Natalina beyrichi (Martens, 1890)

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 : 47-50

Natalina beyrichi (Martens, 1890)

Figs 3D , 8A , 14E , 15A , 30–32

Aerope beyrichi: Martens 1890: 85 ; 1894: 1; 1897: 35, pl. 6, figs 1–3. Type loc.: Pondoland [C. Beyrich]. Natalina beyrichi: Melvill & Ponsonby 1898: 170 ; Sturany 1898: 30; Möllendorff 1903: 21, pl. 4, figs 1–3;

Connolly 1912: 90; 1939: 106, pl. 4, figs 1–3; Herbert & Kilburn 2004: 222.

Etymology: Named for Conrad Beyrich (dates not known), a German engineer. In 1888 he travelled through Pondoland (north-eastern E. Cape) with fellow German, Frans Ewald Bachmann, visiting localities from the Mtamvuna River south to Port St Johns.

Identification: A relatively easily identified species on account of its depressed shape, comparatively strongly sculptured base, wide umbilicus and coastal distribution in the north-eastern E. Cape; a range which overlaps only with that of N. cafra eumacta which is taller, more globose and has a narrower, partially obscured umbilicus.

Description ( Fig. 30 ): Shell large and relatively depressed, thin and fragile; periphery at or below mid-whorl; suture somewhat above mid-whorl, but descending to a variable degree prior to aperture at maturity. Protoconch diameter typically 7–8 mm, but its limit difficult to determine in many specimens. Apical surface sculptured by close-set axial riblets which remain obvious on base; junction between dull upper surface and more shiny base forming a relatively distinct line at the periphery; umbilicus wide, not obscured at all by columella lip when viewed basally; long axis of aperture more or less horizontal or only slightly oblique; outer lip not thickened.

Periostracum olive-green to olive-brown with frequent radial bands in darker shades, particularly on last whorl.

Dimensions: Largest specimen (NMSA W5414, Port St Johns), diameter 63.1 mm; H:D of adults 0.57–0.74 (N=28).

Living animal ( Fig. 15A ): Head-foot grey to greyish brown or brown, dorsal neck region and optic tentacles somewhat darker, generally lacking pale longitudinal stripes extending backward from optic tentacles; sides of foot paler, particularly beneath shell; pedal margin tinged with orange, tail sometimes brightly so; mantle edge bright orange.

Radula ( Fig. 31 ): Formula 1+5+~22 (N=2); length in adult 34–38 mm, with 44–56 transverse rows of teeth.

Distal genitalia: Epiphallus with a well-developed bulla near its junction with vas deferens; internally this has a hollow central core continuous with the epiphallus lumen, its junction with the latter being bounded by a raised circular flange.

Spermatophore ( Fig. 14E ): Well preserved allospermatophores have been found in two specimens, collected in early November (NMSA W4123, W4125). Straightened length 18–26 mm. In general form these resemble those of N. cafra subspp. and were strongly curved in situ in the oviduct caecum. Notably, they differ in having a well-developed thumb-like projection on the outer side, at the base of the recurved tail region. This is more substantial than the similar projection sometimes seen in the spermatophores of N. c. eumacta and N. c. natalensis . It is clearly formed in the epiphallus bulla.

Type material: Nine syntypes in Berlin Museum ( MNHU: 42394). We designate the specimen figured by Martens (1897) and re-illustrated here ( Figs 30A–C ) to be the lectotype, diameter 59.5 mm, height 38.0 mm (Martens gave the dimensions as diameter 62 mm, height 40 mm, but this may refer to the largest specimen rather than the one figured). Connolly’s mention of the ‘type in Zool. Mus. Berlin’ ( Connolly 1912) does not constitute a lectotype designation since he did not specify any one specimen in particular .

