New stygobiont genus and new species ( Gastropoda , Hydrobiidae ) from the Rif ( Morocco )

Stygobiont valvatoid hydrobiids living in the groundwater were collected from a survey in the wells in the Rif region, in northern Morocco. The description of the shells, the male and the female genitalia revealed a character combination for a new genus, Rifia n.gen. The map of the distribution is given.

The new valvatoid hydrobiid described here, Rifia n. gen., is stygobiont and found widespread in the phreatic waters in the Rif region, north of Morocco. The anatomical characters are distinct from all known valvatoid hydrobiids. The terms used in the description of shell and soft parts are those in Hershler & Ponder (1998) and Bodon et al. (2001).Comparison were made using the synopsis of the European hydrobiid genera with valvatiform shell proposed by Bodon et al. (2001) and the comparison of character-state scores for thirtyfour valvatoid genera (Radea et al. 2016, Table 2).
Type specimens are deposited in the Muséum d'Histoire Naturelle of Paris (France). Other material examined conserved in Coll. GHA (collection Ghamizi), at the Museum of Natural History of Marrakesh (Morocco), and in Bodon collection (Italy).

Results
The specimens collected from the nine wells along the Rif border in northern Morocco ( Fig. 1) have the same shell structure and the same anatomical characters; the combination of which, with the type of habitat, would make it possible to introduce a new genus.

Diagnosis:
The new taxa is clearly distinguished by the following combination of characters: shell valvatiform, almost planispiral; operculum with outgrowth at centre of inner face as well-developed peg; penis with two small non-glandular lobes and without stylet; female genitalia with two seminal receptacles and a medium-size bursa copulatrix; duct of bursa copulatrix entering bursa on anterior side. Etymology: After the Rif region (Northern Morocco) where type species has been collected.
Female genitalia with two seminal receptacles, elongated and equal in size; bursa copulatrix arising from renal oviduct, medium size, oval, with slender elongated duct entering bursa on anterior side (   Type locality: Well at 1 km of west of Guercif, near Taniat Labghal; UTM VC 69; altitude=500 m.; temperature=18°C; conductibility=870 s/cm; protected well (by a small edge of the ground and by a cover at the top).
The two valvatoid hydrobiid genera recently described from Morocco and collected from the springs, have pigmented bodies and eye spots (Glöer et al. 2020b, Figs. 2(2), 3(5)); the genus Ifrania Glöer, Mabrouki & Taybi 2020 (Type species: Ifrania zerroukansis Glöer, Mabrouki & Taybi 2020) has a long and thin penis without penial lobes and genus Fessia Glöer, Mabrouki & Taybi 2020 (Type species: Fessia aouintii Glöer, Mabrouki & Taybi 2020) has a penis described as « flat, relatively thick at the basis with a small bulge and tapered at the distal end» (Glöer et al. 2020b). Islamia tifertensis Glöer, Mabrouki & Taybi 2020 was collected from a spring and is described only on empty shell (Glöer et al. 2020a) and assigned to Islamia without known its anatomy; however, hydrobiid species are characterized by the penis and the shell shape (Szarowska 2006). The new genus Rifia differs quite from the above three valvatoid genera reported from Morocco by its penis with two small non-glandular lobes at mid part of the penis (Figs. 3 C, D, E). This character coupled with the female genitalia with two seminal receptacles (Figs. 3 G, H) and associated with endemic distribution resulting from its poor dispersal capacity and its stygobiont features (depigmented body and no eye spots) suggesting that a new genus should be introduced. The new species Rifia yacoubii n.sp. differs by its almost planispiral shell, that more depressed than in I. tifertensis which anatomical characters and operculum are lacking. I. tifertensis has been collected from a spring as empty shells will be probably a subterranean species. The spring Tifert, type locality of I. tifertensis (Glöer et al. 2020a) is situated at downstream of the Moulouya basin, at 180 km from the nearest well (type locality) where R. yacoubii has been collected (Fig. 1). If we consider that is the same phreatic basin (Moulouya basin), I. tifertensis could be assigned to the new genus Rifia as a second species. The genus Islamia Radoman 1973, having penis bilobed and no bursa copulatrix (Radoman 1983;Bodon et al. 2001;Arconada & Ramos 2006), should therefore be disregarded, as its presence in Morocco is not yet anatomically confirmed.
Habitat and distribution: All specimens collected are from wells. The new species seems to be widespread in phreatic waters and found, until now, in nine wells along the south border of the Rif region, in the upstream of Moulouya, Sebou and Loukkos basins (Fig. 1). Specimens collected with whole animal have depigmented bodies, without eye spots and are adapted to groundwater (stygobiont species).
Status: the species is reported as nomina nudum (Pseudoislamia yacoubii) and listed as Critically Endangered species (CR) among the threatened freshwater molluscs of North Africa (Van Damme et al. 2010).