Nanocochlea stylesae, 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 : 45-47

Nanocochlea stylesae n. sp.

Figures 4C ; 6I, J ; 14D ; 15D–F ; 17D, E .

Type material

Holotype: AMS C.439398, Malani Creek , stn 14, 28 DEC 1991.

Paratypes: AMS C.201476, same data, 1 dry, 20+ wet ; QVM, 9:20542 (5 wet).

Other material examined First crossing, Damper Creek: AMS C.203686, stn PBs­1A (2 dry, 1 wet).

Etymology

Named for Julie Styles who assisted one of us (SE) in the collection of the bulk of the material used in this paper.

Description

Shell ( Fig. 6I–J ; 14D ; 15D–F ). Length up to 2.0 mm; narrowly conical (SW/SL 0.47– 0.56, mean 0.52, n = 21); spire tall, straight to slightly convex in outline; last whorl evenly rounded; suture simple or indented/impressed. Protoconch microsculpture not examined in detail. Teleoconch up to 3.5 whorls in adult; umbilicus closed in juveniles; aperture oval to pear­shaped; moderate size, shorter than spire (AL/SL 0.33–0.42, mean 0.37, n = 21); outer lip orthocline, weakly thickened in adult, straight, without reflection; posterior notch absent; inner lip thin and narrow, in partial contact or narrowly separated from parietal wall.

Dimensions. See Table 11.

Operculum. Inner surface simple or with small slightly thickened lump near nucleus (possibly rudimentary peg).

Eyes. Unpigmented.

Pallial cavity. Ctenidium narrow; 9–11 very small filaments; osphradium near posterior end of ctenidium; hypobranchial gland very weakly­developed to apparently absent; renal organ extends forward ca. ⅓ into pallial cavity; pericardium up to ⅓ in pallial roof.

Radula ( Fig. 17D, E ). Central teeth: dorsal edge with deep indentation; 5 lateral cusps, median cusp narrow, blunt to sharply pointed, about twice as long as adjacent cusps. Lateral teeth: dorsal edge with shallow to moderate indentation; with 5–6 cusps on outer and 5 on inner side; median cusp narrow, sharply pointed, less than twice as long as adjacent cusps; ratio of cutting edge to shaft about ⅓; basal projection pointed to bluntly pointed. Marginal teeth: Inner with 24–38 cusps; outer with 20–28 cusps.

Stomach. Stomach with posterior chamber and anterior chamber about equal in size.

Male genital system. Testis of about 2.0 whorls; prostate gland about ½ in pallial roof; oval to elongate pyriform; oval in section. Pallial vas deferens strongly undulating at prostate, straight between prostate and penis and at base of penis. Penis ( Fig. 4C ) with weak swelling in mid­distal portion; distal end long, papilla­like; medial section tapering to parallel sided; of medium length; penial duct straight to slightly undulating; base of penis moderately wide; with moderate folds; penial duct straight to weakly undulating.

Female genital system. Ovary of 0.7 whorls; oviduct extends to posterior edge of bursa copulatrix; joins bursal duct at posterior pallial wall. Bursa copulatrix of medium size, not extending to posterior pallial wall; globular; with bursal duct arising from middle of anterior edge of bursa; straight. Seminal receptacle at middle of inner wall of bursa copulatrix; ovoid. One third of albumen gland in front of posterior pallial wall; capsule gland about same length as albumen gland; circular in section; anterior end tapering to blunt; ventral channel simple, approximately parallel­sided throughout; vestibular area indistinct; genital opening terminal.

Distribution and habitat This species is apparently restricted to surface streams flowing from Precipitous

Bluff—it is known from Malani Creek, approximately 1.3 km north of Damper Creek and in Damper Creek itself where a few specimens were found together with N. damperensis .

Remarks

Nanocochlea stylesae is somewhat similar in shape to N. exigua but has a short ctenidium, lacks a distinct opercular peg and tends to have more cusps on the inner marginal teeth. It differs from N. damperensis in its narrower shell (P<0.001) and less convex whorls and fewer ctenidial filaments.

Figures

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 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 14. Shells of Nanocochlea species and Pseudotricula progenitor. A ­ C, Nanocochlea exigua, A, holotype, C.439393, Cane Toad Abuse Streamway, Damper Cave; B, C, C.201465, main streamway, Damper Cave; D, Nanocochlea stylesae, holotype, C.439398, Malani Creek; E–G, Nanocochlea damperensis, E, C.203685, paratype, first crossing, Damper Creek; F, holotype, C.439399, first crossing, Damper Creek, F, C.201282, Near New River Lagoon, E side, Limestone Ck, where tagged track crosses; H, I, Pseudotricula progenitor, H, paratype, C.439397, Persephone Streamway, Bauhaus; I, holotype, C.439396, Persephone Streamway, Bauhaus. Scales: 500 m.

FIGURE 15. Shells of Nanocochlea species and Pseudotricula progenitor. A ­ C, Nanocochlea exigua, A, C.203674, outside Damper Cave, Damper Creek B, C.166855, Persephone Pot, Bauhaus, C, C.201465, main streamway, Damper Cave; D–F, Nanocochlea stylesae, D, C.201476, paratype, Malani Creek, E, F, C.203686, first crossing, Damper Creek; G­I, Nanocochlea damperensis, G,H, C.303685, seepages at Bauhaus entrance, I, C.203685, paratype, first crossing, Damper Creek; J–L, Pseudotricula progenitor, J, L, C.201463, paratype, Persephone streamway, Bauhaus, K, C.201454, Persephone, Bauhaus. Scales: 1 mm.

FIGURE 17. Radulae of Nanocochlea species Pseudotricula progenitor. A ­ C, Nanocochlea exigua, A, C.201475, Honey and Cream Streamway, Damper Cave, B, D, C.201465, main streamway, Damper Cave; D– E, Nanocochlea stylesae, C.201476, paratypes, Malani Creek; G–K, Nanocochlea damperensis, G, H, C.203685, paratypes, first crossing, Damper Creek, I–K, C.201282, Near New River Lagoon, E side, Limestone Ck, where tagged track crosses; L–O, Pseudotricula progenitor, C.201821, main streamway, Bauhaus. A, E, central and lateral teeth; B, F, I, M, central, lateral, inner and outer marginal teeth; C, D, J, N central teeth; G, L, lateral teeth; H, central lateral inner and outer marginal teeth; K, outer marginal teeth. Scales: A, G–H, K, L, 10 m; B, I, M, 20 m; C, D, J, N, 5 m.