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Article

Four New Sudanonautes Species of Freshwater Crabs (Crustacea: Decapoda: Potamonautidae) from Cameroon, Central Africa †

by
Pierre A. Mvogo Ndongo
1,2,3,*,
Paul F. Clark
4,
Thomas von Rintelen
2 and
Neil Cumberlidge
5
1
Département de Gestion des Écosystèmes Aquatiques, Institut des Sciences Halieutiques, Université de Douala à Yabassi, Douala-Bassa P.O. Box 7236, Cameroon
2
Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstrasse 43, 10115 Berlin, Germany
3
Unit of Biodiversity Discovery and Conservation, Cameroon Association for Research on Crustaceans and Others Aquatic Resources, Obala P.O. Box 43, Cameroon
4
Department of Life Sciences, The Natural History Museum, London SW7 5BD, UK
5
Department of Biology, Northern Michigan University, Marquette, MI 49855-5376, USA
*
Author to whom correspondence should be addressed.
†
lsid:zoobank.org:pub:163E4D9E-A14C-4971-A9C5-4B31D2D38D8D.
Diversity 2024, 16(6), 345; https://doi.org/10.3390/d16060345
Submission received: 17 May 2024 / Revised: 3 June 2024 / Accepted: 5 June 2024 / Published: 14 June 2024
(This article belongs to the Special Issue Taxonomy, Systematics, Evolution and Biogeography of Freshwater Decapod Crustaceans)
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Abstract

:
Four new species of freshwater crab are described from material collected in northern and southwestern Cameroon and assigned to Sudanonautes Bott, 1955. Sudanonautes cameroonensis sp. n., S. eyimba sp. n., S. ngaoundere sp. n. and S. nkam sp. n., are distinguished by characters of the carapace, thoracic sternum, chelipeds, mandibles, adult male gonopods, and in addition by genetic analyses using the mitochondrial CO1 and 16S rRNA genes. Diagnoses, illustrations, and a phylogenetic tree based on mtDNA sequences are provided, as well as a discussion of the threats and conservation of all species.

1. Introduction

Sudanonautes Bott, 1955 is a Central and West Africa freshwater crab genus whose species are found in rivers, streams, and wetlands in rainforest, Guinea or woodland savanna, Sudan savanna, and forested mountains [1]. This genus comprises 14 species: S. africanus (A. Milne-Edwards, 1869), S. aubryi (H. Milne Edwards, 1853), S. floweri (De Man, 1901), S. chavanesii (A. Milne-Edwards, 1886), S. faradjensis (Rathbun, 1921), S. granulatus (Balss, 1929), S. kagoroensis Cumberlidge, 1991, S. koudougou Cumberlidge, Mvogo Ndongo & Clark, 2021, S. monodi (Balss, 1929), S. nigeria Cumberlidge, 1999, S. orthostylis Bott, 1955, S. sangha Cumberlidge & Boyko, 2001, S. tiko Mvogo Ndongo, Schubart & Cumberlidge, 2017, and S. umaji Cumberlidge, Mvogo Ndongo & Clark, 2021 [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. These species share the following characters: the postfrontal crest is distinct and almost horizontal, and its ends reach the carapace margins; the third maxilliped has an exopod with a long setose flagellum; the thoracic sternal sulcus S3/4 is obscure except for two short notches at the sides of the sternum; the terminal article of gonopod 1 is long, at least two-thirds as long as the subterminal article; and gonopod 2 has an extremely short terminal article, only one-fifteenth the length of the subterminal article [1,15,16].
The present study describes four new Sudanonautes species collected from rainforest habitats in Yabassi near the Eboforest and from Mt. Nlonako Wildlife Reserve that are both located in a key biodiversity hotspot in southwestern Cameroon. Eboforest is the type locality of the threatened freshwater crab Louisea yabassi Mvogo Ndongo, von Rintelen & Cumberlidge, 2019 (Cumberlidge 1999; Mvogo Ndongo et al. 2019), while Mt. Nlonako Wildlife Reserve is the type locality of two threatened freshwater crabs, Buea nlonako Mvogo Ndongo, von Rintelen & Cumberlidge 2020 and L. nkongsamba Mvogo Ndongo, von Rintelen & Cumberlidge, 2019 [17,18]. The four new species are recognized because each exhibits a unique combination of characters of the carapace, thoracic sternum, chelipeds, mandibles, and male first gonopods. In addition, the fourth species was collected further north in Cameroon near Ngaoundéré in the Guinea savanna zone of that country. The new species are also distinguished as distinct lineages from other Cameroonian Sudanonautes species based on DNA sequence differences in mitochondrial genes CO1 and 16S rRNA. Notes on the ecology of the four new species are discussed.

2. Material and Methods

2.1. Sampling

The Sudanonautes specimens reported here were collected during field surveys of the rivers, streams, wetlands, and nearby land in the humid lowland and mountain rainforests of southwestern Cameroon from 2013 to 2023 using fishing nets and dip nets. Specimens were collected from Yabassi in Eboforest and Mt. Nlonako Wildlife Reserve, both in the Littoral Region of southwestern Cameroon. In addition, the fourth species was collected further north in Cameroon near Ngaoundéré in the Guinea savanna zone of that country. All specimens were identified using an established key [1]. A few specimens were preserved in ethanol for further detailed morphological and molecular analyses.

2.2. Morphological Analyses

All measurements (in mm) were taken with digital callipers. Contemporary terminology [1], and classification [16] is followed. Characters of the gonopods, carapace, thoracic sternum, chelipeds, third maxillipeds, and mandibles were examined in detail, and photographs were taken using a Leica microscope (model Z16A POA), and LAS V4 and Helicon Focus 6.7.1 software. Post processing of the images was undertaken using Adobe Photoshop CC5. The holotype and paratype specimens of the new Sudanonautes species are deposited in the Museum für Naturkunde, Berlin, Germany (ZMB) and in the zoological collection of the Cameroon Association for Research on Crustaceans and others Aquatic Resources. The following abbreviations are used: PL, pleonal article or pleomere; PL5/6, sulci between adjacent pleomeres; ASL, above sea level; CW, carapace width measured at widest point; CL, carapace length measured along medial line from anterior to posterior margin; CH, carapace height measured at maximum height of cephalothorax; DM, dorsal membrane on dorsal face of male first gonopod at junction between terminal and subterminal articles; E, episternite; FW, front width measured along anterior frontal margin between inner angles of orbits; G1, male first gonopod; G2, male second gonopod; P2–5, pereiopods 2–5 or ambulatory/walking legs 1–4; SA, subterminal article of G1 or G2; S4/E4, S5/E5, S6/E6, S7/E7 episternal sulci between adjacent thoracic sternites and episternites; S, thoracic sternite; S1/2, S2/3, S4/5, S5/6, S6/7, sternal sulci between adjacent thoracic sternites; TA, terminal article of mandibular palp, G1, or G2.

2.3. Molecular Analysis

Genomic DNA was extracted from a tissue sample of up to 25 mg cut from the pereiopod muscle of 70% ethanol-preserved specimens using the Qiagen DNeasy Blood & Tissue kit. Polymerase chain reaction (PCR) was used to amplify two mitochondrial gene fragments, a ~638 bp region of the 16S ribosomal RNA gene (16S) using primers 16L29 and 16HLeu or 16H10 [19], a ~594 bp region of the 12S ribosomal RNA gene (12S) using primers 12L4 and 12H2 ([19]), and a 648 bp fragment of the Cytochrome Oxidase subunit I gene (COI) using primers COL6a [19] and COH1b [19], COH6 [20], or CO1a [21]. PCR was performed in 25 μL volumes containing 1x Taq buffer, 1.5 mM MgCl2, 200 μM each dNTP, 1 U Taq polymerase, ca. 50–100 ng DNA and ddH2O up to volume. After an initial denaturation step of 4 min at 94 °C, cycling conditions were 35 cycles at 94 °C for 30 s, 45 °C for 60 s, and 72 °C for 90 s, with a final elongation step of 5 min at 72 °C. The same primers were used in PCR and sequencing.
PCR products were sent to Macrogen Europe for purification and cycle sequencing of both strands of each gene. The sequences obtained were proofread manually using Chromas [22] and aligned with Bioedit [22]. Results from these genes were concatenated into a single alignment that was then converted into a Nexus file with FaBox [23]. The best evolutionary model was determined with jModeltest v.2.1.7 [24] based on the Akaike information criterion [25] and resulted in the GTR + I + G (COI) and GTR + G (16S) models. These models were applied in partitioned analyses as outlined below. The phylogenetic reconstruction was conducted with Maximum Likelihood (ML) using the software RAxML [26]. Bayesian Inference (BI) was performed to infer phylogeny by using MrBayes v. 3.2.2 [27]. The MCMC was run with four independent chains for 10,000,000 generations, samplefreq = 500, and burnin = 10,001. Analyses were also conducted separately for each gene to test for topology congruence. The trees were drawn to scale, with branch lengths measured as the number of substitutions. All sequences generated for this study have been uploaded to GenBank (Table 1). This paper was registered on Zoobank, lsid:zoobank.org:pub:163E4D9E-A14C-4971-A9C5-4B31D2D38D8D.

