"Thiara" aspera (Lesson, 1831)

Boonmekam, Dusit, Krailas, Duangduen, Gimnich, France, Neiber, Marco T. & Glaubrecht, Matthias, 2019, A glimpse in the dark? A first phylogenetic approach in a widespread freshwater snail from tropical Asia and northern Australia (Cerithioidea, Thiaridae), Zoosystematics and Evolution 95 (2), pp. 373-390 : 379-381

"Thiara" aspera (Lesson, 1831) * Figs 1 , 6 , 7

Melania aspera Lesson, 1831 in Lesson (1830-1831: 357-358) [type locality: "La Nouvelle-Guinée” (= New Guinea), restricted to Manokwari by Glaubrecht and Podlacha (2010)].

Melania rudis Lea & Lea, 1851: 186 [type locality: ‘Amboyna’ (= Ambon)].

Melania microstoma Lea & Lea, 1851: 186 [type locality: mountain streams, isle of Negros, Philippines].

? Melania armillata Lea & Lea, 1851: 195-196 [type locality: India].

? Melania broti Reeve, 1859 in Reeve (1859-1861: pl. 22 fig. 160) [type locality: Ceylon (= Sri Lanka)].

? Melania hybrida Reeve, 1859 in Reeve (1859-1861: pl. 13 fig. 163) [type locality: not given].

? Melania chocolatum Brot, 1860: 256-257, pl. 16, fig 2 [type locality: “Ceylon” (= Sri Lanka)].

? Melania (Tiaropsis) rudis var. spinosa Brot, 1877 in Brot (1874-1879: 306) [type locality: not given, see also Brot (1868: 33, pl. 1, fig. 7)].

? Melania (Tiaropsis) drilliiformis Martens, 1897: 305 [nomen nudum].

? Melania fortitudinis Fulton, 1904: 51-52, pl. 4, fig. 3 [type locality: "Soekaboemi, Java" (= Sukabumi, Java)].

? Melania rudis var. cylindrica Schepman, 1915: 27 [type locality: West Ceram, Kairatu (= West Seram Island, Kairatu)].

Diagnosis.

Thiarid with a turreted, subcylindrical to elongate-ovoid, strongly ornamented high-spired shell with usually rather flattened whorls and a narrowly pyriform aperture that at most reaches half the total shell height, but usually less. Ornamentation of the shell consisting of sinuous axial ribs that usually reach to the base of the body whorl and spiral chords that form nodes where they intersect the ribs; spiral chords usually present on the entire whorl but strongest at the base of body whorl.

Remarks.

The examined type specimens of M. aspera , M. rudis , and M. microstoma correspond well to each other in overall shell shape and sculpture and are here regarded as conspecific because of this. As already noted by Brot (1874-1879: 307) and Glaubrecht and Podlacha (2010: 200), the name Melania aspera Lesson, 1830 has priority over the somewhat more frequently used name Melania rudis (e.g., van Benthem Jutting 1937, 1956; Subba Rao 1989; Ramakrishna and Dey 2007; Budha 2010; Patil and Talmale 2011 as T. rudis ). The holotype of Melania aspera is unusual in possessing a very small aperture in relation to overall shell height, possibly explaining its isolated position in the PCA 1 vs PCA 2 scatter plot ( Fig. 4A ). The nominal taxa M. armillata , M. broti , and M. chocolatum described from India or Sri Lanka were regarded by Brot (1874-1879) as closely related to M. rudis and are here tentatively synonymised with M. aspera , largely following the views of Rensch (1934) and van Benthem Jutting (1937, 1956) who synonymised these taxa with M. rudis . According to Brot (1874-1879: 307-308) Melania hybrida is based on a teratological specimen with an unusual aperture formation and is here tentatively synonymised with M. aspera . The nominal taxon Melania (Tiaropsis) rudis var. spinosa Brot, 1877 is an individual variation of M. aspera with somewhat longer shoulder spines. The original figures and descriptions of Melania fortitudinis and M. (Tiaropsis) rudis var. cylindrica from Java and West Seram Island also correspond well with the holotype of M. aspera and are herein treated as synonyms of the former.

Type material examined.

Holotype of Melania aspera Lesson, 1831, MNHN 21098, "La Nouvelle-Guinée”; syntype of Melania rudis Lea & Lea, 1851, USNM 119778, “Amboyna”; syntype of Melania microstoma Lea & Lea, 1851, USNM 119722, 'mountain streams, isle of Negros, Philippines’.

