The genus Bostryx in central western Argentina : anatomical and distributional description of four of its southernmost species ( Gastropoda , Bulimulidae )

The genus Bostryx Troschel, 1847 is endemic to South America, extending from Ecuador to Chile and Argentina. The southernmost Argentinian species of the genus that inhabit San Luis, San Juan and Mendoza provinces, specially the pre-Andes, Andes and Sierras Pampeanas mountain ranges, were examined. This is the first time the anatomy of Bostryx pastorei (Holmberg, 1912), Bostryx reedi (Parodiz, 1947) and Bostryx strobeli (Parodiz, 1956) has been described. Bostryx cordillerae (Strobel, 1874) is re-described regarding shell and anatomy due to new morphological data. The main differences among the species examined are based on shell characters. The distribution of Bostryx mendozanus (Strobel, 1874) and Bostryx cuyanus (Pfeiffer, 1867), other species found in this region, was also discussed.

The genus Bostryx Troschel, 1847 is endemic to South America, extending from Ecuador to Chile, along the Pacific coastal desert and the western Andean slopes.In contrast, in Argentina, Paraguay and Bolivia, it is mainly found east of the Andes mountain range.The Cordillera de los Andes runs along the Pacific coast of South America from Venezuela to Argentina, and it shows a relative decrease in height from North to South.The Andes have a direct mechanical influence on the climatology of South America due to that induced precipitations along the eastern flanks of the Andes and blocking western currents from the Pacific (Insel et al., 2009).This contrast determines a continuous and arid vegetation belt (around 30°S) that crosses diagonally from SE to NW, separating the region of the Chilean-Argentinian southern forests from other forests in South America, the so called Arid Diagonal of South America (Villagran & Hinojosa, 1997;Abrahan de Vazquez et al., 2000).In Argentina, Bostryx is the genus of Bulimulidae with most species (Cuezzo et al., 2013).Of the 19 species found in the country, 17 are endemic whereas Bostryx stelzneri (Dohrn, 1875) is distributed throughout Bolivia and Bostryx torallyi (d'Orbigny, 1835) throughout Bolivia, Paraguay and Peru (Quintana, 1982;Ramírez et al., 2003).All Argentinian species of the genus have originally been described based on shell characters and only a few descriptions include jaw and radula.Anatomical information is known only for 9 species (Hylton Scott, 1954;Breure, 1978;Miranda & Cuezzo, 2014;Miranda, 2015).
The provinces of Mendoza, San Juan and San Luis are located in the central west of Argentina and cover an area of approximately 315.226 km 2 , between 28°22'-33°17'S and 66°20'-70°36'W.This region has arid climatic conditions with low relative humidity and limited water availability.Between 29°S and 33°S latitude, the Andean Cordillera of San Juan and Mendoza provinces is characterized by parallel mountain ranges with North-South direction: The Cordillera Principal (spanning Argentina and Chile), the Cordillera Frontal, the Argentinian Precordillera and the Sierras Pampeanas (from west to east) (Siame et al., 2006).The Precordillera extends for about 450 km in the West of Argentina (28°-33°S), from La Rioja to south of the Mendoza river; peaks can reach altitudes between 3,000 m-4,900 m (Roig-Juñent et al., 2003).The southern part of the Precordillera comprises the Sierra de Tontal, Sierra de Villavicencio and Sierra de Uspallata (Furque & Cuerda, 1979).The eastern slopes are more humid because they receive winds from the Atlantic Ocean that provide water and even form banks of fog.The western slopes are drier because they receive dry winds that may even reduce the little water available in the environment (Roig-Juñent et al., 2003).The Uspallata-Calingasta valley is a small area located between the Andean Cordillera (5,000-6,000 m) and the Precordillera, from northern San Iheringia, Série Zoologia, Porto Alegre, 105(4):484-498, 31 de dezembro de 2015 Juan to north of Mendoza province, with very scarce vegetation (Roig-Juñent et al., 2001).According to the classification proposed by Olson & Dinerstein (1998) and Olson et al. (2001), this region is characterized by the presence of seven dry ecoregions (Southern Andean Steppe, Central Andean Puna, High and Low Monte, Dry Chaco, Patagonian Steppe and Espinal).In this region the genus Bostryx has a notably high richness, and is represented by 9 of its 19 Argentinian species (Miquel, 1993(Miquel, , 1995;;Cuezzo et al., 2013).