3. Systematic Account

Infraorder Brachyura Latreille, 1802
Superfamily Potamoidea Ortmann, 1896
Family Potamonautidae Bott, 1970
Subfamily Liberonautinae Cumberlidge & Daniels, 2022
Genus Sudanonautes Bott, 1955
Sudanonautes cameroonensis sp. n.
(Figure 1A, Figure 2A, Figure 3A, Figure 4A, Figure 5A–E and Figure 6A–C)
Material examined: Cameroon.Types: Holotype, adult ♂ (CW 48.0, CL 32.9, CH 18.1, FW 14.3 mm), near Eyimba (04°53′30.7″ N, 009°59′05.1″ E, 835 m ASL), Mount Nlonako Wildlife Reserve, coll. P.A. Mvogo Ndongo, 14 March 2018 (ZMB Crust. 33351). Paratype, adult ♂ (CW 48.0, CL 33.3, CH 19.2, FW 14.3 mm), (CARC-17), same details as holotype. Non-types: 3 subadult ♂♂ (CWs 32.5, 33.0, 40.6, CLs 23.4, 23.2, 28.7, CHs 11.6, 12.5, 16.0, FWs 10.1, 10.7, 13.0 mm), subadult ♀ (CW 38.2, CL 26.6, CH 15.0, FW 10.8 mm), (CARC-18), same details as holotype; 3 subadult ♂♂ (CWs 32.6, 33.2, 33.5, CLs 24.4, 24.1, 25.0, CHs 13.3, 14.5, 14.0, FWs 10.3, 10.1, 10.8 mm), subadult ♀ (CW 36.6, CL 26.7, CH 15.2, FW 11.4 mm), (04°24′59.3″ N, 010°12′07.7″ E), Ndogbanguene Eboforest Wildlife Reserve, coll. P.A. Mvogo Ndongo, 02 December 2019 (CARC-19X); 3 subadult ♂♂ (CWs 39.7, 39.3, 39.8, CLs 27.5, 27.7, 27.9, CHs 15.2, 15.5, 15.9, FWs 11.8, 11.7, 10.7 mm), adult ♀ (CW 39.0, CL 26.7, CH 15.2, FW 11.4 mm), Nziemben (05°01′19.3″ N 009°42′11.1″ E), east of Bakossi National Park, 305 m ASL, coll. P.A. Mvogo Ndongo, 15 March 2017 (CARC-19).
Diagnosis: Medium sized species, adult size range CW 47–48 mm. Postfrontal crest distinct yellow colour, complete, lateral ends curving downwards, meeting carapace lateral margin behind epibranchial tooth (Figure 1A, Figure 2A and Figure 3A). Exorbital tooth large, triangular; intermediate tooth small, pointed; epibranchial tooth small granule (Figure 1A, Figure 2A and Figure 3A). Lateral carapace margin granulated (Figure 2A and Figure 3A). Semi-circular, urogastric, cardiac, cervical, transverse branchial carapace grooves all shallow (Figure 1A and Figure 2A). Pterygostomial region of carapace sidewall heavily granulated medially, otherwise smooth (Figure 3A). Anterior thoracic sternum S3, S4 margins thin, not raised (Figure 4A). Mandible, proximal superior margin of palp TA with small rounded accessory lobe ca. ¼ length of TA (Figure 5D). Major cheliped dactylus with no large teeth (Figure 5A). First male gonopod G1TA long (0.8–0.9 × G1SA length), margins lacking setae (Figure 6A,B).
Description: Carapace high (CH/FW 1.31, N = 14), wide (CW/FW 3.30, N = 14) (Figure 1A and Figure 2A). Carapace surface smooth, cervical, urogastric, cardiac, branchial grooves shallow (Figure 1A and Figure 2A). Exorbital tooth large, clearly distinct, intermediate tooth large and triangular, epibranchial tooth small, granulated (Figure 1A, Figure 2A and Figure 3A). Postfrontal crest distinct yellow in colour, complete, lateral ends curving downwards, meeting carapace lateral margin behind epibranchial tooth, mid-groove on postfrontal crest short, forked (Figure 1A, Figure 2A and Figure 3A). Lateral carapace margin granulated (Figure 2A and Figure 3A). Carapace branchiostegite with 2 sutures, 1 longitudinal, 1 vertical, dividing sidewall into 3 parts (Figure 3A and Figure 4A); longitudinal suture dividing suborbital, subhepatic regions from pterygostomial region, beginning at respiratory opening, curving backward across sidewall; short vertical suture dividing suborbital region from subhepatic region; vertical suture beginning at base of intermediate tooth, marked by row of granules, curving sharply down to meet longitudinal suture (Figure 3A and Figure 4A). Pterygostomial region of carapace sidewall heavily granulated medially, otherwise smooth (Figure 3A). S2/3, completely crossing sternum, but shallow; S3/4 incomplete, reduced to one small notch at each side (Figure 4A). Mandible, proximal superior margin of palp TA with small rounded accessory lobe ca. ¼ length of TA (Figure 5E). Third maxillipeds filling entire buccal cavern except for transversely oval efferent respiratory openings visible at superior lateral corners (Figure 3A, Figure 4A and Figure 5D); exopod with well-developed slender flagellum; ischium with faint vertical sulcus (Figure 3A and Figure 4A).
Cheliped carpus with 2 pointed teeth, distal tooth larger than proximal; inferior margins of merus each with series of small granulated teeth, lacking large teeth (Figure 1A and Figure 5C). Chelipeds of adult male unequal, major cheliped longer, more robust than minor cheliped (Figure 1A and Figure 5K,L), cutting edges of fixed (propodus) and moveable (dactylus) fingers without large teeth (Figure 5A), minor cheliped lined by row of small serrated teeth (Figure 5A,B). Walking legs (pereiopods 2–5) moderately robust, posterior margins of propodi serrated with small pointed teeth, dactyli tapering, each bearing rows of downward pointing large sharp spines (Figure 1A).
Male pleon and telson together broadly triangular with straight edges (Figure 4A).
Male first gonopod G1TA long (0.8–0.9 × G1SA length), margins lacking setae; in ventral view G1TA distal half curving outward, evenly tapering to pointed tip, G1SA broad basally, tapering to narrow width distally at G1TA-G1SA junction (Figure 6A,B). G2 shorter than G1, reaching only to G1SA-G1TA junction. G2TA extremely short, only one-fifteenth as long as G2SA; G2SA widest at base, then tapering sharply inward, forming long, thin, pointed, upright process supporting G2TA; rounded collar at G2SA-G2TA junction (Figure 6C).
Colour in life: Dorsal carapace and appendages green. Articulations between carpus and merus of cheliped and ambulatory legs dark brown. Preserved specimens uniformly light brown.
Type locality: Close to Eyimba (04°53′30.7″ N, 009°59′05.1″ E, 835 m ASL), Mount Nlonako Wildlife Reserve, Cameroon.
Distribution: This species is currently known from the montane forests of Mount Nlonako Wildlife Reserve, and from lowland forests near Eboforest Wildlife Reserve and near Bakossi National Park.
Habitat: Sudanonautes cameroonensis sp. n. was collected either in streams where crabs were found in cracks in rocks, under small stones, or near streams in burrows dug in moist soils. It is likely that this species is semi-terrestrial.
Etymology: The new species is named for Cameroon, in recognition of this country as a key biodiversity area for freshwater crabs. The species name “cameroonensis” is a noun in apposition.
Common name: Cameroon freshwater crab.
 
