Margarya melanioides, NEVILL, 1877

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 : 769-775

MARGARYA MELANIOIDES NEVILL, 1877

( FIGS 10 , 11 )

Margarya melanioides Nevill, 1877: 30 (‘Lake Tali’ = Lake Erhai, Dali City, Yunnan Province, China); Nevill in Anderson, 1878: 891; Nevill, 1881: 155, pl. 5, fig. 1; Dautzenberg & Fischer, 1905: 421–422; Kobelt, 1909: 188–190, pl. 37, figs 1, 2, 7–9; Annandale, 1924: 54–66, fig. 4D–F; Prashad, 1928: 170, figs 25– 29; Yen, 1939: 41, pl. 2, fig. 60; Yen, 1943: 128; Tchang & Tsi, 1949: 741–744, pl. 1, figs 1–6; Liu et al., 1979; Xia, 1982: 340–341, fig. 9; Pan, 1984: 116–117, pl. 1, figs 1–6; Zhang, 1986b: 152–154, pl. 4, fig. left; Zhang, 1993: pl. 2, fig. 11; Liu et al., 1995: 14; Zhang et al., 1995: 178–179; Zhang et al., 1997: 17; Liu & Wu, 2005: 299–300; Wang, 2005; Shu et al., 2010: 19–21, fig. 2; Du et al., 2013: fig. 2A–B; He, 2013: 4–5.

Paludina margeriana Anderson, 1878 : pl. 80, fig. 5 (unjustified emendation of original name in the accompanying plate).

Vivipara (Tulotoma) margeriana – Neumayr, 1883: 24–25 (‘Talifu’ = Dali City).

Vivipara (Tulotoma) margeriana var. tuberculata – Neumayr, 1887: 649, pl. 3, fig. 2a, b (‘Talifu’ = Dali City).

Vivipara (Tulotoma) margeriana var. carinata – Neumayr, 1887: pl. 3, fig. 3a, b (‘Talifu’ = Dali City).

Margarya melanioides var. carinata – Dautzenberg & Fischer, 1905: 422.

Margarya melanioides carinata – Yen, 1943: 128.

Margarya carinata – Xia, 1982: 341; Zhang et al., 1995: 178–179; Zhang et al., 1997: 18; Liu & Wu, 2005: 299–300.

Vivipara delavayi Mabille, 1886: 66 , pl. 2, fig. 1a, 1b3 (‘Lac Tali’ = Lake Erhai).

Margarya melanioides var. delavayi – Dautzenberg & Fischer, 1905: 422.

Margarya melanioides (type A) – Zhang, 1986a: 65–69, pl. 1, fig. 1.

Taxonomic remarks

Nevill (1877) described M. melanioides based on a dried shell collected from Lake Erhai, but without illustrating the type specimen. Anderson (1878) cited Nevill’s description and illustrated the type specimen ( Fig. 10A ) under the incorrect name ‘ Paludina margeriana ’. Using this incorrect name, Neumayr (1887) introduced two varieties of ‘ Vivipara margeriana ’, i.e. the variety tuberculata for specimens with large spines ( Fig. 10D ) and the variety carinata for specimens with prominent spiral keels but without any spines ( Fig. 10J ). The variety name tuberculata has consistently been treated as a synonym of M. melanioides (e.g. Dautzenberg & Fischer, 1905; Yen, 1943), and this is upheld herein. By contrast, the variety name carinata has by some authors been considered a valid species ( Xia, 1982; Zhang et al., 1995, 1997; Liu & Wu, 2005); however, Tchang & Tsi (1949) regarded it as a synonym of M. melanioides . We agree with Tchang & Tsi (1949) because the number of spines varies greatly in M. melanioides and no other differences between ‘ carinata ’ specimens and typical specimens of M. melanioides were found. The name Vivipara delavayi ( Fig. 10G ) was introduced for specimens with a second prominent keel on the body whorl and few spines. It has consistently been considered as a junior synonym of M. melanioides ( Tchang & Tsi, 1949; Shu et al., 2010). This treatment is also confirmed here.

Being the type species of Margarya , M. melanioides was considered as the only species of Margarya by many earlier researchers, whereas all the other taxa were initially introduced as varieties or subspecies (e.g. Dautzenberg & Fischer, 1905; Yen, 1943). In fact some workers considered M. melanioides to be a highly polymorphic species, delineating several unnamed varieties (A–D; Zhang, 1986a; Shu et al., 2010; Du et al., 2012; He, 2013); however, comparative morphology and molecular phylogenetics support the existence of several species within this complex. In particular characters of juvenile shell suggest that the unnamed types B, C, and D belong to other species than M. melanioides ; only type A is a genuine M. melanioides .

Material examined

Museum material. Lake Cibi (coll. Yueying Liu, 1965.4.7, ethanol-preserved material), IZCAS FG164272–164285 .

