Cremnoconchus cingulatus, 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 : 124-126

CREMNOCONCHUS CINGULATUS SP. NOV.

( FIGS 4G , 5O, P, 11Q–U, 13E, F, 14D–I)

Types: Holotype ZSI / WGRS /IR.INV-2316 (Fig. 11 R, S); 3 paratypes ZSI / WGRS /IR.INV-2317, 2318, 2319 (Fig. 11Q, T, U); Hulikal Ghat , Udupi Dist., Karnataka, India (13.71742°N 74.99445°E).

Etymology: Latin cingulatus , girdled, in reference to sculpture of base.

Diagnosis: Shell globular; one rib on base; pseudumbilicus narrow, perforated; surface with satin sheen, microstriae weak or absent. Operculum weakly calcified, no internal ridge. Penis with distal glandular pad, slender filament. Western Karnataka State.

Shell ( Figs 4G , 11Q–U): Shell H 3.5–6.7 mm. Shape ( Table 1) globular; whorls rounded; a weak rib close to suture outlines the flattened sutural area, but rib becomes obsolete on largest shells; suture impressed; peripheral angle absent; apex eroded; base slightly swollen, with thick rib at one-third radius. Columella narrow, wider at base. Pseudumbilicus narrow, 0.2– 0.6 mm, perforated. Surface with satin sheen; spiral striae indistinct or absent, weakly present on base ( Fig. 4G ). Colour: reddish brown, three indistinct darker brown bands at suture, above periphery and at middle of base; aperture and columella purple-brown, with bands showing through.

Animal: Head and tentacles dark grey to black, tip of snout paler; body and sides of foot black. Gills: up to 35 leaflets; black. Operculum ( Table 1; Fig. 5O, P): opercular ratio 0.334 –0.472; weakly calcified, concave, no internal ridge. Penis (Fig. 14D–I): base lightly pigmented, wrinkled, solid, with large glandular pad on left of reverse side; invagination about half length of base in ethanol-fixed specimens; filament slender, protruding in ethanol-fixed specimens. Pallial oviduct: as for genus.

› Figure 14. Anatomy of Cremnoconchus agumbensis (A–C) and C. cingulatus (D–I), all to same magnification. A, B, D–I, penes (all fixed in ethanol); G–I are abaxial, sectioned and adaxial views of same penis. C, pallial oviduct, with transverse sections in three positions. A–C, Agumbe, Udupi Dist., Karnataka (ZSI/WGRS; shell H: A = 9.5 mm; B = 8.8 mm; C = 9.1 mm). D–I, Hulikal Ghat, Udupi Dist., Karnataka (ZSI/WGRS; shell H: D = 3.5 mm; E = 4.6 mm; F = 3.7 mm; G–I = 4.4 mm). Shading conventions as in Figure 6 .

Radula ( Fig. 13E, F ): Relative radula length 1.93– 2.09. Rachidian: length/width 1.10–1.13; 5 cusps (+ 1 outer denticle on either side). Lateral: 5 cusps (sometimes + 1 inner denticle). Inner marginal: 5 cusps. Outer marginal: 4–5 cusps. Major cusp of each of 5 central teeth triangular with rounded and 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-2316, 2317, 2318, 2319) .

Habitat and ecology: In rushing stream on rock face and sides of boulders, in fast-flowing water and spray, partly shaded by trees (Fig. 2C). Altitude 475 m.

Remarks: The conspicuous rib on the base, narrow but deep pseudumbilicus, and concave, weakly calcified operculum are the distinguishing features of the shell of this species. Except for the basal rib, these characters resemble C. globulus , but their respective penes are diagnostic ( Figs 12H–L , 14D–I). Characters of the Cremnoconchus species of Karnataka are summarized in Table 4.

There appears to be sexual dimorphism: shells of males are smaller (males: mean ± sample SD = 3.840 ± 0.619 mm, N = 4; females: 5.575 ± 0.697 mm, N = 12) and the aperture is slightly enlarged.

At Hulikal Ghat it was found together with C. dwarakii and the two occupied different microhabitats. Cremnoconchus cingulatus occurred on rocks in rushing water, while C. dwarakii was found on mossy rocks dampened only by spray.

Figures

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 12. Anatomy of Cremnoconchus hanumani (A–G) and C. globulus (H–L), all to same magnification. A–L, penes (all fixed in ethanol); F, G are intact and sectioned views of same penis. A–C, Hanuman Gundi Falls, Chikmagalur Dist., Karnataka (ZSI/WGRS; shell H: A = 4.9 mm; B = 3.5 mm; C = 3.3 mm). D–G, Greater Kadambi Falls, Chikmagalur Dist., Karnataka (ZSI/WGRS; shell H: D = 3.9 mm; E = 4.0 mm; F, G = 5.0 mm). H–K, Lesser Kadambi Falls, Chikmagalur Dist., Karnataka (ZSI/WGRS; shell H: H = 7.0 mm; I = 6.0 mm; J = 7.0 mm; K = 6.3 mm). L, Greater Kadambi Falls, Chikmagalur Dist., Karnataka (ZSI/WGRS; shell H = 7.9 mm). Shading conventions as in Figure 6.

Figure 13. Radulae of Cremnoconchus species (two views of each radula, flat and at 45°). A, B, C. globulus, Lesser Kadambi Falls, Chikmagalur Dist., Karnataka (ZSI/WGRS; shell H = 7.4 mm). C, D, C. agumbensis, Agumbe, Udupi Dist., Karnataka (ZSI/WGRS; shell H = 9.5 mm). E, F, C. cingulatus, Hulikal Ghat, Udupi Dist., Karnataka (ZSI/WGRS; shell H = 5.7 mm). G, H, C. castanea, Arasinagundi Falls, Udupi Dist., Karnataka (ZSI/WGRS; shell H = 8.5 mm). Scale bars = 50 Mm.