Freshwater gastropods diversity hotspots: three new species from the Uruguay River (South America)

Chilina nicolasi sp. nov.

Urn:lsid:zoobank.org:act:A7D18E3D-1CA1-470F-A5B6-3EB070C994C3 (Figs. 2A, 2B, 3 and 4A–4E).

Type locality and type material: Uruguay River, Alba Posse, Misiones Province, Argentina, (27°33′S; 54°40′W), coll. D.E. Gutiérrez Gregoric, V. Núñez & R.E. Vogler, 23 March 2010.

Holotype: MLP-Ma 13412-2 (foot in alcohol, body in R-H, shell dry); paratypes: MLP-Ma 13412 same data (4 specimens: foot in alcohol, body in R-H, shell dry); MLP-Ma 14134 same data (10 specimens: body in R-H, shell dry).

Etymology: Dedicated to the first son, Nicolás, of the first author of this paper.

Diagnosis: Shell thick, oval, two columellar teeth (upper underdeveloped); radula with first lateral tooth with saw-like external side of mesocone; penis sheath twice the length of the prepuce; penis sheath inner sculpture with triangular regular pustules.

Description:

Shell (Figs. 2A and 2B). Thick, oval, periostracum light brown with weak dark reddish zigzag bands. Spire immersed. Last whorl well developed. Aperture 90% of LWL, slightly expanded, with white callus of terminal portion slightly widened and flattened. Width 73% of LWL. Aperture projected 35% of TW. Two columellar teeth, lower tooth more prominent and developed than upper. Dimensions: see Table 1.

Reproductive System (Fig. 3). (i) Female reproductive system. Bursa copulatrix duct long (n = 2; 7.0 mm, 7.3 mm), five times bursa sac diameter. Bursa copulatrix sac spherical, located on left side of cephalopedal haemocoel between pericardial cavity and columellar base. Secondary bursa copulatrix short, emerging from base of uterus, cylindrical (c. 8% the length of bursa copulatrix duct). Vagina cylindrical, longer than wide, folded over free oviduct and entering female atrium. (ii) Male reproductive system. Prostate gland extending to lower half of uterus and consisting of variable size and with cylindrical acini. Vas deferens coiled twice, overlapping vagina. At level of penis complex, vas deferens bent back on itself. Penis sheath muscular, twice the length of the prepuce, with slight convexity on right side. Penis sheath inner sculpture with triangular pustules over entire surface. Penis elongated (as long as the penis sheath), robust, with outer surface crossed by transverse lamellae, triangular in cross section. Prepuce cylindrical, thin, with constriction marked by oblique lines arranged in a V making connection with penis sheath.

Radula (Figs. 4A–4E). Average number of rows 55 (n = 3; range 52–59). Number of teeth per half row of 40–41 (n = 3). Central tooth asymmetrical, bicuspid, elongated base higher than wide, left cusp more developed. Both cusps with slight sawlike edges. Presence of marked longitudinal groove between cusps. First and second lateral teeth tricuspid or tetracuspid, with mesocone (in tricuspid, Fig. 4A) or second inner cusp (in tetracuspid, Fig. 4B) more developed and with outermost edge saw-like. Outermost teeth with thin base and five to seven cusps similarly developed. Radular formula: 40–1–40 and 41–1–41.

Nervous system (Fig. 3C; Table 2). All connectives between ganglia relatively thin compared to size of both ganglia and central nervous system. Left connective joining the cerebral ganglion with the pleural ganglion longer than the right one (10.1 vs 9.0% of LWL). Right pleuroparietal connective passes over the penis complex. Left pleuroparietal connective shorter than right (3.8 vs 9.2% of LWL). Parietal-subesophageal connective shorter than parietal-visceral connective (15.1 vs 23.3% of LWL). One very short connective (5.7% of LWL) linking subesophageal ganglion to visceral ganglion and closing posterior nerve ring. Pleurovisceral connectives with partial detorsion characteristic of the genus.

Distribution (Fig. 5). Only known from the type locality.

DNA barcoding: The data from the analysis of the COI of 655 bp from a paratype (MLP-Ma 14134, specimen 185) was deposited in GenBank under the number KT830419.

