Gabbia beecheyi, Ponder, 2003

Ponder, Winston F., 2003, Monograph of the Australian Bithyniidae (Caenogastropoda: Rissooidea), Zootaxa 230 (1), pp. 1-126 : 82-85

Gabbia beecheyi n. sp.

Etymology

Named after Mr Des Beechey, Research Associate, Australian Museum, in recognition of his contribution as volunteer field assistant on two field trips to northern Australia.

Type material

N. of Ballys Lagoon, Devils Gate Stn, Gulf of Carpentaria , Qld , 17° 15.210'S, 138° 40.210'E, billabong, 25 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey (Holotype, AMS C.417676, paratypes AMS C.331852, 36 wet, 27 dry, 3 on SEM stubs); same data, mudhole (paratypes AMS C.331875, 9; QM MO71716, 8; NTM P21373, 5) .

Additional material examined

Northern Territory: 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.381470, 4); Burketown­Borroloola Rd, E. of turnoff to Red Bank Mine, 17° 11.740'S, 137° 44.130'E, stream bed spring, under rocks, 26 AUG 1994, W.F.Ponder, G.Wilson & V.Kessner ( AMS C.380806, 20+) .

Queensland: 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.326806, 20+); Ballys Lagoon, Devils Gate Stn, 17° 19.770'S, 138° 38.900'E, on weed, 24 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey ( AMS C.401232, 20+); Judy Lagoon at Armraynald Stn HS on Burketown Normanton Rd, 17° 57.440'S, 139° 45.380'E, on weed and mud, 29 MAY 1997, W.F.Ponder, V.Kessner & D.L.Beechey ( AMS C.401231, 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.331862, 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.332844, 20+); 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.331878, 20+; AMS C.331879, 20+; AMS C.331886, 11; AMS C.381282, 7); 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.332400, 24); 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.326800, 20+); 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.326794, 20+); waterhole W of Pelican Ck, 10.5 km SSE of Wyaaba Ck crossing, 16° 46.920'S, 141° 59.230'E, on grass & substrate, 01 JUN 1997, W.F.Ponder, V.Kessner & D.L.Beechey ( AMS C.332843, 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.326797, 20+) .

Description

Shell ( Fig. 19A,B , 25 F­I) moderately large for genus (up to 10 mm in length), ovate, with up to 4.6 lightly convex whorls usually narrowly and weakly shouldered (shoulder often absent on last whorl). Protoconch ( Fig. 14N,O ) of about 1.3 almost smooth whorls, only sculpture traces of extremely fine spiral striae, last third whorl with very fine axial lines; lost in most adults ( Fig. 19A ). Teleoconch sculptured with fine collabral growth lines and very fine spiral striae, mainly on upper part of whorls; base evenly convex; umbilicus closed. Aperture broadly ovate, subangled anteriorly; peristome thin; outer lip prosocline, simple, very slightly thickened in adults. Colour: opaque to semi­translucent, peristome often dark brown; periostracum thin and smooth, pale yellowish to light brown, sometimes with reddish tinge, rarely olive, often with close, narrow dark brown to palebrown collabral axial stripes.

Dimensions. See Table 21 for dimensions of holotype and figured paratype and Appendix, Table 29 , for summary shell dimensions and whorl counts.

Operculum ( Fig. 27 C­E) typical of genus. Ovate, white, slightly concave; concentric growth ridges distinct but heavy ridges rarely formed; inner surface with muscle scar occupying most of surface, sculptured with low irregular to concentric ridges and weak pustules.

Radula (Appendix Table 30 ; Fig. 28 J­M) typical of genus. Central teeth with 3­5 cusps on either side of median cusp; median cusp up to about twice as long and wide as adjacent cusps, triangular, sharply pointed. Face of central tooth with 1 large pair of cusps and 0­3 small to subobsolete cusps that extend just inside lateral margin forming weakly denticulate to simple ridge, inner pair much larger than others, about half total height of tooth; lateral margins straight, at about 50­70º; basal tongue short, subtriangular to rounded. Lateral teeth with cusp formula 2­4 + 1 + 3­6 (usually 4); with cutting edge about 0.3­ 0.4 length of lateral part of tooth; median cusp about 1.4­1.6 as long as adjacent cusps, and about twice as wide, with rounded to square end; upper edge of lateral part of tooth at about 50­ 60º to cutting edge, lateral edge slightly to moderately concave. Inner marginal teeth with 14­25 cusps, outer marginals with 9­20 cusps.

