Potamonautes kisangani, Cumberlidge & Johnson & Clark & Genner, 2021

Cumberlidge, Neil, Johnson, Emily, Clark, Paul F. & Genner, Martin J., 2021, Unravelling the Potamonautes lirrangensis (Rathbun, 1904) species complex (Potamoidea: Potamonautidae), with the description of two new species, European Journal of Taxonomy 744 (1), pp. 145-178 : 156-162

Potamonautes kisangani sp. nov.

urn:lsid:zoobank.org:act:77F6D732-392A-4B60-AA4A-AA2104D12C01

Figs 1 , 4B , 5A , 6A–B , 7B , 8 , 11A , Table 1

Potamon (Potamonautes) lirrangensis – Rathbun 1921: 413–415, pls 25–26, figs 3, 8.

Diagnosis

Exorbital tooth large, spine-like; lateral margin of exorbital tooth lined by small teeth, angled outward at 45° to midline of carapace, straight, neither bulging outward (convex) nor curving inward (concave); epibranchial tooth small, granular, followed by large granules lining anterolateral margin ( Fig. 4B ); anterolateral margin posterior to epibranchial tooth curving strongly outward ( Fig. 4B ); postfrontal crest distinct, completely traversing carapace between epibranchial teeth; posterior surface of carapace with deep urogastric grooves ( Fig. 4B ). Male thoracic sternal sulcus S3/4 deep, distinct, V-shaped. Ischium of third maxilliped with thin but distinct vertical sulcus. Major chela with 3 large molars at proximal end of both fingers ( Fig. 6A–B ); major chela dactylus (moveable finger) and fixed finger (pollex of propodus) both elongated, straight, slender ( Fig. 6A–B ); cheliped carpus inner margin with 2 large, subequal, forward-pointing spines ( Fig. 7B ); cheliped merus inner lower margin with spine-like tooth distally. P5 carpus, propodus, and dactylus all shortened ( Fig. 8A–B ). G1 TA conspicuously widened by high, rounded dorsal lobe (as wide as TA width at TA-SA junction); G1 TA distal third straight, ending in pointed tip ( Fig. 11A ). G1 SA at junction with G1 TA with horizontal margin on ventral side, U-shaped indentation filled by conspicuous dorsal membrane on dorsal side.

Etymology

The new species is named for Kisangani, D.R. Congo, the locality where it was first collected. The specific epithet is used as a Latin noun in apposition. The vernacular name is the Kisangani freshwater crab.

Material examined

Holotype DEMOCRATIC REPUBLIC OF THE CONGO • ♂ adult (CW 60.5 mm); Kisangani , vicinity of Wagenia fishery ; 25 Apr. 1955; Smithsonian-Bredin Congo Exped., W.L. Schmitt leg.; USNM 98944 .

Paratypes DEMOCRATIC REPUBLIC OF THE CONGO • 2 ♂♂ (CW 59.5, 39.4 mm), 10 ♀♀ (CW 62.7, 61.1, 59.2, 56.9, 56.8, 56, 51.6, 48.3, 44.5, 40.3 mm), 3 ♀♀ ovig. (CW 66.5, 62.8, 54.7 mm); same collection data as for holotype; USNM 98944 .

Other material

DEMOCRATIC REPUBLIC OF THE CONGO • 1 ♂, 1 ♀, 1 ♀ ovig.; Kisangani ; Feb. 1915; A.M. Congo Exped., H. Lang leg.; USNM 54305 • 3 ♀♀ (CW 59.8, 54.9, 45.1 mm), 1 ♀ ovig. (CW 54.8 mm); same collection data as for preceding; Apr. 1915; USNM 54306 • 5 ♀♀ (CW 51.9, 49, 48.9, 45.6, 36.8 mm), 2 ♂♂ (CW 60.2, 29.2 mm); same collection data as for preceding; USNM 54307 • 1 ♂ (CW 59.1 mm); Kisangani , vicinity of Wagenia fishery ; W.L. Schmitt Bredin Exped. leg.; USNM 98939 • 3 ♀♀ (CW 40.4, 40, 24.8 mm); rocky gorge of Tshope Falls, Kisangani; 19 Apr. 1955; Smithsonian-Bredin Congo Exped., W.L. Schmitt leg.; USNM 98940 • 1 ♀ (CW 53.6 mm), 3 juvs; Kisangani , vicinity of Wagenia fishery ; Smithsonian-Bredin Congo Exped., W.L. Schmitt leg.; USNM 98941 • 2 ♀♀ ovig. (CW 56.5, 53.7 mm), 1 ♀ (CW 62.6 mm); Kisangani ; 20 Apr. 1955; Smithsonian-Bredin Congo Exped., W.L. Schmitt leg.; USNM 98942 • 1 ♀ (with hatchlings, CW 60.1 mm); Kisangani ; 20 Apr. 1955; Smithsonian-Bredin Congo Exped., W.L. Schmitt leg.; USNM 98943 • 1 ♂ (subadult CW 47.2 mm); Kisangani ; 22 Jun. 1955; G. Browne leg.; NHMUK 1955.6.22.65 • 1 ♂, 1 ♀; Kisangani ; Apr. 1915; A.M. Congo Exped., H. Lang leg.; MCZ CRU-10613 .

