SYNOPSIS OF THE EGYPTIAN FRESHWATER SNAIL FAUNA

Egypt harbours many species of freshwater snails that transmit parasites causing serious diseases in humans and animals. Due to their significance, it is important to up-date the faunal list regularly. Our objective was to present such an up-date. The twenty eight species known to exist in the country are reviewed, including their synonymy, type localities, diagnostic features and parasitological importance; the shell morphology is illustrated. Besides, snail species thought to be extinct in the country are noted. This review can be used as a field guide for identification of the various species of snails colonising freshwater habitats in Egypt.


INTRODUCTION
Freshwater snails play an important role in their ecosystems and many of them have great medical and veterinary importance.Worldwide, about 350 snail species are estimated to be possible hosts of parasites which cause human and animal diseases (rozendaal 1997).The Egyptian freshwater snail fauna includes many species that transmit serious parasitic diseases such as schistosomiasis and fascioliasis.Though the fauna has been studied for a long time (friedrich 1874, leiper 1916a, sattMann & Kinzelbach 1988, ibrahiM et al. 1999), considering the new data and the taxonomic changes, it is important to up-date the information regularly.The present work was carried out with the aim to present an up-to-date review of freshwater snails of Egypt and their distribution (Fig. 1).All species known to exist in the country are covered, regardless of their medical and veterinary importance.
The taxonomy of class Gastropoda, snails and slugs, is changing rapidly and it will be some time before a classification system for higher taxa becomes generally accepted (haszprunar 1988, ponder & lindberg 1997, bouchet & rocroi 2005).The simplified, now informal system based on the respiratory organs (thiele 1931) is used here.It includes three major groups: prosobranchs (gills anterior to the heart), opisthobranchs (gills posterior and right to the heart) and pulmonates (pallial lung instead of gills).The freshwater snails found in Africa, including Egypt, are either prosobranchs or pulmonates (broWn 1994).

PROSOBRANCHS
Prosobranch snails have thick-walled shells equipped with opercula.They have pectinate gills, called branchia or ctenidia, situated within the man-tle cavity.Most prosobranchs are dioecious (broWn 1994).In the Egyptian freshwater fauna they are represented by nine families.Neritids are small to medium-sized snails, sometimes exceeding 20 mm in length, which inhabit saltwater and freshwater.They have cap-like (hemispherical) shells with few whorls and greatly expanded body whorl.The aperture is D-shaped, and the operculum is strongly calcified, with one or two internal apophyses.The family is represented in Egypt by only one species (broWn 1994): Theodoxus niloti cus (Reeve, 1856).Theodoxus anatolicus (Récluz, 1841) was reported from Fayoum (grabner et al. 2014), but the record needs to be confirmed as the species had not been reported from Africa before (broWn 1994).
1. Theodoxus niloticus (Reeve, 1856) Neritina nilotica Reeve, 1856 Type locality: Egypt, Nile Delta.Distinctive characters (Fig. 2): When fully grown, the shell is 9 × 8 mm in size.Its colour and pattern are highly variable, but commonly with purplish-brown zigzag bands.The operculum is equipped with two apophyses (gardner 1932(gardner , broWn 1994(gardner , ibrahiM et al. 1999)).Distribution (Fig. 1): The species is tolerant to some degree of salinity and is thus usually found in fresh and brackish waters.It is more common in the coastal areas of Lower Egypt (sattMann & Kinzelbach 1988, broWn 1994), but was also found in Upper Egypt and Lake Nasser (sattMann & Kinzelbach 1988, ibrahiM et al. 1999, abd el-WaKeil et al. 2013).It was also reported in Sinai (el-Kady et al. 2000(el-Kady et al. , ibrahiM et al. 2006).Besides, it was abundant in the extinct fauna of aquatic molluscs in the Fayoum Depression (gardner 1932).Parasitological importance: Unknown.

FAMILY VIVIPARIDAE GRAY, 1847
Viviparids are freshwater snails.Their dextral shells are more than 10 mm high.The whorls are generally more numerous than in the neritids.Also, the spire is higher and more conical.The operculum is entirely corneous and concentric.The animal is viviparous and the embryos develop in the lower oviduct.The right tentacle in males is modified as a copulatory organ.The radula is taenioglossate.The central tooth is wide and without basal denticles (broWn 1994).Only one species occurs in Egypt: Bellamya unicolor (Olivier, 1804).(Olivier, 1804) Cyclostoma unicolor Olivier, 1804 Vivipara unicolor (Olivier, 1804) Type locality: Egypt, Alexandria.Distinctive characters (Fig. 3): Fully grown shells are 30 × 20 mm, with the aperture usually occupying about half of the total shell height.The body whorl is slightly flattened at the periphery producing a keel.The umbilicus is either narrow or closed.Spiral rows of small bristles may occur on the shell surface (Mandahl-barth 1973a, broWn 1994).Distribution (Fig. 1): This species is widely distributed in the Nile Valley and Delta (sattMann & Kinzelbach 1988, broWn 1994, el-shazly et al. 2012, abd el-WaKeil et al. 2013).It was found in Lake Nasser (ibrahiM et al. 1999).Besides, it was recorded from Sinai (el-Kady et al. 2000(el-Kady et al. , ibrahiM et al. 2006)).Parasitological importance: Unknown.

