Gabbia affinis
Creators: name: Ponder, Winston F.
Publisher: name: Zenodo
Year: 2003
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Bithyniidae
Gabbia
Gabbia affinis

description: Gabbia affinis (Brazier ms Smith, 1882)
Bithinia affinis Smith (Brazier ms), 1882: 267. Burdekin R, QLD. Types presumed lost (Smith, 1992). Two lots of 2 specimens each in AMS C.2515 and AMS C.5804 ex Brazier, Hillgrove, Limestone Ck, Burdekin R, Qld (from original lot sent by Brazier bearing his manuscript name to E.A. Smith. However, there is no evidence that this material was ever sighted by Smith so it cannot be regarded as syntypes); Smith, 1992: 32 (as incertae sedis).
Gabbia affinis.­ Iredale, 1943: 206.
Material examined
Topotypic material: ex J. Brazier: Hillgrove, 26° 26.000'S, 147° 9.000'E, 1900 (AMS C.2515, 2; AMS C.5804, 2).
Queensland: NE of Julia Ck, ca. 13.8 km NNE of Malpas Hmstd, E side of road, 19° 30.000'S, 142° 17.750'E, muddy pool, 15 SEP 1984, W.F.Ponder & P.H.Colman (AMS C.308008, 20+); Tallaroo Stn, E of Georgetown, hot artesian spring, 18° 7.250'S, 143° 57.617'E, edge of spring where water is cooler, 29 MAR 2001, R. J.Fensham (AMS C.401124, 20+), same locality, 18 MAY 2001, S. Wilson (QM MO69564, 10); Chillagoe, ca. 3 km SW on Royal Arch Caves Rd, 17° 10.580'S, 144° 0.250'E, 15 JUL 1994, J.Stanisic, D.Potter, G.Ingram, C.Eddie (QM MO53452, 19); Kidston, The Oaks Stn, Middle Spring, permanent spring feeding dam, 18° 51.617'S, 144° 7.233'E, 4 JUN 2001, R.J. Fensham (AMS C.401127, 10); NW of Greenvalee, Lyndhurst Stn, Swamp Paddock Spring, 18° 3.633'S, 144° 32.133'E, 5 JUN 2001, R. J.Fensham (AMS C.401126, 17); Mt Garnet, ca. 13 km NW of Mt Garnet­Lynd Rd at Rosella Plains Stn, NEQ, 18° 39.580'S, 144° 35.750'E, in litter near creek, 16 JUL 1994, J.Stanisic, D.Potter, G.Ingram, C.Eddie (QM MO58548, 20 +).
Description
Shell (Fig. 1I, 19C,D, 31A) small (up to 5.8 mm in length), conical, with up to 4.5 convex whorls. Protoconch of about 1.5 smooth whorls. Teleoconch sculptured with fine collabral, closely spaced, somewhat irregular micro­costae over at least some of surface, crossed by very fine, irregular spiral striae (not visible with light microscope); base evenly convex; umbilicus small to very small, closed. Aperture broadly­ovate; peristome thin; outer lip moderately prosocline. Opaque to semi­translucent; periostracum very thin, transparent, yellowish­white to pale brown.
Dimensions. See Table 22 for dimensions of topotypes and Appendix, Table 29, for summary shell dimensions and whorl counts.
Operculum (Fig. 27 F­I) typical of genus. Ovate, dirty white to yellow­brown, with distinct concentric growth ridges; inner surface with muscle scar sculptured with ill­defined irregular shallow pits and weak, irregular, short ridges.
Radula (Appendix Table 30; Fig. 33 A­C) typical of genus. Central teeth with 3­5 cusps on either side of median cusp which is about 1.3 to 1.5 times longer than adjacent cusps and its base about twice as wide; median cusp sub triangular, base about 0.7­0.8 length, with angulation at about half to one third of length often bearing weak denticle, sides near parallel proximal to angulation. Face of central tooth with 3­4 pairs of cusps that lie well inside lateral margin forming denticulate ridge, inner pair much larger than others (one specimen has second pair larger on one side), large (about half total height of tooth); lateral margins slightly concave, at about 50­55º; basal tongue narrow, with rounded end. Lateral teeth with cusp formula 3­4 + 1 + 3­4; with cutting edge about 0.4 length of lateral part of tooth; median cusp up to about 1.5 length of adjacent cusps, tapering and pointed; upper edge of lateral part of tooth at about 60­70º to cutting edge, lateral edge slightly concave. Inner marginal teeth with 16­21 cusps, outer marginals with 9­11 cusps.
. Head­foot and anatomy not examined.
Distribution (Fig. 22) and habitat. North eastern Queensland in the base of Cape York. In spring feed pools and pools in streams.
Remarks
Introduced by Smith (1882: 267) “under the name of G. affinis, Brazier, two specimens found at Hillgrove….” “They differ from those here described in having the last whorl smaller, the increase of volutions appears to be less rapid, and the operculum is much more distinctly concentrically ringed by the lines of growth.” Iredale (1943) treated this taxon as a valid species but Smith (1992) regarded it as incertae sedis. Smith (1992) noted that the type material had not been located but, as far as I am aware, a thorough search of the collections in the BMNH has not been made for this material.
Cotton (1943: 144) noted that “ Gabbia affinis Mousson nom. nud. was renamed and figured [by Cotton, 1942] as Gabbia relata Cotton. ” This is a lapsus for Assiminea affinis and A. relata.
The description of the radula and operculum given above are based on topotypic specimens from far NW Qld (Hillgrove, NE Julia Ck, AMS C.308008). The shells from the original series and the topotypic specimens are very similar. All specimens have at least traces of the same distinctive fine axial costae, rather tall spire and small, closed umbilicus. While the shells, radula and opercula are generally very similar to those of G. vertiginosa, the shells differ in being more elongate (ie., more conical) (P<0.001) and in having fine, regular axial microcostae rather than just fine growth lines. The radulae of the specimens attributed to G. affinis also differ in detail. The median cusps of the central teeth have broader bases (due to their subtriangular shape) and have an angulation (often with a tiny denticle on either side) at about the middle part of the cusp. The median cusps on the central teeth of G. vertiginosa are approximately finger­shaped, with a relatively much narrower base and the proximal half of the tooth having parallel sides and lacking any denticles. In addition, the outer marginal teeth have fewer cusps in G. affinis compared with G. vertiginosa (10­12 ­ one with 15, compared with 10­18, with most more than 12).
The shell of this species is distinctive in possessing microcostae, being conical with convex whorls and non­umbilicate. It is most similar to G. microcosta n. sp. but is much smaller. G. smithii is sometimes rather similar but has a thinner shell, less convex whorls and is usually smooth, although some specimens do develop very weak flat­topped microcostae which are usually only seen on the last whorl.
description: Published as part of Ponder, Winston F., 2003, Monograph of the Australian Bithyniidae (Caenogastropoda: Rissooidea), pp. 1-126 in Zootaxa 230 (1) on pages 85-90, DOI: 10.11646/zootaxa.230.1.1, http://zenodo.org/record/5019111