African chiggers (Acariformes: Trombiculidae) in the collection of Alex Fain, with a description of a new genus and three new species

A series of African chigger mites from the collection donated by Alex Fain (19122009) to the Royal Belgian Institute of Natural Sciences is revised. One new genus and species, Makwacarus petrodromi n. gen., n. sp. from an elephant shrew Petrodromus tetradactylus tordayi Thomas and two new species, Herpetacarus junkeri n. sp. from a snake Boaedon fuliginosus (Boie) and Microtrombicula livingstonei n. sp. from a lizard Holaspis guentheri Gray, are described from DR Congo. One new subjective synonym is proposed: Schoutedenichia musaranei Taufflieb, 1966 (= Schoutedenichia tanzaniaensis Goff, 1983, n. syn). Nineteen species have been recorded in new countries and/or on new hosts for the first time. Nine of them have been found outside their type localities for the first time. In total, the examined collection now includes 27 species belonging to 14 genera and collected from rodents, bats, tenrecs, elephant shrews, primates, birds, lizards and snakes of DR Congo, Rwanda, Kenya, Cameroon, Côte d’Ivoire, Senegal and South Africa.


Introduction
Chigger mites attract the attention of parasitologists since the beginning of last century, as a very diverse and ecologically flexible group of temporary parasites with a significant medical and veterinary importance. Until now, trombiculids provide a wide field for elementary taxonomic investigations including descriptions of new genera and species, as well as inventory of chigger fauna in previously unexplored countries or regions. My recent review of African chiggers (Stekolnikov 2018) outlines the current state of knowledge on this subject more than half a century after previous survey (Zumpt 1961). According to my work, 443 chigger mite species belonging to 61 genera were found previously in Africa, but 73% of this number is still known from their type localities only. It means that we know little about chigger fauna of the continent beyond an approximate data of species composition. Geographic ranges of species, faunistic complexes of different biomes, such as savannah, tropical rain forests or deserts, and true number of endemic species remain unknown.
In these circumstances, any identification of enough diverse new material could contribute greatly to the knowledge on African chigger fauna. Such opportunity was provided to me by the examination of a chigger collection kindly granted me by Alex Fain many years ago. Previous results based on this collection were obtained on chiggers of Australia , Madagascar  and Europe (Stekolnikov et al. 2014). Now, with a complete summary of chigger species described from Africa (Stekolnikov 2018), I am able to finish my work with this source. During this investigation I also had an opportunity to compare unidentified materials with type specimens borrowed by me from the Royal Museum of Central Africa (RMCA, Tervuren, Belgium) in 2016.
Alexander Fain (1912Fain ( -2009 was an outstanding Belgian acarologist who described more than 2300 species, 441 genera and 19 families of mites (Fain 2004). At first stage of his scientific activity (1939)(1940)(1941)(1942)(1943)(1944)(1945)(1946)(1947)(1948)(1949)(1950)(1951)(1952)(1953)(1954)(1955)(1956)(1957) he worked as a director of the medical hospital in Belgian Congo and later as a director of the medical laboratory of the Belgian Congo and Rwanda (Bochkov et al. 2009). During this period he made collections of trombiculids that were identified partly by P.H. Vercammen-Grandjean, one of the leading experts in chigger mite taxonomy in 1950s-70s who also worked in Belgian Congo, as a head of the biological section in the medical laboratory directed by Fain. Fain published some papers on African chiggers in collaboration with Vercammen-Grandjean (Jadin et al. 1954(Jadin et al. , 1955Vercammen-Grandjean & Fain 1957a, b, 1958. Since 1957, he was a professor of the Institute of Tropical Medicine in Antwerp, Belgium, and his mite collection was extended with samples collected in the Natural History Museum of London from ethanol preserved mammals and with specimens received from colleagues (Bochkov et al. 2009).
