Gulella donaikeni, Cole & Herbert, 2022

Cole, Mary L. & Herbert, David G., 2022, Eight new species of Gulella Pfeiffer, 1856 from the south-east coast of South Africa (Gastropoda: Streptaxidae), European Journal of Taxonomy 813, pp. 1-32 : 13-17

Gulella donaikeni sp. nov.

urn:lsid:zoobank.org:act:1AB31B08-9507-4F43-9560-87DAC90A52C5

Figs 5A–D , 6A–B

Diagnosis

Shell minute, cylindrical; smooth and glossy; apertural dentition seven-fold, including a parietal lamella with outer portion oblique and then curving inward, the labral lip is thickened with a cusp at upper and lower ends and a large scoop-shaped plate extending deeply into aperture, a low, inset transverse basal tooth to right of centre, an inset basal tooth to left of centre and a large columella lamella with two rounded teeth, the lower large and broad and the upper relatively small; umbilicus widely open.

Etymology

Named for Don W. Aiken (1930–1988), an enthusiastic collector of South African land snails and author of two important publications dealing with South African Streptaxidae ( Aiken 1981, 1995).

Material examined

Holotype SOUTH AFRICA – KwaZulu-Natal • Port Shepstone area, Marble Delta, Simuma Hill , scarp forest ; 30.6679°S, 30.3471°E; 255 m a.s.l.; Dec. 2013; D. Herbert leg.; NMSA W9640/T4521 .

Paratypes SOUTH AFRICA – KwaZulu-Natal • 1 spec.; Port Shepstone area , Marble Delta, South side of Simuma Hill, woodland/forest, stn S 1; 30.6683° S, 30.3470°E; 237 m a.s.l.; Feb. 2012; J. Harvey leg.; NMSA W8785/T4468 • 2 specs.; same locality as for preceding; NHMUK 20210073 , prev. NMSA W8785 • 1 spec.; same collection data as for preceding; RMNH.MOL.452588 , prev. NMSA W8785 • 1 spec.; same collection data as for preceding, stn S3; 30.6666° S, 30.3447° E; 257 m a.s.l.; NMSA W8788/T4465 • 2 specs.; same collection data as for preceding, stn S6; 30.6687°S, 30.3466° E; 207 m a.s.l.; Feb. 2012; J. Harvey leg.; NMSA W8787/T4470 • 1 spec.; same collection data as for preceding; NHMUK 20210074 , prev. NMSA W8787 • 1 spec.; same collection data as for preceding, stn S2; 30.6672° S, 30.3443° E; 230 m a.s.l.; NMSA W8789/T4469 • 1 spec.; same collection data as for preceding; NMW.Z.2021.012.00003 , prev. NMSA W8789 • 1 spec.; same collection data as for preceding; RMNH.MOL.452589 , prev. NMSA W8789 • 1 spec.; Marble Delta, North side of Mzimkulwana River , base of Simuma Hill , dense riverine thicket/woodland, heavily invaded with Lantana and Chromolaena ; 30.6727° S, 30.3427° E; 72 m a.s.l.; 5 Nov. 2001; D. Herbert leg.; NMSA V9640/T4471 • 3 specs.; Marble Delta; Hlokohloko Valley , middle section, riverine/scarp forest , stn H1; 30.6608°S, 30.3326°E; 188 m a.s.l.; Feb. 2012; J. Harvey leg.; NMSA W8732/T4464 • 1 spec.; same collection data as for preceding; NMW.Z.2021.012.00004 , prev. NMSA W8732 • 2 specs.; same collection data as for preceding, stn H3; 30.6622°S, 30.3386°E; 145 m a.s.l.; NMSA W8767/T4467 • 1 spec.; same collection data as for preceding; ELMD 18759/T 229, prev. NMSA W8767 • 1 spec.; Hlokohloko Valley, lower section, riverine/scarp forest , stn H5; 30.6589°S, 30.3426°E; 122 m a.s.l.; Feb. 2012; J. Harvey leg.; NMSA W8768/T4463 • 1 spec.; Port Shepstone area, Four Man’s Hill , scarp forest , stn S3; 30.6736°S, 30.3360°E; 98 m a.s.l.; Dec. 2013; D. Herbert leg.; NMSA W9596/T4466 • 1 spec.; same collection data as for preceding, stn S5; 30.6721°S, 30.3348°E; 127 m a.s.l.; NMSA W9601/T4473 .