Sudanonautes eyimba sp. n.
(Figure 1B, Figure 2B, Figure 3B, Figure 4B, Figure 5F–J and Figure 6D–F)
Material examined: Cameroon. Types: Holotype, adult ♂ (CW 37.5, CL 25.2, CH 18.0, FW 10.4 mm), close to Eyimba (04°53′30.7″ N, 009°59′05.1″ E, 835 m ASL), Mount Nlonako Wildlife Reserve, coll. P.A. Mvogo Ndongo, 13 March 2018 (ZMB Crust. 33108). Paratypes, adult ♀ (CW 35.0, CL 25.5, CH 16.3, FW 10.8 mm) (ZMB Crust. 33109), adult ♂ (CW 33.7, CL 23.9, CH 16.9, FW 9.5 mm), subadult ♀ (CW 25.1, CL 20.0, CH 12.2, FW 8.3 mm) (CARC-08), same details as holotype.
Diagnosis: Medium sized species, adult size range CW 34–37 mm. Postfrontal crest distinct yellow colour, complete, lateral ends curving downwards, meeting carapace lateral margin at epibranchial tooth (Figure 2B and Figure 3B). Exorbital tooth small, low, distinct; intermediate tooth small, triangular; epibranchial tooth small (Figure 1B, Figure 2B and Figure 3B). Lateral carapace margin smooth (Figure 2B and Figure 3B). Semi-circular, urogastric, cardiac, cervical, transverse branchial carapace grooves all deep (Figure 1B and Figure 2B). Pterygostomial region of carapace sidewall with field of large granules medially, otherwise smooth (Figure 3B). Anterior thoracic sternum S3, S4 margins thickened, raised (Figure 4B). Mandible, proximal superior margin of palp TA with a small ronded accessory lobe about ¼ length of TA (Figure 5I). Major cheliped dactylus with three teeth, two large (one proximal, one at midpoint), one smaller tooth in between (Figure 5F). First male gonopod, distal G1SA near G1TA-G1SA junction widened; G1TA medium length, 0.6 × G1SA length, margins lined by sparse short setae (Figure 6D,E).
Description: Carapace ovoid, high, arched (CH/FW 1.62, N = 4), wide (CW/FW 3.36, N = 4), smooth (Figure 1B, Figure 2B and Figure 3B). Front deflexed, anterior margin highly concave medially (Figure 3B). Carapace surface smooth, cervical, urogastric, cardiac, branchial grooves deep; exorbital tooth blunt, low, intermediate, epibranchial teeth each large, triangular (Figure 1B and Figure 2B). Postfrontal crest distinct yellow colour, rest of carapace darker; completely traversing carapace, lateral ends curving downwards to meet carapace lateral margins at epibranchial teeth; carapace lateral margins smooth behind epibranchial teeth; mid-groove on postfrontal crest short, forked (Figure 2B and Figure 3B). Carapace branchiostegite divided into 3 parts by longitudinal, vertical, sutures (Figure 3B and Figure 4B); longitudinal suture dividing smooth suborbital, subhepatic regions from pterygostomial region, beginning at respiratory opening, curving backward; vertical suture short, granular, dividing suborbital from subhepatic regions beginning at base of intermediate tooth, then curving down to meet longitudinal suture; pterygostomial region with field of large granules medially, otherwise smooth (Figure 3B). S2/3, completely traversing sternum; S3/4 incomplete, reduced to 2 short side notches; side margins of S4 thickened, raised (Figure 4B). Mandible, proximal superior margin of palp TA with small accessory lobe about ¼ length of TA (Figure 5I). Third maxillipeds filling entire buccal cavern except for transversely oval efferent respiratory openings visible at superior lateral corners (Figure 3B and Figure 4B); exopod with well-developed slender flagellum; ischium with distinct vertical sulcus (Figure 5J).
Inferior cheliped merus margins lined by small sharp teeth, inner margin with large distal meral tooth (Figure 4B and Figure 5H). Cheliped carpus distal, proximal teeth both pointed, distal larger than proximal (Figure 5H). Chelipeds of adult male unequal, major cheliped longer than minor cheliped (Figure 1B and Figure 5F,G). Major chela movable finger (dactylus) with three teeth, two large (one proximal, one at midpoint) separated by one smaller tooth (Figure 5F). Minor cheliped with occluding margins of propodus and dactylus lined by small teeth (Figure 5G); Walking legs (pereiopods P2–5) moderately slender, posterior margins of propodi serrated with small blunt teeth, dactyli tapering, each bearing rows of downward-pointing large sharp spines (Figure 1B).
Male pleon plus telson broadly triangular with straight inward-tapering margins (Figure 4B). Male gonopods, in ventral view G1TA distal half straight, tip slightly upcurved (Figure 6D), slim, not widened in mid-section, G1TA medium length, 0.6 × G1SA length, margins lined by sparse short setae, distal G1SA near G1TA-G1SA junction widened (Figure 6D,E). G2 shorter than G1, reaching only to G1TA-G1SA junction. G2TA extremely short, only one-fifteenth as long as G2SA, G2SA widest at base, then tapering sharply inward, forming long, thin, pointed, upright process supporting short G2TA, rounded collar at G2TA-G2SA junction (Figure 6F).
Colour in life: This species has a distinct yellow postfrontal crest contrasting with the black carapace in the anterolateral region and the pale yellow-brown carapace in the posterolateral region. The chelipeds and walking legs (P2–5) are also all pale yellow-brown. Preserved specimens are uniformly light brown.
Type locality: High-altitude forest, near Eyimba (04°53′30.7″ N, 009°59′05.1″ E, 835 m ASL), Mount Nlonako Wildlife Reserve Eyimba, Littoral Region, Southwest Cameroon.
Distribution: This species is currently known only from montane forest in the Mount Nlonako Wildlife Reserve, Southwest Cameroon.
Habitat: Collected from rock cracks and under small rocks in forest wetlands, and at the bottom of burrows that it digs in stream banks. This species is likely to be semi-terrestrial. This species is sympatric with S. cameroonensis sp. n.
Etymology: The species is named for the small village of Eyimba (04°52′52″ N, 009°59′19″ E) on the eastern side of Mount Nlonako (710 m ASL) which is near to the collection locality. The name “eyimba” is used as a Latin noun in nominative singular.
Common name: Eyimba freshwater crab.
 
