Natalina (Tongalina) wesseliana ( Kobelt, 1876 )

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 : 70-75

Natalina (Tongalina) wesseliana ( Kobelt, 1876)

Figs 6D , 10F , 11E, F , 48–52

Helix cafra var. wesseliana: Kobelt 1876: 149 , pl. 5, fig. 1; Pfeiffer 1877: 558. Type loc.: not originally specified, but given as ‘ South Africa (fide Kobelt)’ by Connolly (1939); label with holotype states ‘Natal’.

Aerope caffra [sic] var. wesselliana [sic]: Tryon 1885: 131, pl. 25, fig. 14.

Natalina caffra [sic] var. wesseliana: Melvill & Ponsonby 1898: 170 ; Sturany 1898: 30; Möllendorff 1903: 21, pl. 3, fig. 8; Connolly 1912: 91.

Natalina wesseliana: Connolly 1925: 122 ; 1939: 107; Bruggen 1969: 58; Herbert & Kilburn 2004: 221.

Natalina (Natalina) wesseliana: Bruggen & Appleton 1977: 32 .

Etymology: Perhaps named in honour of Marthinus Wessel Pretorius (1819–1901),

president of the Transvaal Republic and the Orange Free State.

Identification: Shell characterised by its narrow umbilicus which is largely obscured by the reflected columella, and the rapidly expanding, somewhat auriform shell. May possibly be confused with N. cafra natalensis especially when juvenile, but the coarse skin texture of the neck of N. wesseliana and the position of its genital pore are distinctive, as is its northern, low altitude distribution.

Description ( Fig. 48 ): Shell large to very large, thin and fragile; last adult whorl expanding rapidly and suture descending slightly towards aperture; sculptured by close-set axial riblets which sometimes extend on to base; protoconch diameter 7.0– 8.5 mm, the axial riblets generally finer and more close set than in Natalina s.s.; umbilicus narrow, for the most part obscured by reflected columella lip; aperture ovate, large and drooping obliquely downwards (long axis of aperture strongly oblique); outer lip thin, membranous periostracal fringe well developed.

Periostracum olive-green to olive-brown with occasional darker radial bands, particularly just behind outer lip.

Dimensions: Largest specimen (NMSA 2118, ‘Zululand’), diameter 69.0 mm. H:D of adults 0.70–0.88 (N=9).

Living animal ( Fig. 49A ): Head-foot brownish, tinged with orange at pedal margin; mantle edge hypertrophied, the left body lobe comprising two contiguous lobes separated by a sinuous discontinuity ( Fig. 6D ), orange; skin of neck region very coarsely textured with roundly conical projections, each often with a small pit in the centre; posterior region of foot extensive, flattened and pointed; genital pore situated high on neck, well posterior to right optic tentacle ( Fig. 49B ); lung wall variably marked with black pigmentation, usually with some diffuse spiral bands.

Radula ( Fig. 50 ): Like that of Natalina s. s. species; formula 1+5+>20 (N=2); length up to 46 mm (but almost certainly longer in large specimens), with 56–60 broadly Vshaped transverse rows of teeth.

Distal genitalia: Essentially the same as in Natalina s. s. species, except for the position of the genital pore. The penis and epiphallus are strongly sinuous in situ and the papillation of wall of penis lumen has a zig-zag longitudinal orientation. Interior of epiphallus with 6–7 well-developed longitudinal ridges with finer second and third order intermediary ridges.A small bulla is evident on the epiphallus, close to its junction with the vas deferens.

Spermatophore ( Fig. 51 ): Well preserved allospermatophores from the oviduct caecum of two specimens have been examined (NMSA V7668, W5719) collected in late November and late December respectively. These resemble the spermatophores of the larger Natalina s. s. species in bearing keel-like longitudinal ridges and lacking spines. One spermatophore was particularly long (straightened length approx. 32 mm) and slender ( Fig. 51B ), with a pronounced spiral twist; the other one similar but somewhat less slender and not strongly twisted, though still distinctly curved. Spermatophore of more or less uniform width for most of its length, tapering at both ends; 4 or 5 major longitudinal ridges anteriorly, increasing to 6 or 7 in mid region, with occasional weaker intermediaries; crests of major ridges themselves usually appearing bifid. Near spermatophore head, inner surface of spiral bears a deep groove, which becomes progressively broader and more shallow toward mid region, ending at subterminal vent. In one specimen, posterior portion of spermatophore asymmetrically T-shaped and obliquely twisted relative to main shaft of spermatophore ( Fig. 51C ); vent situated at T-junction and extending into arms, one of which comprises the strongly recurved tip of the tail and the other a shorter, less strongly recurved thumb-like process.This posterior spermatophore morphology also evident in the other example, but thumb-like process only weakly developed.