Description

See Diagnosis.

Size

Large-sized species, adult at CW 53 mm, largest known specimen CW 66 mm.

Colour

The colour of living specimens from Kisangani D.R. Congo was provided by Rathbun (1921: 415). The dorsal carapace is either dark blue, dark green, or dark brown, the thoracic sternum is pink with blue/ gray tones, and the pleon is yellow/white. The fixed and movable fingers of the chelae are dark brown/ black in recently preserved specimens ( Fig. 6A–B ), while the arthrodial membranes of the chelipeds are vermillion (vivid red/orange).

Distribution

This species is only known from the vicinity of Kisangani in the D.R. Congo ( Fig. 1 ).

Ecology

Kisangani lies in the Upper Congo Rapids Ecoregion (FEOW #539) ( Thieme et al. 2005; Abell et al. 2008). The field notes of Herbert Lang on the habitat of P. kisangani sp. nov. from Kisangani provided by Rathbun (1921: 415) indicate that although this species is found in large rivers, it favours shallow waters near river banks where drifting logs jam. At the Boyoma Falls near Kisangani these crabs were common above and below the cataracts, while in the Tshopo River crabs were abundant among the rocks and boulder fields above the Tshopo Falls, but were absent below the falls where the water was shallow and had a sandy substrate.

Remarks

This new species was recognized to accommodate a large number of specimens from Kisangani, D.R. Congo that were collected by two U.S. Expeditions: the American Museum Congo Expedition (1909–1915) led by Herbert O. Lang and James P. Chapin, and the Smithsonian-Bredin Expedition to the Belgian Congo, Sudan, Uganda, and Egypt (1955) led by Waldo L. Schmitt. The first U.S. expedition initially deposited a large number of specimens (in 10 samples) in the AMNH and subsequently gifted some of these (USNM 54305, 54306, 54307 and MCZ CRU-10613) to these other museums. All of the specimens from the first U.S. Congo expedition were attributed by Rathbun (1921) to P. lirrangensis s. lat., and she provided a description, photographs, and illustrations of this species ( Rathbun 1921: 413–415, pls 25–26, figs 3, 8). The second U.S. Congo expedition in 1955 also collected a number of specimens (in 7 samples) from Kisangani (examined in the present work) that were also initially attributed to P. lirrangensis s. lat. Figures of the carapace, chelipeds, and G1 of the adult male holotype from Kisangani, D.R. Congo ( Figs 4B , 5A , 6A–B , 7B , 8A–B , 11A ) are provided for comparison with

the other taxa included here. One character that distinguishes this species from P. lirrangensis s. str. is the epibranchial tooth, which is small and granular, followed by large granules lining the anterolateral margin in P. kisangani sp. nov. ( Fig. 4 B ) (vs pointed and as large as the other teeth lining the anterolateral margin in P. lirrangensis s. str. from Liranga; Fig. 4A ). The absence of DNA sequence data for any of the specimens from Kisangani means that it is not possible to test the monophyly of P. kisangani sp. nov. using molecular data.

Comparisons

The epibranchial tooth and anterolateral margin of P. kisangani sp. nov. from Kisangani ( Fig. 4B ) and of P. amosae sp. nov. from Lake Kivu ( Fig. 4C ) and the Malagarasi River ( Fig. 4D ; Reed & Cumberlidge 2006: pl. 5a) are similar in both species: the epibranchial tooth is a small granule that is followed by large granules lining the anterolateral margin. In contrast, the epibranchial tooth of P. lirrangensis s. str. from Liranga ( Fig. 4A ) and of P. orbitospinus from Lake Malawi ( Fig. 4E ) is pointed and as large as the other teeth lining the anterolateral margin.

The male thoracic sternal sulcus S3/4 of P. kisangani sp. nov. from Kisangani ( Fig. 8B ) and of P. orbitospinus from Lake Malawi ( Fig. 10B ) is deep, distinct, and V-shaped, whereas this sulcus is faint in P. amosae sp. nov. from Lake Kivu ( Fig. 9B ) and the Malagarasi River ( Reed & Cumberlidge 2006: pl. 5c).

