Tchangmargarya multilabiata, Zhang & Chen & Yang & Jin & Köhler, 2015

Zhang, Le-Jia, Chen, Shi-Chao, Yang, Li-Te, Jin, Lei & Köhler, Frank, 2015, Systematic revision of the freshwater snail Margarya Nevill, 1877 (Mollusca: Viviparidae) endemic to the ancient lakes of Yunnan, China, with description of new taxa, Zoological Journal of the Linnean Society 174 (4), pp. 760-800 : 785-787

TCHANGMARGARYA MULTILABIATA ZHANG & CHEN SP. NOV.

( FIGS 22 , 23 )

Etymology: Derived from ‘multi’ (Latin for many) and ‘labium’ (Latin for lip), in reference to the many layers of the inner lip.

Material examined

Holotype: Male (H = 48.46 mm, D = 35.77 mm, LA = 25.52 mm, DA = 19.47 mm) from Changhu Lake, Shilin County, Yunnan Province, China, 24°42′ N, 103°24′ E, 2012.7., coll. Lejia Zhang ( IZCAS FG 594250) . Paratypes: Ninety-eight specimens ( CH 1–50, CH 60– 98, two ethanol-preserved specimens, the rest dry shells, eight individulas preserved in IZCAS, FG 594251– 594258 ), Lake Changhu, coll. Lejia Zhang , 2012.7., 2014.2.; 30 specimens (YH 1–30, dry shells), Lake Yuehu , coll. Lejia Zhang , 2014.2.; 15 specimens ( GTZ 1–15 , dry shells), Lake Guangtangzi , coll. Lejia Zhang , 2014.2.; 50 specimens (dry shells), Lake Guangtangzi , coll. Ye Liu , 2013.9.; 19 specimens (dry shells), Lake Changhu , coll. Ye Liu , 2013.9.; ten specimens (dry shells), Lake Yuehu , coll. Ye Liu , 2013.9.

Juvenile shell (taken from): CH 2 (2 individuals).

Short diagnosis

Shell conical to subglobose, always with four strong spiral keels and many axial ribs, forming welldeveloped nodules where keels and axial ribs meet; two strong incomplete spiral keels with elevat- ed nodules in umbilical area, semilunar callus-like structure covering umbilicus completely; nacreous layer thick but semitransparent, showing the wide purple band on calcareous layers of some individuals, the others bluish white in colour; operculum smaller than apercure, with very large opercular scar; radula with one long tongue-like central denticle on each central tooth.

Description

Shell large, conical to subglobose, up to nearly 70 mm in height ( Table 3), very thick, solid, and heavy; dark brown or red–brown periostracum, occasionally with one broad purple spiral band on calcareous layers of each whorl; mostly with seven whorls, including two protoconch whorls, all inflated, each with welldeveloped ramp-like shoulder on upper section, except for the protoconch; whorls mostly with four, rarely five, strong spiral keels and with many axial ribs, forming well-developed nodules where keels and axial ribs meet, nodules small and dense on upper whorls, gradually increasing in size, becoming more sparse on lower whorls, lower keel always covered by suture and thus nearly invisible on spiral whorls; two strong incomplete spiral ribs with elevated nodules extending onto umbilical area. Aperture ovate, nacreous layer thick but semi-transparent, with broad purple band on calcareous layers of some individuals (some individuals have almost all calcareous layers purple), or bluish white from T. yangtsunghaiensis by having a relatively shorter and thicker shell, one additional keel above the suture, overlapping multilayers of inner lip, and tongue-like shape of the central cusps of the centre and lateral teeth differing from the squarish shape in T. yangtsunghaiensis . The feature of such callus-like structure is unique in Viviparidae . Besides, T. multilabiata is the only species with a broad spiral band on calcareous layers amongst the three genera endemic to Yunnan, although only one-third of all specimens have such a band.

in colour, inner lip covered with thick nacreous layers, multiple layers visible on top of each other, from different growing periods, all outward-folding and tightly overlapping, forming semilunar callus-like structure completely covering umbilicus.

Mature juvenile shell large, with four whorls; grass green, brown, purple, or yellow with brown band in colour; first two whorls with two smooth spiral keels, no ramp-like shoulder; third and fourth whorl with obvious ramp-like shoulder, four keels, and many axial ribs crossing into dense regular nodules, lower keel almost covered by upper sutures, and thus nearly invisible on the third whorl; keels under the suture obtuse but with well-developed axial ribs; aperture ovate, inner lip outward folding, about half of shell height.

Operculum corneous, ovate, rather thick and solid, reddish brown or brown, with subcentral nucleus and concentric growth lines; nucleus with few grains or veins; opercular scar very large, relatively rough, outside smooth, obviously thickened but margin of operculum thin; operculum slightly smaller than aperture.

Radula (N = 1) oblong, with 107 rows of teeth. Central tooth bell-shaped, with large, long, tongue-like central denticle, flanked by four or five smaller cusps on either side. Lateral tooth broadly oblong, with one long, tonguelike central denticle and three or four smaller cusps on either side. Marginal tooth slender, slightly oblong; inner marginal tooth with large, blade-like central denticle and two or three long smaller cusps on either side; outer marginal tooth obtuse, with 10–12 small cusps.

Comparative remarks

Differs from all Margarya species , especially nodular specimens of M. oxytropoides ( Fig. 15D ), as following the comparative remarks in Tchangmargarya . It differs Habitat and distribution

Four freshly dead specimens with soft bodies were found in aquatic plants on the bank of the type locality. Found in some nearby lakes in Shilin County (Shilin Lakes), i.e. Lake Changhu, Guangtangzi, Yuehu.

Figures

Figure 15. Shells of Margarya oxytropoides: A, Lake Dianchi, DCXHJ 2, 65.9 mm; B, Lake Dianchi, DCXHJ 44, 53.1 mm; C, Lake Dianchi, DCXHJ 3, 54.1 mm; D, Lake Dianchi, DCHK 41, 62.1 mm; E, Lake Lugu (provided by Liu Ye); F, Lake Dianchi, FG68944, 41.0 mm; G, original figure of Paludina oxytropoides (Heude, 1889); H, juvenile shell, 14.2 mm.

Figure 22. Shells of Tchangmargarya multilabiata sp. nov. from Lake Changhu: A, holotype, male individual, FG594250; B, paratype, male individual, CH 1, 59.2 mm; C, paratype, female individual, CH 2, 52.8 mm; D, paratype, CH 7, 52.4 mm; E, paratype, CH 35, 50.77 mm; F, paratype, five keels variety with totally purple calcareous layers, CHX 1, 53.3 mm; G, inner lip; H, juvenile shell with band, 15.4 mm (provided by Hao Yang).

Figure 23. Scanning electron micrographs of the radula of Tchangmargarya multilabiata sp. nov. from Lake Changhu: A, central tooth; B, lateral tooth; C, inner marginal tooth; D, outer marginal tooth.