Afrocyclus bhaca, Cole, 2019

Cole, Mary L., 2019, Revision of Chondrocyclus s. l. (Mollusca: Cyclophoridae), with description of a new genus and twelve new species, European Journal of Taxonomy 569, pp. 1-92 : 73-75

Afrocyclus bhaca gen. et sp. nov.

urn:lsid:zoobank.org:act:24F095DF-C063-42C8-BA94-4E793764C8B0

Figs 11 E–F, 28D, 29, 32

Diagnosis

Shell very small, depressed, discoidal; periostracum with axial costae producing spiral rows of simple hairs; operculum very fragile and duplex, exterior portion very shallowly concave, with low multispiral lamella terminating in a solid fringe, radula with two large cusps on second lateral tooth and rachidian tooth with slightly serrated upper edge.

Etymology

Named for the amaBhaca people who inhabit the Mount Frere and Umzimkhulu regions, having fled from King Shaka Zulu during the wars of turmoil in the 1820s under King Madzikane.

Type material examined

Holotype

SOUTH AFRICA – KwaZulu-Natal • Ngele Forest, 26 km east of Kokstad, large forest patch divided by N2 national road, Red Trail on the west side of N2 approx. 0.5 km NNW of Ngele Forest Inn hotel; 30.5331° S, 29.6827°E; 1234 m a.s.l.; 15 Apr. 2015; M. and K. Cole leg.; NMSA P1124 /T4282. ( Fig. 11 E–F)

Paratypes

SOUTH AFRICA – KwaZulu-Natal • 1 specimen; same collection data as for holotype ELM D17891/ T177 • 3 specimens; same collection data as for holotype; ELM W03855/T178 • 2 specimens; same collection data as for holotype; 3 Oct. 2018; M. Cole leg.; ELM D18357/T194 • 1 specimen; same collection data as for holotype; ELM W04055/T193 • 1 specimen (dry shell and body in ethanol); same collection data as for holotype; NHMUK 20180583 • 2 specimens; Ngele Forest, Green Trail , small patch of forest approx. 0.5 km SW of hotel; 30.5406° S, 29.6802° E; 1208 m a.s.l.; 7 Apr. 2015; M. and K. Cole leg.; ELM D17900/T179 • 5 specimens; Ngele Forest, near Kokstad , mistbelt Podocarpus forest; 30.31. 5°S, 29.41. 5° E; ± 1350 m a.s.l.; 14–15 Nov. 1995; D. Herbert and L. Davis leg.; in leaf litter; NMSA V2075 /T4284 • 6 specimens; same collection data as for preceding; 30.31.857° S, 29.41.076° E; 3 Mar. 1997; D. Herbert leg.; in leaf litter and under logs; NMSA V8277 /T4285 • 2 specimens; same collection data as for preceding; NHMUK 20180584 • 2 specimens; same collection data as for preceding; NMW.Z.2019.004.0007 • 4 specimens; same collection data as for preceding; sorted from dried leaf-litter sample; NMSA V4889 /T4286 • 2 specimens; same collection data as for preceding; RMNH.MOL.340759 • 1 specimen; Ngele Forest, near Kokstad , mistbelt Podocarpus forest; 30.32°S, 29.38°E; 27 Mar. 1998; C. Symes leg.; in leaf litter; NMSA V6886 /T4287 – Eastern Cape • 8 specimens; Mount Frere, just south of Buffalo Nek village , 10 km NW of Mount Frere; 30.8548° S, 28.8930° E; 1466 m a.s.l.; 7 Apr. 2015; M. Cole leg.; in leaf litter; ELM D17893/T180 • 3 specimens; same collection data as for preceding; ELM W03856/T181 .

Other material examined

SOUTH AFRICA – KwaZulu-Natal • 7 specimens; Ngele Forest , mist-belt Podocarpus forest; 30°32′S, 29°38′E; ± 1350 m a.s.l.; 17 Feb. 1997; D. Barraclough leg.; sorted from dried leaf-litter sample; NMSA V4867 . – Eastern Cape • 2 specimens; Mount Frere, just south of Buffalo Nek village , 10 km NW of Mount Frere; 30.8548°S, 28.8930° E; 1466 m a.s.l.; 4 Oct. 2018; M. Cole leg.; in leaf litter; ELM D18356 • 7 specimens; same collection data as for preceding; ELM W04054 .

Description

SHELL. Very small, very depressed, discoidal, adult diameter 2.49–3.72 mm, height 0.97–1.78 mm, diameter:height 1.83–2.58 (n = 19) ( Fig. 32 A–C). Spire almost flat, sometimes concave, usually with only the weakly mammillate protoconch projecting ( Fig. 32A ). Embryonic shell ( Fig. 28D ) just over two whorls, microscopically malleate, junction between embryonic shell and teleoconch evident with development of axial costae on teleoconch. Teleoconch comprising two whorls, very rapidly increasing, convex, suture impressed. Aperture circular, last whorl descending steeply nearing aperture, peristome simple, continuous and free. Umbilicus very wide, exposing all the whorls. Periostracum glossy and lacquer-like with well-spaced lamellate axial costae at regular intervals, the number on last whorl varying between 46 and 65 ( Table 5), which produce spiral rows of simple hairs varying from 4–15 on last whorl (4–5 and 14–15 respectively in the two populations examined) ( Fig. 32B, D ), longest at periphery and shortest around umbilicus; intervals between costae with approx. nine microscopic axial threads. Shell translucent when fresh.