Additional material examined (all NMSA unless otherwise indicated): SOUTH AFRICA: E. Cape: Mkambati Nat. Res., ‘ Super Bowl’ forest at junction of Msikaba and KwaDlambu rivers (31.2955°S: 29.9292°E), indigenous forest, in leaf-litter, M. Bursey, 05/iii/2001 (V9220 body only, shell in ELM D13333 ) ; ditto (31.2955°S: 29.9292°E), indigenous forest, in leaf-litter beneath Trichilia dregeana Sonder, D. Herbert , 05/ iii/2001 (V8916) ; Mbotyi, various sites beside road through upper section of forested scarp ( Ntsubane Forest ) (31.4298°S: 29.7261°E), coastal forest, in leaf-litter, D. Herbert, 03/iii/2003 (W0591) ; Mbotyi Forest (31.43107°S: 29.72656°E), ca 300 m, indigenous forest, in leaf-litter, A. Moussalli & D. Stuart-Fox, 3/xi/ 2005 (W4123) ; Magwa Falls, Egossa Forest (31.4333°S: 29.6333°E), ca 500 m, R. Botha, 08/vii/2006 ( ELM W02995 ) ; Port St Johns area , east bank of Mzimvubu R., 26 km upstream of mouth (31.509722°S: 29.448883°E), M. Bursey, 24/i/2006 ( ELM D14771 ) ; Mntafufu , north side of river (31.5559°S: 29.6261°E), coastal forest, in leaf-litter, one individual found eating Gittenedouardia carinifera (Melvill & Ponsonby, 1897) , D. Herbert, L. Davis & M. Bursey, 23/iv/2005 (W1831, W2969, W2970, W3025) ; ditto, south side of river (31.55021°S: 29.61777°E), coastal scarp forest, amongst talus and leaf-litter at base of road cutting, D. Herbert & M. Bursey, 29/iv/2004 (W1823) ; Port St Johns , east bank, 1 km from river mouth (31.60833°S: 29.55000°E), R. Botha, 06/vii/2006 ( ELM W03000 ) ; ditto, Isinuka sulphur springs and travertine deposit (31.60953°S: 29.47989°E), woodland/forest, in leaf-litter, D. Herbert, 04/iii/2003 (W0538) ; ditto, southern side of Mt. Thesiger (31.61185°S: 29.50202°E), scarp forest, in leaf-litter, D. Herbert, L. Davis & M. Bursey, 23/iv/2005 (W3029) ; ditto, north of Mzimvubu R. (31.61519°S: 29.54526°E), indigenous forest, in leaf-litter, A. Moussalli & D. Stuart-Fox, 08/xi/2005 (W5414); Port St Johns (not further localised) (A7044, A7130, V2013, E7862, BMNH 1937.12.30.1304) ; ditto, Second Beach (31.64819°S: 29.51746°E), 100 m, coastal forest, in leaf-litter, A. Moussalli & D. Stuart-Fox, 05/xi/2005 (W4125, W5413) ; ditto, Silaka Nat. Res. (31.64903°S: 29.50339°E), M. Bursey, 05/iii/2003 ( ELM D13835 ) ; Nothintsila , ca 20 km NW of Hluleka Nat. Res. (31.74733°S: 29.20008°E), 395 m, indigenous forest, in leaf-litter, A. Moussalli & D. Stuart-Fox, 14/xi/2005 (W4734) ; Mpande (31.74738°S: 29.37078°E), coastal forest north of river mouth, in leaf-litter, D. Herbert, L. Davis & M. Bursey, 21/iv/2005 (W2849, W2870, W2872, W2873) ; Hluleka Nat . Res. (31.8203°S: 29.30303°E), coastal forest, in leaf-litter, D. Herbert, L. Davis & M. Bursey, 20/iv/2005 (W3023, W2895, W2896) ; ditto (31.82333°S: 29.30550°E), coastal forest, in leaf-litter, D. Herbert, L. Davis & M. Bursey, 20/iv/2005 (W3047) ; Xora R. mouth area, Kwaqana Forest (32.13833°S: 28.98750°E), M. Bursey, 15/ix/2005 ( ELM D14544 ) ; Xora River mouth (32.150°S: 28.983°E), washed into mangroves, V. van der Walt, 1997 (V5311) ; Xora, east bank of Xora river (32.15167°S: 28.99222°E), M. Bursey, 26/viii/2001 ( ELM D13345 ) ; ditto, Kumqolo Forest (32.15888°S: 28.98481°E), M. Bursey, 12/vii/2003 ( ELM D13686 ) ; ditto, Kumqolo Forest , small patch of coastal forest on west bank of river (32.159°S: 28.985°E), in leaf-litter, M. Bursey, 14/ix/2005 (W5395) ; The Haven Nat.Res. , vicinity of camp ground (32.24435°S: 28.90600°E), 15 m, coastal dune forest, in leaf-litter, A. Moussalli & D. Stuart-Fox, 16/xi/2005 (W4149) ; Dwesa Nat. Res. (32.280°S: 28.842°E), coastal forest, in leaf-litter, D. Herbert, 06/iii/2000 (V7869); Qora , east bank of river (32.433°S: 28.667°E), M. Bursey, 21/ii/2006 ( ELM D14798 ) ; Mpetu area, Tyityaba, Belladonna farm (32.56833°S: 28.12500°E), 340 m, C. Vernon, 26/vii/1986 ( ELM D10040 ) .

Distribution ( Fig. 32 ):A restricted-range E. Cape endemic, known only from the coastal hinterland between Mkambati Nature Reserve and the Kei River valley (Mpetu area). Its distribution seldom reaches far inland (maximum recorded distance from coast ± 30 km) and extends along the coast for ± 230 km; occurs from sea-level to 500 m.

Habitat: Primarily associated with scarp forests in the Transkei Coastal Belt, but extending also into forest patches within the Eastern Valley Bushveld; in leaf-litter and under logs; locally common.