Remarks: Of the Chilinidae species for which characters of the radula have been described so far, C. nicolasi is the only one with the first and second lateral tooth of the outer edge of the mesocone (tricuspid) or second inner cusp (tetracuspid) serrated. The radulae of C. gallardoi and C. nicolasi have a similar number of rows and teeth per row, but the outermost lateral teeth in C. nicolasi can have up to seven cusps, while those of C. gallardoi have only five (Table 3). The radula of C. iguazuensis has more rows (57–65 vs 52–59) and teeth per half-row (43–63 vs 40–41) than C. nicolasi (Gutiérrez Gregoric & Rumi, 2008). Only three species, C. fluminea, C. rushii and C. lilloi, have seven cusps on the outermost lateral teeth, but the number of rows is lower (49, 48, and 44 respectively); and in C. fluminea and C. lilloi the central tooth is tricuspid (Lanzer, 1997; Gutiérrez Gregoric, 2008; Ovando & Gutiérrez Gregoric, 2012). The shells of C. gallardoi and C. nicolasi have two columellar teeth in the aperture, but in C. gallardoi both teeth are strong (as occurs in C. fluminea and C. rushii). The AL/LWL ratio in C. gallardoi is lower than in C. nicolasi (78 vs 89%: Gutiérrez Gregoric, 2010) while in C. iguazuensis it is greater (100%; Gutiérrez Gregoric & Rumi, 2008). In addition, C. gallardoi has a keel (or sub-keel) along the whorls (as does C. rushii), a character absent in C. nicolasi (and all other species).

Chilina santiagoi sp. nov.

LSID urn:lsid:zoobank.org:act:4238E0F8-4452-4818-A1F2-7C1A5D8FFC4E (Figs. 2C, 2D, 4F–4H and 6).

Type locality and type material: Horacio Foerster Falls, Misiones Province, Argentina (27°08′S; 53°55′W), coll. D. E. Gutiérrez Gregoric, V. Núñez & R.E. Vogler, 24 March 2010.

Holotype: MLP-Ma 14135 (body in R-H, shell dry); paratypes: MLP-Ma 13417 same data (five specimens in alcohol); MLP-Ma 14136 same data (six specimens: body in R-H, shell dry).

Other material examined: MLP-Ma 14137 Horacio Foerster Falls, Misiones Province, Argentina (27°08′S; 53°55′W), coll. C. Galliari, May 2009 (four dry shells); MLP-Ma 14138 Moconá Falls, Misiones Province, Argentina (27°08′S; 53°53′W), coll. C. Galliari, May 2009 (12 specimens: alcohol); MLP-Ma 14139 Moconá Falls, Misiones Province, Argentina (27°08′S; 53°53′W), coll. A. Rumi, S.M. Martín & I. César, October 20, 2011 (10 specimens: body in R-H, shell dry); MLP-Ma 14140 Yerba Falls, Paraíso Stream, El Soberbio, Misiones Province, Argentina (27°14′S; 54°02′W), no collector and date (two specimens: alcohol).

Etymology: Dedicated to the second son, Santiago, of the first author of this paper.

Diagnosis: Shell small, thin, aperture projection 50% of TW; radula with asymmetrical bicuspid central tooth; penis sheath inner sculpture with regular conical pustules and longitudinal folds.

Description:

Shell (Figs. 2C and 2D). Small, thin, oval, of 3¼ whorls. Spire low and conical. Last whorl large (97% of the TL). Width 80% of LWL. Aperture expanded, 94.5% of LWL, with strong white callus. One columellar tooth. Aperture projection 50% of TW. Light brown periostracum with strong thin longitudinal reddish bands. Dimensions: see Table 1.

Reproductive System (Fig. 6). (i) Female reproductive system. Bursa copulatrix duct (average 4.5 mm; range 4.1–5.3; n = 4) nine times bursa sac diameter. Bursa copulatrix sac oval. Secondary bursa copulatrix long (c. 18% the length of bursa copulatrix duct), comprising of a long duct and expanded at the distal end. (ii) Male reproductive system. Muscular penis sheath, nearly twice as long as prepuce. Penis sheath inner sculpture with pustules of conical aspect and longitudinal folds. Penis slightly longer than penis sheath, robust, with outer surface cut by transverse lamellae, triangular in cross-section. Prepuce inner sculpture with numerous smooth, very tight longitudinal folds.

