Natalina quekettiana quekettiana (Melvill & Ponsonby, 1893)

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 : 54-58

Natalina quekettiana quekettiana (Melvill & Ponsonby, 1893)

Figs 13C , 35A, F , 36–38

Helix (Macrocyclis) quekettiana: Melvill & Ponsonby, 1893: 103 , pl. 3, fig. 1; Moss 1894: 24, pl. 1, fig. 4 (radula). Type loc.: Town Bush, Pietermaritzburg [Quekett].

Macrocyclis quekettiana: Sturany 1898: 33 .

Rhytida (Afrorhytida) queckettiana [sic]: Möllendorff 1903: 63, pl. 11, fig. 4.

Natalina quekettiana: Melvill & Ponsonby 1898: 170 ; Connolly 1912: 96; 1939: 107; Watson 1915: 168, 185; 1934: 158, pl. 19, fig.5; Peile 1932: 103, fig. 2 [deformed radula tooth]; Herbert & Kilburn 2004: 223.

? Helix (Dorcasia) inhluzana Melvill & Ponsonby, 1894: 91 , pl. 1, fig. 4. Type loc.: Inhluzan (i) Mountain [Nhlosane], Dargle , KwaZulu-Natal [Mrs Shaw]. See below.

Etymology: Named for Frederick Quekett (1849–1913), first curator of the Natal Society Museum’s collections (1886–95) (the precursor of the NMSA) and subsequently curator of the Durban Natural History Museum (1895–1909).

Identification: Very similar to the montane N. q. dracomontana and N. q. montistempli , and at this stage cannot be reliably separated from them morphologically, given that the extent of intra-taxon variation in the latter two taxa is poorly known. May perhaps differ conchologically in that the last whorl is more strongly descendant prior to the aperture, the umbilicus a little wider and the base somewhat smoother in N. q. quekettiana . In addition, the shell periphery often lies below mid-whorl. Frequently resembles N. q. lucaris in shell and body colour, but is smaller and has more numerous lateral teeth in the radula (8–9 pairs per row compared to 6). N. reenenensis also has fewer lateral teeth (5 pairs per row) and is generally paler and greener, though the shells available are all old.

Description ( Fig. 36 ): Shell generally lenticular, but height of spire somewhat variable; adult shell comprising up to 4.75 whorls, the last usually noticeably descending prior to aperture in adult specimens; whorls rounded, periphery usually slightly below mid-whorl, suture a little above mid-whorl; base glossy, apical surface less so. Protoconch 4.5–5.0 mm in diameter, with distinct axial riblets throughout. Apical surface of teleoconch sculptured by close-set axial riblets, these becoming much weaker at periphery and scarcely evident at all on base except around and within umbilicus; base also with traces of spiral striation in some specimens; aperture suboval, somewhat obliquely descending outwards; outer lip of adult frequently thickened basally, but sometimes also retaining a membranous periostracal fringe; adapical portion of outer lip often flattened; upper part of columella lip reflected; umbilicus of moderate width, not obscured to any appreciable degree by reflected columella lip.

Periostracum of living specimens dark chestnut-brown on apical surface ( Figs 36H–J ), extending a little below periphery to outer region of base, contrasting with lighter yellowish green umbilical and peri-umbilical region; empty shells paler, fading to yellowish brown or light olive-green in older museum material ( Figs 36D–G ).

Dimensions: Largest specimen (NMSA W6646, Ferncliffe Nat. Res.), diameter 31.3 mm; H:D of adults 0.58–0.68 (N=13).

Living animal ( Fig. 35A ): Head-foot dark grey-brown to grey-black, lacking paler longitudinal stripes on neck; tentacles similarly dark; skin texture finely granular; posterior portion of foot flat and elongate, tip of tail rather acutely pointed; pedal margin paler, frequently tinged with yellow; skin around genital pore also pale; mantle edge greyish yellow; lung wall variously mottled with dots and anastomosing blotches of black pigmentation, sometimes heavily so; labial palps present.

Radula ( Fig. 37 ): Formula 1+(8–9)+(10–17) (N=7, one in BMNH); length up to 29 mm, with 68–80 broadly V-shaped transverse rows of teeth (see also Moss 1894). The number of marginal teeth in all members of the N. quekettiana complex is lower than in the larger species of Natalina s.s. (<20 vs>20 per half row in adults), although this is probably a function of their smaller size, since juveniles of the larger species have proportionately fewer marginal teeth.

