Natalina cafra eumacta ( Melvill & Ponsonby, 1892 ), 2010

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 : 39-42

Natalina cafra eumacta ( Melvill & Ponsonby, 1892) , stat. rev.

Figs 14C, D , 15F–H , 16 , 24–26

Helix (Aerope) eumacta: Melvill & Ponsonby 1892: 237 , pl. 13, fig. 4. Type loc.: originally cited as ‘Natal’,

but label with type states ‘ Bashee River , Idutywa’, E. Cape [Crawford] .

Natalina eumacta: Pilsbry 1893 in 1892–93: 135; Melvill & Ponsonby 1898: 170; Sturany 1898: 31;

Möllendorff 1903: 22, pl. 3, fig. 9; Connolly 1912: 93; 1939: 106.

Identification ( Fig. 24 ): For general description see N. c. cafra . Much less variable in shape than N. c. cafra , all adult specimens being somewhat globose and more similar to N. c. amathole , particularly in terms of the relatively weak axial ribbing and the slightly more broadly patent umbilicus, but evidently attains a larger size than the Amathole subspecies and the periostracum is commonly brown rather than green, although some distinctly green individuals ( Fig. 15F ) may co-occur with brown ones ( Fig. 15G ). Characteristically, the radula has eight pairs of lateral teeth per transverse row.

Dimensions: Largest specimen (NMSA E2067, The Haven), diameter 56.4 mm; H:D of adults 0.70–0.86 (N=23).

Living animal ( Figs 15F, G ): Head-foot pale to dark grey-brown; dorsal part of neck usually darker; paler longitudinal neck stripes usually indistinct; pedal margin and mantle skirt commonly bright orange or orange-red.

Radula ( Fig. 25 ): Formula 1+8+(20–30) (N=5); length in adult up to 43 mm, with 59– 76 transverse rows of teeth. A juvenile specimen (NMSA W4627) with a radula of 15.5 mm in length similarly possessed eight lateral teeth per half row. Another specimen (NMSA W4005) had eight laterals on the left of the rachidian and nine on the right.

Distal genitalia:As in Natalina c. cafra . A small, but distinct bulla is present on the epiphallus in some populations (e.g., northern coastal localities at The Haven and Dwesa), but evidently not all.

Spermatophore ( Figs 14C, D ): Auto and allospermatophores have been found in specimens collected in late November and late February (NMSA W4044, W4055,

W4160, W4161), suggesting that mating occurs throughout the summer months. Spermatophore closely resembles that of N. c. amathole , but is less slender, anterior two-thirds with 6–8 primary longitudinal ridges, posterior third smooth; straightened length up to 18.5 mm. In one allospermatophore, a small, slender, finger-like process was present in the mid-line on the outer side of recurved tail ( Fig. 14C ). It is not present in all cases and appears to be correlated with the presence of a bulla on the epiphallus. It is far less robust than the thumb-like process present in N. beyrichi . Spermatophores from other individuals from the same locality lacked this structure ( Fig. 14D ).

Type material:According to Melvill and Ponsonby (1892) there were two original specimens. One is present in the BMNH (1905.1.26.2) and is to be considered lectotype (designated Connolly 1912: 93), diameter 30.3 mm (immature) ( Figs 24A–C ). The present location of the second specimen is unknown.