After his retirement in the early 1980s, Fain donated his collection to the Royal Belgian Institute of Natural Sciences (IRSNB, Brussels, Belgium) and worked in the Institute as a volunteer. In 2003 Fain offered me to identify chiggers preserved in his collection and then he sent the specimens through my Russian colleagues who visited Brussels at that time. Besides other materials, that shipment included 89 slides with chiggers collected from hosts captured in Africa. The territories covered by this collection include DR Congo, Rwanda, Kenya, Cameroon, Côte d'Ivoire, Senegal and South Africa, while the host spectrum includes rodents, bats, tenrecs, elephant shrews, primates, birds, lizards and snakes. Especially valuable is the presence of chiggers extracted from nasal cavities of hosts in Fain's collection, since this ecological group of parasites is not collected frequently during parasitological surveys. By now I have identified the main part of chigger specimens in the collection; the results of my work are given in the present paper. Since exact identification of the rest would require an examination of additional materials, I intend to finish now my investigation and return all slides to IRSNB.

Materials and methods
The present work was based on the examination of 89 microscope slides borrowed from IRSNB and originating from the collection of A. Fain. All slides contained unidentified specimens of chigger mites and had the labels containing logo of the Institute of Tropical Medicine in Antwerp ("Inst. Méd. Trop. Anvers") and the name of A. Fain. The name of IRSNB was printed or handwritten on a few labels. These slides were a part of two parcels: 1) 27 Mar. 2003, IRSNB loan No. Ent 03/52, 82 slides, transported by A.V. Bochkov; 2) 9 May 2003, without a loan form, 51 slides, transported by I.V. Shamshev. All slides will be returned to IRSNB after examination.
Some of slide labels were incomplete, i.e. without data on exact locality, date of collection or name of collector. Specimens collected before 1939 or after 1957 (time span over which Fain was not in Africa) were presumably found on ethanol preserved mammals in a museum. The collection has no accession numbers and a catalogue; thus, all collection data are restricted to the information containing in slide labels.
Type specimens of chigger mites were borrowed from RMCA (loan No. 2429f, 22.09.2016) during my visit to this museum. Note that types of many trombiculid species deposited in RMCA are unsuitable for examination, as described in my review of this collection (Stekolnikov 2018); such specimens were not included in the present work.
Coordinates of collection localities were obtained from the database of US National Geospatial Intelligence Agency (http://geonames.nga.mil/namesgaz/). Names of mammalian hosts are given after Wilson & Reeder (2005); avian hosts -after the online database Zoonomen (Zoological Nomenclature Resource): Birds of the World (http: //www.zoonomen.net/avtax/frame.html); reptilian hosts -after the Reptile Database (http://www.reptile-database.org). Host names originally given in slide labels are cited in brackets in case they are different from the modern ones, e.g. Gerbilliscus (Taterona) kempi (Wroughton) (= Tatera dichrura). The same way of citation is used for the names of localities, e.g. Mbandaka (= Coq'ville). Slide labels are translated from French.
All slides were examined in the Zoological Institute of the Russian Academy of Sciences (ZIN, Saint Petersburg, Russia) using a compound microscope MBI-3 (LOMO plc, Saint Petersburg, Russia) supplied with phase-contrast optics. Measurements were made with an ocular micrometer and converted to micrometres. Drawings were prepared using a drawing tube. I used also a Leica DM5000B microscope (Leica Microsystems GmbH, Wetzlar, Germany) with differential interference contrast to confirm the results of examination for most obscure morphological characters. I use diagnostic formulas and abbreviations for morphological traits following the standards generally accepted in chigger mite taxonomy (Goff et al. 1982). Their explanation may be obtained from many sources including those published in open access (Stekolnikov & Kar 2015;Stekolnikov 2018).
Identification was carried out on the base of my key for chigger mite genera and a checklist of African chigger species (Stekolnikov 2018), using original descriptions of species and revisions of the genera Schoutedenichia Jadin et Vercammen-Grandjean, 1954, Schoengastia Oudemans, 1910, Microtrombicula Ewing, 1950and Herpetacarus Vercammen-Grandjean, 1960published by Vercammen-Grandjean (1958a, b, 1965, revision of sub-Saharan Gahrliepia Oudemans, 1912(Taufflieb 1965b) and revision of the genus Leptotrombidium s.l. of the world (Vercammen-Grandjean & Langston 1976). For nine species, the identification was confirmed by a comparison with type specimens.