Bellamya unicolor
FAMILY AMPULLARIIDAE GRAY, 1824(PILIDAE PRESTON, 1915) Ampullariids are medium to large snails.Fully grown shells exceed 15 mm in height.The shell is depressed to ovate, and externally may appear either dextral or sinistral.The whorls are strongly rounded, either angular or carinate.The operculum is concentric, either entirely corneous or with calcareous inner layer.In addition to the tentacles, there is a tentacle-like process (pseudopodium) on each side of the snout.Near each tentacle there is an epipodial lobe: the left lobe forms an inhalent siphon and the right one forms an exhalent siphon.The snails are oviparous.The male copulatory organ is formed by a modified part of the mantle edge.The central tooth is broad and without basal denticles.Some species live in seasonal waterbodies which dry out for long periods (broWn 1994).This family is represented in Egypt by only two species: Lanistes carinatus (Olivier, 1804) and Pila ovata (Olivier, 1804).Two other species: Lanistes varicus (O.F. Müller, 1774) and Pila wernei (Philippi, 1851) were mentioned among the snails rarely found in Egypt (ibrahiM et al. 1999) and reported from Assiut (abd el-WaKeil et al. 2013).However, none of the two was mentioned among the Egyptian freshwater snails (broWn 1994).Based on the data accumulated during our previous malacological survey in Egypt (lotfy et al. 2005), and after a comprehensive literature review we conclude that the presence of the two species in the country needs to be confirmed by further studies.(Olivier, 1804) Lanistes bolteni (Chemnitz, 1786) Lanistes boltenianus (Röding, 1798) Ampullaria carinata Oliver, 1804 Type locality: Egypt, Alexandria.Distinctive characters (Fig. 4): The shell appears sinistral and is 25 × 35 mm in size.It is depressed to ovately conic.The whorls vary from evenly curved to angular and carinate.The umbilicus may be widely open or closed.The operculum is entirely corneous.The eggs are deposited on aquatic vegetation as gelatinous clusters (broWn 1994(broWn , ibrahiM et al. 1999)).Distribution (Fig. 1): The species is widely distributed in the Nile Valley and Delta (sattMann & Kinzelbach 1988, broWn 1994, el-shazly et al. 2012, abd el-WaKeil et al. 2013).It was also found in Sinai (el-Kady et al. 2000(el-Kady et al. , ibrahiM et al. 2006)).

FAMILY VALVATIDAE GRAY, 1840
Valvatids have dextral discoid to ovate smooth shells.Their fully grown shell is less than 10 mm in height and has a large umbilicus.The aperture is circular and the operculum is multispiral.Valvatids are hermaphroditic and oviparous.They have a feather-like gill and a tentacle-like appendage on the mantle edge, on the right side.The central tooth has no basal denticles (broWn 1994).

FAMILY HYDROBIIDAE TROSCHEL, 1857
Hydrobiids have smooth colourless shells, less than 10 mm in height, and higher than wide.The operculum is ovate, entirely corneous and paucispiral.The radula has no accessory plate.This family is represented in Egypt by Hydrobia musaensis Frauenfeld, 1855 andEcrobia ventrosa (Montagu, 1803) (broWn 1994).A third species, Hydrobia aponensis Martens, 1858, was reported from Fayoum and Upper Egypt (gardner 1932, gauthier 1980).Most probably it is now extinct in the country (ibrahiM et al. 1999).Recently this species was reported from Assiut (abd el-WaKeil et al. 2013), but as mentioned before the results of this survey need to be confirmed by further studies.