Additional material examined (all NMSA unless otherwise indicated): SOUTH AFRICA: E. Cape: Mbashe R. valley, nr Bashee Bridge (N2) (31.92461°S: 28.45113°E), 470 m, riverine thicket, in leaf-litter and under fallen aloes, A. Moussalli & D. Stuart-Fox, 23/xi/2005 (W4627, W5371); Collywobbles , overlooking vulture colony (31.9917°S: 28.5917°E), 585 m, sparse valley thicket invaded with Lantana , in leaf-litter under aloes and bushes, D. Herbert & L. Davis, 20/ii/ 2006 (W4077/8); ditto (31.9833°S: 28.5833°E), C. Vernon, 20/iv/1985 ( ELM D11080 ) , 29/iii/1991 ( ELM D12585 ) ; Xora, Kumqolo Forest (32.1500°S: 28.9833°E), D.J. Hodgkinson, 12/viii/2003 ( ELM W02620 ) ; between Nkanya and Bulungulu rivers (32.1500°S: 28.9833°E), Wood, 15/vi/1939 ( ELM D06209 ) ; 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 (W4150); Mbashe R. mouth, nr The Haven , bush just above sand hills (32.250°S: 28.883°E), ex Albany Mus. (E2067); Dwesa Nat. Res. (32.280°S: 28.842°E), coastal forest, in leaf-litter, common, D. Herbert, 06/iii/2000 (V7868) ; ditto (32.304°S: 28.828°E), coastal forest, in leaf-litter, D. Herbert, 05/iii/ 2000 (V7885); Qora Mouth, forest along north bank of estuary (32.4433°S: 28.6750°E), coastal forest, in leaf-litter, D. Herbert & L. Davis, 21/ii/2006 (W4018); Manubi Forest (32.44321°S: 28.59800°E), coastal forest, M. Bursey, 13/iv/2005 (W3015) ; ditto (32.44433°S: 28.5983°E), coastal forest, in leaf-litter, D. Herbert & L. Davis, 22/ii/2006 (W4055, W4067) ; ditto, ~ 7 km west of Mazeppa Bay (32.45255°S: 28.60487°E), 190 m, coastal forest, in leaf-litter, A. Moussalli & D. Stuart-Fox, 19/xi/2005 (W4160); Mazeppa Bay (32.47700°S: 28.65409°E), 71 m, coastal dune forest, in leaf-litter, A. Moussalli & D. Stuart-Fox, 20/xi/2005 (W4161) ; ditto (32.48008°S: 28.6431°E), dune forest, in leaf-litter, D. Herbert & L. Davis, 23/ii/2006 (W4044, crop contained anterior half of large earthworm); Mcelwana estuary , between Cebe and Mazeppa Bay (32.49741°S: 28.61445°E), C. Vernon, 01/i/2005 ( ELM D14989 ) ; Kentani (32.500°S: 28.332°E), wattle plantation (V7289); Nxaxo, second dune (32.56918°S: 28.54153°E), coastal forest, M. Bursey, 14/iv/2005 (W3012); Qolora R. mouth, west bank, nr Trennery’s Hotel (32.6167°S: 28.4167°E), M. Bursey, 05/iv/2006 ( ELM D14778 ) ; Mpetu, Ocean View farm (32.64806°S: 28.09383°E), C. Vernon, 01/xii/1993 ( ELM D13140 ) ; ditto (32.64898°S: 28.09741°E), forest, in leaf-litter, D. Herbert, L. Davis & M. Bursey, 03/iii/2007 (W5213, W5217); Komga District, Holme Park farm (32.670278°S: 27.971945°E), riverine forest, M. Bursey, 25/i/2008 (W5990); Morgan Bay , northern side of Inchara R. (32.70667°S: 28.35333°E), coastal bush, in leaf-litter, Herbert , Davis & Bursey, 03/iii/2007 (W5173); Viskop , east bank of Cefane R. (32.804720°S: 28.133055°E), M. Bursey, 20/xi/2006 ( ELM W03061 ) ; Gonubie River mouth, J.H. Power, ( BMNH 1937.12.30.7147–48); East London , Thorn Park farm (32.89028°S: 25.88806°E), M. Bursey, 07/xi/1993 ( ELM W02414 ) ; ditto, Nahoon R. valley (32.9650°S: 27.8733°E), Bigalke, 16/xii/1975 ( ELM W00852 ) ; ditto, Bonza Bay (32.97472°S: 27.96110°E), C. Vernon, 20/vii/ 1986 ( ELM D11288 ) ; ditto, Umtiza Nat. Res. (33.016°S: 27.809°E), coastal forest, in leaf-litter, A. Moussalli & D. Stuart-Fox, 26/xi/2005 (W5467) ; ditto, Sunnyridge (33.0333°S: 27.8500°E), C. Quickelberge, 15/ xii/1973 ( ELM D05167 ) ; ditto (33.0333°S: 27.8500°E) ( ELM D05988 /9) .

