Poecilochirus

Poecilochirus is a holarctic genus of mites in the family Parasitidae.[1] They are relatively large (ca. 0.5-1mm[2]) and often found on rotting corpses, where they are transported by beetles.[3][4] Deuteronymphs are characterized by two orange dorsal shields and in many species a transverse band on the sternal shield. The juvenile development consists of a larval stage (three pairs of legs), protonymph, and deuteronymph, but no tritonymph. Females are smaller than males. Males guard female deuteronymphs shortly before these mate, and pairs mate venter-to-venter.[5]

Poecilochirus
Poecilochirus carabi
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Arachnida
Subclass:	Acari
Order:	Mesostigmata
Family:	Parasitidae
Genus:	Poecilochirus G. & R. Canestrini, 1882
Type species
Poecilochirus carabi G. & R. Canestrini, 1882

Reportedly, some nematodes in the family Allantonematidae are parasites of mites in this genus.[6] Although some species from this genus have been described and sampled on previous real forensic cases or successional studies on carcasses, their usefulness as a forensic marker in forensic entomology has been recently appreciated.[7]

Phoresy on carrion beetles

Nicrophorus humator carrying Poecilochirus mite deutonymphs

At least eight species of the genus are carried from one food source to another by beetles of multiple genera in the family Silphidae, most notably burying beetles. The mite deutonymphs sit on the adult beetles, typically between the coxae or under the elytrons. The beetles breed on carrion, which they bury. Once arrived on carrion, the mites leave the beetles, feed on the carrion, and develop into adults.[8] The entire life cycle of the mites takes place on the carrion, and the young mites later leave again with the beetles.[4]

The probably best studied species are from the Poecilochirus carabi species complex that consists of at least two species (P. carabi and P. necrophori).[3][4][9] In Europe, the two mite species are specialized on two different species of burying beetles, Nicrophorus vespilloides and Nicrophorus vespillo. The mites can recognize their main host beetle species and can produce more offspring along their preferred host beetle.[4][9] Similarly, two genetic lines of Poecilochirus carabi mites have been reported from North America, which specialize on different sets of Nicrophorus hosts in some populations.[10]

Poecilochirus (Gamasoides) carabi drawing by Oudemans

It is debated whether the mites harm the beetles or benefit them. Under certain conditions, the mites appear to protect the beetles' larvae or their food supply from fly larvae,[11][12] but the presence of mites on beetle-tended carcasses also reduces male beetle life span and the number of beetle offspring.[13][14][9][15][8]

Species and Identification

There is no recent treatment of the genus Poecilochirus. Identification keys mostly rely on the extent of a dark band across the sternal shield, the size of the dorsal shields, the doral chaetotaxy (mainly the length of the setae), and appendices of the fixed digit of the chelicerae.[2] The first description of all life stages was published by Neumann.[16]

Sternal shield of Poecilochirus necrophori, with the typical dark transversal band

Species	Synonyms	Habitat / Host species
Poecilochirus armatus Trägårdh, 1912
Poecilochirus austroasiaticus Vitzhum, 1930	P. nordi[2]	Nicrophorus and other Silphid beetles[17][2]
Poecilochirus belkahvensis Ramaraju & Madanlar, 1998		mushroom compost
Poecilochirus belovae Davydova, 1975	P. donatus[18]
Poecilochirus britannicus Hyatt, 1986
Poecilochirus carabi G. Canestrini & R. Canestrini, 1882	Gamasoides carabi, P. fucorum[2]	Nicrophorus vespilloides (main host[4][9]), other Nicrophorus & Silphid beetles[17]
Poecilochirus coimbatorensis Vishnupriya & Mohanasundaram, 1988
Poecilochirus coleophorae Ramaraju & Mohanasundaram, 1997		beetles: Rutelidae, Scarabaeidae
Poecilochirus davydovae Hyatt, 1980		Nicrophorus and other Silphid beetles[2][17]
Poecilochirus hyatti Ramaraju & Madanlar, 1998		mushroom compost
Poecilochirus macgillavryi Oudemans, 1927
Poecilochirus monospinosus Wise, Hennessey & Axtell, 1988		chicken manure
Poecilochirus mrciaki Masan, 1999		Nicrophorus and other Silphid beetles[17]
Poecilochirus necrophori Vitzthum, 1930[19]		Nicrophorus vespillo (main host[4][9]), other Nicrophorus & Silphid beetles[17]
Poecilochirus pilosula Banks, 1904		Nicrophorus beetles[17]
Poecilochirus rutellae Ramaraju & Mohanasundaram, 1997		beetles: Rutelidae, Scarabaeidae
Poecilochirus sexclavatus Skljar, 2002		Nicrophorus and other beetles[17]
Poecilochirus simplisetae Ramaraju & Madanlar, 1998		mushroom compost
Poecilochirus subterraneus Muller, 1859		Nicrophorus and other Silphid beetles[2][17]
Poecilochirus torbaliensis Ramaraju & Madanlar, 1998		mushroom compost

