Chondrocyclus trifimbriatus 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 : 30-33

Chondrocyclus trifimbriatus Connolly, 1929

Figs 15 , 16A

Chondrocyclus trifimbriatus Connolly, 1929: 241 , pl. xiv, figs 35–39 (type loc.: Karkloof, bush behind Karkloof Falls [Falcon]).

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

Diagnosis

Shell small, depressed, lenticular; periostracum with dense axial costae developing five rows of flanges on last whorl: just below suture, at periphery, around umbilicus and two weaker rows on either side of periphery; operculum duplex, exterior portion shallowly concave with step-shaped multispiral lamella terminating in a long solid fringe reflexed over peristome; radula with three large cusps on second lateral tooth, cusps of rachidian, first and second lateral teeth fairly uniform in size; penis flattened dorsoventrally and laterally expanded on left side from about midway down the shaft, intromittent organ relatively long.

Etymology

The specific name is derived from the Latin ‘ tres ’, meaning ‘three’, and ‘ fimbriae ’, meaning ‘fringe’, with reference to the three spiral cords of compacted flange-like bristles on the last whorl.

Type material examined

Holotype

SOUTH AFRICA – KwaZulu-Natal [Natal] • Karkloof, Natal; presented by W. Falcon; NHMUK 1928.3.16.5. ( Fig. 15A )

Other material examined

SOUTH AFRICA – KwaZulu-Natal • 6 specimens; Karkloof River valley, southwest of ‘ The Start’ ; 29.3150° S, 30.250° E; 1350 m a.s.l.; W. Falcon coll.; NMSA A 8000 • 2 specimens; Nkandla Forest Reserve, Chibini area , scarp forest; 28.7227°S, 31.1282°E; ± 1200 m a.s.l.; 20 Oct. 2003; D. Herbert, M. Bursey and T. Nangammbi leg.; under logs and in leaf litter; NMSA W 1115 • 1 specimen; Entumeni Forest, 7 km west of Eshowe ; 28.8852°S, 31.3797°E; 680 m a.s.l.; 29 Oct. 2010; M. Cole leg.; ELM D16966 • 1 specimen; same collection data as for preceding; ELM W 3692 • 1 specimen; same collection data as for preceding; 13 Jan. 2010; ELM D17003 • 3 specimens; same collection data as for preceding; ELM W03661 .

Description

SHELL ( Fig. 15 A–C). Small, depressed, lenticular, adult diameter 3.9–4.37 mm (4.37–5.32 mm Entumeni population), height 1.95–2.66 mm (2.39–2.86 mm Entumeni population), diameter:height 1.65–2.0 (1.62–2.02 mm Entumeni population) (n = 5 C. trifimbriatus from type locality; n = 6 Entumeni population). Spire not much raised, protoconch sub-mammillate ( Connolly 1929). Embryonic shell two whorls, microscopically malleate, junction between embryonic shell and teleoconch evident with development of costae on teleoconch. Teleoconch comprising 2.75 whorls, 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. Periostracum glossy, honeybrown and lacquer-like with dense lamellate axial costae at regular intervals, approx. 150–155 (n = 4) on last whorl in specimens from the type locality, but varying between populations (see Remarks below), expanded into quadrangularly-shaped flanges at periphery, immediately below the suture and around the umbilicus, the row at the periphery the strongest, and with two less prominent rows of lower-standing flanges on either side of periphery. Shell translucent, glossy, corneous yellow-brown when fresh.

LIVING ANIMAL. Creamy white with slight pigmentation on tentacles.

OPERCULUM ( Fig. 15D, F ). Duplex, lamella of outer multispiral portion with 4.25 whorls, step-shaped; on outer surface of lamellar blade a long, solid fringe curves upwards and then outwards forming a groove between fringe and lamellar blade, spanned by a very loose network of bristles; a very short solid horizontal fringe emanates just below main fringe; upper edge of lamella thin and projects above fringe in side view; outer surface of lamellar blade tuberculate at high magnification.

RADULA ( Fig. 15E ). Rachidian with five cusps, approx. equivalent length; first and second lateral teeth similar, each with five cusps, first three cusps approx. equivalent in size, the fourth very small and the fifth (from centre) vestigial; cusps increase in size very slightly from central tooth outwards, but there is not a large difference in size between cusps.

PENIS ( Fig. 15G ). flattened dorsoventrally and laterally expanded on left side from about midway down the shaft, with numerous annular rugae, smooth distal end narrows, intromittent organ relatively long.

Distribution and habitat

Originally known only from Karkloof River Valley, downstream of Karkloof Falls, but the species appears to have disappeared from the Karkloof vicinity ( Fig. 16A ). Specimens recently discovered at Entumeni and Nkandla forests are considered here to be C. trifimbriatus based on comparison with type material.

No habitat data available for original specimens, but indigenous Eastern Mistbelt Forest ( von Maltitz et al. 2003) occurs in the Karkloof vicinity. Recently collected specimens occur in Scarp forests (Entumeni) and Mistbelt/Scarp (Nkandla) in leaf litter.

Remarks

There are morphological differences between populations from different localities. Specimens from Entumeni ( Fig. 15 B–C) lack the spiral row of flanges just below the suture and the weak row below the periphery. Specimens from Nkandla also bear fewer spiral cords than C. trifimbriatus : there is a spiral cord just below suture and one between periphery and umbilicus but the weak cords on either side of periphery are absent. Although not many specimens were available to measure (four from Karkloof, six from Entumeni and two from Nkandla), D:H ratio is similar throughout but the axial costae on last whorl are more dense in Entumeni specimens (approx. 200) and less dense in Nkandla specimens (117) compared to 150–155 in Karkloof specimens. The opercula of specimens from Entumeni and Nkandla are similar to the operculum of C. trifimbriatus from the type locality ( Fig. 15D ). The radulae of all populations agree with the descriptions and figure of Connolly (1929, 1939).

Few specimens were available for study since they seemed to be very rare in the two forests where they were found, and more sampling from these and other forests in north-central KwaZulu-Natal are required to resolve more conclusively whether C. trifimbriatus occurs throughout the region or whether there may be additional narrow-range species. The only localities represented in the molecular study were Entumeni and Ngome (considered to contain a separate species, C. pulcherrimus sp. nov.). The highly fragmented forests of north-central Kwazulu-Natal contain many examples of species, in unrelated taxa, with extremely narrow distributions (e.g., Huber 2003; Herbert & Kilburn 2004; Tilbury & Tolley 2009) suggesting that the observed morphological differences between populations may indicate undescribed species.

Figures

Fig. 15. Chondrocyclus trifimbriatus Connolly, 1929. A. Holotype (NHMUK 1928.3.16.5). B. Dorsal view (ELM W3661). C. Ventral view (ELM W3661). D, F. Operculum (NMSA A8000). E. Portion of radula (ELM W3661). G. Penis, dorsal view (NMSA W1115). Scale bars: A = 3 mm; B–C = 2 mm; D, F–G = 500 µm; E = 20 µm.

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.