Sudanonautes ngaoundere sp. n.
(Figure 1C, Figure 2C, Figure 3C, Figure 4C, Figure 5K–O and Figure 6G–I)
Material examined: Cameroon. Types: Holotype, adult ♂ (CW 53.4, CL 34.6, CH 21.1, FW 13.7 mm), Guinea savanna, near Lake Tison (07°15′17.8″ N, 013°34′36.0″ E, 1,172 m ASL), south of Ngaoundéré, Adamaoua Region, Northern Cameroon, coll. P.A. Mvogo Ndongo, 23 October 2022 (ZMB Crust. 33300). Paratype (CW 45.9, CL 31.6, CH 24.3, FW 12.1 mm) Guinea savanna, near Lake Mbakaou (fed by the Sanaga River) east of Tibati, Adamaoua Region, Northern Cameroon (05°27′59.4″ N 012°38′51.0″ E, 850 m ASL), coll. P.A. Mvogo Ndongo, 23 October 2022 (ZMB Crust.33301). Non-types: 2 adult ♂♂ (CWs 48.0, 56.3, CLs 33.3, 37.7, CHs 19.2, 27.6, FWs 14.3, 14.1 mm), same details as paratype (CARC-08X).
Diagnosis: Medium sized species, adult size range CW 46–53 mm. Postfrontal crest distinct yellow colour, incomplete, lateral ends not meeting either epibranchial tooth or carapace lateral margin (Figure 2C and Figure 3C). Exorbital tooth large, triangular; intermediate tooth small, pointed; epibranchial tooth obscure (Figure 1C, Figure 2C and Figure 3C). Lateral carapace margin smooth (Figure 2C and Figure 3C). Semi-circular, urogastric, cardiac, cervical, transverse branchial carapace grooves all shallow (Figure 1C and Figure 2C). Pterygostomial region of carapace sidewall with field of small distinct granules medially, otherwise smooth (Figure 3G and Figure 4H). Anterior thoracic sternum S3, S4 margins thickened, raised (Figure 4C). Mandible, proximal superior margin of palp TA with small rounded accessory lobe ca. ¼ length of TA (Figure 5O). Major cheliped dactylus with three large proximal teeth, then gap, with one large tooth at midpointand small teeth distally (Figure 5K). Male gonopod G1TA in ventral view proximal half straight, distal half angled outward at 45 degrees, tip not upcurved; G1TA long (G1TA length subequal to G1SA length, margins lined by short sparse setae (Figure 6D,E).
Description: Carapace ovoid, high, arched (CH/FW 1.5), wide (CW/FW 3.9), smooth (Figure 1C, Figure 2C and Figure 3C). Front deflexed, anterior margin highly concave medially (Figure 3C). Carapace surface smooth, cervical, urogastric, cardiac, branchial grooves all shallow; exorbital tooth large, triangular; intermediate tooth small, pointed; epibranchial tooth obscure (Figure 1C, Figure 2C and Figure 3C). Postfrontal crest distinct yellow colour, incomplete, lateral ends not meeting either epibranchial tooth or carapace lateral margin (Figure 2C and Figure 3C); carapace lateral margins smooth behind epibranchial teeth; mid-groove on postfrontal crest short, forked (Figure 2C and Figure 3C). Carapace branchiostegite divided into 3 parts by longitudinal, vertical, sutures (Figure 3C and Figure 4C); longitudinal suture dividing smooth suborbital, subhepatic regions from pterygostomial region, beginning at respiratory opening, curving backward; vertical suture short, granular, dividing suborbital from subhepatic regions beginning at base of intermediate tooth, then curving down to meet longitudinal suture; pterygostomial region with field of small distinct granules medially, otherwise smooth (Figure 3G and Figure 4H). S2/3, completely traversing sternum; S3/4 incomplete, reduced to 2 short side notches; anterior thoracic sternum S3, S4 margins thickened, raised (Figure 4C). Episternal sulcus S5/E5 distinct, S4/E4, S6/E6, S7/E7 all obscure, smooth (Figure 4C). Proximal superior margin of palp TA with small rounded accessory lobe ca. ¼ length of TA (Figure 5O). Third maxillipeds filling entire buccal cavern except for transversely oval efferent respiratory openings visible at superior lateral corners (Figure 3C and Figure 4A); exopod with well-developed slender flagellum; ischium with distinct vertical sulcus (Figure 5O).
Inferior cheliped merus margins lined by small sharp teeth, inner margin with large distal meral tooth (Figure 4C and Figure 5M). Cheliped carpus with distal teeth, proximal teeth both pointed, distal larger than proximal (Figure 5M). Chelipeds of adult male unequal, major cheliped longer than minor cheliped (Figure 1C and Figure 5K,L). Major chela, movable finger (dactylus) with three large proximal teeth, then gap with one large tooth at midpoint and small teeth distally (Figure 5K). Minor cheliped with occluding margins of both fingers lined by small teeth (Figure 5L). Walking legs (pereiopods P2–5) moderately slender, posterior margins of propodi serrated with small blunt teeth, dactyli tapering, each bearing rows of downward-pointing large sharp spines (Figure 1C).
Male pleon plus telson broadly triangular with straight inward-tapering margins (Figure 4C). Male gonopod G1TA in ventral view, proximal half straight with distal half angled outward at 45 degrees, tip not upcurved (Figure 6G), G1TA mid-section widened; G1TA long (G1TA length slightly shorter than G1SA length), margins lined by sparce short setae (Figure 6G,H). G2 shorter than G1, reaching only to G1TA-G1SA junction; G2TA extremely short, only one-fifteenth as long as G2SA (Figure 6I); G2SA widest at base, then tapering sharply inward, forming long, thin, pointed, upright process supporting short G2TA; rounded collar at G2TA-G2SA junction (Figure 6I).
Colour in life: This species has a distinctive yellow postfrontal crest that contrasts with the darker carapace surface, and its chelipeds and walking legs (P2–5) are all pale yellow-brown. In life, the distal tips of the meri of P1–5 are yellow. Preserved specimens are uniformly light yellow.
Type locality: On land near Lake Tison (07°15′17.8″ N, 013°34′36.0″ E, 1,172 m ASL), south of Ngaoundéré, Adamaoua Region, Guinea savanna, Northern Cameroon.
Distribution: This species is currently known from two localities near Ngaoundéré in the Guinea savanna zone of Cameroon, one on land near Lake Tison and the other close to Lake Tibati.
Habitat: Sudanonautes ngaoundere sp. n. was collected by excavating its burrows made in the softer ground in the vicinity of Lakes Tison and Tibati. This species is not found in these lakes but prefers the nearby land close to these water bodies. This species has a semi-terrestrial lifestyle.
Etymology: The new species is named for Ngaoundéré, Cameroon because both localities are in the vicinity of this town. The species name “ngaoundere” is a noun in apposition.
Common name: Guinea savanna freshwater crab.
 