Newly collected material. Adult shell: Lake Erhai : Caicun Village , 25°43′15.3″ N, 101°31′28.8″ E, 1 m deep, 2012.2. ( EHCC 16–48 ; 32 dried shells); Lake Jianhu , 26°28′52.8″ N, 99°55′29.8″ E, 8 m deep, 2012.8. ( JH 7– 13 , 2 females and 4 males, living specimens); Lake Xihu , 26°0′48.6″ N, 100°2′33.7″ E, on the bank, 2012.2. ( XH 1 , 1 dried shell); Kunming City : Guandu Town , buried in earth, 2011.8. ( KMGD 1–3 , 3 subfossils); Lake Dianchi: Chenggong, 24°51′32.2″ N, 102°46′58.9″ E, 4 m deep, 2012.2.7. ( DCWLB 2–20 , 19 living specimens); Lake

Values given are averages (minimum–maximum) of height (H) and width (W) of shell for N measured specimens.

Dianchi, Xihuajie, 24°52′42.2″ N, 102°39′46.3″ E, on the bank, 2011.8. ( DCXHJ 8 , 9 ; 2 dried shells); Lake Dianchi , Baiyukou, 24°48′34.1″ N, 102°39′23.4″ E, on the bank, 2012.2. ( DCBYK 3 , 8–10 , 19 ; 5 dried shells); Lake Dianchi, Guanyinshan, 24°50′34.5″ N, 102°39′51.6″ E, on the bank, 2012.2. ( DCGYS 2 , 3 , 10 , 17 ; 4 dried shells). Juvenile shell (taken from): JH 7 (5 individuals); JH 8 (3 individuals); DCGYS 2 (3 individuals); DCWLB 2–6 (each 3–6 individuals). These specimens were collect- ed by Lejia Zhang and Lite Yang .

Short diagnosis

Shell conical, always with three spiral keels, third one always at suture; spiral keels on early four whorls (viz. mature juvenile shell) supporting sparse spiral rows of nodules; second keel particularly well developed compared with other keels, supporting spines or wavelike protuberances (less common) at lower teleconch and body whorls; between three and five rather weak spiral ribs decorated around the umbilicus.

Description

Shell large, conical, up to 100 mm in height ( Table 3); thick, solid, greenish brown or brown; mostly with seven whorls, including two protoconch whorls, each with welldeveloped ramp-like shoulder on upper section, except for protoconch whorls; whorls mostly with three, rarely four, strong spiral keels, first keels on shoulder of whorls reduced, bearing spiral row of small, regular nodules on early whorls and obtuse, large nodules on last two whorls; second keel at periphery of whorls most strongly developed, with regular prominent nodules on early whorls and spines or large, irregular nodules or wavelike protuberances on last two whorls; third keel always covered by upper suture, thus becoming almost invisible on sprial whorls; between three and five weakly developed spiral ribs extending onto umbilical area. Aperture ovate, usually less than shell height, with spine on middle of outer lip and angle on upper part, inner surface whitish blue, sometimes purple. Umbilicus covered by inner lip.

Mature juvenile shell large, with four whorls, moderately transparent, light green or brown in colour, first two whorls with two smooth spiral keels; no ramplike shoulder; third and fourth whorl with ramp-like shoulder and three spiral keels with regularly arranged nodules, lower keel almost covered by upper suture on the third whorl; two or three obtuse keels in umbilical area; aperture ovate, nearly half of shell height.

Operculum corneous, ovate, rather thin, reddish to yellowish brown, with subcentral nucleus and concentric growth lines; nucleus large, with grains or veins; opercular scar large, relatively rough, outside smooth, thickened; operculum almost as large as aperture.

Radula (N = 3) oblong, with about 108–117 rows of teeth. Central teeth bell-shaped, with large, broad, securiform central denticle, flanked by five or six smaller cusps on either side. Lateral teeth broadly oblong, with one large, square central denticle and four or five smaller cusps on either side. Marginal teeth slender, slightly oblong; inner marginal teeth with large, oblong central denticle and three or four smaller cusps on either side; outer marginal teeth obtuse, with 10–13 small cusps.

Comparative remarks

Distinguished from other Margarya species , especially M. monodi , by having a juvenile shell with three spiral keels with large, sparse nodula, and second prominent keel with spines or protuberances on lower teleoconch and body whorls.

Habitat and distribution

Lives on muddy to sandy substrates without aquatic plants, at depths of 3–8 m in Lakes Dianchi (mostly in northern and eastern areas), Erhai, Xihu, Jianhu, and Cibi, as well as the Haixihai Reservoir. Adapts to feed on dry Chlorella powder and mostly lives more than 6 months in the laboratory.

Figures

Figure 10. Shells of Margarya melanioides: A, original figure of M. melanioides (Anderson, 1878); B, Lake Cibi, FG164279, 66.2 mm; C, living individuals in the market of Dali City, harvested from Lake Erhai (photo taken by Ye Liu, 2011.6.); D, original figure of variety tuberculata (Neumayr, 1887); E, Lake Dianchi, DCGYS 2, 63.2 mm; F, Lake Jianhu, JH 7, 94.7 mm; G, original figure of variety delavayi (Mabille, 1886); H, variety with four keels, Lake Dianchi, DCXHJ 8, 52.9 mm; I, Lake Erhai, EHCC10, 55.4 mm; J, original figure of variety carinata (Neumayr, 1887).

Figure 11. Scanning electron micrographs of the radula of Margarya melanioides, Lake Jianhu: A, central tooth; B, lateral tooth; C, inner marginal tooth; D, outer marginal tooth.