Hydrobia musaensis Frauenfeld, 1855
Type locality: North Africa.Distinctive characters (Fig. 7): Compared with other species of the genus this snail has a small, relatively broad shell, consisting of six whorls.The whorls are rather flat and the sutures are shallow (broWn 1994(broWn , ibrahiM et al. 1999)).The shell length is 3 mm, while the width of the body whorl reaches 1 mm.The aperture is oval but asymmetrical, the outer lip being more rounded than the inner one (tchernov 1971).Distribution (Fig. 1): It was originally described by frauenfeld in 1855 from Suez.It inhabits fresh and brackish waters in the Nile Delta, Fayoum, Sinai (craWford 1949, tchernov 1971, van daMMe 1984, abo-Madyan et al. 2005), Quseir, and Siwa Oasis (craWford 1949, sattMann & Kinzelbach 1988).

FAMILY BITHYNIIDAE TROSCHEL, 1857
The bithyniid shell is small to medium-sized (less than 15 mm in height).It is dextral and depressed to ovately conical.The aperture is fairly large, with a continuous thickened and often dark peristome.The operculum is thick and calcareous with outer concentric area and usually a spiral nucleus.In fully grown specimens the operculum fits into the peristome.The exhalent siphon (epitaenial fold) is usually present on the right side, in connection with the ciliary feeding mechanism.The snails are oviparous.The penis is equipped with an accessory appendage and duct (hold-fast organ).Egg capsules have exit holes closed by plugs.The central radular tooth is usually provided with basal denticles (broWn 1994).According to broWn (1994), there is no species of Bithynia known to occur in Egypt, and the family is represented by only one species, Gabbiella senaarien sis (Küster, 1852) (broWn 1994).However, there are some reports of the genus Bithynia from Egypt (gardner 1932, tohaMy & MohaMed 2006, abd el-WaKeil et al. 2013).Such reports need to be confirmed by more detailed taxonomic studies.(Küster, 1852) Paludina senaariensis Küster, 1852 Type locality: Sudan, Senaar.Distinctive characters (Fig. 9): The shell is 8.5 × 5.5 mm in size.The spire is distinctly higher than the aperture, and is often decollate.In the fully grown shell the total of four whorls are completed at about 5 mm height (broWn 1994(broWn , ibrahiM et al. 1999)).Distribution (Fig. 1): The species was reported from the Nile Valley and Delta (sattMann & Kinzelbach

FAMILY THIARIDAE TROSCHEL, 1857
The thiarid shell is small to large, dextral, ovately to narrowly conical.The fully grown shell is more than 10 mm in height.It is commonly thick-walled and strongly sculptured.The basal margin of aperture is entire.The operculum is entirely corneous, and is either paucispiral or concentric with spiral nucleus.The mantle edge is either with or without papillae.The snails are commonly ovoviviparous; species of some genera are parthenogenic.The offspring develops in a brood pouch.The males lack penis, except in Tiphobia, and are rare or unknown for some species.Thiarids inhabit fresh and brackish waters (broWn 1994).Results of molecular studies have shown the family to be polyphyletic (lydeard et al. 2002).9. Cleopatra bulimoides (Olivier, 1804) Cyclostoma bulimoides Olivier, 1804 Cleopatra cyclostomoides (Küster, 1852) Type locality: Egypt, Alexandria.Distinctive characters (Fig. 10): It is a very variable, polytypic species including many named forms whose conspecificity needs to be tested by further evidence, especially genetic.The typical form measures 16 × 9 mm, while the slender form measures 22 × 9 mm.The typical form has lower whorls, evenly curved and smooth, carinations are confined to the apical whorls; usually with one or more dark brown bands (broWn 1994).Distribution (Fig. 1): The species was reported from the Nile Valley and Delta, Lake Nasser, Fayoum, and Sinai (schutt 1986, sattMann & Kinzelbach 1988, broWn 1994, ibrahiM et al. 1999, el-Kady et al. 2000, ibrahiM et al. 2006, abd el-WaKeil et al. 2013).Parasitological importance: It is the first intermediate host of the digenean Prohemistomum vivax which parasitises the Egyptian kite (abdel-aziM 1933) and may infect humans (nasr 1941(nasr , Witenberg 1964)).It also transmits the paramphistome Gastrodiscus ae gyptiacus -an intestinal parasite of African equines (MaleK 1971, fahMy et al. 1977).In addition, the snail was found to be naturally infected with larvae of P. cantonensis in Egypt (el-shazly et al. 2002a, ibrahiM 2007).Remarks: Some Egyptian authors still treat C. bu limoides and C. cyclostomoides as distinct species (ibrahiM et al. 2006, ibrahiM 2007).According to broWn (1994) they are synonyms.

