Sudanonautes granulatus ( Balss, 1929 )

Cumberlidge, Neil, Mvogo Ndongo, Pierre A. & Clark, Paul F., 2021, Disentangling the Sudanonautes granulatus (Balss, 1929) species complex (Potamoidea: Potamonautidae), with the description of two new freshwater crabs from Nigeria and Côte d’Ivoire, West Africa, Zootaxa 4948 (2), pp. 201-220 : 203-205

Sudanonautes granulatus ( Balss, 1929) sensu stricto

(Figs. lA, B, 4A, 5A, B, G, 6A–C, 7D, E, 8)

Potamonautes decazei granulata Balss, 1929: 119–120 .

Potamon granulatus, Chace, 1942: 211 .

Sudanonautes (Sudanonautes) decazei decazei, Bott, 1955: 300–301 (in part).

Sudanonautes granulatus, Ng et al. 2008: 172 (in part); Cumberlidge 1998: 207 (in part).

Not Sudanonautes orthostylis, Cumberlidge, 1989: 231–237 (in part), figs. 1 a–g, 2a–c; tabs. 1, 2 = S. tiko .

Not Sudanonautes granulatus, Cumberlidge, 1993a: 806–807 , 812 (in part), figs. 1a, b, 2a–d, 3a–c, 4a, b = S. tiko .

Not Sudanonautes granulatus, Cumberlidge, 1993a: 806 , 810 (in part), figs. 3 h–j, 4e, f = S. umaji n. sp.

Not Sudanonautes orthostylis, Cumberlidge, 1993b: 520–521 (in part), tab. 2 = S.tiko .

Not Sudanonautes granulatus, Cumberlidge, 1997: 576 , = S. umaji n. sp.

Not Sudanonautes granulatus, Cumberlidge, 1999 : 174,175, 198–201 (in part), figs. 31B, 32G, 33G, 34G, 35G, 36J, 37G, 39B, 53W, 54–57, 60G, 67H, tab. IX = S. tiko .

Lectotype. MNB Crust.11257 ( CW 26 , CL 18, CH 11, FW 8 mm), Missahoe , Klouto District (6.933081°N, 0.572483°E), 740 m asl, coll. G. Smend, selected from the syntype series by Bott (1955).

Paralectotypes. MNB Crust. 8980, 3 adult females (CWs 31.0 ovigerous, 30.5, 23.1 mm), 2 subadult females, (CWs 19.5, 18.8 mm), Missahoe, Klouto District (6.933081°N, 0.572483°E), 740 m asl, 30 Mar. 1893, coll. E. Baumann. ZSM 1214 /8, 5 adult males ( CW 25.0, CL 18.0, CH 9.5, FW 7.8 mm, CW 25.5, CL 18.2, CH 8.93, FW 7.6 mm, CW 23.6, CL 16.9, CH 8.9, FW 6.9 mm, CW 22.0, CL 15.7, CH 8.2, FW 6.5 mm, CW 23.3, CL 15.9, CH 7.5, FW 6.7 mm, subadult male, CW 16.1, CL 11.6, CH 5.6, FW 5.3 mm), Missahoe , Klouto District (6.933081°N, 0.572483°E), 740 m asl, coll. E. Baumann. MNB Crust. 8977, adult male ( CW 23.0 mm), Bismarckburg (8.178194°N, 0.686241°E), 590 m asl, coll . R. Büttner . MNB Crust. 8978, subadult male ( CW 18.8 , CL 13.6, CH 6.4, FW 6.1 mm) plus several other specimens, Bismarckburg (8.178194°N, 0.686241°E), 590 m asl, 20 Jul. to 20 Sep. 1890, coll . R. Büttner . MNB Crust. 20170, female, 2 Jan. 1893 . MNB Crust. 20171, 2 males, 2 females, coll. S. Conradt. MNB Crust. 20173, Bismarckburg (8.178194°N, 0.686241°E), 590 m asl, coll . R. Büttner . MNB Crust. 20194, adult female ( CW 22.2 , CL 16.1, CH 8.0, FW 7.6 mm), Bismarckburg (8.178194°N, 0.686241°E), 590 m asl, 15 May 1893, coll. S. Conradt. MNB Crust. 20244, 4 females, Bismarckburg (8.178194°N, 0.686241°E), 590 m asl, 24 Feb. 1904, coll. C.W.M. Schr ̂der. MNB Crust. 21312, 3 adult females (largest CW 27 mm), Bismarckburg (8.178194°N, 0.686241°E), 590 m asl . MNB Crust. 21313, male, Bismarckburg (8.178194°N, 0.686241°E), 590 m asl, coll . R. Büttner . ZSM 1214 /1, adult male ( CW 25.0, CL 17.2, CH 9.0, FW 7.8 mm), adult female ovigerous ( CW 23.1 , CL 16.2, CH 7.8, FW 6.7 mm), subadult male ( CW 18.1 , CL 13.5, CH 6.7, FW 5.6 mm), Bismarckburg (8.178194°N, 0.686241°E), 590 m asl .

