A checklist of subterranean arthropods of Iran

Understanding subterranean biodiversity is important, yet vast regions of the world remain poorly explored. Here, we provide the first step towards cataloguing the subterranean arthropods of Iran. After review and analysis of the available literature and the examination of samples collected by us from Iranian caves, we listed 89 cavernicolous species (from 42 caves and 5 karstic springs) belonging to four arthropod subphyla: Chelicerata (1 class, 4 orders, 36 species), Crustacea (2 classes, 3 orders, 15 species), Hexapoda (2 classes, 5 orders, 34 species) and Myriapoda (2 classes, 3 orders, 4 species).


Introduction
Although relatively poorly studied in comparison with the epigean ecosystems, subterranean ecosystems show a rather high biodiversity at the global scale.Globally, over 7000 aquatic subterranean dwellers have been catalogued (Botosaneanu 1986), but unfortunately, such data are not available for the terrestrial subterranean fauna.It is likely that subterranean habitats harbor even larger numbers of terrestrial species, e.g.Coleoptera alone includes more than 1927 underground-limited species (Gibert andDeharveng 2002, Juberthie andDecu 1998).Culver and Holsinger (1992) proposed a potential biodiversity of about 50,000 to 100,000 obligate terrestrial subterranean species on the basis of nested regional estimates.
In spite of more than a century of taxonomic and biogeographic studies, large-scale patterns of diversity of the obligate cave-dwelling fauna have remained obscure.The two major apparent determinants of biodiversity for the subterranean terrestrial fauna, i.e. productivity and habitat availability, are the same as for many other faunas (Hawkins et al. 2003, Turner andHawkins 2004).Culver et al. (2003) hypothesized a connection between surface productivity and the amount of food available in caves: in nearly all caves, there is no significant chemoautotrophy so that all available food results from the surface productivity.Hotspots are most commonly referred to as areas of high biodiversity, followed by areas of high productivity (Briscoe et al. 2016).There are potential subterranean hotspots in the karst regions of western Caucasus in Georgia and possibly the Tien Shan Mountains in Kyrgyzstan.Although biologically poorly-studied, based on their positive relationship to the productivity maps and the presence of major cave regions they seem to be promising research subjects (Gvozdetski et al. 1994, Klimchouk 2004a, b).These regions are the closest to Iran which somehow have been studied in term of caves fauna.There are a lot of similarities between them and the north and western parts of Iran.Based on the studies conducted on these regions as well as some sporadic studies on Iranian caves in the mentioned areas, we could consider that there are some hotspots there.From east of Kyrgyzstan to the eastern coast of the Asian continent, the climate is probably too dry to support any subterranean hotspots (Culver et al. 2006).
Covering 164.8 million hectares in western Asia at the interface between three zoogeographic realms, Palaearctic, Oriental (Indo-Malayan) and Afrotropical (Ethiopian), Iran is situated at the conjunction of three climatic zones: the Mediterranean, the arid West Asian, and the temperate humid/semi-humid Caspian zone.Nevertheless, it lies predominantly in an arid environmental zone.The Zagros and Alborz Mountains are the two main mountain chains in western and northern Iran, which comprise nearly a third of the Iranian land area.Geologically, Iran is a part of the Alpine-Himalayan orogenic belt, divided into five major structural zones: a) Zagros Range, b) Sanandaj-Sirjan Range, c) Central Iran, d) East and South-East Iran and e) Alborz and Kopet-Dagh Ranges.However, more detailed divisions exist.The number of described caves is more than 2000 (Raeisi et al. 2012), with many more to be added.
During the last decade, several faunistic studies have been carried out in Iran, resulting in new records of already known species, as well as the descriptions of many new ones.However, despite the vast amount of collected faunistic data, the Iranian subterranean fauna remains inadequately known, and most reported species from the caves are in fact trogloxenes (Esmaeili-Rineh and Sari 2013).Nevertheless, 16 obligate cave-dwellers are reported from Iran, of which as many as 13 have been described since 2013.Fifteen species of these troglobionts are restricted to Iran.The only known troglobiotic vertebrates are three fish species: Garra typhlops (Bruun & Kaiser, 1944), G. lorestanensis Mousavi-Sabet &Eagderi, 2016 andParacobitis smithi Smith, 1976 (Cypriniformes) (Farashi et al. 2014, Mousavi-Sabet andEagderi 2016).Troglobiotic invertebrates include a spider, a diplopod and 11 crustaceans.In this paper, we aim to provide the first checklist of Iranian subterranean arthropods, based on the available literature and our unpublished material.

