Description of a new genus and species as the first gastropod species from caves in Iran

We report on a new stygobiont truncatelloid gastropod from the sulfidic ponds of Tashan Cave in the Zagros Mountains of Southwest Iran. The hydrogen sulfide habitat resembles those hitherto known for gastropods from sulfide-rich caves in Romania, Italy and Greece. The newly described genus Trogloiranica n. gen. with a newly described T. tashanica n. sp represent the first true stygobiont gastropods found in Iran. The phylogeny inferred from the mitochondrial (cytochrome oxidase subunit I) and the nuclear (histone 3) genomes, as well as anatomical evidence, place T. tashanica in the family Moitessieriidae Bourguignat, 1863. The new genus may represent an evolutionary relict from the post Miocene before the split of the families Moitessieriidae and Cochliopidae Tryon, 1866. INTRODUCTION The freshwater Mollusca of Iran have been a focus of research during past two decades (Mansoorian, 2001; Glöer and Pešić, 2009, 2012; Moghadam and Chegini, 2009; Mowlavi et al., 2009; Shahabuddin et al., 2012; Ektefa et al., 2013; Nouroozi, 2014), and the taxonomic position of the local Ponto-Caspian Hydrobiidae has been clarified only recently (Dellicado et al., 2016). Iran is situated at the interface of three zoo-geographic realms, Palaearctic, Oriental (Indo-Malayan), and Afrotropical (Ethiopian). The karstifiable carbonate formations cover around 11% of Iran’s surface area with more than half (55.2%) being located at the Zagros Mountains in western Iran (Raeisi and Laumanns, 2012). Thus, it is not surprising that more than 90% of known Iranian troglobiont taxa are found in the Zagros karst formations (Malek-Hosseini and Zamani, 2017). Tashan Cave, located near the Sarjooshar Village, harbors a unique ecosystem. The recent discovery of a blind fish, Garra tashanensis Mousavi-Sabet, Vatandoust, Fatemi and Eagderi, 2016, and of the isopod Stenasellus tashanicus Khalaji-Pirbalouty, Fatemi, Malek-Hosseini, Kuntner, 2018, has been followed by other discoveries including the new gastropod genus and species reported here. The Tashan Cave represents a specific hypogean habitat with several cave ponds containing groundwater rich in hydrogen sulfide. Earlier studies performed in sulfide-rich caves by Hose et al. (2000); Engel (2012); and Jones et al. (2014) have shown that chemoautotrophic sulfur-oxidizing microorganisms thrive in such environments using the redox interface between the sulfide in the water and the oxygen in the atmosphere to produce food in situ, independent of the external light energy. Sulfuric acid is a product of the bacterial sulfur oxidation and accelerates the dissolution of the limestone bedrock in the process called sulfuric acid speleogenesis (SAS), which results in the formation of sulfide caves (Engel et al., 2004; Porter et al., 2009). It is estimated that hydrogen sulfide-rich phreatic waters and microbially-generated sulfuric acid were involved in the speleogenesis of around 10% of worldwide known caves (Palmer, 2007). However, only a few of these caves remain active ducts containing hydrogen sulfide-rich groundwater. The sulfide caves host interesting ecosystems with unusually rich and diverse invertebrate communities dominated by crustaceans (Peterson et al., 2013; Por, 2014), insects (Tobler et al., 2013) and occasionally fishes (Reisch et al., 2010; Roach et al., 2011; Mousavi-Sabet at al., 2016). While sulfide-based ecosystems are usually well-recognized inside deep sea trenches (Deming and Baross, 1993), the groundwater sulfide ecosystems remain poorly studied (Engel, 2007). The sulfide cave ecosystems received attention with the studies of Sarbu et al. (1996). The first studied cave containing a sulfide ecosystem was Movile Cave in Romania (Sarbu and Popa, 1992; Sarbu et al., 1996; Sarbu, 2000; Engel, 2012), followed by the Frasassi caves and Grotto Azzurra in Italy (Macalady et al., 2007; Peterson et al., 2013), Tito Bustillo and Maltravieso caves in Spain (Schabereiter-Gurtner, 2002; Arrozo et al., 1997), Fiume Coperto Cave in Italy (Latella et al., 1999), Melissotrypa Cave in Greece (Falniowski and Sarbu, 2015), El Hamma in Tunisia (Por, 1963), Ayalon Cave and the Tabgha Spring in Israel (Por, 1963; 2007; 2011), Kugitangtou caves in Turkmenistan (Maltsev and Korshunov, 1998), Cueva de Villa Luz in Mexico (Hose et al., 2000; Engel, 2007), Bungonia and Nullarbor caves with Bunder Sinkhole in Australia (Holmes et al., 2001; Jaume et al., 2001), Lower Kane