Chondrocyclus bathrolophodes Connolly, 1929

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 : 42-44

Chondrocyclus bathrolophodes Connolly, 1929

Figs 16B , 20–21

Chondrocyclus bathrolophodes Connolly, 1929: 239 , pl. xiv, figs 30–34 (type loc.: Kowie East [Kincaid]).

Chondrocyclus bathrolophodes – Connolly 1939: 538 . — Herbert & Kilburn 2004: 92.

Diagnosis

Shell small, depressed, lenticular; periostracum with dense axial costae expanded into three spiral rows of flanges on last whorl: at periphery, around umbilicus and below suture; costae and flanges bear numerous tiny vertical ridges; operculum duplex, exterior portion with cup-shaped multispiral lamella with horizontal shelf of interwoven bristles spiralling up on inside of cup, fused to a very long, loose fringe reflexed over peristome; radula with three large cusps on second lateral tooth; penis flattened dorsoventrally with lateral expansions of shaft towards distal end, more prominent on left side.

Type material examined

Holotype

SOUTH AFRICA – Eastern Cape • Cape Province, Kowie East ; NHMUK 1928.3 .16.4. ( Fig. 20 A )

Other material examined

SOUTH AFRICA – Eastern Cape • 10 specimens; Port Elizabeth, Baakens River; 33.967° S, 25.333° E; Sep. 1998; ex Durban Museum; NMSA V 6683 • 28 specimens; Alexandria Forest, Langebos, vicinity of forest station; 33.6533° S, 26.4083° E; 2 Feb. 2009; M. Cole leg.; ELM D15950 • 7 specimens; same collection data as for preceding; top of ridge with beacon tower; 33.6951° S, 26.3542° E; 24 Nov. 2006; M. Bursey leg.; ELM D14938 • 1 specimen; same collection data as for preceding; 23 Nov. 2009; M. Cole leg.; ELM D16960 • 27 specimens; same collection data as for preceding; ELM W 03658 • 32 specimens; same collection data as for preceding; vicinity of hikers huts; 33.6991° S, 26.3636° E; 21 Nov. 2009; M. Cole leg.; ELM D16924 • 14 specimens; same collection data as for preceding; ELM W 03617 • 5 specimens in ethanol; same collection data as for preceding; NHMUK 20120274 • 5 specimens; Cannon Rocks, dune thicket; 33.7333° S, 26.5500° E; 2 Feb. 2009; M. Cole leg.; in leaf litter; ELM D16002 • 12 specimens; Port Alfred, coastal forest east of Kowie River mouth, dune forest behind tall dunes; 33.5919° S, 26.9047° E; 26 Nov. 2006; M. Bursey and T. Moffat leg.; in leaf litter; ELM D14998 • 50 specimens; same collection data as for preceding; 12 Oct. 2009; M. Cole leg.; ELM D16922 • 32 specimens; same collection data as for preceding; ELM W 03616 • 3 specimens in ethanol; same collection data as for preceding; NHMUK 20120273 • 2 specimens in ethanol; same collection data as for preceding; NMW. Z.2012.065.00005 • 66 specimens; same collection data as for preceding; 6 Apr. 2011; R. Daniels leg.; ELM D16923 • 12 specimens; Tharfield, east bank of Riet River, dune forest; 33.5589° S, 27.0150° E; 30 Jan. 2008; M. Cole leg.; ELM D15882 • 2 specimens; The Glen on Pig Island Farm on Kleinemonde River; 33.4833° S, 26.9333° E; 12 Jan. 2007; M. Bursey leg.; ELM W 03192 • 22 specimens; same collection data as for preceding; ELM D15394 • 25 specimens; same collection data as for preceding; 1 Feb. 2009; M. Cole leg.; ELM D16150 • 2 specimens; same collection data as for preceding; ELM W 03635 • 8 specimens; Kap River Nature Reserve, south bank, thin strip of forest at base of dry north-facing cliffs; 33.4821° S, 27.0758° E; 35 m a.s.l.; 21 Dec. 2002; M. Bursey leg.; ELM D16925 • 1 specimen; Kap River Nat. Res., north bank, in ravine; 33.4812° S, 27.0873° E; 42 m a.s.l.; 30 Dec. 2002; M. Bursey leg.; leaf litter; ELM D16926 • 3 specimens; same collection data as for preceding; 13 May 2011; M. Cole leg.; ELM D16927 • 6 specimens; same collection data as for preceding; ELM W 03618 • 32 specimens; Gess farm, indigenous forest in north-facing ravine leading into Kap river; 33.4803° S, 27.0634° E; 31 m a.s.l.; 28 May 2011; M. Cole leg.; ELM D16928 • 24 specimens; same collection data as for preceding; ELM W 03619 • 84 specimens; Kap River, north bank, indigenous riverine forest on shady, south-facing slope; 33.4830° S, 27.0807° E; 9 Jun. 2012; M Cole leg.; ELM D17002 • 1 specimen; Kei River, tributary on west bank 6 km upstream of mouth, forest on steep slope, south facing; 32.6300° S, 28.3483° E; 11 Feb. 2006; M. Bursey leg.; ELM D14990 • 7 specimens; Umthombe Kei Resort, west bank of Kei River, 6 km upstream of mouth, watercourse with steep banks, rocky in places; 32.6313° S, 28.3469° E; 42 m a.s.l.; 7 May 2018; M. Cole leg.; ELM D18355 • 10 specimens; same collection data as for preceding; ELM W 04053 • 1 specimen; Qolora estuary, west bank, steep slope with Strelitzia nicolai ; 32.6333° S, 28.4277° E; 14 m a.s.l.; 4 May 2006; D.- J. Hodgkinson leg.; ELM D14853 • 6 specimens; same collection data as for preceding; 11 Jun. 2018; M. Cole leg.; ELM W 04071 • 5 specimens; Kobonqaba, coastal forest on east side of mouth; 32.6058° S, 28.4933° E; 17 m a.s.l.; 23 Apr. 2015; M. Cole leg.; ELM D17932 • 3 specimens; same collection data as for preceding; ELM W 03868.

