Caecum intortum, Vannozzi & Pizzini & Raines, 2015

Vannozzi, Angelo, Pizzini, Mauro & Raines, Bret, 2015, Revision of South African Caecidae (Mollusca: Gastropoda), African Invertebrates 56 (1), pp. 99-99 : 108-109

Caecum intortum sp. n.

Figs 6A–F , 7 , 22J , 23J , 24C, D , 25Q

Etymology: From the Latin adjective intortus (= twisted) due to the twisted shape of the tube.

Description: Tube cylindrical, only slightly arched. The tube shows a clear dextral torsion. Tube smooth without sculpture, colourless, dull. Aperture preceded by a slight swelling. The aperture is oblique in both ventral and lateral direction, being contracted on the left side. Surface with only oblique, fine growth lines. Septum dome­shaped, granulated, with a broad nail-like mucro directed toward the right side. Macula large, ill­defined, expanded, with a frosted appearance, clearly displaced to the left side. Juveniles rather different from adults, more conical and showing a clear dextral torsion. Larval stage not determined with certainty, probably with a multispiral protoconch. Periostracum light brown. Operculum, corneous, circular, multispiral, composed of a small central nucleus surrounded by an open spiral of 6­7 whorls. External side flat, internal side with a concave nucleus.

Length: 1.9–2.6 mm.

Type locality: SOUTH AFRICA: Western Cape: Walker’s Point, west of Knysna.

Holotype ( Figs 6A–C , 22J , 23J ): SOUTH AFRICA: Western Cape: sh, Walker’s Point, W of Knysna , leg. J.P. Marais iii.1991, ( NMSA W9668 / T3358 ), length 2.12 mm, min. diam. (posterior end) 0.38 mm, diam. in the middle of the tube 0.45 mm, max. diam. (apertural end) 0.49 mm.

Paratypes: SOUTH AFRICA: Western Cape: 2 sh, Hermanus (between False Bay and Cape Agulhas), v.1990 ( JPM) ; 1 lv, Walker’s Bay , W of Knysna, iii.1991 ( JPM) ; 4 sh, Knysna, Gericke Point , Sedgefield ( NMSA W9670 / T3361 ) ; 2 lv and 8 sh, same data as holotype ( NMSA W9669 / T3360 ) ; Eastern Cape: 1 sh, Algoa Bay , vi.1976 ( JPM) ; 1 sh, Algoa Bay, Humewood sand, don. F. Graeve v.1977 ( NMSA W9667 / T3359 ) .

Additional material examined: SOUTH AFRICA: Eastern Cape: 1 sh (juv), Port Alfred , (J. Hutt colln, ex Albany Museum, 1980) ( NMSA W9666 ) .

Comparative material examined: C. crassum de Folin, 1870 , lectotype (MNHN-IM-2000-27586) selected by Linden & Moolenbeek (2000: 82, fig. 3); SENEGAL: 8 sh, Gambia, ­ 7 m (F. Swinnen colln, Lommel, Belgium) ; MAURITANIA: 1 lv + 34 sh, Banc d’Arguin , intertidal, leg. E. Rolán ( MP) ; GABON: 2 sh (1 juv) ( MP) .

Distribution: Southern coast of South Africa from Hermanus to Algoa Bay ( Fig. 7 ).

Remarks: The species most similar to Caecum intortum is C. crassum de Folin, 1870 ( Fig. 25S,T ), an endemic species of western African coasts (from West Sahara to Ghana), having in common the general shape of the tube and the typology of the septum, but differing in the smaller dimensions and in the exasperate torsion of the tube not observed in C. crassum . Additionally, C. intortum shows a different shape of the macula, which is also clearly displaced toward the left, and lacks the longitudinal microsculpture that is observed in C. crassum ( van der Linden & Moolenbeek 2000) . Caecum intortum resembles both C. austrafricanum sp. n. and C. knysnaense sp. n., from which it can be separated by a wider tube, a more cylindrical shape, a clearly twisted tube and the position of the mucro, lateral rather than dorsal.

Figures

Fig.6.Caecum intortum sp.n., SouthAfrica,Walker’s Point,W of Knysna:(A–C) holotype (NMSAW9668/ T3358) — (A) right side, (B) ventral side, (C) microsculpture; (D–F) paratype (NMSA W9669/ T3360) — (D) right side, (E) ventral side, (F) operculum (inner side). Scale bar = 1 mm (A, B, D, E); 250 µm (C); 200 µm (F).

Fig. 7. Distribution map of Caecum knysnaense sp. n. („), C. austrafricanum sp. n. (S) and C. intortum sp. n. (T). White symbol indicates the type locality.

Fig. 22. Detail of the septum of South and western African Caecum species (right side): (A–C) C. subquadratum Carpenter, 1859 — (A) Walker’s Point, W of Knysna (NMSA S3729), (B) Walker’s Point, W of Knysna (JPM), (C) juv, Langebaan Lagoon, Saldanha Bay (JPM); (D, E) C. morgan sp. n., Cape Morgan Lighthouse — (D) holotype (NMSA B7132/T3377), (E) paratype (NMSA W9676/ T3378); (F–H) C. austrafricanum sp. n., Algoa Bay — (F) holotype (NMSA W9655/T3349), (G) paratype (JPM),(H) paratype (juv) (JPM); (I) C. knysnaense sp.n., holotype, Knysna, Gericke Point, Sedgefield (NMSA S7625/T3362); (J) C. intortum sp. n., holotype, Walker’s Point, W of Knysna (NMSA W9668/T3358); (K) C. inhacaense Albano & Pizzini, 2011, Aliwal Shoal, off Umkomaas area (JPM); (L, M) C. incisum sp. n. — (L) holotype, Walker’s Point, W of Knysna (NMSA S3728/ T3355), (M) paratype, Knysna,Gericke Point, Sedgefield (NMSA W9661/T3357);(N, O) C.maraisi sp.n.—(N) holotype, Knysna, GerickePoint,Sedgefield (NMSA W9765/T3376),(O) paratype (juv), Fish R. mouth (between Port Alfred and East London) (JPM 2117); (P, Q) C. leilae sp. n. — (P) holotype, Mzamba (NMSA D3032/T3374), (Q) paratype, Umtamvuna R. mouth (NMSA V3999/ T3884); (R) C. cf. glabrum (Montagu, 1803), Knysna, Gericke Point, Sedgefield (NMSA W9658); (S, T) C. glabrum (Montagu, 1803) — (S) Porto Mindelo, Ilha de São Vicente, Cape Verde (MP), (T) St. Malo, France (MP). Scale bar = 100 µm.