Other material

SOUTH AFRICA – KwaZulu-Natal • 4 specs.; Port Shepstone area, Marble Delta, Hlokohloko Valley , lower section, riverine/scarp sorest, stn H4; 30.6609°S, 30.3416°E; 130 m a.s.l.; Feb. 2012; J. Harvey leg.; NMSA W8769 • 3 specs.; Simuma area, Hlokohloko Valley , 08-036, scarp forest ; 30.6512°S, 30.3443°E; ca 110 m a.s.l.; 5 May 2008; D. Herbert and L. Davis leg.; NMSA W6279 • 2 specs.; Port Shepstone area, Four Man’s Hill , scarp forest , stn S5; 30.6721°S, 30.3348°E; 127 m a.s.l.; Dec. 2013; D. Herbert leg.; NMSA P1608 , prev. NMSA W9601 .

Description

SHELL ( Fig. 5 ). Shell minute, cylindrical, length 1.8–2.3 mm, width 0.8–0.9mm, L:W 2.2–2.6 (n = 16); smooth and glossy with microscopic growth lines. Protoconch approx. 0.7 mm in diameter, comprising approx. 2.5 whorls, smooth; junction between protoconch and teleoconch not distinct. Teleoconch comprising approx. 3.5 whorls; whorls relatively flat-sided ( Fig. 5A–B ). Aperture sub-quadrate, rounded at base, markedly constricted by teeth; peristome thickened and reflected, broadly interrupted in parietal region; dentition seven-fold ( Fig. 5C ): 1) a parietal lamella, outer portion strongly oblique (almost transverse) and then curving inward; 2–3) labral lip thickened, forming a vertical ridge which bears a cusp at its upper and lower ends, each inside aperture edge, the upper cusp defines lower part of labral sinus; beginning just behind thickened labral lip a large, shallow scoop-shaped plate with a sharp ridge around its border extends deeply into aperture beyond level of columella lamella in aperture view; 4) a low, deeply inset transverse basal tooth to right of centre; 5) an inset oblique basal tooth to left of centre; 6–7) a large columella lamella with two well-spaced rounded teeth, the lower one large, broad and sloping outward toward outer lip, the upper one smaller and more deep-set. Labral tooth corresponds with a shallow indentation behind outer lip ( Fig. 5B ); basal tooth to left of centre corresponds with a narrow external furrow ( Fig. 5D ). Umbilicus open, relatively wide and deep with a conspicuous pit underlying columella lamella, approx. 0.2 mm across, peri-umbilical region with distinct axial pleats ( Fig. 5D ). Shell almost transparent when fresh, orange-red coloration of dried tissue of animal visible internally.

Distribution ( Fig. 6 )

Known only from an area approx. 16 km NW of Port Shepstone in southern KwaZulu-Natal, mainly from the Marble Delta, and the neighbouring Four Man’s Hill and Hlokohloko Valley. G. donaikeni sp. nov. has only been recorded south of the Mzimkulu River and G. calcicola sp. nov. (see below) only north of the river.

Habitat

Patches of dense valley thicket (Low & Rebelo 1996), also referred to as Eastern Valley Bushveld ( Rutherford et al. 2006) and KwaZulu-Natal Scarp forest ( Mucina et al. 2018b); in leaf-litter and under logs. The indigenous vegetation has been heavily invaded by alien plants, notably Chromolaena odorata (L.) R.M.King ( Asteraceae ), and Lantana camara L. ( Verbenaceae ), both from South and Central America.

Remarks

In terms of its minute size, smooth glossy shell and dentition, Gulella donaikeni sp. nov. resembles G. tietzae , G. kenbrowni sp. nov. and G. mkombeni sp. nov. It is distinguished from G. tietzae by the large rounded lower tooth on the columella lamella and the presence of a low inset basal tooth to

the right of centre. The labral complex extends further into the aperture than that of G. kenbrowni sp. nov., and G. mkombeni sp. nov. and the lower columella tooth is rounded and not ridge-like.

Conservation

Gulella donaikeni sp. nov. has been found in a very small, degraded area and its habitat continues to be threatened by mining. The lower portion of the Hlokohloko Valley has been sacrificed to provide a waste rock dump for the quarry. The species evidently meets the criteria for red-listing as Critically Endangered. Conservation remarks pertaining to Gulella calcicola sp. nov. (see below) also apply to G. donaikeni .

Figures

Fig. 5. Gulella donaikeni sp. nov., holotype (NMSA W9640/T4521), length 1.85 mm, width 0.84 mm. A. Aperture view. B. Side view. C. Oblique view into aperture. D. Oblique view of base showing umbilicus. Scale bar = 0.5 mm.

Fig. 6. A. Distribution map of Gulella donaikeni sp. nov. (red circles) and G. calcicola sp. nov. (blue triangles) in the Marble Delta region of southern KwaZulu-Natal. B. Google Earth image of distribution of G. donaikeni (red symbols) south of the Mzimkulu River and G. calcicola (blue symbols) north of the Mzimkulu River.