In situ, the spermatophore head lay pressed against the extreme end of the oviduct caecum and the posterior portion was situated such that the recurved tail extended into the base of bursa copulatrix duct and the thumb-like process into the vagina. In this position the vent lay immediately beneath the end of the free oviduct, and it seems likely that the function of these posterior processes is to anchor the spermatophore in place, once it is in the correct position.

Unusually, in specimen NMSA W5719 the caecum was distended and sack-like and contained two spermatophores, one relatively fresh (situated as described above) and the other partially degraded. In a third specimen (NMSA V7668) the caecum contained three more extensively degraded spermatophores, each compacted into an oval mass.

Type material: Holotype of Helix cafra var. wesseliana Kobelt, 1876 ( Figs 48A–C ) in Senckenberg Museum (SMFD 8287), Natal, coll. Kobelt, ex Maltzan, 1878, diameter 46.0 mm, height 40.5 mm (fide Ronald Janssen).

Additional material examined (all NMSA unless otherwise indicated): MOZAMBIQUE: Praia do Xai-Xai camping grounds (25.11324°S: 33.74019°E), 24 m, dune forest, in leaf-litter, A. Moussalli & D. Stuart-Fox, 27/xii/2006 (L7364) ; Maputo area, environs of Lagoa Ricatla [Rikatla] (25.767°S: 32.617°E), H. Junod ( BMNH 1937.12.30.1330–31); Ponta do Ouro (26.833°S: 32.892°E), dune forest, in leaf-litter, M. Evans, x/ 2006 (L7491) . SOUTH AFRICA: KZN: Kosi Bay (26.958°S: 32.833°E), F. Toppin, 1906 (B0020); ditto ( SAMC A34748 ); Kosi Bay (26.86922°S: 32.88258°E), coastal dune forest, transect E, Symes, Lovell & Combrink, 21/x/2003 (W1430) ; Bhanga Neck (27.005°S: 32.863°E), O. Bourquin, i/1965 (B0077) ; Bhanga Neck , behind visitors quarters (27.005°S: 32.863°E), coastal dune thicket, R. Fregona, 12/vii/1987 (D9888) ; Lebombo Mts , Hlatikulu Nat. Res. (27.32466°S: 31.98981°E), 647 m, scarp forest, in leaf-litter, A. Moussalli & D. Stuart-Fox, 29/xii/2007 (W5719) ; ditto (27.32622°S: 31.99813°E), scarp forest, A. Moussalli & D. Stuart-Fox, 19/v/2003 (W4831) ; Mkhuze Game Res. [station MAxC], Acacia xanthophloea grove beside Msunduzi River (27.74705°S: 32.28982°E), dead amongst plant debris around tree trunks [perhaps flood borne], Earthwatch Team 5, 23/xi/2003 (W1326) ; Makowe (27.967°S: 32.117°E), J. Crosly (1489); Hluhluwe Game Res. (28.075°S: 32.055°E), 400 m, scarp forest, in leaf-litter, Herbert, Seddon & Tattersfield, 30/xi/ 1998 (V7668) ; ditto, (28.077°S: 32.045°E), 460 m, scarp forest, in leaf-litter, Herbert, Seddon & Tattersfield, 29/xi/1998 (V7684) ; ditto, Hilltops Camp walk (28.0830°S: 32.0417°E), 400 m, scarp forest, D. Herbert, 01/vii/1996 (V3820) ; ditto, in forest between research station and perimeter fence (28.097°S: 32.067°E), 460 m, scarp forest, in leaf-litter, D. Herbert, 15/i/1995 (V0573) ; St Lucia system: False Bay Park (27.95852°S: 32.35919°E), sand forest, in leaf-litter and under logs, Earthwatch Team 9, 15/i/2005 (W3060) ; ditto (27.96460°S: 32.37869°E), closed woodland/forest on fossiliferous sediments beside lake, in leaf-litter and under logs, Earthwatch Team 8, 05/xi/2004 (W2447) ; ditto (27.969750°S: 32.372615°E), sand forest, under dead log in leaf-litter, A.Armstrong et al., 06/iii/2001 (V9188) ; ditto, Mpophomeni Trail (27.975°S: 32.358°E), 30 m, woodland thicket and sand forest, D. Herbert, 03/i/1996 (V2166); Cape Vidal, Bhangazi Hill (28.123°S: 32.555°E), 60–80 m, dune forest, in leaf-litter, specimen found eating Cochlitoma vestita, Herbert, Seddon & Tattersfield , 27/xi/1998 (V7976, V7980) ; ditto (28.130°S: 32.547°E), 60–80 m, dune forest, in leaf-litter, Herbert, Seddon & Tattersfield, 27/xi/1998 (V7943) ; Eastern Shores forest walk (28.23°S: 32.49°E), coastal lowland forest, under log, D. Herbert, 19/x/1997 (V5381) . SWAZILAND: Ingwavuma Road (27.083°S: 31.967°E), 275–370 m, A.C. & W.H. van Bruggen, 01/xi/1964 (B0096).

