Gulella mkombeni, 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 : 10-13

Gulella mkombeni sp. nov.

urn:lsid:zoobank.org:act:B79335B5-A9E1-4A2A-86D5-97F364CA3A66

Figs 2 , 4A–D

Diagnosis

Shell minute, cylindrical; smooth and glossy; apertural dentition seven-fold, including a parietal lamella with a notch in its lower margin, a large labral complex extending deeply into aperture with ridge-like upper and lower margins bounding a broad sunken mid region, a low, inset transverse basal tooth to right of centre, an inset oblique ridge-like basal tooth to left of centre and a columella lamella set with two ridge-like teeth, the lower stronger and extending to near lip edge; umbilicus widely open with distinct peri-umbilical pleats.

Etymology

Xhosa for ‘place of the ikomba palm’, or Pondo palm ( Jubaeopsis caffra Becc. ), another of the several species narrowly endemic to the Mkambati Nature Reserve and immediate vicinity.

Material examined

Holotype SOUTH AFRICA – Eastern Cape • Mkambati Nature Reserve, “Superbowl” Forest , 5 km upstream of Msikaba River mouth, East side of Msikaba River, below steep krantzes along rim of bowl; 31.2978°S, 29.9293° E; 5 Mar. 2001; D. Herbert leg.; NMSA P1674/T4518 .

Paratypes SOUTH AFRICA – Eastern Cape • 1 spec.; same collection data as for holotype; NMSA V8921/ T4479 • 1 spec.; same collection data as for preceding; NMW.Z.2021.012.00002 , prev. NMSA V8921 • 1 spec.; same collection data as for preceding; M. Bursey leg.; ELMD 13693/T 224 • 1 spec.; same collection data as for preceding; NHMUK 20210069 , prev. ELMD 13693 • 1 spec.; same collection data as for preceding; NMW.Z.2021.011.00001 , prev. ELMD 13693 • 1 spec.; same locality as for preceding, prev. litter; 7 Mar. 2001; M. Bursey leg.; ELMD 14257/T 225 • 1 spec.; same locality as for preceding; 18 Oct. 2005; M. Bursey leg.; ELMD 15588/T 226 • 6 specs.; Mkambati Nature Reserve, Gwe Gwe Forest ; 31.2904°S, 29.9897°E; 4 Mar. 2004; D-J. Hodgkinson leg.; ELMD 14258/T 227 • 1 spec.; Mkambati Nature Reserve, East bank of Mkambati River, between Mkambati and Strandloper waterfalls; 31.2738°S, 30.0236°E; 17 Mar. 2019; M. Cole leg.; ELMD 18473/T 228 • 1 spec.; same collection data as for preceding; NHMUK 20210070 , prev. ELMD 18473 • 1 spec.; same collection data as for preceding; RMNH.MOL.452586 , prev. ELMD 18473 • 2 specs.; Mkambati Nature Reserve ; 31.2734° S, 30.0233°E; 10 m a.s.l.; 27 Jan. 2008; Earthwatch ECMF13 leg.; NMSA W6462/T4481 ; • 1 spec.; same collection data as for preceding; RMNH.MOL.452587 , prev. NMSA W6462 • 1 spec.; Mkambati Nature Reserve ; 31.2980° S, 29.9283° E; 186 m a.s.l.; 31 Jan. 2008; Earthwatch ECMF26 leg.; NMSA W6470/T4478 • 1 spec.; Mkambati Nature Reserve ; 31.3171°S, 29.9676° E; 28 m a.s.l.; 28 Jan. 2008; Earthwatch ECMF11 leg.; NMSA W6438/T4523 • 1 spec.; Mkambati Nature Reserve ; 31.2903°S, 29.9903° E; 50 m a.s.l.; 26 Jan. 2008; Earthwatch ECMF11; NMSA W6443/T4477 .

Other material

SOUTH AFRICA – Eastern Cape • 3 specs.; NMSA P1610 ex NMSA V8921 • 1 spec.; Mkambati Nature Reserve; East bank of Mkambati River, between Mkambati and Strandloper waterfalls; 31.2738° S, 30.0236° E; 15 Feb. 2011; M. Cole leg.; ELMD 18753 • 1 spec.; Mkambati Nature Reserve ; 31.2734°S, 30.0233° E; 10 m a.s.l.; 27 Jan. 2008; Earthwatch ECMF13 leg.; NMSA P1612 , prev. NMSA W6462 • 1 spec.; Mkambati Nature Reserve ; 31.3171° S, 29.9676° E; 28 m a.s.l.; 28 Jan. 2008; Earthwatch ECMF11 leg.; NMSA P1677 , prev. NMSA W6438 .

