Gabbia carinata, Ponder, 2003

Ponder, Winston F., 2003, Monograph of the Australian Bithyniidae (Caenogastropoda: Rissooidea), Zootaxa 230 (1), pp. 1-126 : 106-109

Gabbia carinata n.sp.

Etymology Carinatus (L.) – keeled.

Type material

Two mudholes, by Walker Ck, Qld, 17° 28.030'S, 141° 10.790'E, in fine mud around edges, 31 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (Holotype, AMS C.417683; paratypes AMS C.331877, 1018 wet, 30+ juveniles, 10 dry, 4 on SEM stubs; NTM P21379, 15; QM MO71721, 10) .

Additional material examined

Northern Territory: Tawarrila Ck, S. of Bing Bong, W . Gulf of Carpentaria , 15° 46.580'S, 136° 25.170'E, amongst macrophytes, 23 AUG 1994, W.F.Ponder, G.Wilson & V.Kessner ( AMS C.327927, several) .

Queensland: 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 23956, 20 +; AMS C.318640, 6); 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 23955, 20 +; AMS C.318576, 6); billabong above Tully Inlet, W. of Mornington Is ., Gulf of Carpentaria, 16° 45.710'S, 138° 8.960'E, amongst weed & macrophytes, 25 AUG 1994, W.F.Ponder, G.Wilson & V.Kessner ( AMS C.327879, several; AMS C.327893, 20+); billabong off road to beach nr Tully Inlet, W. of Mornington Is , Gulf of Carpentaria , 16° 46.900'S, 138° 10.140'E, 25 AUG 1994, W.F.Ponder, G.Wilson & V. Kessner ( AMS C.327883, 20+); permanent billabong E of Settlement Ck., Wollogorang Stn , Gulf of Carpentaria , 16° 46.920'S, 138° 10.170'E, 25 AUG 1994, V.Kessner ( VKC 23957, 20 +; AMS C.318618, 6); 65 km by road NE of Woologorang HS, nr Qld border , Gulf of Carpentaria , 16° 47.000'S, 138° 10.170'E, in shallow billabong, in mud, 29 AUG 1988, V.Kessner ( AMS C.300776, 3; VKC 13881, 14; AMS C.318591, 3); 7 km SSE Scrutton Ck crossing, Gulf of Carpentaria , 17° 35.750'S, 138° 26.420'E, small billabong in Cliffdale Ck drainage, 30 AUG 1988, V.Kessner ( AMS C.300777, 1; VKC 13882, 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.326805, sev); 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.331861, 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.332842, 20+); Brannigan Ck at Karumba to Normanton Rd (side channel with waterholes), 17° 28.660'S, 141° 10.600'E, 31 MAY 1997, W.F.Ponder, V.Kessner & D.L. Beechey ( AMS C.331863, 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.333670, 1; AMS C.381244, 5); waterhole on Dogwood Ck on Burke Developmental Rd , 16° 51.730'S, 141° 58.060'E, on weed & mud, 1 JUN 1997, W.F.Ponder, V.Kessner & D.L. Beechey ( AMS C.326793, 20+); Clarks Lagoon, Dunbar Stn on Burke Dev Rd , 16° 1.030'S, 142° 25.010'E, on weed, 3 JUN 1997, W.F.Ponder, V.Kessner & D.L. Beechey ( AMS C.381474, 14); 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.346293, 20+) .

Description

Shell ( Figs 26H,J , 36E,F ) small (up to 5.6 mm in length), trochiform with strong spiral ridges, up to 4.4 convex whorls shouldered in upper third by upper­most spiral ridge. Protoconch of about 1.3­1.5 smooth whorls. Teleoconch sculptured with heavy, flat­topped spiral ridges, 3 on penultimate whorl, 6­11 on last whorl; intermediate cords present between main ridges, especially on last whorl, with one between main ridges on upper part of whorl and, usually, 3 between upper and lower basal ridges; weak spiral lines and threads also present; spiral sculpture crossed by much finer collabral growth lines; base convex, subangled by lower basal ridge; umbilicus wide, rimmed by lower basal spiral ridge and with 1 or 2 ridges within. Aperture broadly ovate; peristome moderately thickened in adults; outer lip prosocline. Colour: shell opaque to sub­translucent; periostracum thin to moderate, yellow­white to brown. One or two varices typically present, represented by rather irregular lines or breaks.

Dimensions. See Table 28 for dimensions of holotype and Appendix, Table 29 , for summary shell dimensions and whorl counts.

