanical adaptations enable phoretic mite species to occupy distinct spatial niches on host burying beetles

Niche theory predicts that ecologically similar species coexist by minimizing interspecific competition through niche partitioning. Therefore, understanding the mechanisms of niche partitioning is essential for predicting interactions and coexistence between competing organisms. Here, we study two phoretic mite species, Poecilochirus carabi and Macrocheles nataliae that coexist on the same host burying beetle Nicrophorus vespilloides and use it to 'hitchhike' between reproductive sites. Field observations revealed clear spatial partitioning between species in distinct host body parts. Poecilochirus carabi preferred the ventral side of the thorax, whereas M. nataliae were exclusively found ventrally at the hairy base of the abdomen. Experimental manipulations of mite density showed that each species preferred these body parts, largely regardless of the density of the other mite species on the host beetle. Force measurements indicated that this spatial distribution is mediated by biomechanical adaptations, because each mite species required more force to be removed from their preferred location on the beetle. While P. carabi attached with large adhesive pads to the smooth thorax cuticle, M. nataliae gripped abdominal setae with their chelicerae. Our results show that specialist biomechanical adaptations for attachment can mediate spatial niche partitioning among species sharing the same host.

Mesostigmata diversity by manure type: a reference study and new datasets from southwestern Iran

Manure-inhabiting Mesostigmata mites are important biological control agents of pest flies. However, the biodiversity of this mite community is mainly known from Europe and America, and especially from cattle manure. This study examined the diversity and abundance of Mesostigmata mites associated with various types of manure in an (intensive) agricultural region of the Middle East, i.e., the city Ahvaz and its suburbs, in southwest Iran. Mite samples were extracted from manure of cattle, buffalo, sheep, horse, poultry and quail in 30 livestock and poultry farms. In total, 40 species belonging to 24 genera and 16 families were identified. The most diverse families were Laelapidae with eight species, Macrochelidae with seven and Parasitidae with six. Macrocheles muscaedomesticae and Uroobovella marginata were the most widespread species, recorded in 28 and 27 out of 30 collection sites, respectively. Two species, M. sumbaensis and U. marginata, were found in all studied manures. Simpson's diversity index recorded the highest diversity in buffalo and sheep manure. Real and theoretical species richness (rarefaction curves) were congruent in number of individuals. The presence of seven species of Macrochelidae in the manure confirms that these are important predators of the house fly for the region of Ahvaz and its suburbs. Members of the Parasitidae were highly prevalent, with one species known as a specialized predator of house fly eggs. This work aims to encourage further studies on the diversity of Mesostigmata in these agricultural settings, and further continue assessing the feasibility of these mites as effective biocontrol agents of filth flies in different types of manure and from different corners of the world.

The impact of the decomposition process of shallow graves on soil mite abundance

Burial of a cadaver results in a slower decomposition rate, due to more stable below-ground temperatures and restricted access to necrophagous insects. In such circumstances, analysis of the soil mesofauna, with emphasis on mites (Acari) may be more valuable in time-of-death estimations. The production of volatile organic compounds of cadaveric decay results in changes, especially in the soil pH, which in turn would affect the abundance and diversity of the associated mites. In general, the effects of decomposition and the consequently altered pH levels on the abundance of mites in shallow graves, as well as the effects of fluctuating above-ground environmental parameters (temperature, relative humidity, and precipitation) remain unknown. Here, we found that the decay of three pig cadavers buried in shallow graves (<30 cm below) caused a significant increase in the soil pH throughout decomposition, from neutral to alkaline. Cadaver decay attracted an abundance of mites: with 300 mites collected from the three pig cadavers compared to 129 from the control soil samples at the same depth. Mites rapidly became more abundant in cadaver-associated soils than in control soils after the fresh stage. Increasing soil pH had a positive impact on the abundance of mites in graves and there was a significant interaction between cadaver body temperature and soil pH. Above-ground fluctuations in temperature, relative humidity, and precipitation were found to have no significant direct effect on mite abundance in grave or control soils.

