Gabbia spiralis, Ponder, 2003

Ponder, Winston F., 2003, Monograph of the Australian Bithyniidae (Caenogastropoda: Rissooidea), Zootaxa 230 (1), pp. 1-126 : 104-105

Gabbia spiralis n.sp.

Etymology Spiralis (L.) – spiral.

Type material

Waterhole on Eight Mile Ck on Karumba ­ Chillagoe Rd, Qld, 17° 12.217'S, 141° 12.1'E, on weed etc. mainly along edges, 1 JUN 1997, W.F.Ponder, V.Kessner & D.L.Beechey (Holotype, AMS C.417682; paratypes AMS C.331849, 655, 16 dry, 6 on SEM stub; QM MO71720, 12; NTM P21378, 8) .

Additional material examined

Queensland: Waterhole W of Pelican Ck, 10.5 km SSE of Wyaaba Ck Crossing, 16° 46.920'S, 141° 59.230'E, on grass & substrate, 1 JUN 1997, W.F. Ponder, V. Kessner & D.L. Beechey ( AMS C.332834, 20+); waterhole 300m N of Gilbert R on Burke Developmental Rd, 17° 9.880'S, 141° 46.120'E, on mud & weed along edges, 1 JUN 1997, W.F.Ponder, V. Kessner & D.L.Beechey ( AMS C.338815, 20+); waterhole in river flood channel of Gilbert R, ca. 0.2 km S of Gilbert R, 17° 10.450'S, 141° 45.990'E, on weed & mud, 1 JUN 1997, W.F.Ponder, V.Kessner & D.L.Beechey ( AMS C.326799, 20+); Twelve Mile Ck waterholes at Karumba to Normaton Rd , 17° 31.730'S, 141° 9.570'E, 31 MAY 1997, W.F.Ponder, V.Kessner & D.L. Beechey ( AMS C.332839, 20+) .

Description

Shell ( Figs 1L , 26D,G , 36C,D ) small to moderate (up to 5.6 mm in length), broadlyovate to ovate­conic, with up to 4.0 convex, narrowly shouldered whorls. Protoconch of 1.3­1.5 whorls, smooth except for traces of fine spiral striae. Teleoconch sculptured with numerous strong spiral cords (about 25­30 spiral cords on last whorl) with about equal to linear interspaces and crossed by fine collabral growth lines; one cord on upper part of whorl slightly stronger, with weak shoulder above; base evenly convex; umbilicus open, moderate size. Aperture broadly ovate; peristome moderately thickened in adults; outer lip prosocline. Colour: shell opaque to sub­translucent; periostracum thin, yellowish­white to orange­brown. A few thin, dark varices typically present.

Dimensions. See Table 27 for dimensions of holotype and Appendix, Table 29 , for summary shell dimensions and whorl counts.

Operculum ( Fig. 32N,M ) typical of genus. Ovate, translucent and colourless to yellowish­white or white; concentric growth ridges poorly demarcated (outer surface often appears almost smooth) to distinct; inner surface with muscle scar occupying much of surface, sculptured with folds, pits or pustules.

Radula (Appendix Table 30 ; Fig. 37D,E ) typical of genus. Central teeth with 4­5 cusps on either side of median cusp which is about 1.3­1.6 longer than adjacent cusps and its base about twice as wide; median cusp evenly tapering to sharp point to parallel sided proximally with peg­like projection distally ( Fig. 37E ). Face of central tooth with 3­5 pairs of cusps that extend well inside lateral margin and parallel to it forming cuspate ridge, inner pair larger than others but second pair almost equal in size; inner pair about half total height of tooth; lateral margins straight to slightly concave, at about 50­60º; basal tongue short, blunt to pointed. Lateral teeth with cusp formula 4­5 + 1 + 4­5; with cutting edge about third length of lateral part of tooth; median cusp up to about 1.4 length of adjacent cusps, parallel sided to slightly tapering, distal end bluntly pointed to rounded; upper edge of lateral part of tooth at about 50­60º to cutting edge, lateral edge slightly to moderately concave. Inner marginal teeth with 21­24 cusps, outer marginal teeth narrow, with 8­11 cusps.

Head­foot with pale grey to black snout, pigment extending onto middle part of head in more heavily pigmented specimens, tentacles with wide grey to black longitudinal streak in middle part; bases of tentacles, foot and siphon unpigmented. Mantle roof unpigmented, or with grey or black pigment and tiny white spots in anterior half fading to absent posteriorly, mantle edge unpigmented. Visceral coil unpigmented or with dorsal grey to black smudge.

Anatomy. Gill with apices at quarter to third gill width from right; 64­67 filaments (n=3). Osphradium slightly anterior to middle of gill. Penis ( Fig. 7H ) with accessory lobe slightly shorter than penial lobe, distal end swollen; accessory gland moderately long. Pallial oviduct ( Fig. 34C ) similar to G. vertiginosa , bursa copulatrix rather narrow, and almost reaches posterior pallial wall (AMS C.331849).