Material and methods
Unique adaptations of troglofauna have evolved in relations to the significant characteristics of subterranean environments such as caves, e.g.darkness, constant climatic conditions and restricted food supply.Based on their life style and adaptations to the conditions of the unique habitat, cave organisms (troglofauna) are divided into three categories: 1) troglobionts (organisms that display characteristics of troglomorphism, such as depigmentation and loss of eyes, and are considered "obligatory" residents of the underground environment), 2) troglophiles (organisms that can live and complete their life cycle either in the cave or in the surface; some biospeleologists subdivide this group into the eutroglophiles and subtroglophiles) (Gavish-Regev et al. 2016, see Sket 2008); 3) trogloxenes (organisms only occurring sporadically in hypogean habitat and unable to establish a subterranean population that habitually enter caves but must return periodically to the outside for certain of their living requirements, usually food) (Sket 2008, Romero 2009, Culver and Pipan 2009).We classified cave organisms into the mentioned three groups, based on the classification used in the available literature or on our own observations.Troglomorphic and non-troglomorphic species that were found in all cave zones throughout the year are classified as troglophiles.Trogloxenes were found either around cave entrances or within the entrance zone of smaller caves.Ectoparasites of bats were not categorized, however, they could be considered as troglophiles or trogloxenes.Major structural zones of Iran and the distribution of all troglobionts have been shown in Figure 1.Specimens from caves were collected by means of diverse sampling items (e.g. the plankton net, small hand net and aspirator), and placed directly into 96% ethanol.The collected specimens were brought to the laboratory and identified using identification keys and also with the assistance of specialists.Records of undetermined species are not referenced in this catalog.Material is deposited in the Zoological Museum of University of Tehran (ZUTC) and in the Collection of Biology Department, Zoological Museum of Shiraz University, Shiraz, Iran (ZM CBSU).

Phylum Arthropoda von Siebold, 1848 Subphylum Chelicerata Heymons, 1901 Class Arachnida Lamarck, 1801 Order Araneae Clerck, 1757
Based on the World Spider Catalog (2016), 45,987 species of spiders, grouped in 3,985 genera and 114 families have been described so far.To date, more than 600 spider species of 243 genera and 48 families have been recorded from Iran (Zamani et al. 2016).Only a few recent publications deal exclusively with the cave spider fauna of Iran (Marusik et al. 2014, Malek Hosseini et al. 2015a, b), while in previous reports only scattered records are provided (e.g.Brignoli 1970, Senglet 2008, Moradmand and Jäger 2011).Here, we have listed 29 species from 15 families and 21 genera, most of which have been classified as edaphic troglophiles and trogloxenes, and one troglobiont.Records: Roodafshan Cave (Tehran Province) (Zamani et al. 2014), Shirabad Cave (Golestan Province) (present study).

Order Pseudoscorpiones Haeckel, 1866
According to our own unpublished data, 56 species and subspecies of pseudoscorpions, from 12 families are known from Iran, of which, only one troglophile species is listed here.

Subclass Acari Leach, 1817
This subclass is with probably over 45,000 described species and has very complex systematics.There are more than 1,000 described species reported from caves with some being troglomorphic or troglophiles to some degree, generally showing reduction or loss of eyes and depigmentation, as well as elongation of appendages and welldeveloped sensory setae (Romero 2009).No detailed study of Acari in caves (e.g., as ectoparasites or guanobionts) has been done in Iran so far, and only five species of bat's ectoparasites are listed in here.We have collected several undetermined species that some of them are guanophilic and some other are associated with beetles.