Distal genitalia ( Fig. 13C ): Epiphallus lumen lined by 3 or 4 longitudinal ridges; interval on inner wall (adjacent to penis) smooth, relatively broad and thin-walled; wall of outer part of epiphallus thicker and the remaining intervals between ridges with numerous, close-set, transverse, slit-like pockets representing openings of diverticulae in thickened epiphallus wall; these strongest in mid to anterior part of epiphallus, but less well defined in posterior third and absent near junction with vas deferens; no epiphallus bulla evident.

Spermatophore: Unknown, but structure of epiphallus wall indicates that, as in N. quekettiana lucaris , it will have a smooth underside and well-developed scale-like spines in the mid to anterior region, on its convex outer surface.

Type material: Three specimens were mentioned in the original description, one in BMNH (1905.1.26.1) was designated lectotype by Connolly (1912: 96), diameter 30.0 mm, height 18.0 mm ( Figs 36A–C ). The location of the other two specimens is unknown .

Additional material examined (all NMSA unless otherwise indicated): SOUTH AFRICA: KZN: Pietermaritzburg , Ferncliffe Nat. Res. (29.565°S: 30.345°E), mist-belt Podocarpus forest, in leaf-litter, A. Moussalli, D. Stuart-Fox, D. Herbert & L. Davis, 1/iv/2005 (W4262) ; ditto (29.54848°S: 30.34481°E), mist-belt Podocarpus forest, in leaf-litter accumulations amongst rocks beside path (common), D. Herbert & L. Davis, 16/xii/ 2008 (W6646) ; ditto (29.555°S: 30.333°E), mist-belt Podocarpus forest, R. Kilburn, D. Herbert & L. Davis, 12/viii/1994 (V782) ; Pietermaritzburg , Town Bush (29.565°S: 30.345°E), A.C. van Bruggen, 09/i/1962 (W3675) ; ditto (29.565°S: 30.345°E), mist-belt Podocarpus forest, D. Herbert, xi/1984 (V2149); ditto (29.565°S: 30.345°E), H.C. Burnup & H.A. Wager, 29/viii/1908 (A7055) ; ditto (29.565°S: 30.345°E), (A7054, A7058); Pietermaritzburg, S. slopes of Hogsback Mountain (29.55°S: 30.35°E), 975–1036 m, beneath rock, C. Griswold & P. Croeser, 20/xi/1984 (V6543) ; Pietermaritzburg , mist-belt Podocarpus forest, among dead leaves, R. Kilburn & B. Lamoral, 6/x/1969 (V2147); Pietermaritzburg, Boschkop [locality not known], 16/ xii/1921 (A7062) ; Pietermaritzburg , Hilton Road (29.583°S: 30.330°E) (A7059); Pietermaritzburg (A7057, 1490); Pietermaritzburg and Hilton, H. Burnup ( BMNH 1937.12.30.1328–29); Bulwer area, 3 km to north (29.78160°S: 29.77577°E), ~ 1500 m, highly disturbed montane Podocarpus forest beside stream, in leaf-litter, A. Moussalli, 06/xii/2003 (W1490).

Distribution ( Fig. 38 ): Traditionally considered to be endemic to the escarpment north-west of Pietermaritzburg, but a juvenile, identified on the basis of DNA, has recently been collected in the Bulwer area, suggesting a wider distribution in the central KwaZulu-Natal Midlands (cf. N. inhluzana ); occurs at altitudes of 1000–1500 m.

Habitat: Known only from southern mist-belt forest; in leaf-litter and under logs; very local and generally scarce except in Ferncliffe Nature Reserve, Pietermaritzburg where it is patchily common.

Notes: Connolly (1939) described the shell of Natalina quekettiana as being ‘golden brown above and greenish yellow beneath’, but whilst this is true of empty shells, particularly older museum specimens, it does not describe the shell coloration of living animals, in which the apical surface is substantially darker brown. In terms of its rather distinctly bicoloured shell, dark head-foot colour, and yellowish mantle and pedal margin, topotypic N. q. quekettiana resembles N. q. lucaris. That subspecies, however, attains a larger size and its radula has only six pairs of lateral teeth per transverse row. In terms of its size, N. q. quekettiana is more similar to the montane taxa in the N. quekettiana complex, but differs from these in that the shell periphery generally lies below mid-whorl, the last whorl is more strongly descendant prior to the aperture, the umbilicus a little wider and the base somewhat smoother. However, given that the montane taxa are all known from relatively few specimens and even fewer adult individuals, the reliability of these characters as species discriminators is not proven. As discussed above, the evidence for these taxa being distinct derives primarily from molecular data. N. reenenensis , for which we have no molecular data, is typically greener, but information on the colour of fresh or living shells is wanting. Its radula possesses only five pairs of lateral teeth per transverse row. We believe that N. inhluzana (Melvill & Ponsonby, 1894) will prove to be a synonym of N. q. quekettiana (see below).