References

1. Joel Hallan (ed.). "Parasitidae Species Listing". Biology Catalog. Texas A&M University. Retrieved September 4, 2010.
2. Hyatt, Keith H (1987). "Mites of the genus Holoparasitus Oudemans, 1936 (Mesostigmata: Parasitidae) in the British Isles". Bulletin of the British Museum (Natural History). 52: 139–164. doi:10.5962/bhl.part.18305. ISSN 0007-1498.
3. Brown, Jonathan M.; Wilson, David Sloan (1992). "Local Specialization of Phoretic Mites on Sympatric Carrion Beetle Hosts". Ecology. 73 (2): 463–478. doi:10.2307/1940753. JSTOR 1940753.
4. Müller, J K; Schwarz, H H. "Differences in carrier-preference and evidence of reproductive isolation between mites of Poecilochirus carabi (Acari, Parasitidae) living phoretically on two sympatric Necrophorus species (Coleoptera, Silphidae)". Zoologische Jahrbücher, Abteilung für Systematik, Ökologie und Geographie der Tiere. 117: 23–30.
5. Schwarz, H.H.; Walzl, M.G. (September 1996). "Pairing, oviposition and development in two sibling species of phoretic mites (Acari: Mesostigmata: Parasitidae: Poecilochirus spp.) associated with burying beetles (Coleoptera: Silphidae: Nicrophorus spp.)". Journal of Natural History. 30 (9): 1337–1348. doi:10.1080/00222939600771251. ISSN 0022-2933.
6. Capinera, John L., ed. (2008). Encyclopedia of Entomology. Springer reference (2nd ed.). Dordrecht; London: Springer. p. 756. ISBN 978-1-4020-6242-1. OCLC 156813127. Retrieved 23 July 2009.
7. González Medina A, González Herrera L, Perotti MA, Jiménez Ríos G (March 2013). "Occurrence of Poecilochirus austroasiaticus (Acari: Parasitidae) in forensic autopsies and its application on postmortem interval estimation". Experimental & Applied Acarology. 59 (3): 297–305. doi:10.1007/s10493-012-9606-1. PMID 22914911.
8. Nehring, Volker; Teubner, Heide; König, Sandra (2019-09-01). "Dose-independent virulence in phoretic mites that parasitize burying beetles". International Journal for Parasitology. 49 (10): 759–767. doi:10.1016/j.ijpara.2019.05.011. ISSN 0020-7519.
9. Nehring V, Müller JK, Steinmetz N (December 2017). "Phoretic Poecilochirus mites specialize on their burying beetle hosts". Ecology and Evolution. 7 (24): 10743–10751. doi:10.1002/ece3.3591. PMC 5743630. PMID 29299254.
10. Brown, Jonathan M.; Wilson, David Sloan (1992). "Local Specialization of Phoretic Mites on Sympatric Carrion Beetle Hosts". Ecology. 73 (2): 463–478. doi:10.2307/1940753. ISSN 1939-9170.
11. Backlund, Doug (1994). "American Burying Beetle". South Dakota Department of Game, Fish and Parks, Division of Wildlife. Archived from the original on 2008-04-30. Retrieved 2008-07-21.
12. "Decomposition: Mites". Australian Museum. 2003. Archived from the original on 2008-06-27. Retrieved 2008-07-21.
13. Wilson, David Sloan; Knollenberg, W. G. (April 1987). "Adaptive indirect effects: the fitness of burying beetles with and without their phoretic mites". Evolutionary Ecology. 1 (2): 139–159. doi:10.1007/bf02067397. ISSN 0269-7653.
14. De Gasperin O, Kilner RM (December 2015). "Friend or foe: inter-specific interactions and conflicts of interest within the family". Ecological Entomology. 40 (6): 787–795. doi:10.1111/een.12259. PMC 4678582. PMID 26681822.
15. De Gasperin O, Kilner RM (2016-03-17). "Interspecific Interactions and the Scope for Parent-Offspring Conflict: High Mite Density Temporarily Changes the Trade-Off between Offspring Size and Number in the Burying Beetle, Nicrophorus vespilloides". PLOS One. 11 (3): e0150969. doi:10.1371/journal.pone.0150969. PMC 4795767. PMID 26985819.
16. Neumann, K-W (1943). "Die Lebensgeschichte der Käfermilbe Poecilochirus necrophori Vitzth. nebst Beschreibung aller Entwicklungsstufen". Zool. Anz. 142: 1–21.
17. Perotti, M. Alejandra; Braig, Henk R. (October 2009). "Phoretic mites associated with animal and human decomposition". Experimental and Applied Acarology. 49 (1–2): 85–124. doi:10.1007/s10493-009-9280-0. ISSN 0168-8162.
18. Haitlinger, R. (1988). "[Mites (Acari) occurring in Poland on beetles of the genus Carabus Linnaeus 1758 (Insecta, Coleoptera, Carabidae)]". Wiadomosci Parazytologiczne. 34 (3): 329–346. ISSN 0043-5163. PMID 3232387.
19. Baker, Anne S.; Schwarz, Horst H. (July 1997). "Morphological differences between sympatric populations of the Poecilochirus carabi complex (Acari: Mesostigmata: Parasitidae) associated with burying beetles (Silphidae: Nicrophorus)". Systematic Parasitology. 37 (3): 179–185. doi:10.1023/a:1005822702267. ISSN 0165-5752.