Melania tuberculata O. F. Müller, 1774
Type locality: India, Coromandel Coast.Distinctive characters (Fig. 11): The shell measures 27 × 9 mm (complete shell with 11 whorls).However, some morphs are smaller (less than 20 mm high) or larger (nearly 50 mm high).The shell is narrowly conical, and the whorls are regularly increasing, moderately convex, with ribs and spiral ridges forming a highly varied sculpture, though commonly tuberculate.The shell colour is often pale with reddish-brown patches aligned with the ribs (making flame-like markings), sometimes uniformly brownish.The central tooth has 7-12 cusps (broWn 1994).Conchological variations could be due partly to parthenogenic propagation of clones, as some populations are predominantly or perhaps entirely females.

FAMILY MELANOPSIDAE H. ADAMS ET A. ADAMS, 1854
Melanopsids are medium to large snails with fully grown shells more than 10 mm in height.The shell is ovately or more narrowly conical, smooth or strongly sculptured.The operculum is paucispiral with basal nucleus.The mantle edge is smooth.Both sexes are present.The snails are oviparous (Morrison 1954, houbricK 1988, broWn 1994).(1980).There is no direct evidence of genetic differences between these different shell morphs and they all seem to belong to a single, circum-Mediterranean superspecies (glaubrecht 1992, 1993).Distribution (Fig. 1): The snail inhabits various waterbodies; it can tolerate high temperature, desiccation and high content of dissolved chemicals (dupouy 1979(dupouy , dupouy et al. 1980(dupouy , Meier-brooK et al. 1987)).In Egypt, it was found only in Sinai (tchernov 1971).Parasitological importance: Unknown.

FAMILY POTAMIDIDAE H. ADAMS ET A. ADAMS, 1854
Potamidids are medium to large snails with fully grown shells more than 10 mm in height.The shell is dextral, narrowly conical, and sculptured.A notch is present at the basal margin of the aperture.The operculum is multispiral.The family is restricted to brackish waters, usually at the coast (broWn 1994).Early studies suggested that the family was polyphyl-

PULMONATES
They are non-operculate snails with thin-walled shells.They lack gills, and the mantle cavity serves as an air-breathing organ (broWn 1994).

FAMILY PHYSIDAE FITZINGER, 1833
Physids are medium-sized sinistral snails with sharply pointed spire and smooth whorls.The tentacles are long and slender.The foot is pointed.The pseudobranch is absent.The mantle is expanded to varying extent, and its margin ranges from smooth to scalloped and digitate.The physid shells are like those of some species of Bulinus, but distinguishable by the generally more pointed spire, shallower suture and smoother surface.In addition, they could be distinguished from Bulinus by the expanded mantle fringe, simple penis, oblique rows of radular teeth, and the lack of both pseudobranch and blood haemoglobin.Their eggs are deposited in soft elongate masses unlike the capsules of Bulinus which are flatter, firm and circular in outline (broWn 1994).The classification of the family at any level is far from stability (te 1980(te , taylor 1988(te , broWn 1994)).13.Haitia acuta (Draparnaud, 1805) Physa acuta Draparnaud, 1805 Physella acuta (Draparnaud, 1805) Physa heterostropha (Say, 1817) Physa subopaca (Lamarck, 1822) Type locality: France, River Garonne.Distinctive characters (Fig. 14): The shell measures 15 × 9 mm, and resembles that of Bulinus trun catus (ibrahiM et al. 1999).For quick identification it could be distinguished from B. truncatus by the following characters: the shell is stronger, more conical and pointed at the spire, whorls without shoulder angle, twisted columella; the body whorl has no umbilicus, and upon crushing a living H. acuta a bluish blood oozes out, instead of the reddish coloured blood that comes out of B. truncatus (broWn 1994).Distribution (Fig. 1