Conservation: Natalina q. quekettiana was previously thought to occur only in the Pietermaritzburg area, but the data now available indicates that its distribution is more extensive, particularly if N. inhluzana (see below) is indeed a synonym. Nonetheless, given that the indigenous forests of the KwaZulu-Natal Midlands are some of the malacologically most well-known habitats in South Africa, the number of records for both N. q. quekettiana and N. inhluzana is surprisingly small. Despite targeted sampling, very few shells and only one living example have been found in recent years outside the Pietermaritzburg area. Notable is the absence of recent records from forests in the Karkloof region, the most extensive mist-belt forest complex in the KwaZulu-Natal Midlands.At present, the only locality at which the species can be described as common (albeit patchily so) is the Ferncliffe Nature Reserve, north-west of Pietermaritzburg. Whether this is due to a favourable edaphic characteristic of this locality (?doleritic soils) is not known, but it is clear that this municipal reserve should be considered the most important site for the conservation of this snail. As such it should be afforded a high conservation status.

Figures

Fig. 13. Distal genitalia of Natalina s.s. (all NMSA): (A) N. cafra natalensis subsp. n. (1392), lower male tract with penis and epiphallus cut open to show internal structure; (B) N. cafra cafra (W4220), external view of epiphallus showing bulla at base of epiphallus, close to its junction with vas deferens; (C) N. quekettiana quekettiana (W6646), epiphallus opened longitudinally to show internal ridges and intervening diverticulae; (D) N. c. natalensis subsp. n. (1392), lower female tract showing oviduct caecum (caecum dissected away from free oviduct and spermoviduct base to which it is fused with connective tissue in life) and vagina which has been opened longitudinally to reveal internal folds.Abbreviations: bd – bursa copulatrix duct, ct – connective tissue web, d – slit-like diverticulae in epiphallus wall, eb – epiphallus bulla, ep – epiphallus, er – internal epiphallic ridge, fod – free oviduct, ga – genital atrium, obd – opening of bursa copulatrix duct, oc – oviduct caecum, p – penis, pl – penis lumen with micropapillate lining, pp – penis papilla, pr – penial retractor muscle, sod – spermoviduct, v – vagina, vd – vas deferens.

Fig. 35. Natalina quekettiana complex, living animals and eggs (all NMSA):(A) N. q. quekettiana, Ferncliffe, Pietermaritzburg (W6646), shell diameter 31.3 mm; (B) N. q. lucaris subsp. n., Ngome Forest (paratype, V2249/T2563), shell diameter 29.4 mm; (C) N. q. dracomontana subsp. n., Injasuthi (holotype, V7992/T2451), shell diameter 27.2 mm; (D) N. q. dracomontana subsp. n., Monk’s Cowl area (paratype, W4101/T2452), shell diameter 26.4 mm; (E) N. q. montistempli subsp. n., Oqalweni, Cathedral Peak (holotype, W4084/T2422), shell diameter 23.9 mm; (F) N. q. quekettiana, eggs (W6646), scale in millimetres.

Fig.36. Natalina quekettiana quekettiana (Melvill & Ponsonby, 1893):(A–C) holotype of Helix (Macrocyclis) quekettiana Melvill & Ponsonby, 1893 (BMNH 1905.1.26.1), diameter 30.0 mm; (D–F) faded specimen, Pietermaritzburg (NMSAA7057), diameter 30.2 mm; (G) elevated specimen, subadult, Pietermaritzburg (NMSA V6543), diameter 27.7 mm; (H–J) living specimen showing dark chestnut brown apex and greenish yellow base, Ferncliffe Nat. Res., Pietermaritzburg (NMSA W6646), diameter 31.3 mm.

Fig. 37. Natalina quekettiana quekettiana (Melvill & Ponsonby, 1893), radula (NMSA V6543): (A) rachidian and lateral teeth, scale bar = 0.5 mm; (B) vestigial marginal teeth, scale bar = 100 µm.

Fig. 38. Distribution of Natalina quekettiana quekettiana (Melvill & Ponsonby, 1893) (squares), N.q. lucaris subsp. n. (triangles) and Natalina inhluzana (Melvill & Ponsonby, 1894) (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.