Gabbia iredalei Cotton, 1942

Ponder, Winston F., 2003, Monograph of the Australian Bithyniidae (Caenogastropoda: Rissooidea), Zootaxa 230 (1), pp. 1-126 : 29-31

Gabbia iredalei Cotton, 1942

Bithinia australis :­ Tate, 1896: 210 (R Neales and Storm Ck, near Oodnadatta,, South Australia (alive ­ type locality of G. iredalei ); in dry bed of Blood's Ck and Boggy Flat (not seen), near Mt Daniel (not seen); Hedley (1896: 220, fig. A (head­foot, operculum), B (radula) in text). Non Tryon, 1865.

Gabbia iredalei Cotton, 1942: 126 . Storm Ck, Oodnadatta, etc., South Australia. Holotype SAMA D14098 ( Smith, 1992: 33, as incertae sedis).

Gabbia centralia Iredale, 1943: 206 ; Oodnadatta, South Australia. Based on the material described by Tate (1896) and Hedley (1896), other type material not designated; Smith, 1992: 32 (as synonym of G. australis Tryon ).

Gabbia australis :­ Ponder & DeKeyzer, 1998: 760, fig. 15.116A. Non Tryon, 1865.

Material examined

Types: Holotype of G. iredalei ; other topotypic material from Horn Expedition ( MV F.54870; MV F.54829; AMS C.2151).

Other material:

Queensland: Goyder Lagoon Dam , AMS C. 45 miles S of Birdsville, 26° 53.817'S 138° 57.050'E, 22 MAY 1975, J.Blyth, ( AMS C.417602, 20+) .

Northern Territory: Finke Gorge , Central Australia, 23° 43.800'S, 132° 39.700'E, 1912, W.B.Spencer ( MV F 751 , 3 ) .

South Australia: Storm Ck, near Oodnadatta , 27° 17.000'S, 135° 29.000'E, 1897, W.B.Spencer ( MV F 54829 , 2 ), same locality, “waterfall”, 1912, W.B.Spencer ( MV F 54870 , several); Neales R, near Oodnadatta, 27° 33.000'S, 135° 27.000'E, MAY 1894 ( AMS C.2151, 2); NW Branch of Coopers Ck, 27° 30.000'S, 140° 9.000'E, ephemeral pool, 18 FEB 1987, J.T.Puckridge ( SAM TD 14431 , 6 ) .

Description Shell ( Figs 1B , 2F ) of moderate size for genus (up to 7.9 mm in length), ovate­conic, with up to about 4.6 convex whorls. Protoconch not examined. Teleoconch sculptured with fine collabral striae; base evenly convex; umbilicus closed (represented by a chink) to narrowly open. Aperture broadly ovate; peristome thickened on inner lip in adults; outer lip prosocline, thickened slightly within in adults; adults with one or a few varices. Shell opaque to slightly translucent; periostracum thin to moderate, yellow­brown to brown.

Dimensions. See Table 2 for dimensions of holotype and Appendix, Table 29 , for summary shell dimensions and whorl counts.

Operculum ( Fig. 4F ) typical of genus. Ovate, yellowish­white, with few, distinct concentric growth ridges; inner surface not examined.

Radula (Appendix Table 30 ; Fig. 5G,H ) typical of genus. Central teeth with 3 short, rather blunt cusps on either side of median cusp which is about 1.3­1.4 longer and its base wider, than adjacent cusps; median cusp broadly triangular, tip bluntly pointed. Face of central tooth with 4­6 pairs of cusps that extend just inside lateral margin forming denticulate ridge, inner pair much larger than others, sharp and large (about half total height of tooth); lateral margins straight, at about 60º; basal tongue long, narrow. Lateral teeth with cusp formula 3 + 1 + 3; with cutting edge about 0.4 length of lateral part of tooth; median cusp about 1.4 length of adjacent cusps, triangular, bluntly pointed; upper edge of lateral part of tooth at about 60º to cutting edge, lateral edge distinctly concave with angle. Inner marginal teeth with about 16­20 cusps, outer marginals with 8­11 cusps.

Head­foot and anatomy not examined.

Distribution ( Fig. 9 ) and habitat. Central Australia, in pools and waterholes in temporary creek beds. One record from a dam.

