A NEW ISLAMIA SPECIES ( GASTROPODA : HYDROBIIDAE ) FROM CYPRUS

A new valvatiform hydrobiid, Islamia mylonas, from the Troodos Mts, Cyprus, is described. The shell characters, radula and soft parts anatomy are studied in detail and illustrated. The differences between the new species and its congeners from the Balkan Peninsula and the Mediterranean Basin are extensively discussed.


MATERIAL AND METHODS
Few specimens and empty shells of the hydrobiid in question were found during sorting of lot FC 13145 collected from a spring in the Troodos Mts in 2010.Shell characters were studied and four shell measurements (shell height and width, aperture height and width) were taken from 13 specimens using the micrometer of a Stemi 2000-C stereomicroscope.Additionally, four ratios were calculated: shell height : shell width, aperture height : aperture width, shell height : aperture height and shell width : aperture width.Three males and three females were anatomically examined after dissecting under a stereomicroscope Stemi 2000-C, Zeiss, Germany using very fine needles and pointed watchmaker's forceps.Prior to dissection, the shells were removed by soaking in Pereny solution.The soft parts characters were documented using a camera (Canon EOS 1000D) coupled with the stereomicroscope.
The radulae and the opercula were cleaned with KOH solution (5 g/l) at room temperature, rinsed in distilled water and air-dried before being mounted on stubs and spray-coated with gold-palladium.They were photographed in a scanning electron microscope Jeol JSM-35 operating at 25 kV.The morphological terminology follows that of heRshleR & PondeR (1998).

Etymology:
The specific name derives from the last name of Prof. Moissis Mylonas, who has given a strong impetus to the study of Greek and Cypriot malacofauna and inspired many Greek students, including ourselves.
Diagnosis: Shell minute, valvatiform, operculum circular paucispiral without peg; single pair of basal cusps on central radular tooth; penis with muscular pleat protruding on the left side and large trapezoidal penial lobe overgrowing the apex of penis proper; penial lobe with more or less prominent secondary lobe on its right apical edge; bursa copulatrix absent, two seminal receptacles arising at a distance from each other, renal oviduct with a secondary lateral loop.

Description:
Shell (Figs 1-11, Table 1).Valvatiform, minute (maximum height 0.76 mm, maximum width 1.15 mm) with up to 3.5 whorls, thin, colourless, transparent; spire more or less depressed; whorls rounded, regularly growing with shallow sutures.Periostracum cream-coloured; aperture roundish, prosocline adhering to the body whorl; peristome continuous, thickened and reflected at columellar margin, outer margin simple; umbilicus open, deep and wide.Operculum .Circular, paucispiral, thin, corneous, light yellowish (in preserved specimens); inner surface weakly convex without any peg; nucleus central.Soft body pigmentation.Preserved specimens unpigmented; large eye spots present.Ctenidium-osphradium (Fig. 14).Ctenidium with ca.7 filaments; filaments broader than high; osphradium of medium width, less than twice longer than broad, opposite posterior part of ctenidium.Digestive system apart from radula (Fig 15).Style sac smaller than stomach, not protruding to intestinal loop, intestine Z-shaped.Radula .Central tooth trapezoidal, its dorsal edge strongly concave; basal tongue broadly V-shaped and roughly equal to elongated lateral margin; one pair of medium-sized basal cusps (bc2); median cusp long, narrow, rounded, protruding, followed by 5 narrow cusps of decreasing size on each side, the fifth cusp being much reduced in size; lateral tooth face taller than wide; central cusp longer than lateral cusps, 4 lateral cusps on outer side, 3 smaller lateral cusps on inner side; inner marginal tooth with ca.25-30 long, narrow cusps; cusps almost equal in size, the first 2-3 outer ones being very small; outer marginal tooth with ca.14-18 cusps.Penis .Large relative to head, long, wide, dorso-ventrally flattened, folded, apically bifid due to the penial lobe on its left side and penis proper on the right side; penial lobe large, exceeding the tapered distal end of penis proper, trapezoidal with a more or less distinct secondary lobe on its right apical edge and an ovate refringent area on the left; base of penis expanded; large muscular pleat in the middle of penial lobe on ventral side of penis protruding at the left side of penis; penial duct undulat- Albumen gland of irregular shape; bursa copulatrix absent; renal oviduct unpigmented and well-developed with a narrow vertical primary loop and a secondary lateral loop; two elongate seminal receptacles located at a distance in opposite positions of renal oviduct; proximal seminal receptacle (RS2) with an orange-pink pearl shine emerging from the top of renal oviduct primary loop; distal seminal receptacle (RS1) smaller than proximal one, without distinct duct; one female with pseudopenis on the head.
The protoconch and the nervous system were not studied because of the small number of available specimens and the fragility of the preserved shells.
Habitat and distribution.Known only from the type locality, a spring in Periochi Tzionia CY2000013 which is a Site of Community Importance (SCI) and a Special Protection Area (SPA) of Natura 2000 network.