Distribution ( Fig. 26 ): Endemic to the coastal region of the eastern E. Cape, extending from the East London area to just north of the Mbashe River; primarily coastal, but extending inland along the Kei and Mbashe river valleys, to an altitude of approximately 600 m.

Habitat: Occurs in dune and coastal scarp forest as well as in drier, more open thicket habitats in river valleys; in forest leaf-litter, under logs and fallen aloes, and buried beneath bush clumps. Locally common in coastal scarp forest.

Notes: The most distinctive morphological feature of this subspecies is the greater number of lateral teeth per row in the radula (8 pairs rather than 5 or 6 pairs). Efford (2000) has documented similar non-overlapping subspecific variation in the number of radula teeth per row in Wainuia urnula (Pfeiffer, 1855) .

We associate this material with Helix eumacta Melvill & Ponsonby, 1892 , with some hesitation. Survey work has revealed the presence of two distinct rhytidid species at its type locality, firstly the Natalina cafra material under discussion here, and secondly a species of Afrorhytida ( A. burseyae sp. n.). The lectotype of Helix eumacta , however, is clearly not a species of Afrorhytida , having an protoconch diameter of approx. 7.0 mm, and it must therefore be considered a species of Natalina . Connolly (1939) noted that it much resembled a worn juvenile N. cafra , but mentioned minor differences in spire height and strength of sculpture. Compared with the N. cafra material under discussion, the lectotype of H. eumacta is both less globose and lower spired (H:D=0.70), sufficiently so to suggest that it may not be conspecific (compare Figs 24A and 24E , but ignore colour difference as the lectotype is over 100 years old and probably much faded). No further specimens resembling the lectotype have been found in the vicinity of the type locality; however, an immature specimen from the Komga area (Holme Park farm, NMSA W5990) is proportionately close to the lectotype and has a similar spire profile ( Fig. 24D ). This specimen, and all others examined from the vicinity of the type locality, have a radula with eight pairs of lateral teeth typical of this lineage. Consequently we have chosen to employ the name eumacta for the present subspecies and consider the lectotype to be a juvenile and unusually low-spired specimen.

Conservation: The distribution of Natalina c. eumacta is not extensive, spanning only a distance of approx. 150 km along the coast and extending only approx. 60 km inland. However, it has been recorded from more than 20 localities within its range and appears to be relatively common in coastal scarp forests, some of which fall within formally conserved areas (e.g., Dwesa Nat. Res. ). There is at present, therefore, little to suggest that the species is threatened. Nonetheless, such forests, even those in nature reserves, are threatened by a number of factors including subsistence harvesting, invasive alien plants and trampling by cattle, and their efficacy as conservation refuges in the long term will depend much on political considerations. The possibility of future threat thus remains.

Figures

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. 16. Distribution of Natalina cafra subspecies: N. c. cafra (triangles), N. c. amathole subsp. n. (stars), N. c. natalensis subsp. n. (circles), N. c. eumacta (squares).

Fig. 24. Natalina cafra eumacta (Melvill & Ponsonby, 1892): (A–C) lectotype (juvenile) of Helix (Aerope) eumacta Melvill & Ponsonby, 1892 (BMNH 1905.1.26.2), diameter 30.3 mm; (D) juvenile, Holme Park farm, Komga District (NMSA W5990), diameter 36.6 mm; (E–G) adult, Dwesa Nat. Res. (NMSA V7868), diameter 51.8 mm.

Fig. 25. Natalina cafra eumacta (Melvill & Ponsonby, 1892) radula, Dwesa Nat. Res. (NMSA V7868): (A) rachidian and lateral teeth, scale bar = 1.0 mm; (B) vestigial marginal teeth, scale bar = 250 µm.

Fig. 26. Distribution of Natalina cafra eumacta (Melvill & Ponsonby, 1892). Triangles with a white centre indicate localities for specimens used in DNA analyses (Moussalli et al. 2009); contour at 1000 m.