Remarks

This species differs from G. vertiginosa (which is restricted to the eastern parts of the northern half of NSW and southern­most coastal Queensland), in having a more inflated shell which has a larger last whorl (and hence aperture) and very small to (usually) absent umbilicus. While variation is encountered in both taxa, most specimens can usually be separated on shell characters. The radula of a topotypic specimen is similar to that of G. vertiginosa but differs in the cutting edge of the central teeth being narrower, and the cusps shorter and blunter (narrowly triangular rather than finger­shaped). The outer marginal teeth have fewer cusps (8­11 compared with 10­18) and the median cusps on the lateral and central teeth are only slightly larger than the adjacent cusps. The outer edges of the lateral teeth are sharply bent ( Fig. 5G ), whereas in G. vertiginosa it is slightly concave to nearly straight. Hedley (1896) illustrated the radula of one of the topotypes and, although his drawing is rather crude, it shows the same bent outer edge of the lateral teeth. His illustration incorrectly shows many small cusps on the lateral teeth (up to about 18).

Smith (1992) treated G. centralia as a synonym of Gabbia australis (= G. vertiginosa ) but listed G. iredalei under Incertae sedis although the synonymy of these two taxa was previously correctly noted by Cotton (1943). Cotton (1942) gave the dimensions as 7 mm x 5.5 mm, and his species was distinguished from G. australis (p. 127) by its “general shape and comparatively greater width.” Cotton's material was, although he did not state it, based on specimens collected by the Horn Expedition ( Tate, 1896). Almost at the same time Iredale (1943) introduced the name Gabbia centralia , which Smith (1992: 32) treated as a nomen nudum. However, Iredale (1943: 206) states “As pointed out by Tate, the Centralian shell is larger.”, a statement that could be construed as “differentiating the taxon” (ICZN, Art. 13.1.1). Fortunately the question of the validity of Iredale's name is unimportant because of Cotton's prior name and because both names are based on the same material from the Horn Expedition, in which only a single species is found.

Hedley (1896: 221) incorrectly described the operculum of topotypes as seeming “corneous instead of calcareous”. Tate (1896: 211) noted that the northern South Australian specimens collected by the Horn Expedition reached a larger size than the east coast New South Wales material with which they otherwise “fairly agree”.

This species is capable of surviving for long periods sealed in its shell. Hedley (1896: 220) recorded specimens in mud from central Australia reviving promptly after being placed in water after “more than a year”. A similar observation was noted by Spencer (1896: 16) who reported that specimens collected in the bed of a dried up water hole and kept in a tin match box were alive 15 months later.

Specimens from a small sample from southeast South Australia in the vicinity of Naracoorte (Yelloch Ck, at Wattonbully Rd, South Australia 37° 1.000'S, 140° 53.000'E, 22 OCT 1998, C. Madden [AMS C.405556, 6] ­ see Fig. 9 ; Appendix, Tables 29 , 30 ) have a similar shell to G. iredalei . The radula differs from topotypic material of G. iredalei but there is insufficient material to determine whether or not these specimens represent a distinct taxon and it is tentatively referred to as G. aff. iredalei

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 2. Shells: A – E, Gabbia vertiginosa, A, AMS, C.203392, B ­ D, AMS, C.308015, E, AMS, C.332890; F, Gabbia iredalei, AMS, C.337418; G – K, Gabbia campicola, G, AMS, C.344345, H, holotype, C.417664, I, paratype, C.332829, J, K, MV, F.54869; L­N, Gabbia kendricki, L, holotype, WAM S10877, M,N, paratypes, AMS C.203378; Scales: A – E, L­N, 500 m, F, 2 mm, G – K, 1mm.

FIGURE 4. Opercula: A ­ E, Gabbia vertiginosa, A, B, AMS, C.203392, C, D, AMS, C.308015, E, AMS, C.332890; F, Gabbia iredalei, MV F.54870; G ­ I, Gabbia campicola, paratype, AMS, C.332829; J ­ L, Gabbia kendricki, AMS, C.337372; A, C, E ­ H, J, K, outer side; B, D, I, L, inner side; Scales: 500 m.

FIGURE 5. Radula: A – F, Gabbia vertiginosa, A, B, F, AMS, C.203392, C, AMS, C.332890, D, E, AMS, C.308015; G, H, Gabbia iredalei, MV, F.54870; A, C, D, H, central teeth, B, half rows of teeth, E, marginal teeth and lateral teeth, F, lateral teeth, G, half rows of teeth and second row of lateral teeth; Scales: 20 m.

FIGURE 9. Distribution of Gabbia vertiginosa (o), G. iredalei (), G. cf. iredalei (), G. campicola (), G. fontana (), G. pallidula (☆), G. davisi () and G. rotunda (