Head­foot very weakly pigmented, with dark grey patch to cluster of small black spots behind eyes. Tentacles unpigmented except for central pale to dark grey stripe. Mantle roof unpigmented to pale grey or black with white spots (mottled appearance).

Anatomy. Gill ( Fig. 6B ) with apices at about fifth to quarter of gill width from right, 72­97 filaments (n=4). Osphradium slightly posterior to slightly anterior to middle of gill. Penis ( Fig. 7E ) and accessory lobe slightly shorter than penial lobe to about equal in length, distal end of accessory lobe simple; accessory gland long. Pallial oviduct immature in all specimens examined (AMS C.332843, AMS C.332844, AMS C.331879).

Distribution ( Fig. 29 ) and habitat. Coastal plains of the Gulf of Carpentaria into the western base of Cape York. In billabongs and other large semiperment pools where it lives mainly on submerged macrophytes.

Remarks

This species is very similar to G. kessneri which it appears to replace in the Gulf Country. The shell is usually smaller (although there is overlap in size – see Fig. 30A and Appendix, Table 29 ) and is typically paler in colour.

The radulae in the two species also differs in G. beecheyi having a prominent inner pair of basal cusps that extend below the basal margin, whereas these are small and well above basal margin in G. kessneri (compare Fig. 28F,I with 27K,L).

The whorls are typically (but not always) narrowly and weakly shouldered just below the suture (there is no shoulder in G. kessneri ), although the shouldering is often absent on the last whorl. The suture is not markedly margined in G. beecheyi (distinctly narrowly margined in G. kessneri , this especially obvious in semi­translucent specimens). The outer lip of the aperture is simple in G. beecheyi but is very slightly reflected in G. kessneri . The aperture also differs in being slightly angled anteriorly in G. beecheyi where the inner and outer lips meet, whereas this part of the aperture is evenly convex in G. kessneri . While the shell differences separating these two taxa are rather subtle they appear to be consistent in the large range of material available.

Several lots were examined for anatomy but most were heavily parasitized and, females in particular, were not sexually mature. It is probable that this species reproduces during the wet season, as all available material was collected in the dry season.

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 14. Protoconchs and microsculpture: A, Gabbia cf. rotunda, AMS, C.385439; B, C, Gabbia fontana, AMS, C.380856; D – F, Gabbia obesa, D, E, paratype, AMS, C.417603, F, AMS, C.318584; G – J, Gabbia smithi, G, H, AMS, C.318692, I, AMS, C.202831, J, AMS, C.331867; K – M, Gabbia kessneri, K, M, paratype, AMS, C.322308, L, AMS, C.203385; N, O, Gabbia beecheyi, AMS, C.331878. A, C, I ­ M, microsculpture, B, D ­ H, N, O, protoconch; Scales: A, D, H ­ J, 50 m, B ­ C, E ­ G, K ­ O, 100 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 25. Shells: A ­ E, Gabbia kessneri, A, holotype, AMS, C.417675, B, E, paratype, AMS, C.322308, C, D, AMS, C.203385; F ­ I, Gabbia beecheyi, F, G, AMS, C.332843, H, paratype, AMS, C.331852, I, holotype AMS, C.417676; Scales: A ­ I, 1 mm.

FIGURE 27. Opercula: A, B, Gabbia kessneri, paratype, AMS, C.322308; C ­ E, Gabbia beecheyi, paratype, AMS, C.331852; F ­ I, Gabbia affinis, AMS, C.308008; J ­ L, Gabbia microcosta, paratype, AMS, C.318641. A, C, E ­ H, J, K, outer side, B, D, I, L, inner side. Scales: 500 m.

FIGURE 28. Radulae: A ­ E, Gabbia smithii, A, D, AMS, C.202810, B, C, AMS, C.202831, E, AMS, C.331867; F ­ I, Gabbia kessneri, paratype, AMS, C.322308; J ­ M, Gabbia beecheyi, J ­ L, paratype, AMS, C.331852, M, AMS, C.331862; A, B, H, J, K, half rows of teeth, C, central and lateral teeth, D, F, I, L, central teeth, E, G, M, lateral teeth; Scales: 20 m.

FIGURE 29. Distribution of Gabbia kessneri (o) and G. beecheyi ().

FIGURE 30. A, B ­ Plots of shell dimensions. A, shell length (SH) and aperture length (AH); x G. kessneri; O G. beecheyi. B, shell length (SH) and shell width (SW); x G. microcosta; O G. affinis..