Radula (Figs. 4F–4H). Average number of rows 44 (n = 3; range 43–44). Number of teeth per half row 32–33 (n = 3). Central tooth asymmetrical, bicuspid, elongated base higher than wide, right cusp more developed and serrated, with weak longitudinal groove between the two cusps. First lateral tooth tricuspid with mesocone more developed, base of tooth same width as apical part (cusp area). Second lateral tooth tricuspid (mainly) or tetracuspid, with mesocone (of the tricuspid) or the outermost second cusp (in the tetracuspid) more developed, base of tooth narrower than apical part of tooth. Outermost teeth with thin base, having five similarly developed cusps. Radular formula: 32–1–32 and 33–1–33.

Nervous system (Fig. 6; Table 2). Left connective joining the cerebral ganglion with the pleural ganglion slightly longer than the right one (12.2 vs 11.2% of LWL). Left pleuroparietal connective shorter than right one (4.5 vs 12.8% of LWL). Long connective (19.3% of LWL) linking left parietal ganglion to subesophageal ganglion, located above posterior half of columellar muscle. Long connective (20.1% of LWL) linking right parietal ganglion to visceral ganglion. One very short connective (3.5% of LWL) linking subesophageal ganglion to visceral ganglion and closing posterior nerve ring.

Distribution (Fig. 5). Horacio Foerster Falls is in the Yabotí Biosphere Reserve. It is a small waterfall on the Oveja Negra Stream, which flows into the Uruguay River. Water quality parameters of the Horacio Foerster Falls measured 24 March 2010, were: water temperature 23.2 °C; pH 7.62; dissolved oxygen 6.3 mg/l; conductivity 0.015 ms. Moconá Falls is in the Moconá Provincial Park, which is also in the Yabotí Biosphere Reserve. This waterfall is peculiar in the sense that it spills along a ridge parallel to the river course. Its height varies with the level of the river and it is the second largest waterfall in Misiones Province after the Iguazú Falls.

DNA barcoding: The data from the analysis of the COI of 655 bp and Cyt b of 388 bp from a paratype (MLP-Ma 14136, specimen 6) were deposited in GenBank under the numbers KT820416 and KT820424 respectively.

Remarks: The spire is not preserved in all specimens. This loss occurs in several species of Chilinidae, especially in those that inhabit fast-running water such as C. iguazuensis (Gutiérrez Gregoric & Rumi, 2008). Chilina megastoma, which inhabits waterfall environments, differs from C. santiagoi mainly in size reaching a maximum last whorl length of 9.6 mm, whereas that of C. megastoma is up to 17.3 mm (Gutiérrez Gregoric, 2008). Chilina megastoma has a striated shell, which C. santiagoi does not, and two columellar teeth, while there is one in C. santiagoi. Both species have thin shells. In C. megastoma there is a slight swelling not forming a true ganglion between the left pleural and the subesophageal ganglia (Ituarte, 1997; Gutiérrez Gregoric, 2010), but this was not detected in C. santiagoi. Compared with C. nicolasi, the shell of C. santiagoi is thinner, has a conical and low spire (inmersed in C. nicolasi), strong rather than weak bands, higher AL/LWL, AP/TW and TW/LWL ratios (94.5 vs 90%, 50 vs 34%, 80 vs 73%, respectively), and has one columellar tooth whereas there are two in C. nicolasi. Chilina santiagoi differs from C. nicolasi in the length of the secondary bursa copulatrix (18% of bursa copulatrix duct length vs 8%), and internal sculpture of the penis sheath (conical and longitudinal pustules vs triangular pustules). Regarding the radula, C. santiagoi has fewer rows of teeth (average 44 vs 55 in C. nicolasi) and fewer teeth per half row (average 32 vs 40); the developed cusp of the central tooth (in both the tooth is bicuspid) is the right cusp (left in C. nicolasi) and the cusp has only one serrated edge (both in C. nicolasi), and the outermost lateral teeth have five cusps (up to seven in C. nicolasi).

Chilina luciae sp. nov.

LSID urn:lsid:zoobank.org:act:FE46F318-BA47-4D5B-8AD2-266C63EB87A4 (Figs. 2E, 2F, 4I–4K and 7).

Type locality and type material: Pesiguero stream, Misiones Province, Argentina (27°58′S; 55°26′W), coll. D. E. Gutiérrez Gregoric, March 21, 2010.

Holotype: MLP-Ma 14141 (alcohol); Paratypes: MLP-Ma 13413 same data (5 specimens: foot in alcohol, body R-H, shell dry); MLP-Ma 14142 same data (4 specimens: alcohol).

Etymology: Dedicated to the daughter, Lucía, of the first author of this paper.