Results
Identified African chigger specimens from the collection of IRSNB belong to two subfamilies (Gahrliepiinae and Trombiculinae, including tribes Schoengastiini and Trombiculini), 14 genera and 27 species listed below. Subfamily Leeuwenhoekiinae is represented in the collection by one specimen of Acomatacarus, which was not identified due to unsuitable quality of the slide. Species of the subfamily Apoloniinae are absent in the collection. Several species of Schoengastia could be identified only roughly (S. cf. equina from South Africa and S. cf. andrei from DR Congo). Their exact identification requires a complete revision of the genus including examination of types preserved in different museums of Africa and Europe (Stekolnikov 2018). Two specimens of Microtrombicula (M. cf. viverida from Cote d'Ivoire and M. sp. from DR Congo) and one Schoutedenichia (S. sp. from DR Congo) cannot be identified exactly without examination of an additional material. Two specimens of Afrotrombicula will be included in my forthcoming revision of this genus. A minor part of slides was leaved without identification due to their unsuitable condition.
Remarks -This species was found on many species of small mammals in Rwanda and DR Congo (Stekolnikov 2018). Here it is recorded on G. (T.) kempi for the first time.
Remarks -This species was known from two specimens (holotype and paratype) collected from Crocidura sp. in Bangui, Central African Republic. Here it is recorded outside the type locality, in Côte d'Ivoire and on L. sikapusi for the first time. Remarks -This species was known only from its holotype. Here it is recorded outside the type locality and on Desmodillus auricularis for the first time.
Remarks -This species was described from a bat Hipposideros caffer (Sundevall) (Chiroptera: Hipposideridae) and C. hottentotus in Durban, and later it was recorded in Johannesburg and Sierra Leone from two more rodent species (Stekolnikov 2018 Remarks -This species was found in Central African Republic, Congo, DR Congo, Uganda and Angola on many species of small mammals (Stekolnikov 2018). Here it is recorded in Côte d'Ivoire, on L. sikapusi and U. ruddi for the first time. Remarks -This species was also recorded on P. velox in Angola (Dundo) (Taufflieb 1965a). The specimens from IRSNB constitute third known sample of this species.
According to the database of US National Geospatial Intelligence Agency, there are four populated places in Cameroon with the name Foulassi; thus, exact coordinates of the collection locality remain unknown.
The material from IRSNB differs from holotype in the presence of 6 setae in 2 nd dorsal row vs. 8 setae. Moreover, according to the original description, AM = PL in H. causicolus, while AM > PL in the additional material. Since all other characters in this material, including measurements (Table 1), do not expose significant dissimilarities with the type series, I regard these differences as an example of intraspecific variation.
Scutum -Nearly hexagonal, much wider than long, with concave anterior margin, with longitudinal cracks in all specimens examined, with small puncta, posterior margin almost straight medially; AM situated far posterior to level of ALs; SB situated posterior to level of PLs (P-PL -PSB = 2 -5); PL > AM > AL; AM and ALs similar to caudal idiosomal setae, PLs similar to dorsal idiosomal setae, with bulbous base; sensilla slightly expanded, fusiform, 3 -4 μm wide, covered by long barbs.

Host -four-toed elephant shrew (Macroscelidea: Macroscelididae: Petrodromus tetradactylus).