Acari community in association with delayed pig carrion decomposition

Acari community structure and function associated with delayed pig carrion decomposition has not been examined. In this study, 18 swine carcasses were studied in central Texas, USA, during two consecutive summers (2013 and 2014). Samples of ca. 400 g soil were collected from beneath, aside, and 5 m away from each pig carcass over 180 days. Mites from soil samples were extracted using Berlese funnels and identified to order and family levels and classified according to ecological function. In total 1565 and 1740 mites were identified from the 2013 and 2014 soil samples, respectively. Significant differences were determined for mite community structure at order and family levels temporally on carrion (e.g., day 0 × day 14) regardless of treatments and between soil regions where mites were collected (e.g., soil beneath vs. soil 5 m away from carrion). However, no significant differences were found in mite community structure at the order level between pig carrion with and without delayed Diptera colonization (i.e., treatments). Analysis at the family level determined a significant difference across treatments for both summers. Ecological function of mites did not change significantly following the delayed decomposition of pig carcasses. However, detritivores and fungivores were significant indicator groups during the pig carrion decomposition process. Furthermore, 13 phoretic mite species associated with eight forensically important beetle species were documented. Data from this study indicated that the rate of nutrient flow into the soil impacted associated arthropod communities; however, detecting such shifts depends on the taxonomic resolution being applied.

Assemblages of Acari in shallow burials: mites as markers of the burial environment, of the stage of decay and of body-cadaver regions

The burial of a cadaver results in reduced arthropod activity and disruptions in colonisation patterns. Here, the distribution and diversity of mite taxa was studied across decomposition stages of shallowly buried pig carcasses (Sus scrofa domesticus). In total 300 mites (88 species) were collected from three pig shallow graves compared to 129 mites (46 species) from control (bare) soil samples at the same depth. A successional pattern of Acari higher taxa and families was observed, and species richness and biodiversity fluctuated throughout decomposition, whereas active decay showed the greatest biodiversity. Mesostigmata mites were the most abundant in 'cadaver soils' with a significant difference in the abundance of Parasitidae mites, whereas Oribatida mites (true soil mites) were the most abundant in control soils. Certain mite species were significantly associated with decay stages: Cornigamasus lunaris with 'bloated', Gamasodes spiniger with 'active', Eugamasus sp. and Lorryia reticulata with 'advanced', and Macrocheles matrius and Ramusella clavipectinata in 'dry'. Scheloribates laevigatus was a marker of bare soil at a shallow depth and Vulgoramasus remberti of buried decomposition, not specific to any decay stage. Analysis of mite assemblages associated with head, torso and posterior body showed that Parasitus evertsi and M. matrius are attracted to beneath the thighs, whereas L. reticulata to beneath the head. This study highlights the value of mites as indicator species of decomposition and its stages, confirming (1) a succession of Acari on buried remains and (2) species specificity to body regions.

Feeding design in free-living mesostigmatid chelicerae (Acari: Anactinotrichida)

