Margarya francheti, (MABILLE, 1886)

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 : 775-777

MARGARYA FRANCHETI ( MABILLE, 1886)

( FIGS 13 , 14 )

Vivipara francheti Mabille, 1886: 68–70 , pl. 2, fig. 2, 2. (‘Lac Tali’ = Lake Erhai).

Margarya melanioides var. francheti – Dautzenberg & Fischer, 1905: 424–425.

Margarya melanioides Annandale, 1924: 64–66 , fig. 4B (partim).

Margarya melanioides francheti – Yen, 1939: 41, pl. 2, fig. 61; Yen, 1943:1 28. Margarya francheti – Tchang & Tsi, 1949: 749–750, pl. 1, figs 9–12; Zhang, 1993: pl. 2, fig. 12; Liu & Wu, 2005: 299–300; Du et al., 2013: fig. 2H.

Margarya (Mabillemargarya) francheti – He, 2013: 12, figs 26–28.

Vivipara tropidophora Mabille, 1886: 70–72 , pl. 2, fig. 3, 3. (‘Lac Tali’ = Lake Erhai).

Margarya melanioides tropidophora – Yen, 1943: 128.

Margarya tropidophora – Tchang & Tsi, 1949: 750–751, pl. 2, 17, 18; Liu & Wu, 2005: 299–300; Du et al., 2013: fig. 2D.

Margarya (Mabillemargarya) tropidophora – He, 2013: 12, figs 29–31.

Vivipara (Tulotoma) margeriana var. rotundata Neumayr, 1887 : pl. III, fig. 4a, 4b (‘Talifu’ = Dali City).

Taxonomic remarks

Like M. melanioides , Vivipara francheti Mabille, 1886 was also described from Lake Erhai in Dali City. Subsequently, Neumayr (1887) described and illustrated some specimens from Dali City as well under the name Vivipara (Tulotoma) margeriana var. rotundata . Dautzenberg & Fischer (1905) treated the name francheti as a variety of M. melanioides and its variety rotundata as its synonym, but Tchang & Tsi (1949) maintained M. francheti as a species distinct from M. melanioides because of the absence of nodules on its shell, a more slender body whorl, a mammili-form apex, and presence of only one spiral keel. Margarya tropidophora differs only by having no keel on the shoul- der, according to the original figure ( Fig. 13E, F ); however, because this keel may vary in development between specimens and no other differentiating features exist, we consider M. tropidophora as a synonym of M. francheti . Preference is given to M. francheti , which has usually correctly been used in previous taxonomic literature ( Tchang & Tsi, 1949; Zhang, 1993; Du et al., 2013), whereas M. tropidophora was often confound- ed with other species, such as A. bicostata ( Zhang, 1993) or M. oxytropoides ( Wang, 2005) .

He (2013) introduced a new subgenus, Mabillemargarya, for M. francheti ; however, this taxonomic act is not supported by comparative morphlogy and molecular phylogenetics. Therefore, Mabillemargarya is here considered as a junior synonym of Margarya .

Materials examined

Museum materials. Adult shell: Lake Erhai ( Margarya tropidophora , coll. Tchang Xi, before 1949, dried shell), IZCAS FG 89708. Juvenile shell (taken from): IZCAS FG 89708 (2 individuals).

Newly collected materials. Adult shell: Lake Erhai , Caicun Village , 25°43′15.28″ N, 101°31′28.8″ E, 5 m deep ( EHCC 4–13 , 8 dead and 2 male living specimens); Lake Jianhu, 26°28′52.8″ N, 99°55′29.8″ E, 8 m deep ( JH 1– 6 , 3 female and 5 male living specimens); Lake Dianchi, Chenggong, 24°51′32.2″ N, 102°46′58.9″ E, 4 m deep ( DCWLB 1 , 1 male living specimen). Juvenile shell (taken from): JHFS 1 (5 individuals); JHFS 2 (2 individuals); JHFS 3 (5 individuals). These specimens were collected by Lejia Zhang and Lite Yang.

Short diagnosis

Shell conical, always with one spiral keel with weak nodules at the suture and shoulder, without promient keels on the middle of each whorl; the early four whorls (viz. mature juvenile shell) smooth without keels or decorations; three or four rather weak spiral ribs around the umbilicus.

Description

Shell large, conical, up to nearly 100 mm in height ( Table 3); greenish to red brown, thick, solid; spire elongated, mostly with seven inflated whorls, including two protoconch whorls, with well-developed ramp-like area on upper section of whorls, except for the protoconch; individual taken from uterus almost identical to juveniles of M. melanioides .

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 114–117 rows of teeth. Central tooth bell-shaped, with large, broad, securiform central denticle, flanked by between five and seven smaller cusps on each side. Lateral tooth broadly oblong, with one large, square central denticle and four or five smaller cusps on either side. Marginal tooth slender, slightly oblong; inner marginal tooth with large, oblong central denticle and three or four smaller cusps on either side; outer marginal tooth obtuse, with between ten and 12 small cusps.

Comparative remarks

Distinguished from other Margarya species , especially carinated specimens of M. melanioides , by having a juvenile shell without any nodules and inflated lower teleconch and body whorls with weak keels. Differs from A. bicostata judging only by shell by having welldeveloped axial ribs, several weak spiral ribs around umbilicus, irregular weak nodules on the lower whorls, and is easily distinguished from Anularya species by the comparative remarks in Margarya .

first three whorls smooth, without ramp-like shoul- der; with three or four spiral keels on the lower whorls, the keel on the shoulder of each whorl and the keel at the suture on the body whorl are relatively prominent, the rest of the keels reduced and discontinued, whorls irregularly spaced with wide longitudinal ribs, forming weak and sparse nodules with keels; three or four weakly developed spiral ribs extending onto umbilical area. Aperture ovate, usually less than shell height, with obtuse angles on lower part and shoul- der of outer lip, the inner surface is whitish blue in colour and some individuals are purple in colour. Umbilicus always covered by inner lip.

Mature juvenile shell large, with four whorls, moderately transparent, light green or brown in colour; first three whorls smooth, with no sculpture or ramp-like shoulder, fourth whorl with obvious ramp-like area but still smooth; two or three obtuse keels in umbilical area; aperture ovate, nearly half of shell height. One Habitat and distribution

Lives on muddy to sandy substrates without aquatic plants, always at depths of 3–8 m in Lake Dianchi, Erhai, Jianhu. Adapts to feed on dry Chlorella powder and mostly lives for more than 6 months in the laboratory.

MARGARYA OXYTROPOIDES (HEUDE,

Figures

Figure 13. Shells of Margarya francheti: A, Lake Jianhu, JHFS 1, 86.9 mm; B, Lake Erhai, EHCC 11, 45.1 mm; C, Lake Dianchi, DCWLB 1, 58.3 mm; C, D, Lake Erhai, FG89708, 60.1 mm; E, holotype figure of Margarya francheti; F, holotype figure of Margarya tropidophora (E, F, from Mabille, 1886).

Figure 14. Scanning electron micrograph showing radula of Margarya francheti from Lake Dianchi: A, central tooth; B, lateral tooth; C, inner marginal tooth; D, outer marginal tooth.