The freshwater snails (Gastropoda) of Iran, with descriptions of two new genera and eight new species

Abstract Using published records and original data from recent field work and revision of Iranian material of certain species deposited in the collections of the Natural History Museum Basel, the Zoological Museum Berlin, and Natural History Museum Vienna, a checklist of the freshwater gastropod fauna of Iran was compiled. This checklist contains 73 species from 34 genera and 14 families of freshwater snails; 27 of these species (37%) are endemic to Iran. Two new genera, Kaskakia and Sarkhia, and eight species, i.e., Bithynia forcarti, Bithynia starmuehlneri, Bithynia mazandaranensis, Pseudamnicola georgievi, Kaskakia khorrasanensis, Sarkhia sarabensis, Valvata nowsharensis and Acroloxus pseudolacustris are described as new to science; Ecrobia grimmi (Clessin & Dybowski, 1888), Heleobia dalmatica (Radoman, 1974) and Hippeutis complanatus (Linnaeus, 1758) are reported for the first time from Iran. Additional field work is highly desirable for a more appropriate evaluation of the extant freshwater snail biodiversity in Iran.


Introduction
Considering the geographical position of Iran, a rich fauna of freshwater snails could be expected. A high level of endemism and a diverse mixture of Palaearctic and Paleotropical elements are characteristic of the Iranian freshwater fauna (Pešić and Saboori 2007).
Research of molluscs biodiversity in Iran has a relatively long tradition. In 1862, a group of Italian scientists undertook the first systematic expedition to Persia, which revealed a large number of molluscan samples. The results of this expedition have been published by Issel (1863). Two decades later, the mollusc fauna of the Caspian Sea was studied by Dybowski (1888). The first study on the molluscs diversity of inland water was done at the beginning of the XX th Century by the Indian malacologists Annandale and his coauthors (Annandale and Prashad 1919, Annandale 1921, Annandale and Rao 1925 who studied the molluscan fauna of Seistan and Baluchistan Province. Biggs (1936Biggs ( , 1937Biggs ( , 1971) studied the malacofauna of the Central Plateau of Iran. In 1936 he noted: "Little has been written on the Mollusca of the Iranian Plateau. This was perhaps due to the inaccessibility of the interior in the past when the only method of travelling was by caravan". Forcart (1935) studied molluscs from the Mazandaran Province. Starmühlner and Edlauer (1957) published the results of the Austrian Iran expedition of 1949/50 and 1956. Later on, Starmühlner (1961Starmühlner ( , 1965 studied molluscs from Northern and Eastern Iran collected by the Austrian A. Ruttner. More recently, Mansoorian (1986Mansoorian ( , 1994Mansoorian ( , 1998Mansoorian ( , 2000 published on the molluscan fauna of Iran.
However, our knowledge of freshwater snails of Iran remains scanty. Despite a growing number of data over the last years, resulting from the expeditions of the junior author in 2005, 2007, and 2011, literature records of freshwater snails in Iran have remained scattered and unreviewed, hampering ecological and biogeographical analysis. To what extent is the area of Iran unique and important for freshwater snail biodiversity? This paper attempts to answer such questions by compiling data on water molluscs and their current geographic distribution in Iran.

Material and methods
The checklist of the freshwater snail fauna of Iran was compiled using published records and original data. The data from all publications were brought to the presently accepted state of taxonomy following Subba Rao (1989) (for Asian Fauna), Brown (1994) (for African Fauna) and Glöer (2002) (for the European Fauna), and papers published thereafter. Species referred to in postgraduate theses and scientific meetings are no formal publications and are consequently not considered herein.
During the field work, freshwater snails were collected by hand netting, sorted on the spot and preserved in 75 % alcohol. The data and locations of the sampling sites, where the junior author collected in 2005,2007 and 2011 are listed in Appendix 1. In the section 'New records' collecting site abbreviations derive from the geographical database Pešić. The type material will be deposited in the Zoological Museum Ham-  Remark. According to the original description (Martens 1874) this species is char-Remarks. Starmühlner and Edlauer (1957) provide a detailed description of the anatomy of this species but did not consider the operculum, the most important diagnostic feature. On the other hand, as figured in Starmühlner and Edlauer (1957), the receptaculum seminis and the bursa copulatrix differ in length (while being of equal length in Th. fluviatilis).
The re-examination of the specimens of Theodoxus pallida (Dunker, 1862) from Edlauer's collection in NHMW clearly shows that this species is distinct from Theodoxus fluviatilis due to the shape of shell and the operculum (Fig. 3). As already mentioned by Dunker (1862) the spire in Th. pallida is higher than in Th. fluviatilis, and furthermore the apophysis of the operculum is broader and not attenuated at its basis (Fig. 3c). In addition the callus at border of the operculum in Th. pallida is much stronger (Fig. 3c arrow).

