Cremnoconchus dwarakii, Reid & Aravind & Madhyastha, 2013

Reid, David G., Aravind, Neelavara Ananthram & Madhyastha, Neelavara Ananthram, 2013, A unique radiation of marine littorinid snails in the freshwater streams of the Western Ghats of India: the genus Cremnoconchus W. T. Blanford, 1869 (Gastropoda: Littorinidae), Zoological Journal of the Linnean Society 167 (1), pp. 93-135 : 128-129

CREMNOCONCHUS DWARAKII SP. NOV.

( FIGS 4A , 5C, D, 11BB–EE, 15E–J, 16A, B, F)

Cremnoconchus syhadrensis – Williams et al., 2003: 63 (not Blanford, 1863).

Cremnoconchus dwaraki Madhyastha, 2008 : The Hindu 29 June 2008 (as Cremenoconchus; nomen nudum).

Taxonomic history: This species was misidentified by Williams et al. (2003) as C. syhadrensis , because the two share strong spiral ribs on the shell.

Types: Holotype ZSI / WGRS /IR.INV-2323 (Fig. 11 BB, CC); four paratypes ZSI / WGRS /IR.INV-2324, 2325 (Fig. 11DD); Hulikal Ghat , Udupi District, Karnataka, India (13.71742°N, 74.99445°E).

Etymology: Named after Acharya Dwarakanth, of the Indian Naturalist Club. He was known for his knowledge of animals and plants of Karnataka and, as secretary of the club, supported many research activities and encouraged the younger generation in birding and nature conservation. The name dwarakii is derived from that of the legendary city of Dwaraka in Western Gujarat, the dwelling place of Lord Krishna and the capital of the Yadus who ruled the Anarta Kingdom during the Mahabaratha period.

Diagnosis: Shell turbinate; 8–11 ribs (including base); pseudumbilicus narrow, perforated; surface dull, with fine strong microstriae. Operculum weakly calcified, no internal ridge. Penis with slight glandular flange, slender filament. Western Karnataka State. COI: GenBank AJ 488605 .

Shell ( Figs 4A , 11BB–EE): Shell H 6.0– 9.2 mm. Shape ( Table 1) turbinate; whorls slightly angled at shoul- der; suture impressed; apex slightly eroded; base slightly swollen. Columella narrow. Pseudumbilicus narrow, 0.2–0.7 mm, with sharply angled margin, perforated. Spire whorls with three strong ribs. Last whorl with 8–11 strong ribs, of which largest are sutural rib (outlining flattened sutural ramp, which may also bear an additional riblet) and rib close to pseudumbilicus. Surface dull, covered by fine, strong microstriae, intersecting with fine growth lines to give minutely lamellose effect ( Fig. 4A ). Protoconch ( Fig. 16F ) 1.4 whorls; diameter 0.70 mm; diameter of first whorl 0.45 mm (N = 1). Colour: usually orangebrown, darker brown on spire and with indistinct darker band at suture and outlining pseudumbilicus; occasionally all rib interspaces are dark brown, but fading on last whorl; aperture yellow-brown, columella and pseudumbilicus purple-brown, exterior bands showing through.

Animal: Head, tentacles, sides of foot, and body dark grey to black; tip of snout pale. Gills: up to 36 leaflets; grey to black. Operculum ( Table 1; Fig. 5C, D): opercular ratio 0.385 –0.511; weakly calcified, no internal ridge, slightly concave. Penis (Fig. 15E–I): unpigmented; base wrinkled, tapering to rounded tip; with triangular glandular pad on reverse side, slightly projecting anterolaterally; invagination about half length of base in ethanol-fixed specimens; filament slender, not protruding in ethanol-fixed specimens. Pallial oviduct (Fig. 15J): as for genus. One pallial oviduct contained two eggs 0.40 mm in diameter (ethanol fixed), one at two-cell embryo stage.

Radula ( Fig. 16A, B ): Relative radula length 0.82– 1.25. Rachidian: length/width 1.23; 5 cusps (+ 1 outer denticle on either side). Lateral: 5 cusps (+ 1 inner denticle). Inner marginal: 6 cusps. Outer marginal: 3–5 cusps. Major cusp of each of 5 central teeth leaf-shaped with narrowly rounded or slightly papillose tip; other cusps pointed.

Range ( Fig. 8 ): Western Karnataka State, Hulikal Ghat (95 km north-northeast of Mangalore). Records (Supporting Table S1): Karnataka State: Hulikal Ghat, Udupi District (ZSI/WGRS/IR.INV-2323, 2324, 2325; BMNH 20120036).

Habitat and ecology: On mossy rocks dampened by spray from rushing stream; shaded by trees (Fig. 2B). Altitude 475 m.

Remarks: This species is distinguished from all others in Karnataka by the strong ribs of the shell ( Table 4). These create a superficial resemblance to ribbed forms of C. syhadrensis from Maharashtra ( Fig. 3 ), but in those the ribs are restricted to the upper surface (i.e. above the periphery), the pseudumbilicus is usually wide and the columella is broad; there are also differences in the penes of these two species (Table 3, Fig. 6A, B, D–G , 15E–I).