Distribution ( Fig. 22 ) and habitat. Coastal plains, western base of Cape York, Gulf of Capentaria. In billabongs and pools on mud, although often associated with macrophytes and algae.

Remarks

This species and the next differ from all other Australian bithyniids in dominant spiral sculpture. Gabbia spiralis differs from G. carinata n. sp. in having more numerous, relatively weaker spiral cords, a taller spire and smaller umbilicus. See the remarks under G. carinata relating to the generic placement of spirally lirate species.

Figures

FIGURE 1. Shells of type specimens: A, Bithynia vertiginosa Frauenfeld 1862, holotype, NHMV, shell length 6.79 mm; B, Gabbia iredalei Cotton 1942, holotype, SAM, D14098, shell length 6.97 mm; C, Gabbia australis suspecta Iredale 1944, syntype, AMS, C.51675, shell length 6.54 mm; D, Gabbia australis suspecta Iredale 1944, syntype, AMS, C.100600, shell length 4.65 mm; E; Bithynia schraderi Frauenfeld 1862, holotype, NHMV, shell length 6.46 mm; F, Bithinia hyalina Brazier 1875, syntype, AMS, C.110159, shell length 4.98 mm; G, Bithinia hyalina Brazier 1875, syntype, MMS A69, shell length 6.63 mm; H, Gabbia australis Tryon, 1865, probable paralectotype, AMS, C.110160, shell length 5.43 mm; I, Gabbia affinis Smith 1882, topotype, AMS, C.2515, shell length 4.44 mm; J, Bithinia australis Smith, 1882 (= Gabbia smithii Tate 1882), lectotype, BMNH, 197748, shell length 3.20 mm; K, Gabbia microcosta n.sp., holotype, AMS, C.417677, shell length, 8.51 mm; L, Gabbia spiralis, n. sp., holotype, AMS, C.417682, shell length 4.56 mm.

FIGURE 7. Penis and accessory gland. A, D – Gabbia campicola, A, ventral view, C.332829, D, dorsal view, USNM, 803665; B – Gabbia rotunda, ventral view, AMS, C.400134; C – Gabbia davisi, ventral view, AMS, C.417617; E – Gabbia beecheyi, ventral view, AMS, C.332843; F, G – Gabbia fontana, dorsal view, AMS, C.380863; H – Gabbia spiralis, dorsal view, AMS, C.331849; I, J – Gabbia vertiginosa, dorsal view, AMS, C.203392, I, enlargement of distal end of accessory lobe; K – Gabbia adusta, dorsal view, AMS, C.203394. Scales: 500 m.

FIGURE 22. Distribution of Gabbia obesa (o), G. affinis (), G. microcosta (), G. clathrata () and G. spiralis ().

FIGURE 26. Protoconchs and microsculpture: A ­ C, Gabbia clathrata, A, B, AMS, C.318586, C, paratype, AMS, C.327884; D ­ G, Gabbia spiralis, paratype, AMS, C.331849; H ­ I, Gabbia carinata, paratype, AMS, C.331877; A ­ B, D ­ E, H, protoconchs, C, F, G, I, microsculpture; Scales: A, 500 m, B, D ­ H, 100 m, C, I, 200 m.

FIGURE 32. Opercula: A ­ H, Gabbia adusta, A, AMS, C.331869, B, C, AMS, C.331871, D ­ G, 331876, H, AMS, C. 203381; I, J, Gabbia lutaria, paratype, AMS, C.318599; K, L, Gabbia clathrata, paratype, AMS, C.327884; M, N, Gabbia spiralis, paratype, AMS, C.331849; O, P, Gabbia carinata, paratype, AMS, C.331877; A, C, E, F, I, K, M, O, outer side, B, D, G, H, J, L, N, P, inner side; Scales: 500 m.

FIGURE 34. Pallial oviducts, viewed from the left side. A, Gabbia adusta, AMS, C.203394; B, Gabbia clathrata, AMS, C.346418; C, Gabbia spiralis, paratype, AMS, C.331849; D, Gabbia carinata, AMS, C.326793. Scales: 500 m.

FIGURE 36. Shells: A, Gabbia lutaria, holotype, C.417680; B, Gabbia clathrata holotype, AMS, C.417681; C, D, Gabbia spiralis, paratype, AMS, C.331849; E, F, Gabbia carinata, E, paratype, AMS, C.331877, F, holotype, AMS, C.417683; A ­ F, 500 m.

FIGURES 37. Radulae: A­C, Gabbia clathrata, paratype, AMS, C.327884; D, E, Gabbia spiralis, paratype, AMS, C.331849; F­I, Gabbia carinata, F­H, paratype, AMS, C.331877, I, AMS, C.327927. A, G, half rows of teeth, B, E, H, central teeth, C, lateral teeth, D, lateral and marginal teeth, F, lateral teeth, I, full rows of teeth; Scales: 20 m.