The ischium of the third maxilliped of P. kisangani sp. nov. from Kisangani ( Fig. 5A ) and of P. orbitospinus from Lake Malawi ( Fig. 5C ) has a thin but distinct vertical sulcus, whereas this sulcus is faint and obscure in P. amosae sp. nov. from Lake Kivu ( Fig. 5B ) and the Malagarasi River ( Reed & Cumberlidge 2006: pl. 5c–d).

The chela dactylus (moveable finger) and fixed finger (pollex of propodus) of P. kisangani sp. nov. from Kisangani ( Fig. 6A–B ) are both elongated and slender, whereas the chela fingers in P. amosae sp. nov. from Lake Kivu ( Fig. 6C–D ) and from the Malagarasi River ( Fig. 6E–F ; Reed & Cumberlidge 2006: pl. 5a figs 46–47; NMU TRW1972.04), and in P. orbitospinus from Lake Malawi ( Fig. 6G–H ), are thick and broad.

The major chela has 3 large molars at the proximal ends of both fingers, with older specimens showing fusion of these teeth into a flat surface of the fixed finger in P. kisangani sp. nov. from Kisangani ( Figs 6A–B , 8A ) and in P. amosae sp. nov. from the Malagarasi River (CW 80.1 mm) ( Fig. 6E–F ; Reed & Cumberlidge 2006: pl. 5a figs 46–47), whereas the proximal parts of both fingers of the major chela in P. orbitospinus from Lake Malawi ( Fig. 6G–H ) has enlarged, rounded, separate (unfused) teeth.

The P5 carpus, propodus, and dactylus of P. orbitospinus from Lake Malawi ( Figs 10B , 13 ) are all elongated and slender, whereas these ambulatory leg articles in P. kisangani sp. nov. from Kisangani ( Fig. 8A–B ) and of P. amosae sp. nov. from Lake Kivu ( Fig. 9A–B ) and the Malagarasi River ( Reed & Cumberlidge 2006: pl. 5a) are all short and stocky.

The G1 TA in P. kisangani sp. nov. from Kisangani ( Fig. 11A ) and P. amosae sp. nov. from Lake Kivu ( Fig. 11B–D, F ) and the Malagarasi River ( Reed & Cumberlidge 2006: pl. 5c–d fig. 152) is only slightly widened by a low dorsal lobe and the TA ends in either a straight, or only slightly upcurved tip. This contrasts with the G1 TA in P. orbitospinus from Lake Malawi, which is conspicuously widened by a high, rounded dorsal lobe (as wide as the TA width at the TA-SA junction) and the G1 TA ends in a strongly curved upwards tip ( Fig. 12A–H ).

Figures

Fig. 1. Map showing the updated geographic distribution of Potamonautes lirrangensis (Rathbun, 1904) s. str. The black star on the left is Liranga, République du Congo (MNHN B-3826), the type locality. The black circles show the distribution of Potamonautes kisangani sp. nov. in the vicinity of Kisangani, D.R. Congo. See text for exact localities.

Fig. 4. Dorsal view of the right side of the carapace. A. Potamonautes lirrangensis s. str., holotype, adult, ♀, CW 53.6 mm, from Liranga, République du Congo (MNHN B-3826) (Capart 1954: fig. 28). B. P. kisangani sp. nov., holotype, adult, ♂, CW 60.5 mm, from Kisangani, Democratic Republic of the Congo (USNM 98944). C. P. amosae sp. nov., holotype, adult, ♂, CW 46.5 mm, from Lake Kivu, D.R. Congo (NHMUK 2018.306). D. P. amosae sp. nov., adult, ♂, CW 39.5 mm, from Kigoma District near Lake Tanganyika, Tanzania (NMU TRW 1971.05). E. P. orbitospinus (Cunnington, 1907), lectotype, adult, ♂, CW 56.9 mm, from Nkhata Bay, Lake Malawi, Malawi (NHMUK 1908.1.31.27). Scale bar: A = 8.7 mm; B = 7.9 mm; C = 6.8 mm; D = 5.7 mm; E = 7.9 mm. Photograph E by Phillip Crabb, NHMUK.