Operculum ( Fig. 32O,P ) typical of genus. Ovate, yellowish­white (unless stained), slightly to moderately concave, concentric growth ridges distinct; inner surface sculptured with low, concentric ridges.

Radula (Appendix Table 30 ; Fig. 37F,G ) typical of genus. Central teeth with 3­5 cusps on either side of median cusp; median cusp about 1.3­1.4 longer than adjacent cusps, base about twice as wide, initially parallel­sided to slightly tapering, distally tapering to blunt to sharp point. Face of central tooth with 2­3 pairs of cusps parallel to lateral margin, inner pair much larger than others, about half total height of tooth. Lateral margins straight to slightly concave; at about 50­60º, basal tongue short, rounded. Lateral teeth with cusp formula 3­4 + 1 + 4­6; cutting edge about third length of lateral part of tooth; median cusp up to about twice as long as adjacent cusps, broad, parallel­sided to slightly tapering, with rounded end; upper edge of lateral part of tooth at about 50­60º to cutting edge, lateral edge straight. Inner marginal teeth 21­25 cusps, outer marginal teeth long and very slender with expanded bases, with 5­9 cusps.

Head­foot with unpigmented foot, snout pale grey, tentacles with central pale grey stripe. Mantle roof unpigmented over rectum/kidney – remainder with black with large white blotches.

Anatomy. Gill with apices at about quarter of width from right; 52­58 filaments (n=2). Osphradium opposite middle of gill. Penis and accessory lobe shorter than penial lobe, distal end of accessory lobe lacking swelling or distinct sucker; accessory gland moderate to short. Pallial oviduct ( Fig. 34D ) similar to G. vertiginosa but with relatively shorter albumen gland; bursa copulatrix narrow, extends to posterior pallial wall (AMS C.326793, AMS C.327883).

Distribution ( Fig. 39 ) and habitat. Coastal plains of the Gulf of Capentaria and the eastern base of Cape York. In billabongs and pools on mud, although often associated with macrophytes and algae.

Remarks

This species is very distinctive amongst the Australian fauna with its trochiform shell with an open umbilicus and strong spiral ridges. However, Mysorella costigera has a very similar shell to G. carinata but differs in being much larger (about twice as large), in having a very heavy operculum, in the axial sculpture being heavier and sharper, especially on the base, and in the edge of the outer lip being very slightly reflected in adults (simple in G. carinata ). M. costigera and has been described anatomically (from India) by Seshaiya (1930). The central teeth of the radula reportedly have central teeth with only a single pair of basal cusps ( Annandale, 1920), although Seshaiya (1930) noted 1­3 pairs and Starmühlner (1974) 3 pairs, although the 2 nd and 3 rd pairs are small.

Mysorella costigera is the type species of Mysorella Godwin­Austen, 1919 . Its anatomy, as described by Seshaiya (1930), closely resembles that of Gabbia . No mention of a seminal receptacle is made in the description of the female reproductive system and it was probably overlooked as this structure is present on the outer side of the middle of the albumen gland (opposite the entry point of the coiled renal oviduct) in G. carinata . Similarly, the bursa copulatrix is not recognised as such but is clearly present as the non­glandular arm of the V­shaped lumen ( Seshaiya, 1930, textfig. 27). However, this was open to the oviduct lumen along most of its length rather than having a small anterior opening. This configuration is similar to that seen in sub­mature specimens of G. carinata but differs from the bursa seen in mature specimens, which is closed off from the ventral channel for most of its length. Thus it is likely that the female specimens examined by Seshaiya (1930) were not fully mature, which is also probably the reason that a seminal receptacle was not reported. Given the gradation of spiral sculpture with other shell sculptural patterns, and the lack of any obvious anatomical differences reported for Mysorella [on the assumption that the female system described by Seshaiya (1930) was submature], the recognition of a distinct subfamily Mysorellinae ( Annandale, 1920) for Mysorella , or even a distinct genus, is questionable on the available evidence. Thus, pending a detailed assessment of the relationships of the group, Mysorella is tentatively regarded here as a synonym of Gabbia .

Pseudovivipara Annandale, 1918 and Parafossarulus Annandale, 1924 are the only other Asian bithyniid genus­group name based on species that have spiral ridges on the shell. However, both these taxa, which are probably synonyms (Ponder, pers. observ.), have a larger, tall­spired, non­umbilicate shell. They also differ from most other bithyniid genera in having the basal cusps of the central teeth aligned horizontally, and in a number of anatomical differences.

Figures

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.

FIGURE 39. Distribution of Gabbia carinata.