Observation records: SOUTH AFRICA: KZN: Sodwana Bay, forest beside Lake Mgobezeleni (27.53833°S: 32.66670°E), coastal forest, D. Herbert, 07/ii/2004 ; Cape Vidal , NPB camp site (28.13°S: 32.55°E), ± 20 m, dune forest and Casuarina mosaic, found crawling on track after rain, D. Herbert, 18/x/1997 .

Additional literature records (material not seen): MOZAMBIQUE: Marracuene [Vila Luiza] (25.7369°S: 32.6764°E), P.H. Boshoff (Bruggen 1967: 28, specimen damaged, identification tentative, Bruggen in lit. v/2008). SOUTH AFRICA: KZN: Lake Sibaya environs (27.400°S: 32.733°E), Appleton ( Bruggen & Appleton 1977) .

Distribution ( Fig. 52 ): Central Zululand (Hluhluwe and Cape Vidal) north to the Limpopo R. in southern Mozambique (Xai-Xai), mostly near the coast. To date not recorded further inland than Hluhluwe Game Reserve and the Lebombo Mountains on the Maputaland– Swaziland border, reaching 650 m above sea level, but there are unconfirmed records of large Natalina specimens from Mpumalanga (Nelspruit) which may belong to this species (Sirgel pers. comm.).

Habitat: Recorded from dune, coastal lowland and scarp forest, but may also occur in other well-wooded habitats; in leaf-litter and under logs; locally common.All localities lie within either the Indian Ocean Coastal Belt or the Lowveld Savannah bioregions of Mucina and Rutherford (2006).

Notes: The somewhat auriform and narrowly umbilicate shell of Natalina wesseliana is distinctive. It is currently known only to the north of the Mfolozi R. and is the only

Natalina species so far know from altitudes of less than 1000 m lying north of this river. The living animal is spectacular and the very coarse texture of the skin in the neck region is conspicuous. When actively crawling the animal is reluctant to retreat into its shell. It has been found feeding on Cochlitoma vestita (Pfeiffer, 1855) (Achatinidae) and a large individual was found with a specimen of the carnivorous slug Chlamydephorus gibbonsi Binney, 1879 (Chlamydephoridae) in its crop. The latter was cut into three almost completely detached fragments, which, given the considerable thickness and rigidity of the skin of chlamydephorid slugs, attests to the efficacy of the radula of large Natalina species.

