Gabbia adusta, Ponder, 2003

Ponder, Winston F., 2003, Monograph of the Australian Bithyniidae (Caenogastropoda: Rissooidea), Zootaxa 230 (1), pp. 1-126 : 92-98

Gabbia adusta n.sp.

Etymology Adustus (L.) ­ brown.

Type material

Billabong beside Roper R, NT, 14° 44.410'S, 134° 42.050'E, in mud & weed, 20 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (Holotype, AMS C.418413; paratypes AMS C.203384, 264 wet, 40 dry, 1 on SEM stub; NTM 21375, 8; QM MO71717, 5) .

Additional material examined

Northern Territory: Elsey Cemetery, 11 km S of Mataranka Springs, 15° 5.150'S, 133° 7.440'E, along edges of large drying pond in soft mud and grass, 18 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.333080, 20+), same locality, on mud and algae, 3 JUL 1999, W.F.Ponder (AMS C.381471, 9), in recently dried up pool/swamp, 23 JUN 1996, W.F.Ponder & D.L.Beechey (AMS C.333675, 10), along edges of large drying pond in soft mud and grass, 18 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.417913, 20+), on & in mud & on green algae, 3 JUL 1999, W.F.Ponder (AMS C.371689, 20+); Warloch Ponds, near Elsey Cemetery, S of Mataranka, NT, 15° 5.250'S, 133° 7.330'E, 6 APR 1996, V.Kessner (VKC 24308, 15; AMS C.318629, 3); Newcastle Waters, causeway, 17° 22.370'S, 133° 24.730'E, waterhole, much organic matter & floating weed, 5 JUL 1999, W.F.Ponder (AMS C.371684, 20+); Strangways Ck, waterhole on flood channel near bridge, 14° 54.190'S, 133° 45.100'E, on mud along edges and in a few cm of water, 19 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.331869, 20+); pond beside Roper Hwy, 1/ 2 km towards Roper Bar from Scherwin Ck, 14° 42.270'S, 134° 27.620'E, on mud and weed, 19 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.333673, 20+; AMS C.351061, 20+); waterhole nr Roper Bar, 14° 43.040'S, 134° 30.780'E, mud, 20 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.346417, 20+); lagoon near Hodgson R, 14° 51.680'S, 134° 32.670'E, weed & mud, 20 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.375634, 2); small billabong 2 km W of Ngukurr, S of Roper R, Gulf of Carpentaria, 14° 44.220'S, 134° 42.920'E, 6 APR 1996, V.Kessner (VKC 24310, 20+; AMS C.318589, 6; billabong beside rd opposite Ngukurr Mission, 14° 44.230'S, 134° 42.940'E, 20 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.203394, 20+); swamp on Wulunurrayi Ck, just off rd, 15° 18.350'S, 135° 20.200'E, on weed, 21 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.401225, 1); Nikantyarra Waterhole, Cox R, 15° 20.560'S, 135° 21.190'E, on mud & weeds, 21 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.203396, 1); Rocky Ck, below the bridge at Borroloola, Gulf of Carpentaria, 16° 4.000'S, 136° 18.420'E, pool below the bridge, muddy sand, 16 APR 1996, V.Kessner (VKC 24299, 1); mudhole ca. 9.5 km W of Borroloola on Carpentaria Hwy, 16° 6.660'S, 136° 13.380'E, on mud & weed, 22 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.346423, 20+); Wanmurri Lagoon, 5 km S of Manangoora Stn, 16° 2.660'S, 136° 55.400'E, on mud, 23 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.401228, 16); Surprise Ck crossing, Gulf of Carpentaria, 16° 53.920'S, 137° 12.750'E, 28 AUG 1988, V.Kessner (VKC 13888, 1; AMS C.318637, 1); billabong S of Tully Inlet, 2.5 km W of Settlement Ck, Wollogorang Stn, Gulf of Carpentaria, 16° 45.700'S, 138° 8.950'E, 25 AUG 1994, V.Kessner (VKC 24312, 20+; AMS C.318631, 6); 65 km (by road) NE of Wollogorang, near NT/Qld border, Gulf of Carpentaria, 16° 47.000'S, 138° 10.170'E, 29 AUG 1988, V.Kessner (VKC 13889, 5; AMS C.318612, 1).