Sudanonautes nkam sp. n.
(Figure 1D, Figure 2D, Figure 3D, Figure 4B, Figure 5P–T and Figure 6J–L)
Material examined: Cameroon.Types: Holotype, adult ♂ (CW 41.6, CL 27.9, CH 19.4, FW 10.2 mm), Nkam River (04°28′20.8″ N 009°57′26.0″ E, 225 m ASL) draining lowland moist forest, Parc des Princes, Yabassi City, Littoral Region of Cameroon, coll. P.A. Mvogo Ndongo, 30 August 2015 (ZMB Crust. 33110). Paratypes, adult ♂ (CW 34.7, CL 24.0, CH 16.8, FW 11.2 mm), 2 adult ♀♀ (CWs 39.0, 37.7, CLs 27.8, 26.8, CHs 19.5, 19.0, FWs 10.8, 9.8), Nkam River, Banya (04°27′54.6″ N 009°58′15.4″ E, 211 m ASL), Yabassi City, Littoral Region, coll. P.A. Mvogo Ndongo, 02 September 2015 (ZMB Crust. 33111). Non-types: 2 adult ♂♂ (CWs 37.5, 44.6, CLs 26.8, 28.0, CHs 19.0, 19.8, FWs 9.8, 10.9 mm), adult ♀ (CW 44.6, CL 30.7, CH 21.3, FW 14.4 mm), Banya, Yabassi City, Littoral Region (04°27′54.6″ N 009°58′15.4″ E, 211 m ASL), coll. P.A. Mvogo Ndongo, 01 September 2015 (CARC-09).
Diagnosis: Medium sized species, adult range CW 34–41 mm. Postfrontal crest distinct yellow colour, complete, lateral ends curving backward, not meeting either epibranchial tooth or carapace lateral margin (Figure 2D and Figure 3D). Exorbital tooth small, low, distinct; intermediate tooth small, triangular; epibranchial tooth small (Figure 1D, Figure 2D and Figure 3D). Lateral carapace margin granulated (Figure 2D and Figure 3D). Semi-circular, urogastric, cardiac, cervical, transverse branchial carapace grooves all deep (Figure 1D and Figure 2D). Pterygostomial region of carapace sidewall with field of large granules medially, otherwise smooth (Figure 3D and Figure 4D). Mandible, proximal superior margin of palp TA with large rounded accessory lobe ca. ½ length of TA (Figure 5S). Major cheliped dactylus with three large teeth, two proximal, one at midpoint (Figure 5P). Anterior thoracic sternum S3, S4 margins thickened, raised (Figure 4D). G1TA proximal two-thirds straight, distal third bent outward (Figure 6J), distinctly widened in mid-section by raised dorsal lobe, G1TA long (G1TA length distinctly shorter than G1SA length, margins lined by dense long setae (Figure 6J,K).
Description: Carapace ovoid, high, arched (CH/FW 1.63, N = 8), wide (CW/FW 3.81, N = 8), smooth (Figure 1D and Figure 2D). Front deflexed, anterior margin highly concave medially (Figure 3D). Carapace surface smooth, cervical, urogastric, cardiac, branchial grooves distinct (Figure 1D and Figure 2D). Exorbital tooth small, low, distinct; intermediate tooth small, triangular; epibranchial tooth small (Figure 1D, Figure 2D and Figure 3D). Postfrontal crest distinct yellow colour, complete, lateral ends curving backward, not meeting either epibranchial tooth or carapace lateral margin (Figure 2D and Figure 3D); mid-groove on postfrontal crest short, forked (Figure 2D and Figure 3D). Carapace branchiostegite divided into 3 parts by longitudinal, vertical, sutures (Figure 3D); longitudinal suture dividing smooth suborbital, subhepatic regions from pterygostomial region, beginning at respiratory opening, curving backward; vertical suture short, granular, dividing suborbital from subhepatic regions beginning at base of intermediate tooth, then curving sharply down to meet longitudinal suture; pterygostomial region with field of large granules medially, otherwise smooth (Figure 3D and Figure 4D). S2/3, completely traversing sternum, deep; S3/4 incomplete, reduced to 2 short side notches (Figure 3D). Proximal superior margin of palp TA with large rounded accessory lobe ca. ½ length of TA (Figure 5S).Third maxillipeds filling entire buccal cavern except for transversely oval efferent respiratory openings visible at superior lateral corners (Figure 3D and Figure 4D); exopod with well-developed slender flagellum; ischium with distinct vertical sulcus (Figure 3D, Figure 4D and Figure 5T).
Chelipeds of adult male unequal, right (major) cheliped longer than left cheliped (Figure 1D and Figure 5P,Q). Fingers slim, elongated; movable finger (dactylus) of major chela straight, with three large teeth, two proximally, one at mid-point (Figure 5P); fixed finger with three large teeth proximally (Figure 5P). Minor cheliped with occluding margins of both fingers lined by small teeth (Figure 5Q); cheliped carpus distal, proximal teeth both pointed, distal larger than proximal (Figure 5Q). Inferior cheliped merus margins lined by small sharp teeth, inner margin with large distal meral tooth (Figure 4D and Figure 5R). Walking legs (pereiopods P2–5) moderately slender, posterior margins of propodi serrated with small blunt teeth, dactyli tapering, each bearing rows of downward-pointing large sharp spines (Figure 1D).
Male pleon plus telson broadly triangular with straight inward-tapering margins (Figure 4D). G1TA proximal two-thirds straight, distal third bent outward (Figure 6J), distinctly widened in mid-section by raised dorsal lobe; G1TA long (G1TA length slightly shorter than G1SA length; margins lined by long, dense setae (Figure 6J,K). G2 shorter than G1, reaching only to G1TA-G1SA junction. G2TA extremely short, only one-fifteenth as long as G2SA, G2SA widest at base, then tapering sharply inward, forming long, thin, pointed, upright process supporting short G2TA, with rounded collar at G2TA-G2SA junction (Figure 6L).
Colour in life: This species has a distinctive yellow postfrontal crest that contrasts with the darker carapace surface, and its chelipeds and walking legs (P2–5) are all pale yellow-brown. Preserved specimens are uniformly light yellow.
Type locality: The Nkam River (04°28′20.8″ N 009°57′26.0″ E, 225 m ASL) draining lowland moist forest, Parc des Princes, southwest of Yabassi, Littoral Region, Southwest Cameroon.
Distribution: This species is currently known only from the Nkam River, Parc des Princes, near Yabassi, Littoral Region, Southwest Cameroon.
Habitat: Sudanonautes nkam sp. n. is only found in the Nkam River in a restricted area of the humid rainforests of Southwest Cameroon. The Nkam River rises in Cameroon’s Western High Plateau then joins the Makombé River before flowing into the Wouri River.
Etymology: The species name refers to the Nkam River near Yabassi in Southwest Cameroon where it was collected. The name “nkam” is used as a Latin noun in nominative singular.
Common name: Nkam freshwater crab.

4. Molecular Results

The phylogenetic tree with confidence values according to BI and ML derived from the combination of CO1 and 16S RNA mitochondrial DNA sequences (Figure 7) recovered species of Sudanonautes as two distinct clades. Phylogenetic trees reconstructed in separate analyses of the two genes were completely congruent with each other and the tree recovered in the combined analysis. One of the clades includes Sudanonautes species that are found in small and large water catchments, e.g., S. africanus, S. aubryi and S. cameroonensis sp. n., while the other clade includes semiterrestrial species found in smaller water courses, e.g., S. tiko, S. eyimba sp. n., S. nkam sp. n., S. ngoundere sp. n. and S. floweri that were found to be well-supported independent lineages in the latter clade. Uncorrected p-distances based on CO1 sequence data ranged from 10.12% to 21.31% among the Sudanonautes species included in the present study, and 0% to 0.69% within species. The four new species are distinct from their congeners (Table 2).

5. Discussion

5.1. Morphology

Sudanonautes cameroonensis sp. n., S. eyimba sp. n., S. ngaoundere sp. n. and S. nkam sp. n. conform to the diagnostic characters of the genus [1,15,16]. For example, the G1TA is directed outward and is either medium length or long (either shorter than, or subequal to the G1SA length), curved, and tapers to a pointed tip, the G2TA is noticeably shortened and reduced to a short stub (0.1 × the G2SA length), and the third maxilliped exopod has a long flagellum. Differences between the four new Sudanonautes species are given in Table 3.
Sudanonautes cameroonensis sp. n., S. eyimba sp. n., S. ngaoundere sp. n. and S. nkam sp. n. can be distinguished from S. africanus, S. chavanesii, S. faradjensis, and S. sangha by their medium adult body size with a pubertal moult around CW 35–47 mm (vs. a large adult body size with a pubertal moult at CW 50 mm or greater in the other four species). Sudanonautes nkam sp. n. can be distinguished from all other congeneric species by the mandibular palp terminal endopod article (TA) that has a large hardened lobe on the superior margin about ½ as long as the TA; Figure 5S (vs. a mandibular palp TA with either a small lobe or low ridge in all other Sudanonautes species). Furthermore, the postfrontal crest ends before meeting the carapace lateral margin in S. nkam sp. n.; Figure 3D (vs. a postfrontal crest that meets the carapace lateral margin in all other Sudanonautes species). In addition, the major chela dactylus is straight in S. cameroonensis sp. n.; Figure 5A and S. eyimba sp. n.; Figure 5K (vs. a major cheliped dactylus that is distinctly arched in S. koudougou, S. umaji and S. tiko). The carapace lateral margin behind the epibranchial tooth is granulated in S. cameroonensis sp. n.; Figure 3A and S. nkam sp. n.; Figure 3D (vs. completely smooth in S. monodi, S. kagoroensis and S. granulatus). The G1TA is long (about half length of G1SA) in S. eyimba sp. n.; Figure 6A,C (vs. a G1TA that is extremely long, almost as long as the G1SA in S. nigeria); and the G1TA curves sharply outward in S. eyimba sp. n.; Figure 6D,E (vs. a G1TA that is straight for most of its length, curving sharply outward just before the tip in S. orthostylis). Sudanonautes cameroonensis sp. n. can be distinguished from S. aubryi as follows. The third maxilliped ischium has a faint vertical sulcus in S. cameroonensis sp. n.; Figure 5C (vs. a third maxilliped ischium with a distinct vertical sulcus in S. aubryi; Ref. [7]: Figure 2e); the G1TA margins are smooth (lack setae) in S. cameroonensis sp. n.; Figure 6A,B (vs. a G1TA whose margins are lined by short setae in S. aubryi; Ref. [7]: Figure 1d,e); the carapace surface is smooth, and the cervical, urogastric, cardiac, and branchial grooves are all shallow in S. cameroonensis sp. n.; Figure 1A and Figure 2A (vs. a carapace surface that is smooth in the anterolateral region but granulated in the postlateral region, with cervical, urogastric, cardiac, branchial grooves all deep in S. aubryi; Ref. [7]: Figure 2a); and the epibranchial tooth is a small granule in S. cameroonensis sp. n.; Figure 2A and Figure 3A (vs. a large epibranchial tooth in S. aubryi; Ref. [7]: Figure 1a). Finally, S. ngaoundere sp. n. can be distinguished from the three other new species described here by the postfrontal crest being incomplete and ending just short of meeting the lateral carapace margin at the epibranchial tooth; Figure 2C and Figure 3C (vs. a postfrontal crest that is complete, and meets the lateral carapace margin either at, or close to, the epibranchial tooth in S. cameroonensis sp. n., S. eyimba sp. n. and S. nkam sp. n.; Figure 2A and Figure 3A; Figure 2B and Figure 3B; Figure 2D and Figure 3D, respectively); the epibranchial tooth is obscure; Figure 1C, Figure 2C and Figure 3C (vs. an epibranchial tooth that is either small and pointed, or reduced to a rounded granule in S. cameroonensis sp. n., S. eyimba sp. n. and S. nkam sp. n.; Figure 1A, Figure 2A and Figure 3A; Figure 1B, Figure 2B and Figure 3B; Figure 1D, Figure 2D and Figure 3D, respectively) and the major chela dactylus cutting edge has three large proximal teeth and one large tooth at the midpoint; Figure 5K (vs. a major chela dactylus cutting edge that has either 2 large proximal teeth and one large tooth at the midpoint, or no large teeth at all in S. cameroonensis sp. n., S. eyimba sp. n. and S. nkam sp. n.; Figure 5A, Figure 5F and Figure 5P, respectively).