Conservation: Listed as Vulnerable [B1+2bc] ( IUCN 2010 ) on account of its limited distribution and the on-going threats to coastal forest habitats in south-east Africa. Fortunately, many of the South African localities at which it is known to occur are situated in formally protected areas, namely the iSimangaliso Wetland Park (World Heritage Site, formerly Greater St Lucia Wetland Park) and Hluhluwe Game Res., where it is not uncommon in dune and scarp forest habitats. However, north of Maputo in Mozambique, much of the indigenous vegetation in the coastal hinterland has been lost and only isolated fragments remain .

Figures

Fig. 6. Mantle edge anatomy of Afrorhytida, Capitina and Natalina, showing variation in left body lobe structure (all NMSA): (A) Afrorhytida knysnaensis (W5211); (B) Capitina calcicola sp. n. (W3201); (C) Natalina (Natalina) cafra natalensis subsp. n. (V8415); (D) Natalina (Tongalina) wesseliana (V7668).Abbreviations: lbl – left body lobe of mantle, pn – pneumostome, rbl – right body lobe of mantle.

Fig. 10. Spermatophores of Capitina, Afrorhytida and Natalina (all NMSA):(A) C. calcicola sp. n. (paratype, W5670/T2265), length 8.2 mm; (B) A. burseyae sp. n. (paratype, W5231/T2260), length 10.5 mm; (C) A. kraussi kraussi (W5803), length 20 mm; (D) N. cafra natalensis subsp. n. (paratype, E7682/T2375), length 16.3 mm; (E) N. quekettiana lucaris subsp. n. (paratype, W3305/T2559), length 26.5 mm; (F) N. wesseliana (V7668), length 32 mm. The head of the spermatophore is uppermost in all cases and the lengths given are for the spermatophore as if straightened out.

Fig. 11. Suprapedal glands of Capitina, Afrorhytida and Natalina (all NMSA): (A) C. schaerfiae (W5672), scale bar = 5.0 mm; (B) A. knysnaensis (W3351), scale bar = 5.0 mm; (C, D) N. quekettiana lucaris subsp. n. (W3310): (C) pedal cavity with suprapedal gland in situ, scale bar = 10 mm; (D) dissected gland, scale bar = 5.0 mm; (E, F) N. wesseliana (V7668): (E) entire gland, scale bar = 20 mm; (F) enlargement of distal end showing terminal vesicle, scale bar = 5.0 mm; (G) N. cafra cafra (W4220), scale bar = 10 mm. Abbreviations: asg – aperture of suprapedal gland, pa – pedal artery, v – vesicle at posterior end of suprapedal gland.

Fig. 48. Natalina (Tongalina) wesseliana (Kobelt, 1876): (A–C) holotype of Helix cafra var. wesseliana Kobelt, 1876 (SMFD 8287), diameter 46.0 mm (images courtesy of Ronald Janssen and Eike Neubert); (D–F) Bhanga Neck, Kosi Bay (NMSA D9888), diameter 57.2 mm.

Fig. 49. Natalina (Tongalina) wesseliana (Kobelt, 1876): (A) living specimen, Cape Vidal (specimen not collected), extended length approx. 230 mm; (B) preserved specimen showing dorsal position of genital pore with penis partially everted (NMSA W5719), scale bar = 20 mm.

Fig. 50. Natalina (Tongalina) wesseliana (Kobelt, 1876), radula (NMSA V7668): (A) rachidian and lateral teeth, scale bar = 1.0 mm; (B) vestigial marginal teeth, scale bar = 250 µm.

Fig. 51. Natalina (Tongalina) wesseliana (Kobelt, 1876), oviduct caecum and spermatophore (all NMSA): (A) spermatophore in situ in oviduct caecum (V7668); (B) two views of extracted spermatophore, straightened length 32 mm (V7668); (C) tail region of spermatophore (W5719). Abbreviations: fo – free oviduct, od – oviduct, oc – oviduct caecum, pr – prostate gland, s – spermatophore inside oviduct caecum, sh – spermatophore head, st – spermatophore tail, sv – spermatophore vent, v – vagina, vd – vas deferens.

Fig. 52. Distribution of Natalina (Tongalina) wesseliana (Kobelt, 1876). Triangles with a white centre indicate localities for specimens used in DNA analyses (Moussalli et al. 2009); contours at 1000 m and 1500 m.