Rediagnosis. Carapace surface smooth with no deep grooves, granules, or carinae. Exorbital tooth large, intermediate tooth (between exorbital, epibranchial teeth) small, distinct, pointed, epibranchial tooth reduced to granule ( Fig. 1A ). Anterolateral margin lined by row of small granules; vertical sulcus on branchiostegite granulated, in line with intermediate tooth, dorsal part curving posteriorly just before meeting anterolateral margin at epibranchial tooth, dividing suborbital from subhepatic region ( Figs. 1B , 4A ). Thoracic sternal suture S3/4 reduced to 2 small notches at sides of sternum; outer margins of S3, S4 thickened, raised ( Fig. 1B ). Third maxilliped exopod with long flagellum, ischium with faint vertical sulcus ( Fig. 7D ). Cheliped carpus inner margin distal tooth large spine, proximal tooth small ( Fig. 5G ). G1 TA elongated (TA/SS 0.75), basal half angled slightly outward at 13° to G1 SS longitudinal axis, midpoint curved sharply outward at 72° to G1 SS longitudinal axis, distal third tapering to pointed tip; TA midsection slightly widened, dorsal fold slightly higher than ventral fold ( Fig. 6A, B ); longitudinal sulcus of TA visible on ventral side for proximal two-thirds of TA ( Fig. 6A, B ). G2 ( Fig. 6C ) much shorter than G1 (G2 TA extremely short (G2 TA/SS 0.14), tip only reaching G1 TA-SS junction). Small species, adult size range 21–32 mm.

Redescription. Male paralectotype (MNB Crust.8977). Carapace. Cephalothorax ovoid, carapace 3.5 × as wide as FW (CW/FW 3.5), medium length (CL/FW 2.5), medium height ( CH /FW 1.2) ( Fig. 1A ). Anterior margin of front straight, curving down; posterior margin about two-thirds as wide as CW ( Fig. 1A ). Carapace surface smooth with no deep grooves, granules, or carinae. Anterolateral margin lined by row of small granules. Postfrontal crest smooth, distinct, complete, meeting anterolateral margins; mid-groove broad, shallow. Exorbital tooth large, intermediate tooth between exorbital, epibranchial teeth small, distinct, pointed, epibranchial tooth reduced to granule ( Figs. 1B , 4A ). Longitudinal sulcus on branchiostegite beginning at respiratory opening, curving backwards, dividing suborbital, subhepatic regions from pterygostomial region; vertical sulcus on branchiostegite granulated, in line with intermediate tooth, dorsal part curving posteriorly just before meeting anterolateral margin at epibranchial tooth, dividing suborbital from subhepatic region ( Fig. 1B ).

Thoracic sternum. Sternal suture S1/2 short, complete; S2/3 deep completely traversing sternum; S3/4 reduced to 2 small notches at sides of sternum; outer margins of S3, S4 thickened, raised ( Fig. 1B ). Third maxillipeds filling entire oral field, except for transversely oval efferent respiratory openings; exopod with long flagellum, ischium with faint vertical sulcus ( Fig. 7D ). Mandibular palp with 2 articles, terminal article simple, article junction with fringe of long setae, but lacking either anterior lobe or ledge ( Fig. 7E ). First 5 pleomeres of male pleon (A1–5) broad, short, tapering inward; A6, long, narrow, telson triangular, distal tip rounded ( Fig. 1B ).