Additional material examined

(w: ethanol preserved samples). India: Kolkata, ZMB 107002. Sri Lanka: Colombo, ZMB 107003. Thailand: Samut Sakhon Province, Klong Don Ko, SUT 0311020, ZMB 127535, SUT 0311044, SUT 0311053, ZMB 127534, w; Nakhon Pathom province, Pond in Silpakorn University campus, SUT 0312069, SUT 0312070 = ZMB 127536, w. Indonesia: Bali: South Bali, Yehembang River, ZMB 191279, ZMB 191279a, w, South Bali, at Yehembang, ZMB 106472, w; east of Mendaya, stream southwest of Gumicik, ZMB 191488; Sulawesi: South Sulawesi, Kalena catchment, Angkona river, ZMB 192751, w; southeast Sulawesi, Pohara river, at Pohara, road Kendair to Kolaka, ZMB 191261, w; southeast Sulawesi, Simbune river, 1 km northeast of Raterate, road Kendari to Kolaka, ZMB 191262, ZMB 191262a, w; southeast Sulawesi, stream at Tembeeha, road Tirobus to Kendari, ZMB 191278, w; central Sulawesi, Banggai Islands, Peleng Island, West Peninsula, Tataban river, ZMB 107378, w, ZMB 107377,w. Australia: Northern Territory: Berry Springs, ZMB 106704, w, ZMB 106599a, w, ZMB 127616, w; Wabalaar, Roper River, ZMB 107617, w, ZMB 107614, w, ZMB 127645, w; Salt creek, ZMB 127619, w, ZMB 127636, w, ZMB 127637, w; Roper Bar, ZMB 127620, w; Queensland: O’Shanassy, ZMB 107280.

Shell.

Turreted, subcylindrical to elongate-ovoid, corneous to dark brown, with up to nine whorls (the early whorls usually eroded) ( Fig. 1 ; for juvenile shells, see Fig. 6 ). Whorls rather flat to convex, separated by a slightly impressed to distinctly impressed, undulating suture. Whorls slightly constricted below the suture, ornamented with sinuous ribs and spiral chords that usually form nodules at their intersections. Radial sculpture usually strongest on the upper half of the whorls, with the nodules at the shoulder of the whorls usually largest, sometimes forming spines. Towards the lower part of the body whorl the spiral sculpture often becomes the dominant sculptural element, forming distinct parallel chords. Aperture pyriform, angled in its upper part and rather narrow, wider at the base and appearing truncated in frontal view. Columella thickened, almost straight to curved, abruptly terminating basally. Shell size H = 7.6-48.0 mm, W = 3.1-22.0 mm (Table 2).

Operculum.

The operculum is typical for thiarids, oval and paucispiral, light to dark brown, and with the nucleus being excentric in the lower left corner.

Juvenile shell.

The shells of the juveniles in the brood pouch had up to five whorls, with a maximum height of about 2.5 mm. The protoconch is smooth, with the radial and spiral sculpture developing on the first teleoconch whorls ( Fig. 6 ). For measurements of the embryonic shell, see Table 3.

Radula.

Taenioglossate ( Fig. 7 ), resembling other thiarids. As in all thiarids the central tooth or rachidian is significantly wider than tall; all specimens have a central cusp flanked by three to six triangular denticles on both sides, resulting in up to 12 denticles and a typically 4 –5/1/4– 5 pattern at the upper cutting edge ( Fig. 7A, C, E , Table 4). The laterals are equipped with three to six smaller denticles on the inner side, and three to six denticles outside from the large main cusps ( Fig. 7A, C, E , Table 4). The marginal teeth are moderately long, spoon-shaped, with a varying number of 6-10 denticles ( Fig. 7B, D, F , Table 4).

Reproductive strategy.

The results of the analysis of brood pouch content are summarised in Figure 2 . Juveniles of up to 2 mm (rarely also larger) were found in the populations from Thailand, Indonesia (Bali and Sulawesi) and Australia (Northern Territory) suggesting an euviviparous reproductive strategy for " T. " aspera , i.e, the taxon was found to give birth to crawling and shelled juveniles in accordance with the definitions in Glaubrecht et al. (2009). In a few populations in Thailand and on Bali, gravid females with only early embryos, i.e., veliger larvae in the brood pouch were found.

Distribution.