Description

SHELL ( Fig. 20 A–D). Small, depressed, lenticular, adult diameter 5.32–6.16 mm, height 2.76–3.45 mm, diameter:height 1.73–2.00 (n = 25). Spire depressed, each whorl just rising above the next, apex almost flat ( Fig. 20 A–B). Embryonic shell ( Fig. 21A ) 1.75 whorls, microscopically malleate, roughest in centre, junction between embryonic shell and teleoconch evident with appearance of a few weak axial costae, but not sharply demarcated. Teleoconch comprising 2.75 whorls, moderately convex, rapidly increasing, suture deeply impressed. Aperture circular, last whorl descending near aperture, peristome simple, continuous and free. Umbilicus wide and deep, exposing all the whorls ( Fig. 20D ). Periostracum glossy, honey-brown and lacquer-like with dense lamellate costae at regular intervals, 92–127 (n = 24) on last whorl, expanded into quadrangularly-shaped flanges at periphery, forming a distinct peripheral cord, as well as a row of shorter semicircular flanges below the suture and around the umbilicus ( Fig. 20 A–D); flanges bear numerous axial riblets visible at very high magnification ( Fig. 21B ); intervals between costae with microscopic axial threads ( Fig. 20B ). Shell translucent honey-brown when fresh.

LIVING ANIMAL. Head, tentacles and snout dark grey, underside of foot creamy white.

OPERCULUM ( Fig. 21 C–E). Duplex, outer multispiral portion with 5.5 whorls forming a strongly concave cup, upper edge of lamellar blade thickened, forming a horizontal shelf of interwoven bristles spiralling up the inside of the cup; in the outermost whorl the latter is loosely connected to a very long fringe reflexed over peristome and preventing operculum being withdrawn into shell; in earlier whorls this fringe is not visible and appears fused with the lamella; surface of lamella of last whorl tuberculate at high magnification.