DISCUSSION
The freshwater hydrobiid fauna of Cyprus has not been extensively studied so far.Only two hydrobiid species, Pseudamnicola malickyi Schütt, 1980 and Islamia sp., have been recorded in this country (sChütt 1980, fisCheR 1994, mienis et al. 2012).Several species of Islamia have been found and described in adjacent countries such as Greece, Israel, Lebanon and Turkey (Radoman 1983, sChütt 1991, bodon et al. 2001).
The new species, having a well-developed penial lobe and a muscular pleat on the ventral side of penis, belongs to the "oriental" group of Islamia species which inhabits France, part of Italy, Croatia, Bosnia and Herzegovina, Greece, Turkey, Israel and Lebanon (bodon et al. 1995, bodon & Cianfanneli 2002, 2012).In Spain and part of Italy, Islamia species are characterised by the absence of the muscular pleat A unique character of I. mylonas, which has not been described in any other known Islamia species, is the secondary lateral loop of the renal oviduct.A similar lateral loop is found in Pseudamnicola Paulucci, 1878 (see e.g.Radoman 1983: 27, fig.10).
The new species differs from the other members of the "oriental" group in several characters of shell and soft parts, and displays some similarities to them.It differs from the type species of the genus Islamia described from Bosnia and Herzegovina, namely I. valvataeformis (Möllendorf, 1873), in the position of the seminal receptacles which arise very close to one another in the latter species (Radoman 1983: 124-125, fig.69A, B).However the two species share the same character state in their radulae since I. valvataeformis has only one pair of basal cusps on the central radular tooth (Giusti et al. 1981: 26, fig. 1.1-3).
The Greek species I. trichoniana Radoman, 1978 andI. graeca Radoman, 1973 have shells larger than those of I. mylonas and their seminal receptacles arise very close to one another as it can be deduced from Radoman (1983: 124).Additionally, the penis of I. graeca seems to have a very small penial lobe (Radoman 1983: 125,  The new species differs in its shell morphology and male genitalia from I. mienisi (Schütt, 1991) from Israel and from I. gaillardoti (Schütt, 1991) from Israel and Lebanon.The shell of I. mienisi is ovate-conical and its penis has a pointed lobe and pointed apex (sChütt 1991: 134, fig.5a-c; 135); I. gaillardoti has a larger shell than that of I. mylonas and a different general penis shape (sChütt 1991: 135-136, fig. 6b, bodon & Cianfanelli 2002: 28).
The main features discriminating between I. mylonas and the known Turkish Islamia species, namely I. bunarbasa (Schütt, 1964), I. pseudorientalica Radoman, 1973, I. anatolica Radoman, 1973, and I. burduricus Yildirim, Kaya, Gürlek et Koca, 2017, are the characters of shell and genitalia.All the Turkish species are larger compared to I. mylonas; the shell of I. bunarbasa is ovate-conical and those of I. pseudorientalica, I. anatolica and I. burduricus are trochiform (Radoman 1983: 206, Table 7, 228, figs 154-156, yildirim et al. 2017: 11-12, fig. 3A).All four species are characterised by a relatively narrow penis with a long slit between the penis proper and the penial lobe of the latter reaching or slightly exceeding the penis tip (Radoman 1983(Radoman : 125, D-F, yildirim et al. 2017: 11-12, fig. 3B, C, respectively): 11-12, fig. 3B, C, respectively).An additional character discriminating between I. mylonas and the Turkish Islamia is that the seminal receptacles, at least in the first three species, are located very close to one another as it can be inferred from Radoman (1983: 124).
I. mylonas exhibits interesting similarities with the cavernicolous I. emanuelei Girardi, 2009 from France: the latter species also has a secondary lobe at the right edge of the primary penial lobe (GiRaRdi 2009: 34-35, fig.1A) and the seminal receptacles arise at a distance from each other (GiRaRdi 2009: 35, fig.1D).However, the shell of I. emanuelei is much larger than that of the new species.
The new species shares several anatomical characters with Islamia taxa belonging either to the oriental or to the occidental group.Regrettably, the extremely small number of specimens found did not allow molecular studies of phylogenetic relationship of I. mylonas with its congeners.

Table 1 .
Shell morphometry of Islamia mylonas sp.n.Measurements are in mm.For abbreviations see Material and Methods