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.332841, 1); Nolan Ck at Burke Developmental Rd, 16° 48.670'S, 144° 10.090'E, 4 JUN 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.346413, 20+); billabong E of Settlement Ck crossing, Wollogorang Stn, Gulf of Carpentaria, 16° 53.450'S, 138° 9.280'E, 25 AUG 1994, V.Kessner (VKC 24311, 13; AMS C.318635, 3); Ballys Lagoon, Devils Gate Stn, 17° 19.770'S, 138° 38.900'E, on surface of sediment, 24 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.401226, 20+); swamp between Four Mile Lagoon and Pioneer Waterhole, 17° 17.460'S, 138° 19.200'E, on weed and mud, 24 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.203383, 20+); Bullock Head Yard, E of Devils Gate ca. 14 km, 17° 24.700'S, 138° 28.890'E, on weed and substrate, 24 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.203381, 20+; AMS C.417678, 1); Jam Tin Yard, Devils Gate Stn, 17° 24.600'S, 138° 34.950'E, on mud, 24 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.333676, 20+); near Scrutton Ck crossing, Gulf of Carpentaria, 17° 35.750'S, 138° 26.420'E, 1 km SSE of crossing, small billabong in Cliffdale Ck drainage, 30 AUG 1988, V.Kessner (AMS C.307864, 5), same locality, collector and date, 7 km SSE, 17° 35.750'S, 138° 26.420'E, (VKC 13890, 20+; AMS C.318642, 6); N of Ballys Lagoon, Devils Gate Stn, 17° 15.210'S, 138° 40.210'E, mudhole, 25 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.331876, 20+; AMS C.380859, 20+); same data, billabong (AMS C.331882, 20+); waterhole of Archie Ck System on Lawn Hill to Gregory Downs Rd, 18° 35.280'S, 138° 49.180'E, on bottom amongst weed, 27 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.346419, 20+); Nicholson R crossing, 3 km SE of Doomadgee, Gulf of Carpentaria, 17° 57.750'S, 138° 50.750'E, 30 AUG 1988, V.Kessner (VKC 13891, 3; AMS C.318615, 1); Nicholson R at Doomadgee, 17° 57.640'S, 138° 51.060'E, on side of river channel behind weir, 25 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.331859, 20+); billabong / mudhole, NW of Burketown, 17° 41.570'S, 139° 23.130'E, 28 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.401227, 20+); M Lagoon next to M Ck on Normanton ­ Burketown Rd, 18° 6.070'S, 140° 16.880'E, on mud amongst vegetation, 29 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.331870, 20+); billabong beside Norman R at Gulf Developmental Rd, 17° 51.400'S, 141° 8.110'E, amongst weed and on mud, 30 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.331871, 20+); waterhole on Eight Mile Ck on Karumba ­ Chillagoe Rd, 17° 12.217'S, 141° 12.1'E, mainly along edges, 1 JUN 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.331883, 22).

Description

Shell ( Figs 19C,D , 31 D­L) moderate (up to 6.8 mm in length; usually to about 4­5 mm), broadly­ovate to sub­conic, with up to 4.7 convex whorls. Protoconch of 1.3­1.5 almost smooth whorls, finely granular with some minute spiral wrinkles; last third to half whorl with few axial threads. Teleoconch sculptured with weak to moderately strong axial ribs with rounded to flattened tops and often steep sides, crossed by very numerous fine spiral threads; base evenly convex; umbilicus moderate to closed (with chink) in adults, juveniles usually perforate. Aperture broadly ovate; peristome moderately thickened in adults, inner lip forms narrow reflexion that partially obscures umbilicus in mature specimens; outer lip prosocline. Colour: shell usually opaque, juveniles sometimes sub­translucent, periostracum thin, ranging from white to yellow brown, sometimes stained dark brown or orange brown.

Dimensions. See Table 24 for dimensions of holotype and Appendix, Table 29 , for summary shell dimensions and whorl counts.

Operculum ( Fig. 32 A­H) typical of genus. Ovate, opaque white or yellowish­white, sub­translucent in smaller specimens; concentric growth ridges often distinct; inner surface with muscle scar occupying most of surface, sculptured with weak pustules.

Radula (Appendix Table 30 ; Fig. 33 H­K) typical of genus. Central teeth with 3­5 cusps on either side of median cusp which is about 1.5 to 1.8 length of adjacent cusps and its base nearly twice as wide; median cusp evenly tapering to a sharp point (one sample [AMS C.331869; Fig. 33I ] has median cusp nearly parallel sided proximally with distal end tapering rapidly to point in some teeth while others nearly evenly tapering). Face of central tooth with 2­3 pairs of cusps that extend well inside lateral margin forming a cuspate ridge, inner pair much larger only slightly larger than adjacent pair, a little less than half total height of tooth; lateral margins slightly convex to slightly concave, at about 50­ 60º; basal tongue moderate length, triangular to subtriangular, usually pointed, rarely blunt. Lateral teeth with cusp formula 3­4 + 1 + 3­6; with cutting edge about half to slightly less than half length of lateral part of tooth; median cusp about 1.2­1.5 as long as adjacent cusps, usually parallel­sided and rounded distally, rarely tapering and pointed; upper edge of lateral part of tooth at 50­70º to cutting edge, lateral edge usually straight, rarely slightly concave. Inner marginal teeth with 11­22 cusps, outer marginals with 7­11 cusps.

