Pseudotricula expandolabra, 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 : 15-24

Pseudotricula expandolabra n. sp.

Figures 2B, E ; 3C–H ; 4B ; 5A–F ; 6A–D ; 7A,B ; 8A ; 9C ; 10A–C .

Type material

Holotype: AMS C.439673, Screaming Stals Streamway, Bauhaus, stn 12, 23 Dec, 1991.

Paratypes: AMS C.201493, same locality stn 12 (6 dry, 12 wet) ; QVM, 9:20536 (5 wet).

Figured (shell) paratypes: AMS C.439674, same locality stn 12.

Other material examined

Bauhaus: AMS C.201822, main streamway, stn PB6­1A (16 dry, 18 wet); AMS C.201486, Screaming Stals streamway, stn 11 (8 dry 14 wet); AMS C.201489, same locality, stn 13 (15 dry, 20+ wet); C.201485, Persephone, stn 7 (4 dry, 11 wet); C.201491, Persephone streamway, stn 8 (8 dry, 10 wet); C.201492, same locality, stn 9 (9 dry); C.201495, same locality, stn 10 (8 dry, 6 wet); C.439676, same locality, stn 10, figured specimen; C.201811, Persephone Pot, stn PB17­8R (1 dry, 4 wet); same locality, middle and upper streamway, stn PB17­2a.2 (20+ dry, 20+ wet); C.439675, same locality, stn PB17­2a.2, figured specimen; C.201815, same locality, lower streamway, stn PB17­2a.1, (20+ dry, 20+ wet); C.165055.

Damper Cave: AMS C.201494, seep near The Keg, stn 3 (1 dry); AMS C.201490, Honey and Cream streamway, stn 4 (10 dry, 10 wet); AMS C.203678, Cane Toad Abuse streamway, stn PB1­2A (1 dry, 6 wet).

Etymology

Expando Latin, spread out, labrum, Latin, lip; refers to the expanded outer lip of the aperture.

Description

Shell ( Fig. 2B, E ; 5A–F ; 6A–D ). Length up to 3.8 mm; with conical spire and large, expanded aperture (SW/SL 0.61–0.74, mean 0.69, n = 43); spire low to moderate, straight to slightly convex in outline, last whorl evenly rounded; usually with shallow subshoulder depression on last two whorls. Protoconch microsculpture of distinct, small pits ( Fig. 6B ). Teleoconch of up to 3.6 whorls in adult; aperture oval to pear­shaped; large, about equal to spire or slightly longer (AL/SL 0.52–0.63, mean 0.57, n = 43); outer lip prosocline; straight to or weakly sinuous, with strong reflection; external varix absent; notch present in posterior corner of aperture; inner lip thick, broad, firmly adhering to, or narrowly separated from, parietal wall.

Dimensions. See Table 3.

Operculum ( Fig. 7A, B ). Yellowish; inner surface with or without white smear.

Pallial cavity ( Fig. 8A ). Ctenidium narrow; 12–16 very small filaments; osphradium between posterior end and middle of ctenidium; hypobranchial gland variably developed; renal organ extends forward ca. ⅓–½ into pallial cavity; pericardium more than ½ in pallial roof.

Radula ( Fig. 3C–H ). Central teeth ( Fig. 3E ): dorsal edge with shallow indentation; 4– 5 lateral cusps, median cusp of medium to narrow, sharply pointed, less than twice as long as adjacent cusps. Lateral teeth ( Fig. 3 F, H ): dorsal edge with shallow indentation; with 3– 4 (usually 4) cusps on outer and 3–5 on inner side; median cusp of medium width, sharply to bluntly pointed, less than twice as long as adjacent cusps; ratio of cutting edge to shaft about ¼; basal projection bluntly pointed. Marginal teeth: Inner ( Fig. 3F ) with 16–21 cusps; outer ( Fig. 3D ) with 17–26 cusps.

Stomach ( Fig. 9C ). Stomach with posterior chamber and anterior chamber about equal in size.

Male genital system. Testis of 1.0–1.25 whorls; prostate gland oval to kidney­shaped to elongate pyriform; compressed in section. Pallial vas deferens straight to slightly undulating. Penis ( Fig. 4B ) weak swelling in mid­distal portion; distal end long, papillalike; medial section tapering to parallel sided, of medium length; penial duct strongly undulating; base of penis moderately wide; with moderate folds; penial duct straight to undulating.