Melanopsis kotschyi
Remarks. The species Melanoides pyramis and M. tigrina, which have been mentioned by Annandale and Prashad (1911) from Seistan and Baluchistan, have been listed by Westerlund (1886) as subspecies. However, due to the high morphological plasticity of M. tuberculatus and in absence of any geographical seperation of these taxa, we list all Melanoides taxa under M. tuberculatus.
Distribution. S Asia, Arabia, Near East, Africa.
Remarks. The Euro-Siberian species Bithynia tentaculata (Linnaeus 1758) has often been mentioned from Iran, Turkey and Greece. However, this species could not be found in Greece (Glöer et al. 2010) and probably does not occur in Turkey. The southern distribution border of this species lies possibly in N Bulgaria (Georgiev pers. comm.). An analysis of the specimens from NMB published by Forcart (1935) as Bithynia tentaculata shows that these specimens represent B. forcarti sp. n. (see below). Thus, B. tentaculata most probably does not occur in Iran and has been confused with B. forcarti sp. n. or possibly with Bithynia mazandaranensis sp. n. (see below).
Distribution. Euro-Siberian. Etymology. Named after Lothar Forcart in appreciation on his studies of Iranian freshwater snails.

Bithynia
Description. The whitish shell is conical with 5.5 whorls, which are convex with a deep suture and a small and acute apex. The convex whorls are flattened at the suture.
The umbilicus is open. The aperture is ovate, angled at the top. The margin of the aperture is, from lateral view, slightly sinuated. The surface is smooth with fine growth lines. Shell height 5.5 -7.5 mm, width 5.0 -5.6 mm.
Differentiating features. Due to the shape of the aperture (angled at the top), Bithynia forcarti sp. n. resembles B. mazandaranensis sp. n. (see below). However, from the latter species it can be easily distinguished by the stepped whorls.
Remarks. Formerly (Forcart 1935)  Paratypes. 9 ex. from the type locality. Etymology. Named after Ferdinand Starmühlner, who collected this species in 1949. Description. The whitish shell is elongated conical with 6.5 whorls, which are convex with a deep suture and a small and acute apex. The umbilicus is open. The aperture is ovate. The margin of the aperture is, from lateral view, straight. The surface is smooth with fine growth lines. Shell height 8.2 -10.3 mm, width 4.6 -6.4 mm.
Differentiating features. This slim species is the largest Bithynia sp. known in Iran. It can be easily distinguished from the other Bithynia spp. by the larger dimensions of elongated shell with the stepped whorls and the not angled aperture.
Remarks. This species has been misidentified by Starmühlner and Edlauer (1957)  Holotype (ZMH 79369): Shell height 8.0 mm, width 5.0 mm. Etymology. Named after the region where the species was collected. Description. The horn-coloured shell is conical with 5.5 whorls, which are slightly convex with a clear suture and an acute apex. The umbilicus is closed. The aperture is ovate, angled at the top. The margin of the aperture is, from lateral view, sinuated. The surface bears a lattice structure. Shell height 8.0 mm, width 5.0 mm, aperture height 3.6 mm. Differentiating features. The new species resembles B. tentaculata but differs from it by the following features: (i) the operculum is more angled (Fig. 7c), (ii) the whorls are more convex (Fig. 7a-b), and (iii) the surface has longitudinal and transverse striae (Fig. 7d).
Remarks. Probably this species formerly (e.g., Mansoorian 2000) was confused with B. tentaculata. Because we had only an empty shell of this species, we do not know if it belongs to the genus Bithynia or Pseudobithynia, so our generic assignment is tentative. To address this question, anatomical studies of more specimens are necessary.
Remarks. Probably due to the small size of this species, Biggs (1937) assigned this species belongs to the genus Amnicola, although Mousson (1874) described it as a Bythynia, and pointed out that the operculum is characteristic for Bythinia and different from Amnicola (syn. to Pseudamnicola). Furthermore, Biggs (1937) found his species in the mountains, while the original description of Bithynia ejecta comes from the lowland, indicating the Biggs's species is not conspecific with Bithynia ejecta and probably represents an undescribed species. Remarks. This species could not be found in any of the neighbouring countries of Iran. Eliazian et al. (1979) don't mention the source that led to their identification. The record and taxonomic status of this species is questionable and needs new confirmation.