Fig. 5. Frontal view of carapace. A. Potamonautes kisangani sp. nov., holotype, adult, ♂, CW 60.5 mm, from Kisangani, Democratic Republic of the Congo (USNM 98944). B. P. amosae sp. nov., holotype, adult, ♂, CW 46.5 mm, from Lake Kivu, D.R. Congo (NHMUK 2018.306). C. P. orbitospinus (Cunnington, 1907), lectotype, adult, ♂, CW 56.9 mm, from Nkhata Bay, Lake Malawi, Malawi (NHMUK 1908.1.31.27). Scale bar: A = 8.5 mm; B = 6.3 mm; C = 7.8 mm. Photograph C by Phillip Crabb, NHMUK.

Fig. 6. Outer view of left and right chelae. A–B. Potamonautes kisangani sp. nov., holotype, adult, ♂, CW 60.5 mm, from Kisangani, Democratic Republic of the Congo (USNM 98944). C–D. P. amosae sp. nov., holotype, adult, ♂, CW 46.5 mm, from Lake Kivu, D.R. Congo (NHMUK 2018.306). E–F. P. amosae sp. nov., adult, ♀, CW 80.1 mm, from the Malagarasi River, Tanzania (NMU TRW 1971.05). G–H. P. orbitospinus (Cunnington, 1907), lectotype, adult, ♂, CW 56.9 mm, from Nkhata Bay, Lake Malawi, Malawi (NHMUK 1908.1.31.27). Scale bars: A–B = 10.9 mm; C–D = 8.9 mm; E–F = 11.0 mm; G–H = 8.9 mm. Photographs G–H by Phillip Crabb, NHMUK.

Fig. 7. Dorsal view of right cheliped carpus. A. Potamonautes lirrangensis s. str., holotype, adult, ♀, CW 53.6 mm, from Liranga, République du Congo (MNHN B-3826) (Rathbun, 1904: pl. 14, fig. 8). B. P. kisangani sp. nov., holotype, adult, ♂, CW 60.5 mm, from Kisangani, Democratic Republic of the Congo (USNM 98944). C. P. amosae sp. nov., holotype, adult, ♂, CW 46.5 mm, from Lake Kivu, D.R. Congo (NHMUK 2018.306). D. P. orbitospinus (Cunnington, 1907), lectotype, adult, ♂, CW 56.9 mm, from Nkhata Bay, Lake Malawi, Malawi (NHMUK 1908.1.31.27). Scale bar: A = 5.7 mm; B = 4.8 mm; C = 3.6 mm; D = 4.9 mm. Photograph D by Phillip Crabb, NHMUK.

Fig. 8. Potamonautes kisangani sp. nov. A. Adult, ♀, whole animal, dorsal view. B. Adult, ♂, whole animal, ventral view. Scale bar = 10 mm.

Fig. 11. A. Potamonautes kisangani sp. nov., holotype, adult, ♂, CW 60.5 mm, from Kisangani, Democratic Republic of the Congo (USNM 98944). G1, ventral view. – B–F. P. amosae sp. nov., holotype, adult, ♂, CW 46.5 mm, from Lake Kivu, D.R. Congo (NHMUK 2018.306). C, E. G1, ventral view. B, D. G1, dorsal view. F. G2, ventral view. Scale bar: A, C–D = 3.0 mm; B = 3.1 mm; E = 1.2 mm; F = 1.3 mm.

Fig. 10. Potamonautes orbitospinus (Cunnington, 1907), lectotype, adult, ♂, from Nkhata Bay, Lake Malawi, Malawi, CW 56.9 mm (NHMUK 1908.1.31.27). A. Entire animal, dorsal view. B. Entire animal, ventral view. Scale bar = 11.9 mm. Photographs by Phillip Crabb, NHMUK.

Fig. 9. Potamonautes amosae sp. nov., holotype, adult, ♂, CW 46.5 mm, from Lake Kivu, D.R. Congo (NHMUK 2018.306).A. Entire animal, dorsal view.B. Entire animal, ventral view. Scale bar = 11.3 mm.

Fig. 13. Potamonautes orbitospinus (Cunnington, 1907), living specimen from Lake Malawi, Malawi. Photograph Oliver-Mengedoht.de/Panzerwelten.de.

Fig. 12. Potamonautes orbitospinus (Cunnington, 1907). A–D. Lectotype, adult, ♂, CW 56.9 mm, from Nkhata Bay, Lake Malawi, Malawi (NHMUK 1908.1.31.27). A. G1, ventral view. B–C. G1, dorsal view. D. G2, ventral view. E–H. Adult, ♂, Cape Maclear, Lake Malawi, Malawi (AMG CAW 467A). E. G1, ventral view. F–G. G1, dorsal view. H. G2, ventral view. Scale bar: A–B, E–F = 3 mm; C, G = 1.3 mm; D, H = 1.2 mm.