A model based upon mechanics is used in a re-analysis of historical acarine morphological work augmented by an extra seven zoophagous mesostigmatid species. This review shows that predatory mesostigmatids do have cheliceral designs with clear rational purposes. Almost invariably within an overall body size class, the switch in predatory style from a worm-like prey feeding ('crushing/mashing' kill) functional group to a micro-arthropod feeding ('active prey cutting/slicing/slashing' kill) functional group is matched by: an increased cheliceral reach, a bigger chelal gape, a larger morphologically estimated chelal crunch force, and a drop in the adductive lever arm velocity ratio of the chela. Small size matters. Several uropodines (Eviphis ostrinus, the omnivore Trachytes aegrota, Urodiaspis tecta and, Uropoda orbicularis) have more elongate chelicerae (greater reach) than their chelal gape would suggest, even allowing for allometry across mesostigmatids. They may be: plesiosaur-like high-speed strikers of prey, scavenging carrion feeders (like long-necked vultures), probing/burrowing crevice feeders of cryptic nematodes, or small morsel/fragmentary food feeders. Some uropodoids have chelicerae and chelae which probably work like a construction-site mechanical excavator-digger with its small bucket. Possible hoeing/bulldozing, spore-cracking and tiny sabre-tooth cat-like striking actions are discussed for others. Subtle changes lead small mesostigmatids to be predator-scavengers (mesocarnivores) or to be predator-fungivores (hypocarnivores). Some uropodines (e.g., the worm-like prey feeder Alliphis siculus and, Uropoda orbicularis) show chelae similar in design to astigmatids and cryptostigmatids indicating possible facultative saprophagy. Scale matters-obligate predatory designs (hypercarnivory) start for mesostigmatids with chelal gape > 150 μm and cheliceral reach > 350 μm (i.e., about 500-650 μm in body size). Commonality of trophic design in these larger species with solifugids is indicated. Veigaia species with low chelal velocity ratio and other morphological strengthening specialisms, appear specially adapted in a concerted way for predating active soft and fast moving springtails (Collembola). Veigaia cerva shows a markedly bigger chelal gape than its cheliceral reach would proportionately infer suggesting it is a crocodile-like sit-and-wait or ambush predator par excellence. A small chelal gape, low cheliceral reach, moderate velocity ratio variant of the worm-like feeding habit design is supported for phytoseiid pollenophagy. Evidence for a resource partitioning model in the evolution of gnathosomal development is found. A comparison to crustacean claws and vertebrate mandibles is made. Alliphis siculus and Rhodacarus strenzkei are surprisingly powerful mega-cephalics for their small size. Parasitids show a canid-like trophic design. The chelicera of the nematophagous Alliphis halleri shows felid-like features. Glyphtholaspis confusa has hyaena-like cheliceral dentition. The latter species has a markedly smaller chelal gape than its cheliceral reach would suggest proportionately, which together with a high chelal velocity ratio and a high estimated chelal crunch force matches a power specialism of feeding on immobile tough fly eggs/pupae by crushing (durophagy). A consideration of gnathosomal orientation is made. Predatory specialisms appear to often match genera especially in larger mesostigmatids, which may scale quite differently. Comparison to holothyrids and opilioacarids indicates that the cheliceral chelae of the former are cutting-style and those of the latter are crushing-style. A simple validated easy-to-use '2:1 on' predictive algorithm of feeding habit type is included based on a strength-speed tradeoff in chelal velocity ratio for ecologists to test in the field.

Rodent Ectoparasites in the Middle East: A Systematic Review and Meta-Analysis

Rodents carry many ectoparasites, such as ticks, lice, fleas, and mites, which have potential public health importance. Middle Eastern countries are hotspots for many emerging and re-emerging infectious diseases, such as plague, leishmaniasis, Crimean Congo hemorrhagic fever, and Q fever, due to their ecological, socioeconomic, and political diversity. Rodent ectoparasites can act as vectors for many of these pathogens. Knowledge of rodent ectoparasites is of prime importance in controlling rodent ectoparasite-borne zoonotic diseases in this region. The current systematic review and meta-analysis performs a comprehensive synthesis of the available knowledge, providing an evidence-based overview of the ectoparasites detected on rodents in Middle Eastern countries. Following a systematic search in Pubmed, Scopus, and Web of Science, a total of 113 published articles on rodent ectoparasites were studied and analyzed. A total of 87 rodent species were documented, from which Mus musculus, Rattus norvegicus, and Rattus rattus were found to be the most common. Fleas were the most reported ectoparasites (87 articles), followed by mites (53), ticks (44), and lice (25). Xenopsylla cheopis, Polyplax spinulosa, Ornithonyssus bacoti, and Hyalomma rhipicephaloides were the most commonly described fleas, lice, mites, and ticks, respectively. Based on the reviewed articles, the median flea, louse, mite, and tick indices were highest in Israel (4.15), Egypt (1.39), Egypt (1.27), and Saudi Arabia (1.17), respectively. Quantitative meta-analysis, using a random-effects model, determined the overall pooled flea prevalence in the Middle East as 40% (95% CI: 25-55, I2 = 100%, p < 0.00001), ranging between 13% (95% CI: 0-30, I2 = 95%, p < 0.00001) in Iran and 59% (95% CI: 42-77, I2 = 75%, p < 0.00001) in Israel. The overall pooled louse prevalence was found to be 30% (95% CI: 13-47, I2 = 100%, p < 0.00001), ranging between 25% in Iran (95% CI: 1-50, I2 = 99%) and 38% in Egypt (95% CI: 7-68, I2 = 100%). In the case of mites, the pooled prevalence in this region was 33% (95% CI: 11-55, I2 = 100%, p < 0.00001), where the country-specific prevalence estimates were 30% in Iran (95% CI: 4-56, I2 = 99%) and 32% in Egypt (95% CI: 0-76, I2 = 100%). For ticks, the overall prevalence was found to be 25% (95% CI: 2-47, I2 = 100%, p < 0.00001), ranging from 16% in Iran (95% CI: 7-25, I2 = 74%) to 42% in Egypt (95% CI: 1-85, I2 = 100%). The control of rodent ectoparasites should be considered to reduce their adverse effects. Using the One Health strategy, rodent control, and precisely control of the most common rodent species, i.e., Mus musculus, Rattus norvegicus, and Rattus rattus, should be considered to control the rodent-borne ectoparasites in this region.