Subgenus Gabbia Tryon, 1865
Type species. Gabbia australis Tryon, 1865  Remarks. Some authors (e.g Subba Rao 1989, Nesemann et al. 2007) mention Gabbia as a genus. However, it seems not possible to distinguish the genera of the Bithyniidae by the shape of opercula (Mandahl-Barth 1968) and/or by shell forms, because these characters are found to be variable. On the other hand, the examined material of the family of Bithyniidae can be easily separated by the characteristics of penis morphology (having a penial appendix: Bithynia Leach 1818; or lacking a penial appendix: Pseudobithynia Glöer & Pešić 2006). In our study, we tentatively use the name Gabbia as a subgenus for small Bithynia species with a globular shell, originating from India.  (Biggs 1971).

Remark.
Probably this species has been confused with one of the following species (Ecrobia grimmi, Heleobia dalmatica), so all former records of this species in Iran are questionable. The record for this species is kept until the original material of Biggs could be studied.  Haase et al. (2010) concluded that Ecrobia grimmi from the mixomesohaline Lake Sawa (Iraq) was possibly transported by migrating birds from the Caspian Sea. The identification of our material of Ecrobia grimmi as well of Heleobia dalmatica was confirmed by using molecular techniques (Martin Haase pers. communication). An analysis of the specimens from NHMW published by Starmühlner and Edlauer (1957) as Hydrobia acuta shows that these specimens probably belong to Ecrobia grimmi (see Fig. 8c (Starmühlner 1961(Starmühlner , 1965. Distribution. Iran: Isfahan Province; endemic.
The new genus appears to be close to Pseudamnicola, but can easily be distinguished by the unique morphology of the penis with bulbous and acute apex (vs. a broad elongated triangular penis in Pseudamnicola). Holotype (ZMH 79372): Shell height 2.5 mm, width 1.9 mm. Paratypes (ZMH 79373): 21 ex. from type locality. Etymology. Named for its occurrence in Khorrasan Province. Description. The yellowish shell is conical to globular with 5.5 whorls, which are slightly convex and separated by a clear suture (Fig. 10a). The whorls increase rapidly with a prominent body whorl. The surface is glossy and finely striated. The apex is acute, the aperture is ovate and angled at the top, the umbilicus is closed. Shell height 2.3-2.5 mm, width 1.8-1.9 mm.

Kaskakia khorrasanensis
Animal. The mantle and head are black. The penis is broad at the basis and tapered at the distal end (Figs 10b-d).
Differentiating features. As for the genus. Distribution. Iran: Khorrasan Province; known only from type locality. Etymology. Named after the region where the species was collected. Differential diagnosis. The genus seems to be closely related to Pseudamnicola (in the following, in parentheses), but the unique morphology of the penis, broad at the basis and tapered at the distal end (Figs 10b-c), with a black pigmentation mark (vs. broad and elongated triangular penis), and the presence of broad cylindrical tentacles (slim cylindrical tentacles) will separate the new genus from Pseudamnicola.  Etymology. Named after the region where the species was collected. Description. The yellowish shell is elongated conical with 6.5 whorls, which are slightly convex and separated by a deep suture. The aperture is oval with a sharp periostome, the umbilicus is closed. The surface is dull. Shell height 5.9 mm, width 2.3 mm.