RADULA ( Fig. 21F ). Rachidian with five cusps, central cusp approx. twice length of outer two on each side; first and second lateral teeth similar but second is larger, each with four cusps and a vestigial fifth; first three cusps gradually increasing in size from centre outwards and fourth very small.

PENIS ( Fig. 21 G–H). Shaft dorsoventrally flattened, with lateral expansions of shaft on both sides towards distal end but more prominent on left, with numerous annular rugae, distal end bulbous and smooth, intromittent organ exserted, but not elongated.

Distribution and habitat

Endemic to Eastern Cape coast with a disjunct distribution, occurring between Port Elizabeth and Great Fish River (recorded up to 9 km inland) and between Great Kei and Kobonqaba River (recorded up to 6 km inland) ( Fig. 16B ).

Albany Dune Strandveld on coastal dunes at Port Alfred (Mucina et al. 2006), Alexandria Forest with large trees, classified as Southern Coastal Forest ( Mucina & Geldenhuys 2006) or Albany Coastal Forest ( von Maltitz et al. 2003), Albany Thicket (Kowie Thicket and Buffels Thicket) ( Hoare et al. 2006) and Eastern Cape Dune Forest ( von Maltitz et al. 2003); in leaf-litter.

Remarks

Chondrocyclus bathrolophodes is similar to C. putealis (differences are discussed under the latter species) in periostracal ornamentation, operculum, radula and penis.

Specimens recorded in the vicinity of the Kei and Kobonqaba Rivers would have been difficult to identify on morphological grounds alone, but the molecular phylogeny shows unambiguously that the specimens sequenced are C. bathrolophodes ( Fig. 1 ). The species was previously thought to occur only in the Port Elizabeth–Albany area, but is shown to have a disjunct distribution. In very close proximity to Kobonqaba to the east, in the Nxaxo forest, Chondrocyclus specimens are morphologically very similar to C. bathrolophodes and C. putealis , but are neither of these species on molecular grounds ( Cole et al. 2019; Fig. 1 ). Chondrocyclus bathrolophodes exhibits very little genetic diversity at the end of a relatively long branch, suggesting recent geographical expansion and severe pruning of ancestral diversity by extinctions. All the coastal taxa of the Eastern clade show complex distribution patterns of sympatry, disjunctions and turnover within sharp contact zones. These could be the result of dynamic changes in vegetation over time, with forest contraction and expansion due to climatic oscillations ( Partridge 1993; Partridge et al. 1999). These processes could have caused repeated periods of isolation of populations in shrinking refuges, followed by dispersal and contact.

Figures

Fig. 16. Distribution map of Chondrocyclus species in the Eastern clade. A. Species in KwaZulu-Natal and the eastern half of the Eastern Cape, on the coast and extending inland. B. Species on the Eastern Cape coast. Note that the range of C. pondoensis sp. nov. overlaps with that of C. putealis Connolly, 1939 and C. cooperae sp. nov. T indicates type localities. Major cities and rivers are labelled.

Fig. 20. Chondrocyclus bathrolophodes Connolly, 1929. A. Holotype (NHMUK 1928.3.16.4). B–D. ELM W3616. B. Aperture view. C. Dorsal view. D. Ventral view. Scale bars: A = 3 mm; B–D = 2 mm.

Fig. 21. Chondrocyclus bathrolophodes Connolly, 1929. A. Protoconch (ELM D15882). B. Detail of axial lamellae of periostracum (ELM W3616). C–D. Operculum (ELM W3616). E. Detail of sculpture of wall of operculum (ELM W3616). F. Portion of radula (ELM W3616). G. Penis, lateral view (ELM W3658). H. Penis, dorsal view (ELM W3616). Scale bars: A, E = 200 µm; B, G–H = 500 µm; C–D = 1 mm; F = 50 µm.

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.