FAMILY LYMNAEIDAE RAFINESQUE, 1815
Lymnaeids are small to large snails with dextral shells and pointed spires which vary widely in height.Their tentacles are flat and triangular.They lack both pseudobranch and blood haemoglobin.The two genital orifices are situated on the right side.The eggs are deposited in elongated gelatinous capsules.hubendicK (1951) considered many genera as synonyms of Lymnaea, but it seems justifiable to retain some of these groups, at least as subgenera (broWn 1994  Distinctive characters (Fig. 15): The species is the smallest African lymnaeid (up to 11 × 6 mm), characterised by a spire equal in height to the aperture.The shell consists of 5-6 convex whorls.The columellar margin is straighter and more broadly reflected than in Radix natalensis (broWn 1994(broWn , ibrahiM et al. 1999)).Distribution (Fig. 1): The snail inhabits small streams, seepages and temporary pools of rainwater (broWn 1994) (bargues et al. 2012).Egyptian populations of this snail were found to be naturally infected with Fasciola sp.(el-shazly et al. 2002b, 2012).Successful experimental infections with F. hepatica and F. gigantica were obtained under laboratory conditions (dar et al. 2003a, b, 2004).The snail also serves as an intermediate host of Paramphistomum daubneyi in some African countries (dinniK 1962).However, this paramphistome was not reported to be present in Egypt (sey 1977).Type locality: North America (probably near Philadelphia).Distinctive characters (Fig. 18): The shell (up to 17 × 9 mm) is narrower than that of L. natalensis, and is easily distinguished from it by the close-set spiral lines, which result in a reticulated pattern.The shell consists of 6-8 whorls, with large, expanded body whorl.Aperture large, ovate, usually equal to half of the shell height.Umbilicus usually covered.Shell colour variable, the initial whorls usually darker.Distribution (Fig. 1): This American species is now well-established in Africa.It was reported from the Nile Valley and Delta, Fayoum, and Sinai (nagaty et al. 1959, ahMed & raMzy 1999, el-Kady et al. 2000, el-shazly et al. 2012, abd el-WaKeil et al. 2013, grabner et al. 2014).Parasitological importance: This species is a major host of F. hepatica in North America and the Caribbeans (torgerson & claxton 1999, gutierrez et al. 2011).It also serves as a host for Fascioloides magna (Krull 1933), andTelorchis spp. (echaubard et al. 2010).In Egypt, it was found to be naturally infected with F. gigantica (nagaty et al. 1959, ahMed & raMzy 1999, grabner et al. 2014)  Distinctive characters (Fig. 19): Placement of this species in the genus Radix was confirmed by correa et al. ( 2010).It is a relatively large lymnaeid (up to 23 × 15 mm).The shell shape varies widely.The spire is much shorter than the aperture, and consisting of 4-4.4 whorls.The surface often bears spiral rows of short transverse grooves, and lacks the spiral ridges which characterise Pseudosuccinea columella (broWn 1994(broWn , ibrahiM et al. 1999)).Distribution (Fig. 1): This species is most frequent in permanent streams and impoundments such as small dams (hubendicK 1951(hubendicK , broWn 1994)).It was reported from the Nile Valley and Delta, Lake Nasser, and Wadi El-Natroun (sattMann & Kinzelbach 1988, el-shazly et al. 2002b, 2012, abd el-WaKeil et al. 2013).Also, it was found in Al-Salam Irrigation Canal, North Sinai (ibrahiM et al. 2006).Parasitological importance: The snail is a major intermediate host for F. gigantica in Egypt (broWn 1994(broWn , lotfy et al. 2001)).Experimental infection of R. natalensis with F. hepatica was successful.Thus, R. natalensis can be considered a potential intermediate host of F. hepatica in Egypt (lotfy et al. 2001, dar et al. 2010).In addition, this species was found to be naturally infected with the larvae of P. cantonen sis in Egypt (el-shazly et al. 2002a, ibrahiM 2007).In addition, experimental infection with the parasite was possible, and the first stage larvae reached the infective third stage in the snail (yousif & laMMler 1975).

FAMILY PLANORBIDAE RAFINESQUE, 1815
Planorbids are small to medium-sized snails with long slender tentacles and reddish blood containing haemaglobin.The pseudobranch is present.The shell and anatomy are diverse, especially the male copulatory organ and prostate gland (broWn 1994).

SUBFAMILY PLANORBINAE RAFINESQUE, 1815
Members of this subfamily usually have pseudodextral discoid or lenticular shell.The shell appears dextral, because it is carried inverted so that the side corresponding to the apical side in other snails is the lower side of the planorbine shell.Also, it is considered by some authors as dextral shell but with sinistral animal.The pseudobranch has the form of a simple lobe.One or more prostatic tubules open either directly into the sperm duct or into a separate prostatic duct.The structure of the copulatory organ varies, though it has no 'ultrapenis' of the Bulininae (broWn 1994).Eight species of planorbines have been confirmed to be present in Egypt: Africanogyrus coretus (de Blainville, 1826), Biomphalaria alexand rina (Ehrenberg, 1831), Biomphalaria glabrata (Say, 1818), Gyraulus costulatus (Krauss, 1848), Gyraulus ehrenbergi (Beck, 1837), Planorbella duryi (Wetherby, 1879), Planorbis planorbis (Linnaeus, 1758) and Segmentorbis angustus (Jickeli, 1874).ibrahiM et al. (1999) treated Afrogyrus coretus (de Blainville, 1826) and Afrogyrus oasiensis (Demian, 1962) as distinct species, but broWn (1994) synonymised the two names.Biomphalaria pfeifferi (Krauss, 1848) was reported from Fayoum (gardner 1932(gardner , ibrahiM et al. 1999(gardner , abo-Madyan et al. 2005)), and some sites in Lower Egypt (ibrahiM et al. 1999).However, the snail was not found during our previous malacological survey in Egypt (lotfy et al. 2005).In addition, it was not mentioned by broWn (1994) to be present in Egypt.Its occurrence in the country needs to be confirmed by a taxonomical study.Segmentorbis eus soensis (Preston, 1912) was reported once to occur in Egypt (Mandahl-barth 1973b), but further studies are needed to confirm that it is not synonymous with Segmentorbis angustus (broWn 1994).

