Cristaria bellua (Morelet, 1866)

Konopleva, Ekaterina S., Bolotov, Ivan N., Vikhrev, Ilya V., Inkhavilay, Khamla, Gofarov, Mikhail Yu., Kondakov, Alexander V., Tomilova, Alena A., Chapurina, Yulia E., Van Do, Tu, Pfeiffer, John M., Lopes-Lima, Manuel & Bogan, Arthur E., 2023, A freshwater mussel species reflects a Miocene stream capture between the Mekong Basin and East Asian rivers, Zoosystematics and Evolution 99 (1), pp. 29-43 : 29

Cristaria bellua (Morelet, 1866)

= Anodonta bellua Morelet, 1866: 167.

= Margaron (Dipsas) plicatus - Lea (1870): 74.

= Dipsas bellua - Morelet (1875): 331, Fischer (1891): 222.

= Cristaria (s.s.) bellua - Simpson (1900): 584.

= Cristaria (s.s.) bellua - Preston (1912): 281.

= Cristaria (s.s.) bellua - Simpson (1914): 226.

= Dipsas plicatus - Dautzenberg and Fischer (1905): 198.

= Cristaria (s.s.) plicata plicata - Haas (1969): 387.

= Cristaria plicata - Brandt (1974): 278, He and Zhuang (2013): 39, Do et al. (2018): 5; Lopes-Lima et al. (2020): 9.

= Cristaria bellua - Dang et al. (1980): 537.

Type and type locality.

Lectotype MCZ 175610 (in lacu Touli-Sap, Cambogensi) [Cambodia: Lake Tonlé Sap]; designated by Johnson (1956): p. 107, pl. 1, fig. 1 (Fig. 2B ).

Type material.

Paralectotype MCZ 175610 (in lacu Touli-Sap, Cambogensi) [Cambodia: Lake Tonlé Sap] (Fig. 2A ); Paralectotype NHMUK 1965147 (lac Touli-Sap, Cambodia) [Cambodia: Lake Tonlé Sap] ( Johnson 1971: p. 80; Breure et al. 2018) (Fig. 2C ).

Material examined.

Laos: Nam Ngum River , 18.2123°N, 102.9998°E, Mekong Basin , 26.ii.2020, 3 specimens [RMBH biv 813, all sequenced], Bolotov, Vikhrev, Inkhavilay, Konopleva, Chapurina, and locals leg. (Fig. 2D, F ); Nam Don River, 17.4781°N, 104.7630°E, Mekong Basin, 29.ii.2020, 2 specimens [RMBH biv 853, all sequenced], Bolotov, Vikhrev, Inkhavilay, Konopleva, Chapurina, and locals leg. (Fig. 2E ); tributary of Nam Ngiep River, 18.5783°N, 103.5998°E, Mekong Basin, 05.iii.2020, 9 specimens [RMBH biv 891, including biv 891/1, biv 891/2 and biv 891/5 sequenced], Bolotov, Vikhrev, Inkhavilay, Konopleva, Chapurina, and locals leg. (Fig. 2G, H ). Museum material examined: listed in Table 2 .

Re-description.

Shell rhomboid, rather large, moderately thin and inflated, sub-solid; high posteriorly, young specimens usually with clearly developed wing or somewhat crest smoothing with aging; ventral margin straight or slightly curved; posterior ridge folded. Umbo small, slightly elevated above hinge line. Periostracum of various coloration, from olive-green to brown and blackish; younger individuals usually with dark-green radial rays running from the umbones to the ventral margin, visible on either side of valve; wider stripes usually located on posterior slope. Nacre whitish, may be tinted with yellow; specimens from the tributary of the Nam Ngiep River differ by a pinkish color, mainly for younger shells. Umbo cavity shallow with a few deep pits. Lateral teeth short, more or less developed on each valve. Pseudocardinal teeth extremely thin or underdeveloped. Anterior muscle scars irregular and usually well-developed, posterior muscle scars more shallow, somewhat crescent-shaped.

Habitat and ecology.

The species was recorded from the main channel of the Nam Ngum and Nam Don rivers and a tributary of the Nam Ngiep River, mainly on clay-sandy substrates and at a depth of>1.5-2.0 m. It was found together with representatives of different genera such as Lens , Physunio , Hyriopsis , Pilsbryoconcha , Bineurus , Monodontina , Scabies , and Nyeinchanconcha . Numerous parasitic mites ( Acari: Unionicolidae ) and their eggs were discovered on the mantle and gills of C. bellua , especially from specimens collected in a tributary of the Nam Ngiep River.

Distribution.

Mekong Basin in Laos, Cambodia, and Thailand.

Comments.

Morelet (1866) did not state how many specimens were collected and studied for the description of Anodonta bellua . In the original description, there was only one set of measurements: shell length = 187 mm; shell height = 123 mm; and shell width = 71 mm (Morelet, 1866). In MCZ, there are two specimens under catalog number 175610. One of them was designated by Johnson (1956) as the lectotype of A. bellua and illustrated in his work ( Johnson 1956: pl. 1, fig. 1). This author wrote that "this the first time that this species has been figured". Second (larger) specimen was not discussed. Specimen NHMUK 1965147 was considered a paralectotype ( Johnson 1971).

Figures

Figure 2. Type specimens and newly collected shells of Cristaria bellua (Morelet, 1866) from the Mekong Basin: (A) paralectotype MCZ 175610, Lake Tonle Sap, Cambodia; (B) lectotype MCZ 175610, Lake Tonle Sap, Cambodia; (C) paralectotype NHMUK 1965147, Lake Tonle Sap, Cambodia; (D) specimen RMBH biv 813 / 3, Nam Ngum River, Laos; (E) specimen RMBH biv 853 / 1, Nam Don River, Laos; (F) specimen RMBH biv 813 / 1, Nam Ngum River, Laos; (G) specimen RMBH biv 891 / 1, tributary of Nam Ngiep River, Laos; (H) specimen RMBH biv 891 / 4, the same locality. Scale bar: 2 cm. Photos: Adam J. Baldinger, MCZ [A, B]; Kevin Webb, NHMUK [C]; and Ekaterina S. Konopleva [D-H].