Fig. 23. Detail of the septum of South and western African Caecum species (ventral side): (A–C) C. subquadratum Carpenter, 1859 — (A) Walker’s Point, W of Knysna (NMSA S3729), (B) Walker’s Point, W of Knysna (JPM), (C) juv, Langebaan Lagoon, Saldanha Bay (JPM); (D, E) C. morgan sp. n., Cape Morgan Lighthouse — (D) holotype (NMSA B7132/T3377), (E) paratype (NMSA W9676/ T3378); (F–H) C. austrafricanum sp. n., Algoa Bay — (F) holotype (NMSA W9655/T3349), (G) paratype (JPM); (H)paratype (juv) (JPM); (I) C. knysnaense sp.n., holotype, Knysna, Gericke Point, Sedgefield (NMSA S7625/T3362); (J) C. intortum sp. n., holotype, Walker’s Point, W of Knysna (NMSA W9668/T3358); (K) C. inhacaense Albano & Pizzini, 2011, Aliwal Shoal, off Umkomaas area (JPM); (L, M) C. incisum sp. n. — (L) holotype, Walker’s Point, W of Knysna (NMSA S3728/ T3355), (M) paratype, Knysna, Gericke Point, Sedgefield (NMSA W9661/T3357);(N, O) C. maraisi sp.n.— (N) holotype, Knysna, Gericke Point,Sedgefield (NMSA W9765/T3376), (O) paratype (juv), Fish R. mouth (between Port Alfred and East London) (JPM 2117); (P, Q) C. leilae sp. n. — (P) holotype, Mzamba (NMSA D3032/T3374), (Q) paratype, Umtamvuna R. mouth (NMSA V3999/ T3884); (R) C. cf. glabrum (Montagu, 1803), Knysna, Gericke Point, Sedgefield (NMSA W9658); (S, T) C. glabrum (Montagu, 1803) — (S) Porto Mindelo, Ilha de São Vicente, Cape Verde (MP), (T) St. Malo, France (MP). Scale bar = 100 µm.

Fig. 24. Ventral side of South and western African Caecum species: (A) C. austrafricanum sp. n., paratype, Walker’s Point, W of Knysna (NMSA W9656/T3351); (B) C. knysnaense sp. n., paratype, Knysna, Gericke Point,Sedgefield (NMSA W9673/T3364);(C, D) C. intortum sp.n.— (C)paratype,Walker’s Point, W of Knysna (NMSA W9669/T3360), (D) the same specimen slightly rotated, detail of the macula; (E, F) C. leilae sp. n. — (E) paratype, Mzamba, near Natal border (JPM 2119), (F) the same specimen, detail of the macula; (G) C. inhacaense Albano & Pizzini, 2011, Mzamba, near Natal border (JPM 2119); (H) C. macrum van der Linden & Moolenbeek, 2000, Charbonnier, Senegal (MP); (I) C. crassum de Folin, 1870, Banc d’Arguin, Mauritania (MP). Scale bar = 1 mm (A–C, E, G–I); 300 µm (D, F).

Fig. 25. South and western African Caecum and Parastrophia species: (A) P. avaricosa sp. n., holotype, Mzamba (NMSA E1665/T3354); (B, C) P.ornata sp. n., Mzamba,near Natal border — (B) holotype (NMSA W9677/T3379), (C) paratype (JPM 2119); (D) C. sepimentum de Folin, 1868, Kosi Bay (NMSA S2010); (E) C. cf. oahuense Pilsbry, 1921, Aliwal Shoal, off Umkomaas area (JPM); (F) Caecum cf. gulosum Hedley, 1899, Kosi Bay (NMSA S2869); (G, H) C. succineum de Folin, 1880 — (G) between Bhanga Nek andKosi Bay (NMSAS1586), (H)Aliwal Shoal, off Scottburgh (NMSA W9684); (I) C. cf. glabrum (Montagu, 1803), Knysna, Gericke Point, Sedgefield (NMSA W9658); (J) C. glabrum (Montagu, 1803), Rabat, Morocco (MP); (K) C.lindae sp. n., holotype, Cape Morgan Lighthouse (NMSA W9682/T3924); (L, M) C. cf. musorstomi Pizzini, Raines & Vannozzi, 2013, Landers reef (JPM); (N, O) C.austrafricanum sp.n., paratypes,Walker’s Point,W of Knysna (NMSA W9656/T3351);(P) C.knysnaense sp.n., paratype,Knysna,Gericke Point,Sedgefield (NMSAW9673/ T3364); (Q) C. intortum sp. n., paratype, Walker’s Point, W of Knysna (NMSA W9669/T3360); (R) C. macrum van der Linden & Moolenbeek, 2000, Charbonnier, Senegal (MP); (S, T) C. crassum de Folin, 1870, Gabon (MP): (S) adult; (T) juvenile. Scale bar = 1 mm.