" Thiara " aspera as here understood is a widespread species, with records from Sri Lanka and India ( Subba Rao 1989), Myanmar and Cambodia ( van Benthem Jutting 1956), Indonesia ( Rensch 1934; van Benthem Jutting 1956), and the Philippines ( Lea and Lea 1851; van Benthem Jutting 1956). As our results indicate, the taxon is also present in Thailand and northern Australia, from where it was not previously reported ( Fig. 2 ).

Figures

Figure 1. Shells of " Thiara " aspera (Lesson, 1831). A. Holotype of Melania aspera Lesson, 1831, MNHN 21098, ' La Nouvelle-Guinee' [more specifically Manokwari on New Guinea Island, West Papua, Indonesia, see Glaubrecht and Podlacha 2010]; B. Syntype of Melania rudis Lea & Lea, 1851, USNM 119778, Amboyna; C. Syntype of Melania microstoma Lea & Lea, 1851, USNM 119722, mountain streams, isle of Negros, Philippines; D. ZMB 107002, Calcutta, India; E. ZMB 107003, Ceylon, Sri Lanka; F. ZMB 127534, Don Ko Canal, Nakhon Pathom, Thailand; G. ZMB 127535, Don Ko Canal, Nakhon Pathom, Thailand; H. ZMB 127535, Don Ko Canal, Nakhon Pathom, Thailand; I. ZMB 191279, Yehembang River, Bali, Indonesia; J. ZMB 191279, Yehembang River, Bali, Indonesia; K. ZMB 106472, Yehembang, Bali, Indonesia; L. East of Mendaya, stream southwest of Gumicik, Bali, Indonesia; M. ZMB 191278, stream at Tembeeha, road Tirobus-Kendari, Southwest Sulawesi, Indonesia; N. ZMB 107378, Banggai Islands, Peleng Island, West of Peninsula, Tataban river, Central Sulawesi, Indonesia; O. ZMB 107377, Banggai Islands, Peleng Island, West of Peninsula, Tataban river, Central Sulawesi, Indonesia. river; P, Q. ZMB 107617, Wabalarr, Roper River, Northern Territory, Australia; R. ZMB 106599, Berry Springs, Northern Territory, Australia. Scale bar: 1 cm.

Figure 2. Distribution and reproductive strategy of " Thiara " aspera (Lesson, 1831). Stars: type localities of a) Melania aspera Lesson, 1831, Monokwari, New Guinea, b) Melania rudis Lea & Lea, 1851, Amboyna and c) Melania microstoma Lea & Lea, 1851, mountain streams, isle of Negros, Philippines. Pie charts show the percentages of offspring in the brood pouch of female T. aspera in different size classes as defined in Glaubrecht et al. (2009), see inset. The numbers near the pie charts refer to the number of individuals examined per population. Filled circles: material preserved in ethanol; open circles: dry shells.

Figure 4. Results of the analysis of biometric data of " Thiara " aspera (Lesson, 1831) specimens from Australia (yellow), Indonesia (green), Thailand (red) and India / Sri Lanka (blue) and type material of Melania aspera Lesson, 1831 (holotype, triangle), Melania rudis Lea & Lea, 1851 (syntype, square) and Melania microstoma Lea & Lea, 1851 (syntype, diamond). A. Scatter plot of the first two axes of the principal component analysis (PCA) of biometric data. Coloured lines indicate the outline of the convex hull for each geographic group; B, C. Boxplots of PCA 1 (B) and PCA 2 (C); bars above the box plots indicate significant differences of groups resulting from testing with Dunn's test.

Figure 6. Juvenile and embryonic shells of " Thiara " aspera (Lesson, 1831), SUT 0311020, Samut Sakhon Province, Klong Don Ko. A. Lateral view; B. Apical whorls, lateral, C. Apical view. D. Details of the protoconch. Scale bars: 450 µm (A); 250 µm (B); 200 µm (C); 100 µm (D).

Figure 7. Radulae of " Thiara " aspera (Lesson, 1831) from Thailand. A, B. SUT 0312070, Nakhon Pathom province, pond at Silpakorn University campus; A. Central and lateral teeth; B. Marginal teeth; C, D. SUT 0311020, Samut Sakhon province, Klong Don Ko; C. Central and lateral teeth; D. Marginal teeth. E, F: SUT 0311053, Samut Sakhon Province, Klong Don Ko; E. Central and lateral teeth; F. Marginal teeth. Scale bars: 35 µm (A, E); 5 µm (B, F); 25 µm (C); 10 µm (D).