5.2. Molecular Phylogeny

Sudanonautes cameroonensis sp. n., S. eyimba sp. n., S. ngaoundere sp. n. and S. nkam sp. n. all form a highly distinct lineage each in the molecular phylogeny, supporting their species status (Figure 7). This is underlined by the minimum genetic distance of 10.12% (CO1) from their next congener (Table 2). Sudanonautes eyimba sp. n., S. ngaoundere sp. n. and S. nkam sp. n. form part of the same clade that includes other semiterrestrial and stream species within Sudanonautes, while S. cameroonensis sp. n. is part of a clade that includes several widespread large-bodied river and stream species in this genus.

5.3. Threats, Impacts and Conservation

Sudanonautes eyimba sp. n. and S. cameroonensis sp. n. are sympatric but exploit different parts of this habitat. Both species are found in the Mount Nlonako Wildlife Reserve (641 km2) that has lowland, submontane, and montane rainforest. The reserve lies southeast of Nkongsamba and west of Nkondjock and its eastern boundary is formed by the Nkam River. The shared type locality on Mount Nlonako (at 835 m ASL) is near the village of Eyimba (710 m ASL) on the eastern side of Mount Nlonako (which rises to 1825 m ASL at its highest point).
The short distance between the town of Nkongsamba and the Mount Nlonako Wildlife Reserve has meant that the western and northern slopes of Mount Nlonako have suffered agricultural encroachment, and this disturbance has converted much of the original forest into secondary forest. Only part of Mount Nkonako, however, is impacted by human activities. The submontane and montane forests on the eastern and southern sides of Mount Nlonako where S. eyimba sp. n. and S. cameroonensis sp. n. were collected, are largely undisturbed, with only a few cultivated areas. Although the Mt. Nlonako Wildlife Reserve is a protected area, deforestation and pollution from pesticides sprayed on food crops growing just outside the reserve may impact the habitat of S. eyimba sp. n. and S. cameroonensis sp. n. in the future.
The forests of the Mount Nlonako Wildlife Reserve are continuous with a vast expanse of high-canopy undisturbed lowland forest that stretches south as far as the Nkébé River (a tributary of the Nkam River) in the area around Yabassi. Sudanonautes nkam sp. n. was collected in these forests to the southwest of Yabassi where this new species appears to be facing threats from widespread anthropogenic activities such as habitat destruction, exploitation for human consumption, and detergents and other harmful chemicals from washing clothes that may affect juvenile crabs. It is likely that conservation measures will be needed to protect S. nkam sp. n. from the immediate threats because our regular searches for this species have resulted in few additional specimens. Sudanonautes ngaoundere sp. n. is a semiterrestrial species found in Guinea savanna that is facing threats from anthropogenic activities such as habitat destruction from farming and firewood collection, pollution from agricultural fertilizers and pesticides, and possibly exploitation for human consumption. Further studies are necessary to define the exact distributions and population structures of all four new species so that their extinction risk can be assessed using IUCN Red List protocols.

Author Contributions

P.A.M.N. collected the data, P.A.M.N., P.F.C., T.v.R. and N.C. analysed the data and wrote the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This work was made possible by a grant from the Rufford Small Grant (completion grant ID 35189-C). We also recognize the involvement of Mr Kuate Simo Franclin for collecting additional specimens during his first Rufford Small Grant.

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

Acknowledgments

We are grateful to Bernhard Schurian, and Robert Schreiber from the ZMB, Berlin, Germany for their important collaboration and assistance in the morphological and molecular work during a research visit by the first author in 2021. We should also like to acknowledge the invaluable contributions of local people in Mt. Nlonako and Yabassi for their excellent skills in locating and collecting the specimens of Sudanonautes reported here.

Conflicts of Interest

The authors declare no conflicts of interests.