Head­foot with dark grey snout, otherwise grey to unpigmented. Tentacles with grey middle and unpigmented edges, tentacle bases unpigmented to grey. Mantle roof grey to black with small white spots (appears mottled); visceral coil unpigmented or with grey or black pigment.

Anatomy. Gill ( Fig. 6F ) with apices at or very near (up to about fifth of gill width) right edge except for anterior third where apices may be at about quarter gill width from right; 42­63 filaments (n=4). Osphradium slightly anterior of middle of gill to opposite middle. Penis ( Fig. 7K ) with accessory lobe about equal to slightly shorter than penial lobe, accessory lobe with slightly expanded distal end. Accessory gland moderately long. Pallial oviduct ( Fig. 34A ) similar to G. vertiginosa but with shorter, much wider bursa copulatrix (AMS C.203394).

Distribution ( Fig. 35 ) and habitat. Western base of Cape York across the Gulf of Carpentaria to Arnham Land. In billabongs and pools living mainly on mud, although often obtained in samples along with algae and macrophytes.

Remarks

The shell of this species is distinctive with its short to moderate spire, yellowish to reddish or orange brown colour and weak to moderate, narrow axial ribs with very fine spiral striae. The populations attributed to this species encompass considerable variation in shell size and shape (relative length of spire) and in the degree of umbilication. The sculpture is more consistent, although the axial ribs can vary in strength from very weak to strong and prominent and the prominence of the spiral sculpture varies from being almost invisible under a stereomicroscope in some to quite distinct, as in a population from near Elsie Cemetery ( Fig. 31L ). Populations representing the variation encompassed by this species concept do not appear to differ significantly in shell morphometrics or in radular details from the type population. Although much of the variation in shell morphology can occur both within and between populations, several samples have only a single morph. Given the amount of variation exhibited it is possible that this species concept may eventually prove to consist of more than one taxon.

Hemispherical egg capsules containing a single embryo were found laid individually on some shells in one sample (AMS C.203394).

Gabbia adusta is most similar to G. lutaria n. sp., and is contrasted with it in the remarks under that species.

Figures

FIGURE 6. Gills and osphradia. A, E – Gabbia vertiginosa, A, AMS, C.203392; E, AMS, C.308028; B – Gabbia beecheyi, AMS, C.332844; C – Gabbia fontana, AMS, C.307903; D – Gabbia rotunda, AMS, C.400134; F – Gabbia adusta, AMS, C.203394; G – Gabbia smithii AMS, C.322309; H – Gabbia kessneri, AMS, C.351073. Scales: 500 m. os ­ osphradium.

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 19. Protoconchs and microsculpture: A, B, Gabbia beecheyi, A, paratype, AMS, C.331852, B, AMS, C.332843; C, D, Gabbia affinis, AMS, C.308008; E ­ G, Gabbia microcosta, paratype, AMS, C.318641; H ­ R, Gabbia adusta, H, I, AMS, C.333080, J ­ L, AMS, C.331871, M, N, Q, R, AMS, C.203381, O, AMS, C.318589, P, AMS, C.331876; A, E, H ­ K, Q, protoconchs, B ­ D, F ­ G, L ­ P, R, microsculpture; Scales: A, G, N, 500µm, B ­ C 20µm, D, L, R, 50µm, E ­ F, H ­ K, P, 100µm, M, O, Q, 200 µm.

FIGURE 31. Shells: A, Gabbia affinis, AMS, C.308008; B, C, Gabbia microcosta, paratype, AMS, C.318641, D ­ L, Gabbia adusta, D, AMS, C.331869, E, AMS, C.203394, F, G, AMS, C.203381, H, AMS, C.346419, I, AMS, C.318589, J, holotype, AMS, C.418413, K, AMS, C.331876, L, AMS, C.333080; Scales: A ­ L, 500 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.

FIGURES 33. Radulae: A ­ C, Gabbia affinis, AMS, C.308008; D ­ G, Gabbia microcosta, D, E, paratype, AMS, C.318564, F, G, paratype, AMS, C.318641; H ­ K, Gabbia adusta, H, AMS, C.331869, I, AMS, C.346419, J, K, AMS, C.331876; L, M, Gabbia lutaria, paratype, AMS, C.318599. A, D, E, F, I, M, central teeth, B, J, marginal teeth, C, G, lateral teeth, H, K, central and lateral teeth, L, half row of teeth; Scales: 20 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 35. Distribution of Gabbia adusta () and G. lutaria (o).