The objectives of the present study are to provide information on the anatomy of four species from central west in Argentina and review the taxonomic status and distribution area of all species of this genus in this region.This is the first time Bostryx pastorei (Holmberg, 1912), B. reedi (Parodiz, 1947) and B. strobeli (Parodiz, 1956) have been described based on anatomical systems and B. cordillerae (Strobel, 1874) is newly described incorporating data from new characters.

MATERIAL AND METHODS
The specimens examined come from Argentinian malacological collections: Instituto Fundación Miguel Lillo (IFML-Moll, Tucumán), Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" (MACN-In, Buenos Aires), Museo de La Plata (MLP, La Plata) and Museo de Ciencias Naturales "José Lorca" (Mendoza, MCNL).Shell measurements (mm), such as total shell height (tsh), body whorl height (bwh), spire height (sh), major diameter of the shell (masd), minor diameter (misd), shell apertural height (ah), shell apertural diameter (ad), parietal space length (psl), penultimate whorl height (pwh) and major diameter (pwd), were obtained using a calliper (Figs 1, 2).Measurements of the perimeter and area of the shell and parts of the shell (Figs 3-5) were obtained from digital images of specimens in standardised apertural view (axis of coiling and aperture parallel to the camera lens).The images were used to construct Tps files with TpsUtil version 1.58 (Rohlf, 2013a) software.Shell outline drawings of all species were carried out with TpsDig2 version 2.17 (Rohlf, 2013b) directly on the shell photograph with the Draw Curves tool, using a line of dots around the outline.This outline allows computation of the enclosed area (cm²) and the perimeter (cm) of the outline.Anatomical systems were dissected out from alcohol-fixed specimens.Anatomical description is given in full for Bostryx reedi while only the main differences are presented for the remaining species.
Pallial system.Kidney triangular, 1/3 of pulmonary roof length.Primary ureter bordering kidney along its length and secondary ureter opening at distal portion of pulmonary roof.Ureteric interramus rectangular in shape.Rectum opening at mantle collar.Main pulmonary vein well marked, parallel to rectum.
Reproductive system.Albumen gland bean-shaped (Fig. 12).Hermaphroditic duct divided into thin proximal and distal portions and convoluted seminal vesicle (Fig. 12).Fertilization pouch-spermathecal complex finger-shaped.Bursa copulatrix sac rounded and duct long reaching middle portion of albumen gland (Fig. 12), inner wall with longitudinal zigzag folds.Vagina cylindrical, 1/3 of penis length (Fig. 12), inner wall with thick longitudinal straight folds.Penial retractor muscle inserting terminally in flagellum.Flagellum shorter than epiphallus, inner wall with diagonal folds and central longitudinal fold (Fig. 14).Epiphallus same length as penis, progressively increasing its width towards penis.Proximal epiphallus internal wall sculpture with parallel straight folds, zigzag folds in the distal portion (Fig. 14).Penis with thinner section, which divides it into swollen proximal and cylindrical distal portion (Fig. 13).Proximal portion penis inner wall with relaxed longitudinal zigzag folds, very thin, followed by smooth area and penial gland triangular (Fig. 14).Distal portion with inner relaxed longitudinal zigzag folds (Fig. 14).Penial sheath with retractor muscle on upper end overlapping distal portion of penis.Vas deferens inserting at basal penial sheath.
Remarks.According to labels included in lot MACN 9592-1, Bostryx reedi was identified by Doello Jurado as a new species, under the provisional name of Bulimulus sanzini.However, Parodiz (1947) described and published this new species under the name of Peronaeus (Lissoacme) reedi.Later Breure (1979) classified it under Bostryx, which was maintained by Miquel (1993) and Cuezzo et al. (2013) subsequently.

