Pseudotricula arthurclarkei, Ponder & Clark & Eberhard & Studdert, 2005

Ponder, W. F., Clark, S. A., Eberhard, S. & Studdert, J. B., 2005, A radiation of hydrobiid snails in the caves and streams at Precipitous Bluff southwest Tasmania, Australia (Mollusca: Caenogastropoda: Rissooidea: Hydrobiidae s. l.),, Zootaxa 1074 (1), pp. 1-66 : 28-30

Pseudotricula arthurclarkei n. sp.

Figures 3I ; 7E ; 8B ; 10E ; 11D–F ; 12A .

Type material

Holotype: AMS C.439656, Quetzalcoatl Conduit, stn PB3–1C, 29, MAR, 1994.

Paratypes: AMS C.203671, Quetzalcoatl Conduit, stn PB3–1C, 29, MAR, 1994 (20+ dry, 20+ wet) ; AMS C.203669, Quetzalcoatl Conduit, stn PB3–2B, 29, MAR, 1994 (12 dry, 20+ wet); QVM, 9:20538 (5 wet).

Etymology

Named for Arthur Clarke in recognition of his considerable contributions to the discovery and collection of cave fauna in Tasmania.

Description

Shell ( Figs 11D–F ; 12A ). Length up to 3.1 mm; broadly conical (SW/SL 0.77–0.88, mean 0.81, n = 11); spire low to moderate, straight to slightly convex in outline; last whorl evenly rounded, or angular to subangular in middle of whorl; whorls distinctly convex; suture simple. Protoconch microsculpture of closely­spaced, distinct small pits. Teleoconch up to 2.5 whorls in adult; aperture oval to pear­shaped; large, little longer than spire (AL/SL 0.53–0.67, mean 0.61, n = 11); outer lip prosocline; weakly to moderately thickened in adult; outer lip straight; with or without slight reflection; external varix absent; posterior notch absent; inner lip moderately thickened and of narrow to medium width, firmly adhering to narrowly separated from parietal wall. Shell colour white or yellowish­brown to pale brown.

Dimensions. See Table 6.

Operculum ( Fig. 7E ).Yellowish; inner surface with white smear and 3–6 mediumsized pegs, or with pegs only.

Pallial cavity ( Fig. 8B ). Ctenidium narrow; 14–16 very small filaments; osphradium near posterior end to between posterior end and middle of ctenidium; hypobranchial gland moderately to poorly developed; renal organ extends forward ca. ⅓–½ into pallial cavity; pericardium more than ½ in pallial roof.

Radula ( Fig. 3I ). Central teeth: dorsal edge moderately indented; 5–6 lateral cusps, median cusp narrow, sharply pointed, less than twice as long as adjacent cusps. Lateral teeth: dorsal edge straight to lightly convex or with shallow indentation; with 5–6 cusps on outer and 3–6 on inner side; median cusp of narrow to medium width, sharply pointed, less than twice as long as adjacent cusps; ratio of cutting edge to shaft about ¼–⅓; basal projection rounded to bluntly pointed. Marginal teeth: Inner with 28–33 cusps; outer with 23–27 cusps.

Stomach. Stomach with posterior chamber much smaller than anterior chamber.

Male genital system. Testis of 0.75–2.0 whorls; prostate gland oval to kidney­shaped, oval in section. Pallial vas deferens straight. Penis with weak swelling in mid­distal portion; distal end long, papilla­like; medial section parallel sided, of medium length; penial duct straight to undulating; base of penis moderately wide, with moderate folds; penial duct straight to undulating.

Female genital system ( Fig. 10E ). Ovary of 1.0 whorls; oviduct does not extend to posterior edge of bursa copulatrix; straight distal to seminal receptacle; joins bursal duct in front of posterior pallial wall about half way between posterior pallial wall and capsule gland to about junction of albumen and capsule glands. Bursa copulatrix of medium size, extending to posterior pallial wall; globular to pyriform; with bursal duct arising from middle of anterior edge of bursa; straight. Seminal receptacle at middle of inner wall of bursa copulatrix or near mid ventral edge; pyriform. About ½ to more than ½ of albumen gland in front of posterior pallial wall; capsule gland about same length as albumen gland; compressed oval in section; anterior end tapering to blunt; ventral channel simple, approximately parallel­sided throughout; vestibular area indistinct to distinct; genital opening overlapping anterior end of capsule gland.

Distribution and habitat

Known only from Quetzalcoatl Conduit, where it lives in a stream 3–4 m wide which has a strong flow (estimated at 15–30L/s) with sediments composed mostly of gravel and silt.