Ixodes vespertilionis Koch, 1844
Status: bat ectoparasite.This species shows certain degree of troglomorphism, such as extremely elongated appendages and well-developed sensory setae.

Class Chilopoda Latreille, 1817
Approximately 3,000 species of centipedes are found in the class Chilopoda (Vazirianzadeh et al. 2007).About 60 species have been found in caves (Romero 2009).No checklist is available regarding the number of species in Iran; here we list two troglophile species.Specimens were identified by Dr. Marzio Zapparoli (Tuscia University, Viterbo, Italy.)

Class Diplopoda De Blainville in Gervais, 1844
About 10,000 species of millipedes have been described, of which, about 200 species in five orders have been reported from caves (Romero 2009).Enghoff and Moravvej (2005) listed 50 species of Iranian millipedes, of which only one species was reported from a cave.Here, we list two species, including one troglobiont.

Subphylum Crustacea Brünnich, 1772 Class Malacostraca Latreille, 1802 Order Amphipoda Latreille, 1816
This subphylum is constituted of about 52,000 known living marine, freshwater and terrestrial species with worldwide distribution (Martin and Davis 2006).It is by far the richest and the most diverse group in subterranean waters.A literature search yielded more than 4,800 species of cave, phreatic, and anchialine crustaceans from all over the world, including marine, freshwater, and terrestrial ones (Romero 2009).By far the most species-rich crustacean groups are Amphipoda and Copepoda, although Decapoda (due to their size) are probably the most obvious (Holsinger 1993, White andCulver 2012).With 319 species, niphargoids are the most diverse Palaearctic hypogean amphipods, which include also a few epigean taxa.They are distributed through central and particularly southeastern Europe, where they exhibit high levels of endemism in karst systems.More than 305 species of Niphargus have been described so far, and this is currently the largest freshwater amphipod genus (Fišer et al. 2005, Väinölä et al. 2008).Esmaeili-Rineh and Sari (2010) listed several localities for Niphargus in Iran: Dimeh spring in Chaharmahal and Bakhtiari, Brolan spring in West Azarbayjan, Sasan River in Fars, Ghori-Ghale cave in Kermanshah, Razbashi spring in Lorestan, Ghaemshahr and Danial Cave in Mazandaran and Cheshmeh-Siah in Koh-giluyeh and Boyer-Ahmad Provinces.However, the identification data haven't been published for all of them so far.
Freshwater amphipods from Iran include the family Gammaridae with 18 species (Zamanpoore et al. 2011, Semsar-Kazerooni et al. 2016) and Niphargidae with 10 species of the single genus Niphargus.All Iranian Niphargus have been recorded from caves and karstic springs.Records: Kiler Cave (Kohgiluyeh and Boyer-Ahmad Province) (present study).Species was identified by Dr. Frank Fiers from the Royal Belgian Institute of Natural Sciences.

Subphylum Hexapoda Latreille, 1825 Class Entognatha Stummer-Traunfels, 1891 Order Entomobryomorpha Börner 1913
There are more than 8,600 described species of collembola worldwide (Bellinger et al. 2016), of which, more than 400 are hypogean (Romero 2009).The collembolan fauna of Iran is poorly known, it consists of 112 species, belonging to 18 families and 57 genera (Shayanmehr et al. 2013).There has been no detailed study of cavernicolous collembola in Iran.Three species which have been listed below had been previously reported from soil and leaf litter (Shayanmehr et al. 2013).Specimens were identified according to Fjellberg (2007), by Dr. Masoumeh Shayan Mehr (Sari University of Agricultural Sciences and Natural Resources, Sari, Mazandaran, Iran).