OPERCULUM ( Fig. 32E ). Very fragile and duplex, outer portion consists of multispiral lamella with five whorls, height of lamellar blade very low thus operculum is very shallowly concave to almost flat, thickened horizontal ridge on lamellar blade just above disc surface; starting just after whorl 3 a long fringe of fused bristles emanates from this ridge, fused to blade and then curving outwards, leaving a furrow between fringe and vertical portion of blade, fringe of each whorl is not fused to lamella of following whorl, fringe of outer whorl extends to edge of disc; inner portion of operculum is a thin disc, without a prominent tubercle in centre.

RADULA ( Fig. 32F ). Rachidian with five cusps set a little distance below upper edge of tooth, upper edge mildly serrated, central cusp very long; first lateral tooth with four cusps and a vestigial fifth, third cusp (from centre) very long; second lateral tooth with two large cusps, second cusp (from centre) larger, a third small cusp and a vestigial fourth.

PENIS. Not examined.

Distribution and habitat

Medium altitude forests of the ‘first escarpment’ in the interior of north-eastern Eastern Cape and southern KwaZulu-Natal ( Fig. 29 ).

Eastern Mistbelt and Transkei Mistbelt Forests ( von Maltitz et al. 2003).

Remarks

Afrocyclus bhaca gen. et sp. nov. differed from Afrocyclus isipingoensis gen. et comb. nov. by lacking the spiral row of extremely short hairs immediately below the suture and the protoconch was more strongly sculptured, but less so than that of A. potteri gen. et sp. nov. and A. oxygala gen. et sp. nov. The protoconch was smaller than that of A. potteri gen. et sp. nov. ( Fig. 28 C–D). The two populations examined differed in the arrangement of the spiral rows of hairs: specimens from Ngele had four–five rows concentrated around the periphery ( Fig. 32 A–B), while specimens from near Mount Frere/Buffalo Nek had 14–15 rows on the last whorl, more or less evenly distributed over the whorl ( Fig. 32D ). The latter were relatively more depressed than other populations ( Table 5). Specimens from Mount Frere are tentatively included in A. bhaca gen. et sp. nov., but may prove to be a separate species upon further study. In the molecular phylogeny they were more closely related to specimens from Ngele than to any other specimens in the Afrocyclus isipingoensis gen. et comb. nov. species complex ( Fig. 1 ), although relatively divergent compared to the genetic variation within the majority of species (see Cole et al. 2019).

Ngele and nearby forests appear to be a hot-spot of narrow range endemism in low-vagility, saproxylic invertebrates including other molluscan taxa (e.g., Gulella claustralis Connolly, 1939 ) and Onychophora ( Daniels et al. 2016). The occurrence of two distinct lineages ( A. potteri gen. et sp. nov. and A. bhaca gen. et sp. nov.) in close proximity has also been demonstrated in this region in Onychophora, which belong to ancient lineages that diverged in the Eocene or earlier ( Daniels et al. 2016). This is in contrast to findings in other molluscan taxa where populations across the region are considered to belong to the same lineage ( Herbert 2017).

Figures

Fig. 11. Holotypes of species of Afrocyclus gen. nov. A–B. A. oxygala gen. et sp. nov., diameter 2.86 mm (NMSA P0638/T4153). C–D. A. potteri gen. et sp. nov., diameter 2.86 mm (NMSA P1125/T4283). E–F. A. bhaca gen. et sp. nov., diameter 2.87 mm (NMSA P1124/T4282).

Fig. 32. Afrocyclus bhaca gen. et sp. nov. A. Dorsal view (NMSA V8277). B. Aperture view (NMSA V2075). C. Ventral view (NMSA V2075). D. Juvenile to show detail of axial lamellae of periostracum (ELM D17893). E. Portion of radula (ELM W3856). F. Operculum (NMSA V2075). Scale bars: A, C = 1 mm; B, D = 500 µm; E = 20 µm; F = 200 µm.

Fig. 28. Protoconch detail of species of Afrocyclus gen. nov. A. Afrocyclus isipingoensis (Sturany, 1898) gen. et comb. nov. from Durban (near type locality) (ELM W3648). B. A. oxygala gen. et sp. nov. (ELM W3647). C. A. potteri gen. et sp. nov. (ELM W4052). D. A. bhaca gen. et sp. nov. (NMSA V4889). Scale bars: A–D = 200 µm.

Fig. 29. Distribution map of Afrocyclus gen. nov. T indicates type localities. Provinces and major cities are labelled.

Fig. 1. Bayesian Inference majority consensus tree of the “taxa complete” concatenated CO1-16S sequence dataset for Chondrocyclus s.l. Ancey, 1898 (84 sequences) and seven other caenogastropods with the tree rooted on Pomacea insularum (d’Orbigny, 1837) (modified from Cole et al. 2019). Colours indicate major clades of Chondrocyclus Ancey, 1898 and correspond with colours used in maps. Support values are given as posterior probabilities for Bayesian analysis above nodes (only values ≥ 0.95 are shown) and as bootstrap percentages for ML analysis below nodes (only values ≥ 65% are shown); maximal support (Bayesian = 1, ML = 100%) is indicated by an asterisk. Scale bar indicates substitutions per site.