Mites (Acari) as a Relevant Tool in Trace Evidence and Postmortem Analyses of Buried Corpses

This report interprets the presence of mite species in three clandestine graves in Europe, evaluating their potential use as trace evidence or markers. Grave 1 (Sweden): Two mite species Rhizoglyphus robini Claparède, 1869 and Parasitus loricatus (Wankel, 1861) were recovered from the surface of a body buried in a shallow grave in an area surrounded by trees, in close vicinity to house gardens. Grave 2 (Germany): Phoretic deutonymphs of Gamasodes spiniger (Trägårdh, 1910) were attached to an adult fly (Diptera: Sphaeroceridae) found within a shallow grave containing two human bodies covered in soil and dung. Grave 3 (France): P. loricatus were recovered from the soil around a body buried in a deep grave (80 cm under). In graves 1 and 3 both corpses were undergoing advanced decay and skeletization, the locations match with the subterranean habit of P. loricatus, highlighting the value of this species as a marker of graves or burials in soil and during late decomposition. R. robini is a soil mite that feeds on decayed roots and bulbs; this mite species confirms the location of the corpse within top soil, agreeing with a more specific type of superficial burial, a shallow grave. In case 2, the presence of both coprophiles, the mite G. spiniger and the carrier fly confirm association of remains with dung or animal feces. The three mite species are reported for the first time in human graves. There are no previous records of R. robini from Sweden.

Gamasina Mites (Acari: Mesostigmata) Associated with Animal Remains in the Mediterranean Region of Navarra (Northern Spain)

Mites should not be overlooked as a forensic tool, as many are commonly associated with decomposing animal matter and are closely associated with specific insect carriers and habitats. It is necessary to increase our understanding of the diversity of mites that are found in human and animal remains, their geographical distribution, and their population dynamics. This work is the first study of the role of mites in forensic science in the Mediterranean region of Navarra (northern Spain). Samples were taken using three types of traps (96 modified McPhail, 96 modified pitfall, and 32 carrion on surface) baited with pig carrion during the period between 11 April and 24 June, 2017. Insects were collected in 100% of the traps and only 27% of them contained mites. Information on 26 species of mites belonging to seven families, their ontogenetic phoretic stage/s, their abundance, and presence/absence during the spring season of the study is given. The most abundant species collected were Macrocheles merdarius, Poecilochirus austroasiaticus, and Poecilochirus subterraneus. We are contributing 16 new records for the Iberian Peninsula: seven species of Parasitidae, three species of Macrochelidae, four species of Eviphididae, one species of Halolaelapidae, and one species of Laelapidae.