Sarkhia sarabensis
Differentiating features. The slim elongated conical shell with more than 5 whorls (Fig. 11a) is characteristic and separates this species from Sarkhia kermanshahensis (see below).
Distribution. Iran, Kermanshah Province; only known from type locality. Remarks. This species has originally been placed in the genus Pseudamnicola. However, due to the characteristic shape of the penis and the tentacles it is transfered to Sarkhia gen. n.
Distribution. Iran; Kermanshah and Markazi Provinces.   Records from Iran. Tehran Province -"Frauenfeldia elburensis" Starmühlner and Edlauer (1957). Remarks. Starmühlner and Edlauer (1957) originally described this species as Frauenfeldia elburensis. However, the genus name Frauenfeldia is preoccupied, and thus, the species of this genus have been re-assigned to Belgrandiella, Boleana, Graziana and Sarajana (Radoman 1983). Due to the shape of the aperture in original description (see Starmühlner and Edlauer 1957) we affiliate this species to the genus Belgrandiella.
Remarks. Most probably, Starmühlner and Edlauer (1957) misidentified this subterranean species, known only from its type locality in Slovenia, far away from Iran. The comparison with the description of H. erythropomatia by Radoman (1983) shows that these species are not conspecific as the umbilicus seems to be broader in later species compared with the species depicted by Starmühlner and Edlauer (1957). Unfortunately this species could not be found in Edlauer's collection in NHMW (Anita Eschner, pers. comm.). The record for this species is kept until specimens from the original locality could be studied. Remarks. Starmühlner and Edlauer (1957) mentioned Gangetia uzielliana from many sampling sites in Yazd Province. An analysis of one lot from the Edlauer collection (NHMW) with the specimens from Yazd Province shows that these specimens ( Fig. 13a-b) belong to Farsithyra farsensis. Further, re-examination of the specimens from Lake Taschk in Fars Province identified by Starmühlner and Edlauer (1957)   Etymology. Named for its resemblance with Acroloxus lacustris. Description. The oval limpet shell is transparent. The apex is blunt and bent to the left side (Figs 15a-b).

Family
Differentiating features. The new species resembles A. lacustris, which can be easily distinguished by the shape of apex, which is always acute and not blunt (Figs 15c-d) like in the new species. From Russia, no Acroloxus sp. with a blunt apex is known (Vinarski, pers. comm.).
Remark. An analysis of the two specimens from Forcart's collection (NMB 11516a) identified as Acroloxus lacustris from Mazandaran Province shows that these specimens belong to A. pseudolacustris sp. n.

Radix persica
In addition, Planorbis subangulatus Philippi, 1844 and Planorbis persicus Ancey, 1900 have been mentioned from Iran (Ancey 1900, Biggs 1937). Both species have been described on the basis of the shells, the morphology of which falls within variability of P. intermixtus. Thus we list these species under P. intermixtus.

Planorbis carinatus O.F. Müller, 1774
http://species-id.net/wiki/Planorbis_carinatus Fig. 18a Records from Iran. Northern Iran (Mansoorian 1994 Remarks. The identification of the species of this genus is based on the anatomical features (Glöer and Meier-Brook 2008), so all former records of this genus are questionable and need new confirmation.  Indoplanorbis exustus (Deshayes, 1834) http://species-id.net/wiki/Indoplanorbis_exustus Fig. 18c Records from Iran. Seistan and Baluchestan Province (Mansoorian 1994 Of the 73 species reported in this paper, 12 species have a wide distribution (known from two or more bieogeographical regions), 9 species are Palaearctic, 4 species are W-Palaearctic and 8 species are "Middle East" (Iran, Iraq, Tadjikistan, Uzbekistan, Turkey, Syria, Israel) in their distribution. Insufficient knowledge hampers the determination of the biogeographic status of the rest of the species. Moreover, another 27 (37%) of these species have been indicated as being endemic to Iran.
If we take generic diversity into consideration, we can see that only three genera i.e. Farsithyra Glöer & Pešić 2009, Kaskakia gen. n. and Sarkhia gen. n. are endemic to Iran.
The species-richness of freshwater gastropods in our study was rather low one with an average of 2.12 species and a maximum of 6 spp. per sampling site. Only some common species occur in high abundances [> 20 ind./sampling site], abundances of most species being < 10 ind./sampling site. Most sampling sites in our study were intermittent streams, with perennial surface water only present in the head water section near their source in the mountains. Further downstream, riverbeds are usually seasonally dry with occasionally some standing pools in their middle course (Pešić et al. 2012).
As expected, our current knowledge of the diversity of the freshwater snail fauna is far from being complete. For most Iranian provinces, all available data come from a few surveys with as objective the study of snails as vectors of digenetic trematodes of medical or veterinary importance (e.g., Mansoorian 1994Mansoorian , 1998Mansoorian , 2001. However, large portions of Iran remain unexplored and many important hydrological basins have never been sampled. The number of known species may hence only represent but a part of the total freshwater snail species number in Iran. For example, for Central Europe, an estimated total species number of about 150 appears appropriate (Glöer 2002).
However, the present study is exhaustive and constitutes the most complete list of freshwater snails in Iran, including a complete bibliography of research on the subject. Further studies should focus at a serious improvement of our knowledge on Iranian freshwater snails by intensive collecting activities in little known areas in order to close the large gaps in our knowledge on their diversity. Particularly some specific habitats such as springs and underground habitats are more or less unexplored but may prove to be a major source for freshwater biodiversity.