At Hulikal Ghat this species was found with C. cingulatus (see Remarks on that species).

Figures

Figure 3. Shells of Cremnoconchus syhadrensis. A, Cremnobates syhadrensis W.T. Blanford, 1863, neotype, no locality (BMNH 1906.1.1.2247). B, C, Matheran, Raigad Dist., Maharashtra (two views of same specimen; ZSI/WGRS/IR.INV- 2290). D, E, Anjani, Nashik Dist., Maharashtra (BMNH 1911.8.23.70–71). F, J–L, Torna Fort, Pune Dist., Maharashtra (USNM 317696). G–I, Khandala, Pune Dist., Maharashtra (G, H two views of same specimen; ZSI/WGRS/IR.INV-2293, 2292). M, Torna Fort, Pune Dist., Maharashtra (USNM 317695).

Figure 4. Microsculpture of Cremnoconchus species (viewed by SEM). A, C. dwarakii, Hulikal Ghat, Udupi Dist., Karnataka. B, C. syhadrensis, Matheran, Raigad Dist., Maharashtra. C, C. syhadrensis, Khandala, Pune Dist., Maharashtra. D, C. conicus, 44 km west of Bhor, Pune Dist., Maharashtra. E, C. conicus, 6 km west of Mahabaleshwar, Satara Dist., Maharashtra. F, C. globulus, Lesser Kadambi Falls, Chikmagalur Dist., Karnataka. G, C. cingulatus, Hulikal Ghat, Udupi Dist., Karnataka. H, C. agumbensis, Agumbe, Udupi Dist., Karnataka. I, C. canaliculatus, 10 km west of Mahabaleshwar, Raigad Dist., Maharashtra. J, C. canaliculatus, Dongarwadi, Tamhini, Pune Dist., Maharashtra. K, C. canaliculatus, 5 km south of Mahabaleshwar, Satara Dist., Maharashtra. L, C. castanea, Belkal Thirtha Falls, Udupi Dist., Karnataka. M, C. castanea, Arasinagundi Falls, Udupi Dist., Karnataka. N, C. hanumani, Greater Kadambi Falls, Chikmagalur Dist., Karnataka. O, C. hanumani, Hanuman Gundi Falls, Chikmagalur Dist., Karnataka.

Figure 6. Anatomy of Cremnoconchus syhadrensis. A, B, D–G, penes (A, E–F, fixed in ethanol; B, D, live). E–G are three views of single penis, external (E), with base sectioned (F), and with coiled penial vas deferens displaced to the right to show retractor muscle and with filament sectioned to show continuation of vas deferens to its tip (G). C, pallial oviduct and egg removed from straight section. A, Matheran, Raigad Dist., Maharashtra (BMNH 20120035; shell H = 7.4 mm). B, C, E–G, Matheran, Raigad Dist., Maharashtra (ZSI/WGRS; shell H: B = 7.2 mm; C = 7.2 mm; D = 5.8 mm; E–G = 7.5 mm). D, Khandala, Pune Dist., Maharashtra (ZSI/WGRS). Abbreviations and shading conventions: b, copulatory bursa (dashed outline, visible by transparency); c, cavity surrounding penial vas deferens and retractor muscle (black); d, distal to this point the penial vas deferens is tightly bound to the sheath of the retractor muscle; e.g. egg groove visible by transparency (thick line); f, penial filament; g, opaque glandular region of penial base (medium stipple); gc, firm gelatinous coating of mature egg; i, invagination of penial base (shaded); o, position of terminal opening of pallial oviduct into mantle cavity; oag, opaque part of albumen gland (dense stipple); ov, ovum; pvd, penial vas deferens; rm, retractor muscle of penial filament; ss, straight section of pallial oviduct; tag, translucent region of albumen gland (sparse stipple).

Figure 8. Distribution of Cremnoconchus species (solid circles). Two or more species names (e.g. syhadrensis + canaliculatus) indicate sympatric occurrence. See Supporting Table S1 for locality details. The shaded area is the Western Ghats region as defined by Irfan-Ullah & Davande (2008). Cities indicated by asterisks.

Figure 16. Radula (A, B) and protoconchs (C–F) of Cremnoconchus species. A, B, C. dwarakii (two views of radula, flat and at 45°), Hulikal Ghat, Udupi Dist., Karnataka (shell H = 6.4 mm). C, C. syhadrensis, Matheran, Raigad Dist., Maharashtra. D, C. canaliculatus, 10 km west of Mahabaleshwar, Raigad Dist., Maharashtra. E, C. agumbensis, Agumbe, Udupi Dist., Karnataka. F, C. dwarakii, Hulikal Ghat, Udupi Dist., Karnataka. Scale bars A, B = 50 Mm; C–F = 0.5 mm. White arrowhead marks junction of protoconch and teleoconch.