Africanogyrus coretus (de Blainville, 1826)
Planorbis coretus de Blainville 1826 Afrogyrus coretus (de Blainville, 1826) Anisus oasiensis Demian, 1962 Afrogyrus oasiensis (Demian, 1962) Type locality: Senegal, Podor.Distinctive characters (Fig. 20): The shell is very small, brownish yellow, discoid, flat on both sides; when fully grown it is 0.7 × 2.1-2.5 mm, with 4-5 slowly increasing whorls.The aperture is small, slightly broader than high and not modified by any conspicuous carina.The peristome is simple and very thin.The sculpture consists of fine, close-set, curved growth lines.The umbilicus diameter equals about half of the total shell diameter.The penis has a subterminal orifice and a cup-like stylet (broWn 1994(broWn , ibrahiM et al. 1999)).Distribution (Fig. 1  Distinctive characters (Fig. 21): The shell measures 4.8 × 14.2 mm.It is thin to rather thick and sometimes fragile; it has about 5 spirally coiled whorls.It is umbilicated on the left side and has a more depressed spire with a deep suture on the right side.The sculpture includes slightly curved regular growth lines.The aperture is suboval, distinctly wider than high.The inner lip is closely applied to the columella.The umbilicus is open and wide.The prostatic duct and preputial gland are absent (broWn 1994(broWn , ibrahiM et al. 1999)).Distribution (Fig. 1): Originally, this snail was restricted to the Nile Delta.Starting from the late 1970s, this snail was found at increasing distances upstream as far as Lake Nasser at Aswan and Abu Simbel

Planorbis glabratus Say, 1818
Type locality: South America.Distinctive characters (Fig. 22): The shell (5-8 × 20-27 mm) is widely umbilicate and larger than that of B. alexandrina.The number of whorls increases more rapidly in B. alexandrina than in B. glabra ta.Unlike B. alexandrina, B. glabrata has a renal ridge which is not observed in any African Biomphalaria species (broWn 1994(broWn , ibrahiM et al. 1999)).Distribution (Fig. 1): In the early 1980s, B. glabra ta was reported to be introduced into the Egyptian freshwater habitats in the Nile Delta (pfluger 1982, yousif et al. 1996, 1998a, b, Kristensen et al. 1999, caMpbell et al. 2000).Parasitological importance: This species is the major intermediate host for S. mansoni in the Neotropics (pointier et al. 2005).Experimentally, B. glabrata was found to be susceptible to the Egyptian strains of S. mansoni but showed lower susceptibility than B. alexandrina.Unfortunately, the duration of cercarial shedding was longer and the numbers of cercariae shed per snail were higher in B. glabrata than in B. alexandrina (yousif et al. 1998b).The snail was reported to be infected with the larvae of P. cantonensis under natural conditions (el-shazly et al. 2002a).Also, experimental infection with the parasite was successful, and the first stage larvae reached the infective third stage in the snail (yousif & laMMler 1975).The NIH strain of B. glabrata could easily be infected with the Egyptian strain of Echinostoma liei in the laboratory (jeyarasasingaM et al. 1972).The presence of snails naturally infected with this echinostome needs to be confirmed.(Beck, 1837) Planorbis ehrenbergi Beck, 1837

