Gabbia clathrata, Ponder, 2003

Ponder, Winston F., 2003, Monograph of the Australian Bithyniidae (Caenogastropoda: Rissooidea), Zootaxa 230 (1), pp. 1-126 : 101-103

Gabbia clathrata n.sp.

Etymology Clathratus (L.) – latticed.

Type material

Burketown­Borroloola Rd, E. of turnoff to Red Bank Mine, NT, 17° 11.740'S, 137° 44.130'E, streambed spring, under rocks, 26 AUG 1994, W.F.Ponder, G.Wilson & V.Kessner (Holotype, AMS C.417681; paratypes AMS C.327884, 31 wet, 2 dry, 1 on SEM stub; NTM P21377, 8, QM MO71718, 5) .

Additional material examined

Northern Territory: seasonal waterhole near Sly Ck Crossing, 15° 49.900'S, 135° 25.720'E, on mud & ground, 21 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.346418, 20+); waterhole on trib of Limestone Ck, nr road on E side, 15° 52.360'S, 135° 31.060'E, on leaves & rocks, 21 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.202386, 20+); waterhole on trib of Limestone Ck, nr road on E side, 15° 52.360'S, 135° 31.060'E, on leaves & rocks, 21 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.202387, 20+); pool beside Batten Ck, about 9.5 km SE of Tawallah on Billengarrah ­ Borraloola Rd, 16° 13.520'S, 135° 58.450'E, 22 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.401223, 6); mudhole near Batten Ck, ca. 30 km SW of Borroloola, 16° 10.510'S, 136° 2.620'E, on mud etc. in pool, 22 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (AMS C.378474, 8); 2 km S of Bing Bong Stn HS, Gulf of Carpentaria, 15° 38.500'S, 136° 21.330'E, 16 APR 1996, V.Kessner (VKC 24304, 11; AMS C.318614, 3); waterhole 3 km S of Bing Bong Stn HS, Gulf of Carpentaria, 15° 38.500'S, 136° 21.500'E, 23 AUG 1994, V.Kessner (VKC 24303, 20+; AMS C.318586, 6); Bing Bong Stn, W. Gulf of Carpentaria, 15° 38.570'S, 136° 21.680'E, waterhole, 24 AUG 1994, W.F.Ponder, G.Wilson & V.Kessner (AMS C.327878, 13); unnamed seasonal stream N of Batten Ck, Bing Bong Stn, Gulf of Carpentaria, 15° 50.750'S, 136° 23.670'E, 23 AUG 1994, V.Kessner (VKC 24302, 20+; AMS C.318574, 6).

Queensland: 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.401229, 16); waterhole on Eight Mile Ck on Karumba ­ Chillagoe Rd, 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 ( AMS C.332333, 3); 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.401230, 1) .

Description

Shell ( Fig. 26 A­C, 36B) of moderate size (up to 6.5 mm in length), solid, broadlyovate, umbilicate, with up to 4.9 convex whorls. Protoconch of about 1.5 whorls, first whorl with fine spiral wrinkles, last half with spiral wrinkles crossed with axial lines. Teleoconch sculptured with numerous closely­spaced axial ridges crossed by many mostly flat­topped spiral cords with interspaces about equal to, or narrower than, cords, points of crossing not distinctly gemmate. Base evenly convex; umbilicus open, moderate in size, axial and spiral sculpture extending into umbilicus but much weaker. Aperture broadly ovate; peristome moderately thickened and rounded in adults, inner lip forming narrow reflexion; outer lip slightly prosocline. Colour: shell opaque to sub­translucent, periostracum thin, yellow­white to brown or orange­brown.

Dimensions. See Table 26 for dimensions of holotype and Appendix, Table 29 , for summary shell dimensions and whorl counts.

Operculum ( Fig. 32K,L ) typical of genus. Ovate, semitransparent colourless to yellowish­white or white, slightly concave, with (when present) very heavy concentric growth ridges; inner surface with muscle scar occupying most of surface, sculptured with weak pustules or irregular weak ridges.

Radula (Appendix Table 30 ; Fig. 37 A­C) typical of genus. Central teeth with 2­4 cusps on either side of median cusp which is about 1.2­1.4 longer than adjacent cusps and its base 1.3­1.6 as wide; median cusp tapering gradually proximally, more rapidly distally, end pointed. Face of central tooth with 3­4 pairs of sharp cusps that extend just inside lateral margin forming cuspate ridge, inner pair larger than others, large (about half total height of tooth); lateral margins convex above, then slightly concave, at about 50­60º; basal tongue of moderate length, broad, rounded. Lateral teeth with cusp formula 2­3 + 1 + 3­4; with cutting edge about 0.33­0.40 length of lateral part of tooth; median cusp up to about 1.5 length of adjacent cusps and much broader, with parallel sides and rounded (sometimes bifid) distal end; upper edge of lateral part of tooth at about 70º to cutting edge, lateral edge concave. Inner marginal teeth with 18­21 cusps, outer marginals slender, with broad, tapering base and 9+­10+ cusps.

. Head­foot with dark grey snout, grey neck and tentacle bases (behind eyes), tentacles unpigmented or pale grey, sometimes with black line in middle, foot and opercular lobe unpigmented to pale grey. Mantle roof with some black pigment over gill to uniformly black, visceral coil unpigmented to grey or black.

Anatomy. Gill with apices up to about quarter gill width from right in anterior two thirds, up to about third gill width in posterior third; 55­65 filaments (n=2). Osphradium slightly anterior to middle of gill. Penis with penial lobe and accessory lobe about equal in length, accessory lobe slightly swollen distally, not markedly sucker­like; accessory gland long. Pallial oviduct ( Fig. 34B ) similar to G. vertiginosa but with bursa copulatrix occupying nearly all of inner wall of capsule gland and extending to posterior pallial wall, seminal receptacle lies anterior to coiled oviduct embedded near ventrally in outer wall of anterior part of albumen gland (AMS C.346418).

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

Remarks

This species is very distinctive and unique in its solid, broadly­ovate, umbilicate shell with numerous axial and spiral ridges of about equal strength. The flat­topped spirals cross the rounded axial ridges and, although not actually raised into gemmules at the points of crossing they give the appearance of being weakly gemmate. The shell shape and size is very similar to G. adusta , the two species being indistinguishable using morphometric measurements. The female reproductive system, while similar to B. vertiginosa in most respects, is unlike any other examined Australian species in having the seminal receptacle located in the anterior part of the albumen gland rather than in the middle part.

Figures

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.

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.