Diagnosis: Shell thick, aperture projection 33% of TW; radula, central tooth bicuspid and with saw-like external side, first lateral tetracuspid; prepuce 37% of length of penis sheath; penis sheath inner sculpture with two regions, one with polygonal pustules and the other with longitudinal zigzag folds.

Description:

Shell (Figs. 2E and 2F). Thick, slightly elongated. Spire eroded. Width 74% of LWL. Aperture somewhat expanded, of 83% of LWL, with strong white callus. Two strong columellar teeth. Aperture projection 33% of TW. Light reddish periostracum with some dark brown spots. Dimensions: see Table 1.

Reproductive System (Fig. 7). (i) Female reproductive system. Bursa copulatrix duct (average 4.7 mm; range 4.5–4.8; n = 3) four times bursa sac diameter. Bursa copulatrix sac spherical. Secondary bursa copulatrix short (c. 11% of the length of bursa copulatrix duct), cylindrical, expanded at its distal portion. (ii) Male reproductive system. Muscular penis sheath, a little more than twice the length of prepuce (2.1 vs 0.8 mm). Penis sheath inner sculpture with polygonal pustules and longitudinal zigzag folds. Penis 92% the length of penis sheath, robust, with outer surface crossed by transverse lamellae, triangular in cross section. Inner sculpture of prepuce with numerous smooth, very tight longitudinal folds.

Radula (Figs. 4I–4K). Number of rows 50 (n = 2). Number of teeth per half row 40–41 (n = 2). Central tooth asymmetrical, bicuspid, elongated base higher than wide, both cusps with serrated edges. First lateral tooth tetracuspid with innermost second cusp more developed, base of tooth same width as apical part (cusp area). Second lateral tooth tetracuspid, with innermost second cusp more developed, base of tooth narrower than apical part of tooth. Outermost teeth with thin base, having five similarly developed cusps. Radular formula: 40–1–40 and 41–1–41.

Nervous System (Fig. 7; Table 2). Left connective joining the cerebral ganglion with the pleural ganglion longer than the right one (10.3 vs 8.8% of LWL). Left pleuroparietal connective smaller than the right one (5.9 vs 17.7% of LWL). Long connective (22.1% of LWL) linking left parietal ganglion to subesophageal ganglion, located above posterior half of columellar muscle. Long connective (16.2% of LWL) linking right parietal ganglion to visceral ganglion. One very short connective (3.5% of LWL) linking subesophageal ganglion to visceral ganglion and closing posterior nerve ring.

Distribution (Fig. 5). Only known from the type locality. Pesiguero Stream drains into the Uruguay River and is in the Concepción de la Sierra District of Misiones Province. The Uruguay River is 10 km from the collection site.

DNA barcoding: The data from the analysis of the COI of 655 bp and Cyt b of 388 bp from a paratype (MLP-Ma 14142, specimen 186) were deposited in GenBank under the numbers KT820420 and KT820425 respectively.

Remarks: Chilina luciae, like C. gallardoi and C. rushii, was recorded in the rapids of a stream that flows into the Uruguay River. Chilina luciae differs from both those species by not having a shell keel. Chilina luciae has two strong columellar teeth as in C. gallardoi, C. fluminea and C. rushii; while C. nicolasi also has two columellar teeth, but weak ones. The AL/LWL ratio in C. luciae is lower than in C. nicolasi and C. santiagoi (83 vs 90 and 95% respectively), but higher than in C. gallardoi (78%) (Gutiérrez Gregoric, 2010). The AP/TW and TW/LWL ratios in C. luciae and C. nicolasi are similar (33 vs 35% and 74 vs 73%, respectively) and all lower than in C. santiagoi (50 and 80% respectively). Chilina luciae differs from C. nicolasi and C. santiagoi in the length of the secondary bursa copulatrix (11% of bursa copulatrix duct length vs 8 and 18% respectively), and internal sculpture of the penis sheath (polygonal and zigzag longitudinal pustules vs triangular pustules and conical and longitudinal pustules, respectively. The radula of C. luciae has similarities and differences with other species, but in no case is equal to any of them (Table 3; Gutiérrez Gregoric, 2010; Ovando & Gutiérrez Gregoric, 2012; Gutiérrez Gregoric, Ciocco & Rumi, 2014). The first lateral tooth of C. luciae is tetracuspid like in C. fluminea (Gutiérrez Gregoric, 2010).