Class Insecta Linnaeus, 1758 Order Blattodea Brunner von Wattenwyl, 1882
To date, over 4,500 cockroach (order Blattodea or Blattaria) species have been reported from different parts of the world.The cockroach fauna of Iran includes three families, 14 genera, and 26 species (Hashemi-Aghdam and Oshaghi 2015).Many geographical regions of the country have not been studied yet, hence a systematic research is required to reveal the real cockroach biodiversity of the country.They were observed as guanophilic animals in most of Iranian caves and in some cases with a high density of populations.However, these cavernicolous cockroaches haven't been studied so far.Adaptations to life in darkness such as very long antennae and long legs with numerous sensory hairs and setae, have been observed in some populations.

Order Coleoptera Linnaeus, 1758
There are over 330,000 species of beetles in the world; 1,927 terrestrial and 32 aquatic troglobionts have been described so far (Gibert and Deharveng 2002).The checklists of most families in Iran are not available.

Family Carabidae Latreille, 1802
Azadbakhsh & Nozari (2015) listed 955 species and subspecies in 155 genera, belonging to 26 subfamilies of Carabidae from Iran.Here we have listed 8 species from caves.

Order Diptera Linnaeus, 1758
Here, we have only mentioned ectoparasite Diptera that were collected from bats.The most conspicuous bat ectoparasites are the bloodsucking nycteribiid and streblid flies that are obligatory ectoparasites of bats (Marshall 1982, Theodor 1967).Till now only very limited studies have been done on the ectoparasites of bats in Iran (Benda et al. 2012).Here, 10 species from 6 genera and 2 families of Diptera have been listed.

Discussion
In our checklist, we compiled faunal lists of subterranean arthropods for Iranian caves based on scattered published literature together with unpublished data from our own collections.There are some ongoing projects addressing issues of biodiversity that will improve our knowledge of the cave fauna in this vast country, e.g.studies of cavernicolous pseudoscorpions, myrmecophilid crickets, oniscid isopods and niphargid amphipods by students of the University of Shiraz and Razi University of Kermanshah are being carried out.Moreover, there are other groups of cavernicolous arthropods in our collections that we did not list here because of incomplete identification, e.g.some species of Collembola, Coleoptera, Orthoptera (Grylloidea), Crustacea, Myriapoda, Araneae, Pseudoscorpiones and Acari.Ac- cording to our investigations, caves of Alborz and Zagros chains are rich in fauna.All Iranian troglobionts were described from the central and northern parts of Zagros and northern slopes of Alborz, which are mostly forested.About 10 species of troglobiotic crustaceans from Zagros caves and karstic springs are waiting to be described.The Zagros region exemplifies the continental variant of the Mediterranean climate pattern, while the northern slopes of Alborz are distinctly humid.So, these areas have a high level of productivity.The low species richness of Iranian caves is not realistic and it is due to a lack of comprehensive studies of all taxa (as a comparison, Sket et al. (2004) reported more than 975 terrestrial and 650 aquatic obligate subterranean species for the Balkan Peninsula).
An important problem is related to the identification keys for cavernicolous animals.To date, all studies have been sporadic.There is an ongoing comprehensive study on Niphargus of Iranian caves by Dr. Cene Fišer from University of Ljubljana, Slovenia with Iranian collaborators.The complete keys are needed to help future researchers.
From all 16 identified troglobiont species of Iran (3 terrestrial, 13 aquatic), 13 are arthropods, and out of these, 11 are crustaceans and 10 belong to the genus Niphargus (Niphargidae).From all 89 species of this checklist (from 42 caves and 5 karstic springs), Araneae with 29 species and Coleoptera with 17 species are dominant groups.A problem with some literature records are ambiguous names and localities of some caves that need to be clarified in further studies.Our studies about cave fauna should lead to decisions about conservation approaches.Unfortunately, based on our exploration and some other reports from caving groups, several caves have already been destroyed by human activities, which could cause drastic changes in food chains in these habitats, or even species extinction.