Female genital system ( Fig. 10A–C ). Ovary of 1.0 whorls; oviduct extends to posterior edge of bursa copulatrix; with one bend distal to seminal receptacle; joins bursal duct about half way between posterior pallial wall and capsule gland. Bursa copulatrix large, extending to posterior pallial wall or slightly in front; globular to elongately oval; with bursal duct arising from middle of anterior edge of bursa; straight or with undulations. Seminal receptacle at middle of inner wall of bursa copulatrix or near mid ventral edge; ovoid. More than ½ of albumen gland in front of posterior pallial wall; capsule gland longer than albumen gland; compressed oval in section; anterior end blunt; ventral channel simple, approximately parallel­sided throughout; vestibular area indistinct to distinct; genital opening terminal to overlapping anterior end of capsule gland.

Distribution and habitat

Damper Cave (Honey and Cream and Cane Toad Abuse streamways and seep near The Keg) and Bauhaus (Persephone and Screaming Stals streamways and Persephone Pot). This species is found in narrow (less than 1m in width) streams with gentle to moderate (<1L/s to about 5L/s estimated flows) within the caves. The substrate is mixed cobbles, gravel and silt and the microhabitats pools and riffles. Two samples were also found in seepages associated with this type of stream.

Remarks

Pseudotricula expandolabra is similar to P. eberhardi but its shell differs in having a straight spire outline, a taller spire (P<0.001) and the whorls are indented slightly below the shoulder. While it is rather constant in shape, it varies in size. Specimens from Persephone Pot are typically smaller ( Fig. 5D–F ) than those from the main Bauhaus cave. There also appears to be some notable anatomical variation; a specimen from Persephone Pot ( Fig. 10C ) has the bursal duct showing substantial undulations and the bursa copulatrix being larger and longer but a second specimen from this location is like some specimens from Bauhaus with only a single bend in the bursal duct (others have a straight bursal duct) and a smaller bursa. Given the continuity of these two systems and the similarity in the shells of specimens from the two localities, they are treated as a single species pending more detailed investigation.

Figures

FIGURE 2. Shells of Pseudotricula species. A, Pseudotricula eberhardi, holotype, C.165052, Black Curtain Streamway, Cueva Blanca; B–E, Pseudotricula expandolabra, B, holotype, C.439673, Persephone Streamway, Bauhaus; C, paratype, C. 439674, Persephone Streamway, Bauhaus; D, C.201811, Persephone Pot, Bauhaus; E, C201495, Persephone Streamway, Bauhaus; F, Pseudotricula auriforma, holotype, C.439672, main streamway, Damper Cave. Scales: A F, 500 m.

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 4. Dorsal views of penes of Pseudotricula and Nanocochlea species. A,. Pseudotricula eberhardi; B, Pseudotricula expandolabra; C, Nanocochlea stylesae; D, Nanocochlea damperensis; E, Pseudotricula conica. Scales A, B, E, 0.2 mm; C, D, 0.1 mm. Abbreviations: ds, distal swelling; pd, penial duct.

FIGURE 5. Shells of Pseudotricula species. A–F, Pseudotricula expandolabra, A–C, C.201489, Screaming Stals streamway, Bauhaus, D–F, Persephone Pot, Bauhaus, D, F, C.201811, E, C.201485, Persephone Pot, Bauhaus; G–I, Pseudotricula auriforma G, H, streamway near entrance, Damper Cave, I, main streamway, Damper Cave. Scales: 1 mm.

FIGURE 6. Protoconchs and teleoconch microsculpture of Pseudotricula and Nanocochlea species. A–D, Pseudotricula expandolabra, A, B, D, C.201493, paratype, main streamway, Bauhaus, C, C.201495, Persephone Streamway, Bauhaus; E–G, Pseudotricula conica, E, F, C.201464, Cane Toad Abuse Streamway, Damper Cave, G, Persephone Pot, Bauhaus; Honey and Cream Streamway, Damper Cave; H, Nanocochlea exigua, C.201475; I, J, Nanocochlea stylesae, C.201476, paratypes, Malani Creek; K–M, Nanocochlea damperensis, K, L, C.203685, paratypes, first crossing, Damper Creek, M, C.201282, Near New River Lagoon, E side, Limestone Ck, where tagged track crosses; N, O, Pseudotricula progenitor, C.201821, main streamway, Bauhaus. A, B, E, F, H, K–N, protoconch; C, D, G, I, J, O, microsculpture. Scales: A, C–E, J, K, M, O, 200 m; B, F–I, L, N, 100 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 9. Head, penis and stomach of Pseudotricula species. A, D, Pseudotricula conica, C.203680, main streamway near entrance, Damper Cave; C, Pseudotricula expandolabra, C.201493, paratype, Persephone Streamway, Bauhaus; B, E, Pseudotricula progenitor, C.201821, main streamway, Bauhaus. A, B, head and penis; C–E, stomach. Scales: A–E, 500 m. Abbreviations: dgo, opening from stomach to digestive gland; ey, eye; int, intestine; oes, oesophagus, p, penis; pg, penial duck; sn, snout; ss, style sack; st, stomach; tn, tentacle.

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.