Gyraulus costulatus
Type locality: South Africa, Natal, Umgeni River.Distinctive characters (Fig. 24): The shell measures 1.5 × 6.6 mm.The typical form is depressed, with rapidly increasing whorls and strong, regularly-spaced ribs.The periphery bears a carina with a periosotracal fringe.The shape of the whorls varies widely (broWn 1994).
Distribution (Fig. 1): The species is widespread in the tropical region of Africa.In Egypt, it was reported in the Nile Valley in Assiut and a few localities further south.It was found also in Lake Nasser (sattMann & Kinzelbach 1988).Parasitological importance: Unknown.(Wetherby, 1879) Planorbis duryi Wetherby, 1879 Helisoma duryi (Wetherby, 1879) Type locality: North America.Distinctive characters (Fig. 25): During the earlier fieldwork, it was noticed that some Egyptian field workers misidentified P. duryi as B. glabrata (lotfy et al. 2005).There were similar reports of misidentification of P. duryi as Biomphalaria in other parts of the world.The typical form of P. duryi can be distinguished from Biomphalaria spp.by the presence of prostatic duct and preputial gland, higher shell (7 × 18 mm), more regular whorls, flat surface within the umbilicus, and deeply concave upper side (van bruggen 1974, appleton 1977, ibrahiM et al. 1999).& roushdy 1980& roushdy , roushdy & el-eMaM 1981)).In the early 1990s, the snail was reported to be present further north into the Nile Delta (yousif et al. 1993).The distribution of P. duryi was reported to be further extended as it was found in Kafr El-Sheikh (North-Central Delta), Ismailia (Eastern Delta), Aswan (lotfy et al. 2005), andLake Nasser (ibrahiM et al. 1999).Nowadays, the species is widely distributed in the Nile Valley and Delta.Also, it was found in Al-Salam Irrigation Canal, North Sinai (ibrahiM et al. 2006).(Jickeli, 1874) Segmentina angustus Jickeli, 1874 Type locality: Ethiopia, Hamasen Province, Toquor River at Mekerka (west of Asmara).Distinctive characters (Fig. 27): The shell is lenticular, with convex upper side and flat underside; its size is 2 × 5.5 mm.When fully grown it is about 3 times broader than high, with usually no more than 3 sets of internal septa (broWn 1994).Distribution (Fig. 1): Egypt is not a typical area for this species, and its major distribution is further south in Africa (broWn 1994).It was recorded from Lower and Upper Nile in Egypt.It was found also in Lake Nasser, Lake Qarun, the edge of Lake Maryut, and west of Alexandria, but it is rare in these sites (van daMMe 1984, sattMann & Kinzelbach 1988, ibrahiM et al. 1999).Parasitological importance: Unknown.

SUBFAMILY BULININAE FISCHER ET CROSSE, 1880
Bulinines have small to medium-sized sinistral shells, reaching 25 mm in height or diameter.The shell is either spired (Bulinus) or discoid (Indoplanorbis).The pseudobranch is large, deeply folded, and highly vascularised.The penis does not project freely into the penis sheath, but is a long and coiled eversible tube called "ultra-penis", attached at both upper and lower ends of the sheath.Numerous prostatic tubules are concentrated into a compact organ.Only two genera are known; Bulinus found mainly in Africa and Indoplanorbis in Asia.However, Indoplanorbis was reported, probably introduced, in Africa (broWn 1994).
Only two species: Bulinus forskalii (Ehrenberg, 1831  (broWn et al. 1986(broWn et al. , jelnes 1986)).Bulinus natalensis was not mentioned among the Egyptian freshwater snails (broWn 1994).The species is distributed mainly in eastern Africa from Ethiopia to the coastal region of Natal (broWn 1994).Based on the data accumulated during our previous malacological survey in Egypt (lotfy et al. 2005), and after a comprehensive literature review we concluded that the presence of B. natalensis in the country needed to be confirmed by more studies.Distinctive characters (Fig. 28): The shell measures 17 × 5.4 mm (smaller in many localities).The spire is high and slender in fully grown specimens.The whorls are shouldered to some degree and sometimes carinate.Strong ribs are commonly present and may bear fringes of periostracum.The copulatory organ with penis sheath is almost equal in length to the preputium (broWn 1994).Distribution (Fig. 1): The snail is essentially Afrotropical, reaching the Mediterranean only in Lower Egypt (van daMMe 1984).It was reported from the Nile Valley and Delta, Lake Nasser, Fayoum, and Kharga Oases (sattMann & Kinzelbach 1988, ibrahiM et al. 1999, abo-Madyan et al. 2005).Parasitological importance: Despite some inconclusive reports, there is no confirmed locality for transmission of S. haematobium by B. forskalii worldwide (broWn 1994).However, the snail can serve as an intermediate host for other schistosomes, like Schistosoma bovis (Kinoti 1964) and P. togolense (albaret et al. 1978).In Egypt, the parasites transmitted by this snail need to be confirmed.(Audouin, 1827) Physa truncata Audouin, 1827 Physa alexandrina Bourguignat, 1876 Type locality: Egypt.Distinctive characters (Fig. 29): The shell measures 9.5 × 6 mm (slender form), 9.5 × 7.5 (broad form), and sometimes is almost 20 mm high (broWn 1994).The type specimen is small (only 5 mm high), with a depressed spire (Bouchet & Danrigal 1982).This species is characterised by a combination of characters which is not easy to define: the uneven curvature of the whorls tends to produce a blunt shoulder, the columellar margin is usually narrow and more or less twisted, and the shell colour is pale.The spire height, shape of columellar margin and umbilicus size vary widely.The spire is shorter than the aperture and the apex ranges from obtuse to rather elevated.The umbilicus varies from small to rather big.The aperture varies from elongate ovate to ovoid and almost round (broWn 1994(broWn , ibrahiM et al. 1999)).Distribution (Fig. 1): The species is widely distributed in the Nile Valley and Delta, and Lake Nasser (sattMann & Kinzelbach 1988, ibrahiM et al. 1999, abd el-WaKeil et al. 2013).It was also found in Sinai (el-Kady et al. 2000(el-Kady et al. , ibrahiM et al. 2006)).Parasitological importance: It serves as the intermediate host of S. haematobium (leiper 1915).It was reported to serve as an intermediate host of F. hepatica in Tunisia (haMed et al. 2009(haMed et al. , 2014)).This species is the main intermediate host of the paramphistome Calicophoron microbothrium in North Africa including Egypt (dinniK 1965Egypt (dinniK , rysavy et al. 1974)).This parasite is the most widely reported species causing harm to domestic livestock in Africa (eduardo 1983).Bulinus truncatus was found to be naturally infected with larvae of P. cantonensis in Egypt (el-shazly et al. 2002a).Experimental infection with this nematode was successful, and the first stage larvae reached the infective third stage in the snail (yousif & laMMler 1975).

