Gulella dejae, Bursey & Herbert, 2004

Bursey, M. L. & Herbert, D. G., 2004, Four new narrow-range endemic species of Gulella from Eastern Cape, South Africa (Mollusca: Pulmonata: Streptaxidae), African Invertebrates 45, pp. 249-262 : 252-254

Gulella dejae sp. n.

Figs 6–11 , 24

Etymology: Named for D.-J. Hodgkinson of East London, who has assisted us on many field trips to the Transkei coast.

Diagnosis: Shell minute, sculptured with strong axial ribs; peristome entire, abutting but not fused to preceding whorl in parietal region; aperture markedly constricted by teeth; dentition five-fold, labral tooth morphology distinctive; apertural tube behind columella lip somewhat expanded and collar-like; umbilicus very small, displaced dorsally.

Description: Shell minute, obovate-cylindrical to sub-cylindrical, length up to 2.85 mm, width up to 1.5 mm; length:width 1.84–2.03. Embryonic shell approx. 0.85 mm in diameter, comprising approx. 2.25 whorls; for the most part sculptured with relatively widely, but unevenly spaced microscopic spiral threads ( Fig. 11 ); junction between embryonic shell and teleoconch distinct. Teleoconch comprising approx. 4.75 whorls; whorls moderately convex, suture relatively narrow and strongly indented, thus appearing somewhat channelled; sculptured by well-developed axial ribs, extending from suture to suture (42–47 on penultimate whorl); rib intervals lacking obvious microsculpture and with no evidence of spiral threads ( Fig. 10 ). Peristome flaring outward, more or less entire; abutting base of penultimate whorl in parietal region, but not obviously fused to it. Aperture markedly constricted by teeth, dentition five-fold ( Figs 8, 9 ): 1) a strong parietal lamella, outer portion oblique, partially concealing anal sinus and with a slight hiatus in the peristome behind it (not smoothly continuous with portion of sinus bounded by outer lip); 2) a large, trigonal, wedge-like labral slab, its upper margin in the form of a strong angular ridge running deeply into aperture, more or less parallel to lower margin of parietal lamella, angled progressively more toward columella internally; 3-4) two low, broad, rounded denticles on columella lip, separated by a smoothly curving, shallow indentation; 5) a broad columella lamella, but this scarcely visible through aperture. Labral tooth corresponds with a deep pit behind flaring outer lip. Apertural tube behind columella lip somewhat inflated and collar-like; umbilicus very small, displaced dorsally. Shell translucent, uniformly milky-white when fresh.

Type material: Holotype: NMSA W1840 /T2011, length 2.8 mm, width 1.52 mm. South Africa, Eastern Cape, Pondoland coast, Mntafufu , north side of river (31.55596ºS: 29.62606ºE), coastal scarp forest, sorted from leaf-litter, leg. D. Herbert & M. Bursey, 29/iv/2004.

Paratype 1, NMSA W1883 /T2010, South Africa, Eastern Cape, Pondoland coast, Mntafufu , south side of river (31.55021ºS: 29.61777ºE), coastal scarp forest, beside road through forest, in leaf-litter, leg. D.-J. Hodgkinson, 29/iv/2004 .

Distribution and habitat ( Fig. 24 ): Known only from coastal scarp forest immediately north and south of the Mntafufu River mouth in Eastern Cape; in leaf-litter.

Remarks: Gulella dejae is clearly similar to the Eastern Cape G. phyllisae Burnup, 1925 , in terms of size, shape and strong axial sculpture, and also with regard to the form of the peristome and the presence of spiral threads on the embryonic shell. In G. phyllisae , however, the labral tooth is in the form of a large, quadrate to bluntly trigonal slab which lacks a strong in-running ridge on its upper margin, and it has an additional deep-set basal tooth to the right of centre. Furthermore, the columella, though also somewhat thickened in G. phyllisae , lacks distinct teeth. G. arnoldi (Sturany, 1898) from the KwaZulu-Natal south coast is likewise similar, particularly the ‘variety’ collaris Burnup, 1925, from Port Shepstone, which also has an expanded apertural tube behind the columella lip, but its peristome is generally interrupted in the parietal region, its apertural dentition is closer to that of G. phyllisae and the parietal lamella generally runs smoothly into the outer lip, around the sinus. Southern populations of G. phyllisae (Port Alfred) also show similar expansion of the apertural tube behind the columella lip and have a correspondingly smaller umbilicus.

Figures

Figs 6–11. Gulella dejae sp. n., holotype. 6, 7, apertural and lateral views of shell, length = 2.8 mm; 8, enlarged view of the aperture, bar = 0.3 mm; 9, umbilical region, bar = 0.3 mm; 10, detail of sculpture (start of last whorl), bar = 50 µm; 11, microsculpture on embryonic shell, bar = 40 µm.

Fig. 24. Map of northern Eastern Cape showing distribution of new species.