Natalina reenenensis Connolly, 1939

Herbert, D. G. & Moussalli, A., 2010, Revision of the larger cannibal snails (Natalina s. l.) of southern Africa - Natalina s. s., Afrorhytida and Capitina (Mollusca: Gastropoda: Rhytididae), African Invertebrates 51 (1), pp. 1-1 : 67-70

Natalina reenenensis Connolly, 1939

Figs 43 , 47

Natalina reenenensis: Connolly 1939: 108 , pl. 2, figs 5–8. Type loc.: Van Reenen , KwaZulu-Natal [Burnup];

Herbert & Kilburn 2004: 223.

Etymology: Named after the type locality, Van Reenen, KwaZulu-Natal, South Africa.

Identification: Closely resembles subspecies within the Natalina quekettiana complex; attains a slightly larger size than all except N. q. lucaris; typically has a relatively low profile (H:D<0.60), a more narrowly entering umbilicus and the radula has fewer lateral teeth per transverse row (five pairs).

Description ( Fig. 47 ): Shell lenticular, spire generally low; adult shell comprising up to 4.5 whorls, the last descending slightly prior to aperture in adults; periphery evenly rounded, at or near mid-whorl; suture above mid-whorl; apical surface microscopically sculptured by extremely fine spiral lineation, producing lustreless, silky sheen which continues on to base, only becoming glossy near umbilicus. Protoconch/teleoconch junction generally ill-defined; protoconch ±5.0 mm in diameter, apical portion initially almost smooth, becoming plicate at suture and thereafter with distinct, close-set, axial riblets extending from suture to suture.Axial riblets continue on teleoconch but become more uneven on last half whorl; riblets weaken at periphery, the base generally sculptured only by growth-lines and traces of spiral striae; riblets re-appear in umbilicus; aperture suboval, slightly obliquely descending outwards; outer lip of adult a little thickened, particularly where columella and basal lips merge, but sometimes throughout in gerontic specimens, thin and with membranous periostracal fringe in subadults; upper part of columella lip weakly reflected; umbilicus of moderate width, but narrowing relatively quickly internally, not obscured by reflected columella lip.

Periostracum of museum specimens straw-yellow to light olive-green with darker axial bands in a slightly deeper shade; base not appreciably paler than apical surface. One fresher, but damaged shell recently collected near type locality with a distinctly browner coloration.

Dimensions: Largest specimen (NMSA W4689), diameter 32.4 mm; H:D of adults 0.53–0.59 (N=11).

Living animal: No data available.

Radula: Like that of N. quekettiana , but with fewer lateral teeth; formula 1+5+?16 (radula slide prepared by A.J. Peile in NMSA); length 22.3 mm, with 69 broadly Vshaped rows of teeth. Another radula slide in BMNH (Gwatkin) has the same formula. Type material: Holotype in BMNH (1937.12.30.1307–8) [2 specimens, holotype undamaged and with red dot], diameter 30.3 mm (31 mm fide Connolly 1939), height 17.5 mm ( Figs 47A–C ); paratypes in NMSA, same data as holotype, dated iii/1918 (V2010 /T1356, 8 specimens; V2009 /T1355, 3 specimens).

Additional material examined: SOUTH AFRICA: KZN: De Beers farm, approx. 15 km NE of Van Reenen (28.30403°S: 29.50240°E), 1841 m, afrotemperate forest, dead in leaf-litter, A. Moussalli, D. Stuart-Fox & M. Cunningham, 10/ix/2006 ( NMSA W4689 ) .

Distribution ( Fig. 43 ): Known only from the Drakensberg escarpment in the Van Reenen area, north-western KwaZulu-Natal.

Habitat: No details recorded with original specimens, but presumably found in Afrotemperate forest, ca 1500–1800 m; evidently scarce.