Pereiopods. Chelae unequal, left longer than right ( Fig. 5A, B ). Dactylus of left (major) chela broadened, slightly arched, enclosing long narrow interspace when closed, palm swollen ( Figs. 1A , 5A ). Movable finger (dactylus), fixed finger (propodus) of left chela each lined by pointed teeth, medium size proximally, small size distally. Cheliped merus lower margins both lined by small teeth, distal meral tooth larger, pointed ( Fig. 1B ). Cheliped carpus inner margin distal tooth large spine, proximal tooth small, 1/3 rd size of distal tooth (Figs. lA, 5G). P2–5 ( Fig. 1A ) not elongated, P5 shortest leg; dactyli P2–5 tapering to point, each bearing rows of downward-pointing sharp corneous spines.

Gonopods. G1 TA elongated (TA/SS 0.75), basal half angled slightly outward at 13° to G1 SS longitudinal axis, midpoint turned sharply outward at 72° to G1 SS longitudinal axis, distal third tapering to pointed tip; TA midsection slightly widened, dorsal fold slightly higher than ventral fold ( Fig. 6A, B ); longitudinal sulcus of TA visible on ventral side for proximal two-thirds of TA ( Fig. 6A, B ) sulcus continuing to tip but visible only if gonopod turned to superior view. G1 SS widest at base, narrowest distally, slim, tapering evenly to TA-SS junction (ratio of width of basal margin / distal margin = 2.5); mesial, lateral margins of G1 SS completely smooth; G1 SS distal margin straight ventrally, with U-shaped indentation dorsally; G1 SS ventral side with slim flap folded inward, distally almost meeting outer margin, angled diagonally downwards, leaving heavily setose ventral side of G1 SS exposed ( Fig. 6A ). G2 ( Fig. 6C ) much shorter than G1, only reaching G1 TA-SS junction; G2 TA extremely short (G2 TA/SS 0.14), tip rounded; G2 SS widest at base, tapering sharply inward about one-third along length, with last two-thirds forming long, thin, tapering, upright process that supports short G2 TA ( Fig. 6C ).

Size. Small species, adult size range between CWs 21–32 mm.

Type locality. Togo, Missahoe, near Kpalimé, north of Klouto [= Kloto].

Habitat. Savanna vegetation predominates in most of Togo, except for the southwestern highland region between 600 and 986 m asl where S. granulatus s.s. was collected, where there are tropical semi-deciduous moist forests that receive an annual rainfall between 1,300 and 1,600 mm. This area is part of the southeastern corner of the Volta Freshwater Ecoregion 507 ( Thieme et al. 2005; Abell et al. 2008). The forested highland region where this species occurs is an eastern outlier of the biodiversity-rich Upper Guinea forest of West Africa which extends east from Guinea, Sierra Leone, Liberia, and Côte d’Ivoire, as far east as Ghana and western Togo.

Distribution. Sudanonautes granulatus s.s. is restricted to the highlands of western Togo near the eastern border of Ghana between Missahoe (6.933081°N, 0.572483°E, 740 m asl) and Bismarckburg (8.178194°N, 0.686241°E, 590 m asl.) These two localities are 140 km apart ( Fig. 8 ). It should be noted that the Bismarckburg, Togo locality for S. granulatus s.s. was incorrectly recorded by Cumberlidge (1993a) as “Bismarcksburg (= Aného, 40 km east of Lomé)” when in fact Bismarckburg (the correct spelling) for this German colonial station is in the highlands of western Togo ( Krell 1994).

Remarks. Balss (1929) distinguished P. d. granulata from Togo by its strongly granulated anterolateral carapace margins and small adult body size range between CWs 21–32 mm, confirmed by the size of 3 ovigerous females (CWs 24, 31, and 32 mm) among this material. Balss (1929) contrasted these specimens with the type of Thelphusa decazei A. Milne-Edwards, 1886 , from the Alima River in the République du Congo, which has a larger adult body size (CW 40.4 mm) and smooth anterolateral carapace margins ( Capart 1954: figs. 12, 15). Balss (1929) treated the specimens from Togo as a subspecies of T. decazei because he attributed differences in carapace margin granulation and adult size range between the specimens from Togo and others from Cameroon (that he identified as Potamonautes decazei ) as geographic variation within the same species. Balss (1929) expanded the range of Potamonautes decazei accordingly, and listed the distribution of this species as ‘ Togo, Cameroon, Gabon (Franceville)’. It is likely that the listing from Gabon was an error arising out of the ambiguity of the recording of the type locality of T. decazei as ‘the Alima River, Franceville’ because the Alima River is in the République du Congo, while Franceville is in Gabon.