Remarks

Pseudotricula arthurclarkei and the next two species differ from “typical” members of Pseudotricula in having more cusps on both marginal teeth, a long lateral shaft on the lateral teeth and in lacking a strongly reflected outer lip. Pseudotricula arthurclarkei and P. conica n.sp. appear to be a sister taxa and also differ from other Pseudotricula species in having several weak to moderate curved ridges (reduced pegs) on the inside of the operculum, stronger and more complex protoconch microsculpture and the shell colour is often brown.

Figures

FIGURE 3: Radulae of Pseudotricula species. A, B, Pseudotricula eberhardi, C.165053, Black Curtain Streamway, Cueva Blanca; C–H, Pseudotricula expandolabra, C, D, C.201495, Persephone Streamway, Bauhaus, E, G, H, C.201811, Persephone Pot, Bauhaus, F, C.201822, main streamway, Bauhaus; I, Pseudotricula arthurclarkei, C.203671, paratype, Quetzalcoatl Conduit; J–L, Pseudotricula conica, C.203676, paratype, Cane Toad Abuse Streamway, Damper Cave. A, C, G, K, central, lateral inner and outer marginal teeth; B, E, L, central teeth; D, outer marginal teeth; F, J, lateral and inner marginal teeth; H, lateral tooth; I, central and lateral teeth. Scales: A, B, E, H–J, L 10 m; C, F, G, K, 20 m; D, 5 m.

FIGURE 7. Opercula of Pseudotricula species. A, B, Pseudotricula expandolabra, C.201493, paratypes, main streamway, Bauhaus; C, Pseudotricula auriforma, C.201496, paratype, main streamway, Damper Cave; D, E, Pseudotricula arthurclarkei, C.203671, paratypes, Quetzalcoatl Conduit; F–I, Pseudotricula conica, F, G, C.203680, main streamway, near entrance, Damper Cave; H, I, C.201459, Screaming Stals streamway, Bauhaus; A, D, F, H, outer side; B, C, E, H, I, inner side; Scales: A–I, 200 m.

FIGURE 8. Pallial cavities of male specimens of Pseudotricula and Nanocochlea species. A, Pseudotricula expandolabra, C.201493, paratype, Persephone Streamway, Bauhaus; B, Pseudotricula arthurclarkei, C.203671, paratype, Quetzalcoatl Conduit; C, Pseudotricula auriforma, C.201496, paratype, main streamway, Damper Cave; D, E, Pseudotricula conica, D, C.203680, main streamway near entrance, Damper Cave, E, Cane Toad Abuse Streamway, Damper Cave; F, Nanocochlea exigua, C.203677, paratype, Cane Toad Abuse Streamway, Damper Cave; G, Nanocochlea damperensis, C.203685, paratype, first crossing, Damper Creek; H, Pseudotricula progenitor, C.201821, main streamway, Bauhaus. Scales: A–D, F–H, 500 m, E, 1 mm. Abbreviations: a, anus; ct, ctenidium; ev, efferent vein; os, osphradium; pc, pericardium; pe, pallial edge; ppw, posterior pallial wall; r, rectum; rg, renal gland. The stippled area represents the hypobranchial gland.

FIGURE 10. Female reproductive systems of Pseudotricula species. A ­ C, Pseudotricula expandolabra, A, B, C.201493, paratype, Persephone Streamway, Bauhaus, C, C.201815, Persephone Streamway, Bauhaus; D, Pseudotricula auriforma, C.201496, paratype, main streamway, Damper Cave; E, Pseudotricula arthurclarkei, C.203671, paratype, Quetzalcoatl Conduit; F, G, Pseudotricula conica, F, C203680, main streamway near entrance, Damper Cave, G, Cane Toad Abuse Streamway, Damper Cave. Scale: 500 m. Abbreviations: ag, albumen gland; bc, bursa copulatrix; bd, bursal duct; cg, capsule gland; co, coiled oviduct; po, genital opening; pw, pallial wall; sr, seminal receptacle; vc, ventral channel.

FIGURE 11. Shells of Pseudotricula species. A ­ C, Pseudotricula elongata, Persephone Pot, A, holotype, C.166854; B,C, paratypes, B, C.203713, C, C.201809; D–F, Pseudotricula arthurclarkei, C.203671, paratypes, Quetzalcoatl Conduit. Scales: A ­ C, 500 m; D–F, 1 mm.

FIGURE 12. Shells of Pseudotricula species. A, Pseudotricula arthurclarkei, holotype, C.439656, Quetzalcoatl Conduit; B ­ D, Pseudotricula conica, B, holotype, Cane Toad Abuse Streamway, Damper Cave; C, C.203680, main streamway near entrance, Damper Cave; D, C.201813, Persephone Pot, Bauhaus. Scales: A–D, 500 m.