Notes: In the original description, Connolly (1939) compared this species with Natalina kraussi (now in Afrorhytida ) noting that it was larger and of a much greener colour. Surprisingly, he did not compare his new taxon with N. quekettiana , with which it is much more similar. In reality the material available, even though old and thus faded, is not noticeably greener than some specimens of N. quekettiana of a similar age. The fading of shells which may be rich chestnut-brown when alive to a paler olive-green with advancing time seems a general phenomenon in these snails. Even though Connolly’s original description mentioned the green colour, an old label in paratype lot NMSAV2009/T1355 states ‘live, Mar. 1918 ’. The shells were thus already around 20 years old when Connolly drew up the description. The green colour must thus be viewed with caution, for it is neither distinctive of dead shells of the species, nor is it likely to reflect shell colour in the living animal. A badly broken but recently collected shell was of a much browner hue.

Natalina reenenensis almost certainly belongs within the N. quekettiana clade, but DNA sequence data are needed to confirm this. Although little material is available, the species seems to differ in having a relatively narrow, slightly eccentric umbilicus and the lustreless sheen of the apical surface extends well below the periphery, and only the peri-umbilical region is glossy. In Natalina q. quekettiana the periphery is often less evenly rounded and displaced slightly towards the base, the spire usually taller (H:D 0.58–0.68 compared with <0.60), and the umbilicus is noticeably wider. Natalina q. montistempli is perhaps the most similar taxon, but like all the other subspecies of N. quekettiana , it has more than five pairs of lateral teeth per transverse row. More definitive comment on this species must await the collection of additional living specimens.

Distribution data suggest the existence of a genuine hiatus between the populations of N. reenenensis and those of the geographically closest subspecies in the N. quekettiana complex, N. q. montistempli . Despite extensive sampling in the intervening forests of the Royal Natal National Park (Bruggen, Hamer, Herbert and Moussalli), no Natalina specimens have been found there.

Conservation: Natalina reenenensis is evidently both rare and of limited distribution. Only one damaged shell has been found since the original description. The original sample collected by Henry Burnup evidently contained over a dozen live-taken specimens, suggesting that the species was common, but this was perhaps a very local phenomenon. With a known distribution including only two localities and covering only a 15 km length of the escarpment edge in north-western KwaZulu-Natal, the species would certainly qualify for listing as a threatened species. The extent of its habitat has declined historically and its quality remains threatened, particularly by veld fires encroaching from the neighbouring grasslands. However, this region of the Drakensberg escarpment is not well-sampled and a more meaningful assessment of the conservation status of N. reenenensis must await further survey work.

Subgenus Tongalina subgen. n.

Type species: Helix cafra wesseliana Kobelt, 1876 .

Etymology: With reference to Tongaland, the territory historically encompassing southern Mozambique and northern KwaZulu-Natal.

Diagnosis: Skin texture in neck region coarse; genital pore situated high on neck and well posterior to right optic tentacle; left body lobe of mantle hypertrophied, divided into two lobes, but these confluent, separated only by a sinuous discontinuity.

Notes: Natalina (Tongalina) is monotypic, the only known species being N. wesseliana . In terms of shell morphology it is very close to the larger species of Natalina s.s. and indeed N. wesseliana was initially described merely as a variety of N. cafra . Several character states of the soft parts (see diagnosis), however, differ markedly from those found in Natalina s.s. indicating not only that it is a distinct species, but that it represents a highly divergent lineage of its own. This is supported by molecular data which place it as a basally divergent taxon within Natalina .

Natalina (Tongalina) wesseliana occurs at low altitudes (<700 m) in north-eastern KwaZulu-Natal and southern Mozambique. The distributional data available to date indicate that its range does not overlap with any other species of Natalina .

Figures

Fig. 43. Distribution of Natalina quekettiana dracomontana subsp. n. (squares), N. q. montistempli subsp. n. (triangles) and N. reenenensis Connolly, 1939 (circles). Symbols with a white centre indicate localities for specimens used in DNA analyses (Moussalli et al. 2009); contours at 1000 m and 1500 m.

Fig. 47. Natalina reenenensis Connolly, 1939: (A–C) holotype (BMNH 1937.12.30.1307–8), diameter 30.3 mm; (D–F) paratype (NMSA V2010/T1356), diameter 30.5 mm; (G) paratype, depressed specimen (NMSA V2010/T1356), diameter 29.3 mm.