Bott (1955: 300–301), like Balss (1929) also noted differences in carapace margin granulation and adult size range between the samples of P. d. granulata from Togo and P. decazei Cameroon but treated P. d. granulata as a junior synonym of S. (S.) d. decazei (A. Milne-Edwards, 1886) rather than a subspecies. Later, Bott (1964) judged S. (S.) d. decazei from Central Africa to be a junior synonym of S. (S.) p. pelii ( Herklots, 1861) from Ghana. Subsequently Cumberlidge (1994, 1999) considered S. (S.) p. pelii to be a junior synonym of S. aubryi (H. Milne Edwards, 1853) . These differing opinions regarding the taxonomic status of S. granulatus s.l., are addressed here.

This study is based on a detailed description of the male paralectotype of P. d. granulata from Bismarckburg, Togo ( Fig. 8 ). The carapace, cheliped, sternal, and gonopod characters of this specimen, as well as the adult body size range of the samples, are all similar to those of other adult males in the samples examined by Balss (1929) from Togo, and are all judged to be conspecific. The male paralectotype of S. granulatus s.s. was also compared with other specimens from Côte d’Ivoire, Nigeria, Cameroon, and Bioko identified by Cumberlidge (1993a) as S. granulatus s.l. These specimens were found to be significantly different from each other and from S. granulatus s.s. and are assigned in this work to either a new species, or a revised species. Comparisons of the paralectotype of S. granulatus s.s. with other specimens from Nigeria, Cameroon, Ghana, and the Central African Republic identified by Cumberlidge (1993a) as S. granulatus s.l. indicated that they should be excluded from S. granulatus s.s. on morphological grounds (see below).

All of the specimens attributed by Cumberlidge (1993a) to S. granulatus s.l. examined in the present study belong to Sudanonautes because they share the following combination of characters ( Bott 1955; Cumberlidge 1999; Cumberlidge & Boyko 2001): a distinct intermediate tooth (between the exorbital and epibranchial teeth) on the anterolateral margin, a prominent horizontal postfrontal crest that is complete and meets both anterolateral margins; a thoracic sternal suture S3/4 that is absent except for two short notches on the margins; an elongated G1 TA (TA/SS 0.70–0.85); an extremely short G2 TA (G2 TA/SS 0.14); and a third maxilliped exopod with a long flagellum.

Specimens included by Cumberlidge (1993a) in S. granulatus s.l. are reassigned in the present work to the following taxa. Those from Missahoe, Togo (MNB Crust.8980, MNB Crust.11257, ZSM 1214/8) and Bismarckburg, Togo (MNB Crust.8977, MNB Crust.8978, MNB Crust.20170, MNB Crust.20171, MNB Crust.20173, MNB Crust.20194, MNB Crust.21312, MNB Crust.21313, MNB Crust.20244) are assigned to S. granulatus s.s. The specimen from Koudougou, Côte d’Ivoire (NBL CRUS.D.35246) is described here as S. koudougou n. sp. ( Figs. 3A–D , 5E, F, I , 7 A–C , 8 ). Specimens from Umaji, Nigeria (NMU 9.IV.1983), from the Oban Hills, Nigeria (NMU 5.VI.1979, NMU 29.VI.1979, NMU 3.VIII.1980, NMU 20.X.1980) are all included in S. umaji n. sp. ( Figs. 2A, B , 4B , 5C, D, H , 6D, F , 7 , 8 ). Other specimens from Nigeria (NMU 28.IV.1979), Cameroon (ZIM K27877 ), and Bioko Island (ZIM K5362) are assigned here to S. tiko . A female from Bipindi, Cameroon (MNB Crust.15182) erroneously listed by Cumberlidge (1993a) as S. granulatus s.l. is re-identified here as S. aubryi . Finally, the taxonomic status of several other specimens listed by Cumberlidge (1993a) as S. granulatus s.l. from Nigeria (NHM 1938.7.1.24–25), Cameroon (ZIM K3492, ZIM K30393 , ZIM K30394 , MNB Crust.10194, MNB Crust.20158, MNB Crust.20168, MNB Crust.21304, MNB Crust.21305), Ghana (NHM 1902.8.17.1), and the Central African Republic (ZIM K5357) is now ambiguous and they should be regarded as incertae sedis. It is likely that all of these should be removed from S. granulatus s.l., however, their true identities cannot be established until further studies have been undertaken.