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Diversity 16 00345 g001
Figure 1. Dorsal view of whole crab. (A) Sudanonautes cameroonensis sp. n., holotype, ♂ CW 47.00 mm, Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); (B) S. eyimba sp. n., holotype, ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); (C) S. ngaoundere sp. n., CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); (D) S. nkam sp. n., holotype, ♂ CW 41.6 mm, Nkam River near Yabassi, Cameroon (ZMB Crust. 33110). Scale bar: A = 23 mm, B = 18 mm, C = 26 mm, D = 20 mm.
Figure 1. Dorsal view of whole crab. (A) Sudanonautes cameroonensis sp. n., holotype, ♂ CW 47.00 mm, Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); (B) S. eyimba sp. n., holotype, ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); (C) S. ngaoundere sp. n., CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); (D) S. nkam sp. n., holotype, ♂ CW 41.6 mm, Nkam River near Yabassi, Cameroon (ZMB Crust. 33110). Scale bar: A = 23 mm, B = 18 mm, C = 26 mm, D = 20 mm.
Diversity 16 00345 g001
Diversity 16 00345 g002
Figure 2. Carapace, dorsal view. (A) Sudanonautes cameroonensis sp. n., holotype from Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); (B) S. eyimba sp. n., holotype, adult ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); (C) S. ngaoundere sp. n. CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); (D) S. nkam sp. n., holotype, adult ♂ CW 41.6 mm, from the Nkam River near Yabassi, Cameroon (ZMB Crust. 33110). Scale bar: A = 23 mm, B = 18 mm, C = 26 mm, D = 20 mm.
Figure 2. Carapace, dorsal view. (A) Sudanonautes cameroonensis sp. n., holotype from Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); (B) S. eyimba sp. n., holotype, adult ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); (C) S. ngaoundere sp. n. CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); (D) S. nkam sp. n., holotype, adult ♂ CW 41.6 mm, from the Nkam River near Yabassi, Cameroon (ZMB Crust. 33110). Scale bar: A = 23 mm, B = 18 mm, C = 26 mm, D = 20 mm.
Diversity 16 00345 g002
Diversity 16 00345 g003
Figure 3. Carapace, frontal view. (A) Sudanonautes cameroonensis sp. n., holotype from Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); (B) S. eyimba sp. n., holotype, adult ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); (C) S. ngaoundere sp. n. CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); (D) S. nkam sp. n., holotype, adult ♂ CW 41.6 mm, from the Nkam River near Yabassi, Cameroon (ZMB Crust. 33110). Scale bar: A = 23 mm, B = 18 mm, C = 26 mm, D = 20 mm.
Figure 3. Carapace, frontal view. (A) Sudanonautes cameroonensis sp. n., holotype from Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); (B) S. eyimba sp. n., holotype, adult ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); (C) S. ngaoundere sp. n. CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); (D) S. nkam sp. n., holotype, adult ♂ CW 41.6 mm, from the Nkam River near Yabassi, Cameroon (ZMB Crust. 33110). Scale bar: A = 23 mm, B = 18 mm, C = 26 mm, D = 20 mm.
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Figure 4. Carapace, ventral view. (A) Sudanonautes cameroonensis sp. n., holotype from Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); (B) S. eyimba sp. n., holotype, adult ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); (C) S. ngaoundere sp. n. CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); (D) S. nkam sp. n., holotype, adult ♂ CW 41.6 mm, from the Nkam River near Yabassi, Cameroon (ZMB Crust. 33110). Scale bar: A = 23 mm, B = 18 mm, C = 26 mm, D = 20 mm.
Figure 4. Carapace, ventral view. (A) Sudanonautes cameroonensis sp. n., holotype from Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); (B) S. eyimba sp. n., holotype, adult ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); (C) S. ngaoundere sp. n. CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); (D) S. nkam sp. n., holotype, adult ♂ CW 41.6 mm, from the Nkam River near Yabassi, Cameroon (ZMB Crust. 33110). Scale bar: A = 23 mm, B = 18 mm, C = 26 mm, D = 20 mm.
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Diversity 16 00345 g005
Figure 5. Sudanonautes cameroonensis sp. n., holotype from Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); frontal view of (A) major chela; (B) minor chela; (C) right cheliped merus and carpus; (D) mandibular palp; (E) right third maxilliped; S. eyimba sp. n., holotype, adult ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); frontal view of (F) major chela; (G) minor chela; (H) right cheliped merus and carpus; (I) mandibular palp; (J) right third maxilliped; S. ngaoundere sp. n. CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); frontal view of (K) major chela; (L) minor chela; (M) right cheliped merus and carpus; (N) mandibular palp; (O) right third maxilliped; S. nkam sp. n.; holotype, adult ♂ CW 41.6 mm, from the Nkam River near Yabassi, Cameroon (ZMB Crust. 33110); frontal view of (P) major chela; (Q) minor chela; (R) right cheliped merus and carpus; (S) mandibular palp; (T) right third maxilliped. Scale bars: A, B, C, E, G, H, K, L, M, P, Q, R, S = 5 mm; D, J, O, T = 2 mm; E, I, N, S = 1 mm.
Figure 5. Sudanonautes cameroonensis sp. n., holotype from Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); frontal view of (A) major chela; (B) minor chela; (C) right cheliped merus and carpus; (D) mandibular palp; (E) right third maxilliped; S. eyimba sp. n., holotype, adult ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); frontal view of (F) major chela; (G) minor chela; (H) right cheliped merus and carpus; (I) mandibular palp; (J) right third maxilliped; S. ngaoundere sp. n. CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); frontal view of (K) major chela; (L) minor chela; (M) right cheliped merus and carpus; (N) mandibular palp; (O) right third maxilliped; S. nkam sp. n.; holotype, adult ♂ CW 41.6 mm, from the Nkam River near Yabassi, Cameroon (ZMB Crust. 33110); frontal view of (P) major chela; (Q) minor chela; (R) right cheliped merus and carpus; (S) mandibular palp; (T) right third maxilliped. Scale bars: A, B, C, E, G, H, K, L, M, P, Q, R, S = 5 mm; D, J, O, T = 2 mm; E, I, N, S = 1 mm.
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Figure 6. Sudanonautes cameroonensis sp. n., holotype adult ♂ CW 47.0 mm from Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); right first gonopod (A) dorsal view; (B) ventral view; right second gonopod (C) ventral view; S. eyimba sp. n., holotype, adult ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); right first gonopod (D) dorsal view; (E) ventral view; right second gonopod (F) ventral view; S. ngaoundere sp. n. CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); right first gonopod (G) dorsal view; (H) ventral view; right second gonopod (I) ventral view; S. nkam sp. n., holotype, adult ♂ CW 41.6 mm, from the Nkam River near Yabassi, Cameroon (ZMB Crust. 33110); right first gonopod (J) dorsal view; (K) ventral view; right second gonopod (L) ventral view. Scale bars: A–L = 2.0 mm.
Figure 6. Sudanonautes cameroonensis sp. n., holotype adult ♂ CW 47.0 mm from Eyimba, Mt. Nkonako Cameroon (ZMB Crust. 33351); right first gonopod (A) dorsal view; (B) ventral view; right second gonopod (C) ventral view; S. eyimba sp. n., holotype, adult ♂ CW 37.1 mm, from Eyimba, Mt. Nlonako, Cameroon (ZMB Crust. 33108); right first gonopod (D) dorsal view; (E) ventral view; right second gonopod (F) ventral view; S. ngaoundere sp. n. CW 53.4 mm, Lake Tison, Ngaoundéré (ZMB Crust. 33300); right first gonopod (G) dorsal view; (H) ventral view; right second gonopod (I) ventral view; S. nkam sp. n., holotype, adult ♂ CW 41.6 mm, from the Nkam River near Yabassi, Cameroon (ZMB Crust. 33110); right first gonopod (J) dorsal view; (K) ventral view; right second gonopod (L) ventral view. Scale bars: A–L = 2.0 mm.
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Figure 7. Bayesian Inference (BI) tree topology for the freshwater crab taxa from Cameroon included in this study derived from mtDNA sequences corresponding to two loci (partial 16S rRNA and CO1). Bayesian Inference (BI) and Maximum Likelihood (ML) statistical values (%) on the nodes indicate posterior probabilities and bootstrap support, respectively.