CONCLUDING REMARKS
This review covers a total of 28 snail species currently present in freshwater habitats of Egypt.These species include two which were introduced during the last few decades.The presence of other snail species in the country is questionable and needs to be confirmed by detailed taxonomic studies.The Egyptian freshwater snail fauna and its geographical distribution are changing over time, some snails are now extinct in the country, and therefore it is crucial to update the available information regarding the surviving species and their biogeography.

Fig. 9 .
Fig. 9. Gabbiella senaariensis 11. Melanopsis praemorsa(Linnaeus, 1758)    Buccinum praemorsum Linnaeus, 1758 Type locality: South Europe.Distinctive characters (Fig.12): The shell measures 20 × 11 mm.It is ovate, with a short spire, and a large elongated body whorl.The outer lip of the aperture is thin, but the inner lip has a smooth parietal callus, thickened into a pad over the parietal wall.It is either smooth or with strong spiral ridges or ribs.Four species of Melanopsis were distinguished in Northwest Africa based on shell characters by chevallier (1969), and two by dupouy et al.

Fig. 20 .
Fig. 20.Africanogyrus coretus (sattMann & Kinzelbach 1988, vrijenhoeK &  graven 1992, lotfy et al. 2005).The changes in the hydrology of the Nile Valley and Delta, the controlled water flow, and the new irrigation networks following construction of the Low and High Dams at Aswan, in 1902 and 1968, respectively, have resulted in providing the snail with an increasing number of appropriate habitats (el-gindy 1957, vrijenhoeK & graven 1992).Nowadays, the species is widely distributed in the Nile Valley and Delta.Also, it was found in Lake Nasser, Wadi El-Natroun (sattMann & Kinzelbach 1988), and Sinai (el-Kady et al. 2000, ibrahiM et al. 2006).Parasitological importance: This species serves as the intermediate host of Schistosoma mansoni in Egypt (leiper 1916b, el-gindy 1957, lotfy 2009, abouel-naga 2013).Biomphalaria alexandrina was reported to be naturally infected with F. gigantica (farag & el sayad 1995) and Fasciola sp.(el-shazly et  al. 2002b).However, the snail was not susceptible to infection with F. gigantica under experimental conditions(MohaMed et al. 1998).Also, it was found to be naturally infected with Echinostoma liei(jeyarasasingaM et al. 1972).The species was found to be naturally infected with larvae of P. cantonensis in Egypt(el-shazly et al. 2002a, ibrahiM 2007).Besides, experimental infection with the parasite was successful, and the first stage larvae reached the infective third stage in the snail(yousif & laMMler  1975).

Fig. 22 .
Fig. 22. Biomphalaria glabrata (Fig. 1): The species was introduced into Egypt (pfluger & roushdy 1980).It was studied in field trials as a competitor of intermediate hosts of schistosomes in Egypt (frandsen & Madsen 1979).It was first recorded in Egypt in 1980 and 1981, a few kilometres north of Cairo (pfluger Parasitological importance: Experimental infection of Planorbella sp. with P. cantonensis was successful, and the first stage larvae reached the infective third stage in the snail (yousif & laMMler 1975).