Bostryx pastorei
Distribution.Endemic to San Luis province (32°-34°S, 65°-66°W), this species is the southernmost of the genus in Argentina (in Cerro Varela, Low Monte ecorregion).It is distributed between the Andean Cordillera (west) and the Sierras of San Luis (east), an orographic subsystem belonging to the Sierras Pampeanas, that belongs to the Arid Diagonal of South America.It covers the Dry Chaco, Espinal and Low Monte ecoregions (Fig. 2).Pallial system.Secondary ureter opening at proximal portion of pulmonary roof.
Tab. I. Shell measurements (ad, shell apertural diameter; ah, shell apertural height; bwh, body whorl height; masd, major diameter of the shell; misd, minor diameter; psl, parietal space length; pwd, penultimate whorl major diameter; pwh, penultimate whorl height; sh, spire height; tsh, shell height).(2013) and on basis of the observation of type material of both species, has been reformulated in the present study.

Measurement
Bostryx pastorei shows high variability in shell coloration, body whorl area, aperture shape and spire height.Specimens isolated from Cerro Varela and Quebrada between Quines and Libertador General San Martín, shared shell characters such as the presence of darker shell bands and a more slender configuration of the shell and aperture.In contrast, specimens from Cerro del Morro and Cerro Sololasta were uniformly colored and had a higher spire and a more voluminous body whorl.
Pallial system.Secondary ureter opening at distal portion of pulmonary roof.
Remarks.Bostryx strobeli was described for the first time by Parodiz (1956) as Bulimulus (Scansicochlea) Pilsbry, presenting a protoconch with fine spiral striation.Breure (1979) synonymized Scansicochlea with Bostryx thereby relocating this species as B. strobeli in Bostryx.Miquel (1995)  (2012) indicated that B. strobeli could be classified as Naesiotus Albers.However, according to the sculpture of the protoconch observed, typical of the genus Bostryx, and several anatomical characters such as a penis with cup shape and internally with triangular penial gland and a portion with sculpture (consisting in folds) and other without sculpture, and an epiphallus with variable diameter and two different sculptures in the inner wall, the present study concludes that of B. strobeli must be maintained in Bostryx as proposed by Cuezzo et al. (2013).
Miquel (1995) synonymized B. strobeli and Bulimulus (Scansicochlea) lolae Hylton Scott, 1967 because their shell characters were very similar.B. strobeli does differ from B. lolae by smaller dimensions of the total height and diameter of the shell, higher and more acute spire and by the fact that the teleoconch sculpture has only axial costules, whereas axial costules in B. lolae are intersected by spiral lines in the teleoconch in some specimens.However, B. lolae exhibit big intraspecific variations in their measurements and sculpture of the shells, due to that these differences are considered intraspecific variations, whereby B. strobeli and B. lolae are considered the same species.
Bostryx strobeli and B. pastorei have a similar distribution in San Luis province, but B. strobeli differs from B. pastorei in having a shell that is more elongateovate with a lower spire and a yellowish brown coloration.
Pallial system.Secondary ureter opening at half pulmonary roof length.
Bostryx cordillerae shows variability in spire height and body whorl area.Specimens from Villavicencio and Casa de Piedra (Mendoza province) are more slender and present a higher spire than specimens from Sierra de Tontal (San Juan province).According to Strobel (1874), B. cordillerae is usually found in crevices of schistose rocks like B. mendozanus and B. cuyanus, but B. cordillerae clearly differs from both species.It has smaller shell dimensions, a more slender shell configuration and a higher spire than B. mendozanus.Bostryx cuyanus is the only Argentinian species of the genus with a discoidal shell, and hence the species cannot be confused.