Figure 7. Bayesian Inference (BI) tree topology for the freshwater crab taxa from Cameroon included in this study derived from mtDNA sequences corresponding to two loci (partial 16S rRNA and CO1). Bayesian Inference (BI) and Maximum Likelihood (ML) statistical values (%) on the nodes indicate posterior probabilities and bootstrap support, respectively.
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Table 1. Details of mtDNA markers used in the present study for Sudanonautes species and outgroup species. Present = sequence available in the present study; RMNH = Naturalis Biodiversity Center, Leiden, The Netherlands; LUZY = Zoological Collection of the Laboratory of Zoology, University of Yaounde 1, Cameroon.
Table 1. Details of mtDNA markers used in the present study for Sudanonautes species and outgroup species. Present = sequence available in the present study; RMNH = Naturalis Biodiversity Center, Leiden, The Netherlands; LUZY = Zoological Collection of the Laboratory of Zoology, University of Yaounde 1, Cameroon.
SpeciesCameroon LocalityMuseum Registration NumberDNA ExtractionReferencesGenBank Accession Number
CO116S rRNA
Sudanonautes africanusEdeaLZUY-05 (CARC-18)T263-4[13]KY069942KY069948
S. aubryiEdeaLZUY-06 (CARC-19)R1026-9[13]KY069938KY069950
S. aubryiEdeaLZUY-07 (CARC-20)T273-5[13]KY069943KY069951
S. cameroonensis sp. n. (1)Mt. Nlonako Wildlife ReserveCARC-16DNABer11presentOR887121OR892777
S. cameroonensis sp. n. (2)Bakossi National ParkCARC-17DNABer28presentOR887122OR892778
S. eyimba sp. n. (1)Eyimba, Mt. Nlonako Wildlife ReserveZMB Crust. 33108DNABerA9presentOR887120---
S. eyimba sp. n. (2)Eyimba, Mt. Nlonako Wildlife ReserveZMB Crust. 33109DNABer1x4presentOR887119OR892776
S. ngaoundere sp. n. (1)Near Lake Tison, NgaoundéréCARC-13DNABerB2presentOR887124---
S. ngaoundere sp. n. (2)Near Lake Mbakaou, TibatiCARC-14DNABerA10presentOR887123---
S. nkam sp. n. (1)Near YabassiLZUY-10 T262-3[13]KY069939KY069952
S. nkam sp. n. (2)Near YabassiZMB Crust. 33110DNABerA5presentOR887126---
S. tikoTikoZMB Crust. 29628T262-11[13]KY069941KY069954
S. tikoTikoRMNH.CRUST.57073T273-12[13]KY069945KY069953
Louisea nkongsambaMt. Nlonako Wildlife ReserveZMB Crust. 31618----[19]KP640480KP640444
Buea asylosCameroonNHM 1994.588-591----[28]KP640489KP640453
Table 2. The pairwise uncorrected p-distance (%) of the COI partial sequences of Sudanonautes species treated in this present study.
Table 2. The pairwise uncorrected p-distance (%) of the COI partial sequences of Sudanonautes species treated in this present study.
Sudanonautes SpeciesMax. Distance within Species (%)Distance Range between Species (%)
S. eyimba sp. n.S. nkam sp. n.S. cameroonensis sp. n.S. ngaoundere sp. n.S. tikoS. africanusS. aubryiS. floweri
S. eyimba sp. n.0.00---
S. nkam sp. n.0.1610.12–10.59---
S. cameroonensis sp. n.0.0019.39–20.1919.29–20.23---
S. ngaoundere sp. n.0.6913.56–15.1715.56–16.8916.48–18.62---
S. tiko0.1714.65–15.7613.52–14.0616.75–17.4416.30–17.24---
S. africanus---17.45–18.4717.01–17.0913.90–15.6317.00–21.3718.27–18.31---
S. aubryi0.0020.06–21.4218.51–18.8513.76–14.9117.92–20.0017.77–18-1813.63–13.88---
S. floweri---9.51–10.098.68–8.8819.53–20.7014.13–16.2014.36–14.7217.0318.54–19.08---
Table 3. The diagnostic characters of the four new Sudanonautes species.
Table 3. The diagnostic characters of the four new Sudanonautes species.
CharacterS. cameroonensis sp. n.S. eyimba sp. n.S. ngaoundere sp. n.S. nkam sp. n.
Adult size rangeCW 36 to 47 mmCW 34 to 38 mmCW 46 to 53 mmCW 42 to 45 mm
Semi-circular, urogastric, cardiac, cervical, transverse branchial carapace grooves. All shallow; Figure 1A and Figure 2A. All deep; Figure 1B and Figure 2B. All shallow; Figure 1C and Figure 2C. All deep; Figure 1D and Figure 2D.
Postfrontal crest. Complete, meeting carapace lateral margin behind epibranchial tooth; Figure 2A and Figure 3A. Complete, meeting carapace lateral margin at epibranchial tooth; Figure 2B and Figure 3B. Incomplete, ending just short of meeting lateral carapace margin at epibranchial tooth; Figure 2C and Figure 3C. Complete, lateral end curving backward, not meeting either epibranchial tooth or carapace lateral margin; Figure 2D and Figure 3D.
Carapace lateral margin. Granulated; Figure 1A and Figure 2A. Smooth; Figure 1B and Figure 2B. Smooth; Figure 1C and Figure 2C Granulated; Figure 1D and Figure 2D.
Exorbital tooth. Large, triangular, distinct; Figure 1A, Figure 2A and Figure 3A. Small, low, distinct; Figure 1B, Figure 2B and Figure 3B. Large, triangular, distinct; Figure 1C, Figure 2C and Figure 3C. Small, pointed, distinct; Figure 1D, Figure 2D and Figure 3D.
Intermediate tooth on the anterolateral margin. Small, triangular; Figure 1A, Figure 2A and Figure 3A. Small, triangular; Figure 1B, Figure 2B and Figure 3B. Small, pointed; Figure 1C, Figure 2C and Figure 3C. Small, triangular; Figure 1D, Figure 2D and Figure 3D.
Epibranchial tooth. Small granule; Figure 1A, Figure 2A and Figure 3A. Small, triangular; Figure 1B, Figure 2B and Figure 3B. Obscure; Figure 1C, Figure 2C and Figure 3C. Large, triangular; Figure 1D, Figure 2D and Figure 3D.
Pterygostomial region of carapace sidewall. Field of heavy granules medially, otherwise smooth; Figure 3A and Figure 4A. Field of large granules medially, otherwise smooth; Figure 3B and Figure 4B. Field of small but distinct granules medially, otherwise smooth; Figure 3C and Figure 4C. Field of large granules medially, otherwise smooth; Figure 3D and Figure 4D.
Anterior thoracic sternum S3, S4 margins.S3, S4 margins thin, not raised; Figure 4A.S3, S4 margins thickened, raised; Figure 4B.S3, S4 margins thickened, raised; Figure 4C.S3, S4 margins thickened, raised; Figure 4D.
Mandibular palp terminal article (TA).Proximal superior margin of palp TA with small accessory lobe ca. ¼ length of TA; Figure 5E.Proximal superior margin of palp TA with small accessory lobe ca. ¼ length of TA; Figure 5I.Proximal superior margin of palp TA with small accessory lobe ca. ¼ length of TA; Figure 5N.Proximal superior margin of palp TA with large rounded accessory lobe ca. ½ as length of TA; Figure 5S.
Major cheliped dactylus cutting edge.With no large teeth; Figure 5A.With two large proximal teeth, one large tooth at midpoint, one smaller tooth in between; Figure 5F.With three large proximal teeth, one large tooth at midpoint; Figure 5K.With two large proximal teeth, one large tooth at midpoint; Figure 5P.
G1SA shape near G1TA-G1SA junction.Distal G1SA slim; Figure 6A,B.Distal G1SA wide; Figure 6D,E.Distal G1SA wide; Figure 6G,H.Distal G1SA wide; Figure 6J,K.
G1TA margins.Margins lacking setae, smooth; Figure 6A,B.Margins lined by sparse short setae; Figure 6D,E.Margins lined by short setae; Figure 6G,H.Margins lined by dense long setae; Figure 6J,K.
G1TA relative length.G1TA long (G1TA length 0.8–0.9 × G1SA length); Figure 6A,B.G1TA medium length (G1TA length 0.6 × G1SA length); Figure 6D,E.G1TA medium length (G1TA length 0.5 × G1SA length); Figure 6G,H.G1TA medium length (G1TA length 0.6 × G1SA length); Figure 6J,K.
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Mvogo Ndongo, P.A.; Clark, P.F.; von Rintelen, T.; Cumberlidge, N. Four New Sudanonautes Species of Freshwater Crabs (Crustacea: Decapoda: Potamonautidae) from Cameroon, Central Africa. Diversity 2024, 16, 345. https://doi.org/10.3390/d16060345

AMA Style

Mvogo Ndongo PA, Clark PF, von Rintelen T, Cumberlidge N. Four New Sudanonautes Species of Freshwater Crabs (Crustacea: Decapoda: Potamonautidae) from Cameroon, Central Africa. Diversity. 2024; 16(6):345. https://doi.org/10.3390/d16060345

Chicago/Turabian Style

Mvogo Ndongo, Pierre A., Paul F. Clark, Thomas von Rintelen, and Neil Cumberlidge. 2024. "Four New Sudanonautes Species of Freshwater Crabs (Crustacea: Decapoda: Potamonautidae) from Cameroon, Central Africa" Diversity 16, no. 6: 345. https://doi.org/10.3390/d16060345

APA Style

Mvogo Ndongo, P. A., Clark, P. F., von Rintelen, T., & Cumberlidge, N. (2024). Four New Sudanonautes Species of Freshwater Crabs (Crustacea: Decapoda: Potamonautidae) from Cameroon, Central Africa. Diversity, 16(6), 345. https://doi.org/10.3390/d16060345

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