Etymology -The name of the new genus is combined from the name of type locality (Makwa) and the new Latin word acarus meaning "mite". Differential diagnosis -By the shape of scutum with broadly rounded, protruded posterior margin, globose sensilla, and by the relation between lengths of scutal setae (AL >= PL ≫ AM), the new genus is similar to Helenicula Audy, 1954, Schoengastia Oudemans, 1910, some species of Herpetacarus (Abonnencia) Vercammen-Grandjean, 1960, and some species of Guntheria (Phyllacarus) Vercammen-Grandjean, 1967, first of all, Guntheria innisfailensis (Womersley et Heaslip, 1943) from Australia. The position of tibialae II in distal half of segment and not in tandem is one more trait common for the new genus, Helenicula, and Schoengastia equina Vercammen-Grandjean, 1971. The relation of lengths of leg tarsalae with tarsala II longer than tarsala I and the position of tarsala I distal to microtarsala are also characteristic for the new genus and for Helenicula (Nadchatram & Traub 1971).
Scutum -Nearly pentagonal, wider than long, without puncta, with broadly rounded posterior margin; AM situated slightly posterior to level of ALs; SB situated clearly posterior to level of PLs (P-PL -PSB = 5 -6); AL > PL ≫ AM; all scutal setae similar to dorsal idiosomal setae; sensilla globose, covered by small cilia.
Remarks -This species was known only from its type series collected from Tarentola mauritanica (L.) (Squamata: Phyllodactylidae) in Morocco, Oued Cherrat, 33°48′55′′N, 7°06′36′′W. Here it is recorded outside the type locality, in DR Congo and on a bird host for the first time.

Schoengastia Oudemans, 1910
Schoengastia avis Vercammen-Grandjean, 1958 Type material examined -larva paratype (RMCA 113917) Remarks -This species was previously recorded on two species of birds in Bukavu and Kamaniola (DR Congo) (Stekolnikov 2018). Here it is recorded on reptiles for the first time.
Remarks -This species was described from two larvae collected on Cricetomys gambianus Waterhouse (Rodentia: Nesomyidae) in the surroundings of Brazzaville, Congo. Here it is recorded outside the type locality, in Kenya and on H. glaber for the first time.
Remarks -This species was known only from its type series collected from Nycteris hispida (Schreber) in the region of Butare, Rwanda, 15 Oct. 1955. Probably, the specimen from N. macrotis belongs to the same sample as the type series. Here T. nycteris is recorded outside the type locality and on N. macrotis for the first time.
Remarks -This species was known only from its type series collected from Ardeola ralloides (Scopoli) (Pelecaniformes: Ardeidae) in Mozambique (near Limpopo River mouth).
Here it is recorded outside the type locality, in DR Congo and on Actophilornis africanus for the first time.
Blankaartia gracilis is probably identical with B. ardeae (Trägårdh, 1905) described from Ardea cinerea L. (Pelecaniformes: Ardeidae) in Sudan (White Nile), as one can conclude on the base of its redescription made by Oudemans (1912). However, this redescription is somewhat incomplete (metric data include only length and width of idiosoma and scutum, and lengths of legs). Comparison of type specimens is urgently needed, but places of type deposition are currently unknown for both species (Stekolnikov 2018).
Remarks -This species was known only from its type series collected from Heliosciurus gambianus rhodesiae (Wroughton) (Rodentia: Sciuridae) in DR Congo (Bukama). Here it is recorded outside the type locality, in Senegal and on a primate host for the first time.
Remarks -This species is widely distributed in West and Central Africa (Central African Republic, DR Congo, Congo, Cameroon, Ghana, Nigeria, Côte d'Ivoire). It was found on many small mammal species, including L. sikapusi, on domestic cat and hen (Stekolnikov 2018).  Table 4.
Many of non-specialized leg setae nude or with few cilia, but true mastisetae (recognized by shape of setal base) absent.
includes only 27 species, i.e. 6% of the actual fauna of African chiggers, while collection of RMCA includes 30% (Stekolnikov 2018), it should be noted that quality of slides generally is much worse in the latter that makes many type specimens unsuitable for examination. Therefore, examination of specimens from IRSNB can be more useful for comparative purposes than examination of practically unavailable types preserved in RMCA, for example, in the case of Trombigastia nycteris or Herpetacarus causicolus.