Figures

FIGURE 1. Sudanonautes granulatus (Balss, 1929) s.s. paralectotype from Bismarckburg, Togo (MNB Crust.8977). Whole animal, A. dorsal view; B. ventral view. Scale bars: A = 9.2 mm, B = 7 mm.

FIGURE 2. Sudanonautes umaji n. sp. holotype from Umaji, Nigeria (NMU 9.IV.1983). Whole animal, A. dorsal view; B. ventral view. Scale bars: A = 8 mm, B = 4.1 mm.

FIGURE 3. Sudanonautes koudougou n. sp. holotype from Koudougou, Côte d’Ivoire (NBL CRUS.D.35256). A. whole animal, dorsal view; B. left third maxilliped, frontal view; C. left mandible, external view; D. pleon, ventral view. Scale bars: A = 23.2 mm, B, C= 4 mm, D = 7 mm. Figures A–D are based on those originally published in Cumberlidge (1993a) and are reproduced here with the permission of Oxford University Press, the copyright owner of the Journal of Crustacean Biology.

FIGURE 4. Carapace frontal view. A. Sudanonautes granulatus (Balss, 1929) s.s. paralectotype from Bismarckburg, Togo (MNB Crust.8977); B. S. umaji n. sp. holotype from Umaji, Nigeria (NMU 9.IV.1983); C. S. koudougou n. sp. holotype from Koudougou, Côte d’Ivoire (NBL CRUS.D.35256). Scale bars: A = 3.7 mm, B = 4.5 mm, C = 9.1 mm. Figure C was originally published in Cumberlidge (1993a) and is reproduced here with the permission of Oxford University Press, the copyright owner of the Journal of Crustacean Biology.

FIGURE 5. Sudanonautes granulatus (Balss, 1929) s.s. paralectotype from Bismarckburg, Togo (MNB Crust.8977). A. right chela, external view; B. left chela, external view. Sudanonautes umaji n. sp. holotype from Umaji, Nigeria (NMU 9.IV.1983). C. right chela, external view; D. left chela, external view. Sudanonautes koudougou n. sp. holotype from Koudougou, Côte d’Ivoire (NBL CRUS.D.35256). E. right chela, external view; F. left chela, external view. Right cheliped carpus and merus superior view of G. S. granulatus (Balss, 1929) s.s. (MNB Crust.8977); H. S. umaji n. sp. (NMU 9.IV.1983); I. S. koudougou n. sp. (NBL CRUS.D.35256). Scale bars: A, B = 6.2 mm, C, D = 8 mm, E, F= 3 mm, G–I = 4.9 mm. Figures E, F, and I are based on those originally published in Cumberlidge (1993a) and are reproduced here with the permission of Oxford University Press, the copyright owner of the Journal of Crustacean Biology.

FIGURE 6. Sudanonautes granulatus s.s. (Balss, 1929) paralectotype from Bismarckburg, Togo (MNB Crust.8977). A. right G1 ventral view; B. right G1 dorsal view; C. right G2 ventral view. Sudanonautes umaji n. sp. holotype from Umaji, Nigeria (NMU 9.IV.1983). D. right G1 ventral view; E. right G1 dorsal view; F. right G2 ventral view. Scale bars: A–C = 2.5 mm, D, F = 2 mm.

FIGURE 7. Sudanonautes koudougou n. sp. holotype from Koudougou, Côte d’Ivoire (NBL CRUS.D.35256). A. right G1 ventral view; B. right G1 dorsal view; C. right G2 ventral view. Sudanonautes granulatus s.s. (Balss, 1929) (MNB Crust.8977). D. left mandible, external view; E. left third maxilliped, external view. Sudanonautes umaji n. sp. holotype from Umaji, Nigeria (NMU 9.IV.1983). F. left mandible, external view. Scale bars: A, B, 2.9 mm, C = 2.5 mm, D, F = 5 mm. Figures A–C are based on those originally published in Cumberlidge (1993a) and are reproduced here with the permission of Oxford University Press, the copyright owner of the Journal of Crustacean Biology.

FIGURE 8. Map showing the geographic distribution of Sudanonautes koudougou n. sp. (yellow square), S. granulatus s.s. (Balss, 1929) (red circles), S. umaji n. sp. (blue circles), and S. tiko (black pentagons). Scale bar = 500 km. See text for exact localities.