DISCUSSION
Morphological examinations of shell and anatomical features were carried out to assess morphological differentiation among several Bostryx species distributed in the central west of Argentina.Differences among the examined species are mainly observed in shell size and shape, coloration and spire hight.In all species examined the sculpture of the protoconch corresponded to the pattern previously described for other Argentinian species of the genus.The teleoconch sculpture was similar among the species and consisted of shallow ribs.In the pallial system the position of secondary ureter opening was the only character varying between species.The differences observed in the reproductive system were few and related with length and inner wall sculpture of the organs.Comparison with other species of the genus Bostryx present in Argentina (Miranda & Cuezzo, 2014;Miranda, 2015) allowed to establish a typical pattern in the genital system of Bostryx, penis with cup shape, inner penial gland present, inner wall of penis with folds and a portion without sculpture; epiphallus without uniform diameter and two different sculptures in the inner wall.It is remarkable that in contrast to most land snails, Argentinian Bostryx species have a homogeneous character of the reproductive system, which differs from related-genera (Bulimulus Leach and Naesiotus Albers).The opposite occurs with shell characters, which vary among the species, but are similar to those of related genera.The detection of this typical pattern of the reproductive system allows maintains to B. strobeli in the genus Bostryx, unlike proposed by Breure (2012).A cladistic analysis based on morphological characters (in preparation) will provide support to this classification.
Species of the genera Bostryx, Bulimulus, Naesiotus (Bulimulidae), Epiphragmophora Doering (Epiphragmophoridae), Spixia Pilsbry & Vanatta and Plagiodontes Doering (Odontostomidae) can be found in San Luis province (Cuezzo, 2006;Pizá & Cazzaniga, 2010, 2012;Cuezzo et al., 2013).However, in San Juan and Mendoza provinces, the land snail diversity is low in comparison with other regions such as the Northwest Argentina and Orthalicoidea is almost exclusively represented by the genus Bostryx (Parodiz, 1961;Miquel, 1993Miquel, , 1995;;Cuezzo et al., 2013).The low diversity recorded could be related to environmental conditions of the area, such as low precipitation, high solar radiation and evapotranspiration, little vegetation cover and immature soils with continuous cryoturbation processes, which determine the environment of the Andean desert (Roig & Martínez-Carretero, 1998;Dalmasso et al., 1999).Genera such as Bostryx are distributed in desert ecosystems and they are adapted to survive under harsh climatic conditions (Ramírez & Ramírez, 2013).The species are mainly observed in the Precordillera and the Uspallata-Calingasta valley.
In adittion to the species examined in the present study, species like Bostryx stelzneri (San Juan province), Bostryx mendozanus (Strobel) (Mendoza province) and Bostryx cuyanus (Pfeiffer) (San Juan and Mendoza provinces) have also been recorded.Unfortunately, live specimens of B. mendozanus were not found in the distribution area and malacological collections also did not provide anatomical information about this species.The shell descriptions were provided by Miquel (1993Miquel ( , 1995) ) and the anatomical description of B. cuyanus and B. stelzneri was performed by Hylton-Scott (1954) and Miranda & Cuezzo (2014), respectively.Bostryx mendozanus has a restricted distribution area in the Precordillera of Mendoza (between 1,500-1,800 m, Southern Andean Steppe and High Monte ecoregions of Sierra de Uspallata and Villavicencio).Bostryx cuyanus is restricted to high altitude environments in two isolated areas.One of these areas is the Precordillera (between 2,000-3,400 m, Southern Andean Steppe and High Monte) and the other one is the Principal Cordillera (3,151 m,Southern Andean Steppe).The Principal cordillera consists of great rugged mountains with steep detrituscovered slopes and deep valleys.Between 3,000-4,000 m, it has a Tundra climate while above 4,000 m the climate becomes Polar.Vegetation is typical of steppe, grassland and meadows (Méndez et al., 2006).Although since the valley that separates the precordillera of the Cordillera has a width almost 50 km and only in some places it reaches 100 km, the lack of similarity or relationships between their flora and fauna that has been demonstrated for diverses taxa (Roig & Martínez-Carretero, 1998;Roig-Juñent et al., 2003;Ochoa, 2004).However, Bostryx cuyanus is the only species of the genus present in both mountain ranges.
The criteria most frequently cited for establishing conservation priorities are species richness, endemism and presence of rare species (Benkendorff & Davis, 2002).The central west area of the country meets all three requirements: it includes 42% of the total richness of the genus in the country, with five endemic species and a restricted distribution area.Moreover, gastropods pay a high price for their occupancy of dry and cold terrestrial environments, which is reflected, for instance, in slow growth rates and high stochastic mortality (Dallinger et al., 2001).For these reasons, this Precordillera, should be considered an area with high priority of conservation.