Description

SHELL ( Fig. 4 ). Shell minute, cylindrical, length 2.3–2.7 mm, width 1.0– 1.3 mm, L:W 2.0–2.4 (n = 16); smooth and glossy with microscopic growth lines. Protoconch approx. 0.7mm in diameter, comprising approx. 2.25 whorls, smooth; junction between protoconch and teleoconch not distinct. Teleoconch comprising approx. 4 whorls; first two whorls roundly convex, subsequent ones weakly convex ( Fig. 4A, B ). Aperture sub-quadrate, rounded at base, markedly constricted by teeth; peristome thickened and reflected; dentition seven-fold ( Fig. 4C ): 1) an oblique parietal lamella usually with a notch in its lower margin; 2–3) a large labral complex extending deeply into aperture; a ridge on lip edge more or less in centre of labral complex curves upwards and outwards and continues inwards as a sharp upper margin, a small cusp near lip edge defines lower part of labral sinus; lower margin of labral complex more rounded and does not reach lip edge, becoming narrower further into aperture; upper and lower ridges do not quite meet at inner end of labral slab; between ridges is a wide, sunken area; 4) a low, deeply inset transverse basal tooth to right of centre; 5) an inset oblique ridge-like basal tooth to left of centre which runs inwards and upwards beneath columella lamella; 6–7) a large columella lamella set with two ridgelike teeth, the lower one larger, almost reaching lip edge. Labral complex corresponds with a shallow indentation behind outer lip ( Fig. 4B ); basal tooth to left of centre corresponds with an external furrow ( Fig. 4D ). Umbilicus widely open with a deep indentation underlying columella lamella, peri-umbilical region with distinct axial pleats ( Fig. 4D ). Shell almost transparent when fresh, orange-red coloration of dried tissue of animal visible internally.

Distribution ( Fig. 2 )

Recorded only from the Mkambati Nature Reserve in Pondoland on the north-eastern coast of the Eastern Cape.

Habitat

Pondoland Scarp Forest ( Mucina et al. 2018a; von Maltitz et al. 2003); in leaf-litter and under logs.

Remarks

Gulella mkombeni sp. nov. closely resembles G. kenbrowni sp. nov. which occurs to the north and south of the Mkambati Nature Reserve, but has not been recorded in the reserve itself. Gulella mkombeni sp. nov. is distinguished by the ridge-like lower tooth on the columella lamella which extends much closer to the lip edge. Other differences are that it is larger, the upper and lower margins of the labral complex do not meet within the aperture, the parietal lamella usually has a notch in its lower margin, and the peri-umbilical region is more strongly pleated. Additionally, the basal tooth to the left of centre is longer, extending beneath the columella lamella. The columella lamella is also reminiscent of that of G. tietzae , G. ndibo and G. aprosdoketa , in which the columella lamella extends to the lip edge, but in these three species it is tricuspid.

Conservation

Gulella mkombeni sp. nov. is to date known only from the Mkambati Nature Reserve, despite reasonable collecting efforts along the coast of the Eastern Cape and KwaZulu-Natal. Other taxa also occur only in Mkambati, e.g., G. newmani Bursey & Herbert, 2004 . This region, known as Pondoland, has been shown to be an important centre of cladogenic events in rhytidid molluscs ( Herbert & Moussalli 2010; Moussalli et al. 2009). Pondoland Scarp Forests are known for their diversity and endemism of plants ( van Wyk & Smith 2001; Mucina et al. 2018a) and molluscs ( Herbert & Kilburn 2004; Bursey & Herbert 2004; Herbert & Moussalli 2010; Cole & Herbert 2009; Cole 2019). Mkambati is the only officially protected section of this region, under the authority of the Eastern Cape Parks and Tourism Agency. Many of the remaining Pondoland Scarp Forests are under threat and deserve protection ( Mucina et al. 2018a). The small Mkambati Nature Reserve appears relatively better protected than other small reserves on the Eastern Cape coast due to a buffer zone between local communities and the reserve. This hotspot of biodiversity and endemism extends into southern KwaZulu-Natal and includes two other small reserves, the Mtamvuna Nature Reserve and Oribi Gorge Nature Reserve, but G. mkombeni sp. nov. has not been found outside Mkambati.

Figures

Fig. 2. Distribution map of Gulella kenbrowni sp. nov. (pink circles), G. fordycei sp. nov. (blue squares), G. mkombeni sp. nov. (green triangles) and G. crookesi sp. nov. (orange square). Contour at 1000 m.

Fig. 4. Gulella mkombeni sp. nov., holotype (NMSA P1674/T4518), length 2.45 mm, width 1.14 mm. A. Aperture view. B. Side view. C. View into aperture. D. Oblique view of base showing umbilicus. Scale bar = 0.5 mm.