Notes: Natalina beyrichi is unlikely to be confused with any other species on account of its depressed, widely umbilicate shell and coastal distribution in the north-eastern E. Cape. There is some variation in shell height, with specimens from the Hluleka area often having a more elevated spire and in addition a slightly coarser sculpture ( Fig. 30G ). However, specimens of intermediate height are known and all possess the wide, open umbilicus typical of the species. In analyses of molecular data, elevated specimens cluster together with more typical specimens. Not surprisingly, given its restricted coastal distribution, genetic diversity within N. beyrichi is limited ( Moussalli et al. 2009). The coastal forest habitats favoured by the species would have been largely continuous prior to the impact of humans, facilitating gene flow and preventing the differentiation of local subpopulations. In the south of its range, the distribution of N. beyrichi overlaps with that of N. cafra eumacta , but that taxon is markedly more globose. The zone of sympatry extends for approximately 70 km, between the Kei and Mbashe rivers, but the two taxa have been found to co-occur at few localities. Where they are syntopic, they remain easily separable with no evidence of intergrading.

Individuals have been collected consuming molluscan prey (e.g., Gittenedouardia spp. , Cerastidae ), but microchaetid earthworms ( Microchaetus pondoanus Michaelsen, 1913 ) are often abundant in the coastal forests of Transkei ( Plisko 2003, and pers. observ.) and these may also be important diet items. Captive animals have readily consumed such prey.

Conservation: Natalina beyrichi is a characteristic element of the coastal forests of the Transkei region and is currently listed as Critically Endangered [CR B1+2c] (IUCN 2010). This is due to its restricted distribution and the threats to coastal forest habitats in much of its range. Such threats are on-going and include mining, subsistence harvesting, invasive plants and trampling by cattle. However, despite its limited range, the species may be locally relatively common. It is protected in conserved areas such as Mkambati, Hluleka and Dwesa nature reserves, but the first and last of these are at or near the ends of its range. Populations in the Mbotyi to Port St Johns area, where it is currently most common, are not protected.

Figures

Fig. 3. Feeding in Natalina: (A–C) N. cafra natalensis, captive animals consuming: (A) Achatina immaculata, (B) Cornu aspersum and (C) Elisolimax flavescens; (D) N.beyrichi as found in leaf-litter,Mntafufu, E. Cape, with tail inserted in shell of Gittenedouardia carinifera, extracting calcium (NMSA W2970).

Fig. 8. Radulae of Natalina, Afrorhytida and Capitina (all NMSA):(A) N. beyrichi (Martens, 1890) (W0591), scale bar = 1.0 mm; (B) A. kraussi (Pfeiffer, 1846) (W3351), scale bar = 500 µm; (C) C. calcicola sp. n. (paratype, W3360/T2270), scale bar = 250 µm.

Fig. 14. Natalina s.s. spermatophores (all NMSA): (A) N.cafra amathole subsp. n. (W4193), length 21 mm; (B) N. cafra natalensis subsp. n. (W7136), length 18.3 mm; (C) N. cafra eumacta (W4055, Manubi Forest), distorted spermatophore with finger-like process on tail region, length 12 mm; (D) N. c. eumacta (W4160, Manubi Forest), well preserved spermatophore lacking finger-like process on tail region, length 18.5 mm; (E) N. beyrichi (W4123), length 25.8 mm; (F) N. quekettiana lucaris subsp. n. (paratype, W3305/T2559), length 26.5 mm. The lengths given are for the spermatophore as if straightened out.

Fig. 15. Natalina s.s., living animals of larger species (all NMSA): (A) N. beyrichi, Hluleka (W2895), shell diameter 41.5 mm; (B) N. cafra cafra, Mountain Drive, Grahamstown (W5212), shell diameter 30.0 mm; (C) N. cafra amathole subsp. n., Hogsback (paratype, W6371/T2309), shell diameter 39.0 mm; (D) N. cafra natalensis subsp. n., Pietermaritzburg (specimen not collected), shell diameter approx. 58 mm; (E) N. c. natalensis subsp. n., Mtamvuna (paratype, W0308/T2370), shell diameter 40.3 mm; (F) N. cafra eumacta, Mazeppa Bay (W4044), shell diameter 40.4 mm; (G) N. c. eumacta, Dwesa (V7868), shell diameter 48.3 mm; (H) N. c. eumacta, egg, Manubi Forest (W4067), scale in millimetres.

Fig. 30. Natalina beyrichi (Martens, 1890): (A–C) lectotype of Aerope beyrichi Martens, 1890 (here designated) (MNHU 42394), diameter 59 mm, height 38 mm (photographs courtesy of Thomas von Rintelin and Lothar Maitas); (D–F) Mbotyi (NMSA W0591), diameter 54.7 mm; (G) elevated specimen, Hluleka (NMSA W3023), diameter 41.0 mm; (H) depressed specimen, Port St Johns (NMSA E7862), diameter 57.5 mm.

Fig. 31. Natalina beyrichi (Martens, 1890), radula, Mbotyi (NMSA W0591): (A) entire width of radula, scale bar = 1.0 mm; (B) vestigial marginal teeth, scale bar = 0.5 mm.

Fig. 32. Distribution of Natalina beyrichi (Martens, 1890). Triangles with a white centre indicate localities for specimens used in DNA analyses (Moussalli et al. 2009); contours at 1000 m and 1500 m.