Potamonautes adeleae Bott, 1968

Cumberlidge, Neil, Ahles, Katelyn M. & Daniels, Savel R., 2021, Redescriptions of three species of freshwater crabs from Angola, southern Africa (Brachyura: Potamoidea: Potamonautidae), Zootaxa 5032 (4), pp. 516-532 : 517-518

Potamonautes adeleae Bott, 1968

Adele’s Freshwater Crab

( Figs. 1 , 4A , 5A, B, G, H , 6A, D , 7A , 8 )

Potamonautes (Lirrangopotamonautes) lirrangensis adeleae Bott, 1968: 168–169 , pl. I, figs. 1–4.

Potamonautes adeleae, Cumberlidge & Tavares 2006: 248–249 , 254–256, table 1; Cumberlidge 2008a: 1–7, fig. 1; Ng et al. 2008: 170.

Holotype. SMF 4444 . Adult male (CW 60, CL 45, CH 23, FW 17 mm), Angola, Province of Lunda Norte, Cuango River , Cafunfo (-8.808363, 17.97665), collector and date unrecorded.

Paratypes. SMF 4444 . Adult male (CW 55.3, CL 41.1, CH 17.8, FW 15.7 mm), Angola, Province of Lunda Norte, Cuango River , Cafunfo (-8.808363, 17.97665), collector and date unrecorded. Bott (1968) described this taxon from 38 specimens all from the same locality, and designated the remainder of these specimens (28 males and 9 females) as paratypes .

Rediagnosis. Carapace surface mostly smooth except for distinct fields of carinae at anterolateral corners; postfrontal crest distinct, complete, traversing entire carapace to meet anterolateral margins at epibranchial teeth; cervical grooves deep, long, ending just before reaching postfrontal crest; semicircular, urogastric, cardiac, branchial grooves all deep, distinct ( Fig. 1A ). Exorbital tooth large, pointed, directed forward, outer margin lined by small granules; epibranchial tooth small, low, blunt; anterolateral margin lined by rounded denticles; postfrontal crest, suborbital margin, vertical sulcus on branchiostegite, all granulated ( Figs. 1A, B ). Thoracic sternal suture S3/4 incomplete, separated centrally, comprising 2 shortened sutures that begin at sides of sternum, fade towards middle ( Fig. 1B ). Third maxilliped exopod with long flagellum, ischium with distinct vertical sulcus ( Fig. 1B ). Cheliped carpus inner margin with 2 large pointed teeth, distal tooth larger than proximal tooth ( Fig. 5H ). Cheliped merus lower margin with conspicuous large pointed distal meral tooth ( Fig. 5G ). G1 TA long ( TA /SS 0.54), midpoint angled outward at 64° to longitudinal axis of G1 SS, distal third tapering to pointed, slightly upcurved tip; G1 TA midsection widened by high mesial fold, lateral fold lower; deep longitudinal groove running along whole length of G1 TA between mesial, lateral folds ( Figs. 6A, D ). G2 TA long, flagellum-like (G2 TA / SA 0.65) ( Fig. 7A ). Large species, mature at CW 55 mm.

Redescription: Carapace moderate height ( CH /FW 1.13), width (CW/FW 3.5), length (CL/ FW 2.62). Surface of anterior carapace mostly smooth except for distinct fields of carinae at anterolateral corners; postfrontal crest distinct, complete, traversing entire carapace to meet anterolateral margins at epibranchial teeth; cervical grooves deep, long, ending just before postfrontal crest; semicircular, urogastric, cardiac, branchial grooves all deep, distinct; postfrontal crest, suborbital margin, vertical sulcus on branchiostegite, all granulated; epigastric crests separated by clear, short, forked mid-groove ( Fig. 1A ). Exorbital tooth large, pointed, directed forward, outer margin granulated; epibranchial tooth small, low, blunt; anterolateral margin between exorbital, epibranchial teeth granulated, curving slightly outward, lacking intermediate tooth; anterolateral margin posterior to epibranchial tooth raised, lined by rounded denticles, posterior end curving inward, not continuous with posterolateral margin. Branchiostegite with distinct granulated vertical sulcus, subhepatic region heavily granulated, suborbital, pterygostomial regions smooth ( Figs. 1A, B , 4A ). Third maxilliped exopod with long flagellum, ischium with deep vertical sulcus ( Fig. 1A ). Thoracic sternal sulcus S2/3 deep, completely traversing sternum; S3/4 incomplete, deep at sides, absent in middle, sides slanted inward toward anterior margin of sternopleonal cavity; thoracic episternal sulci S4/E4, S5/E5, S6/ E6, S7/E7 all obscure ( Fig. 1B ).

Male pleon, telson together forming slim triangle, pleon edges slightly indented; telson triangular, apex round- ed, base broadest, sides outwardly sloping; pleomeres PL1–6 rectangular, wider than long, PL 6 longest, more than 1/2 as long as wide ( Fig. 1B ); remaining pleomeres short, less than 1/3 as long as wide. G1 TA long (TA/SA 0.54), midpoint angled outward at 64° to longitudinal axis of G1 SA, distal 1/3 tapering to pointed, slightly upcurved tip; G1 TA midsection widened by high mesial fold, lateral fold lower; deep longitudinal groove running along whole length of G1 TA between mesial, lateral folds ( Figs. 6A, D ); G1 SA distal dorsal side with conspicuous dorsal membrane widest at mesial margin, narrowest at lateral margin ( Fig. 5D ). G2 TA long (G2 TA/SA 0.65), flagellum-like ( Fig. 7A ). Adult size ranging from CW 55 to 60 mm.

Chela unequal, right (major) longer than left (minor) ( Fig. 5A ). Fixed finger (pollex) of propodus, movable finger (dactylus) each with 2 to 3 large teeth interspersed with smaller teeth; dactylus straight, slim, not arched, tips of fingers touching enclosing long thin interspace when closed ( Figs. 5A, B ); propodi of right, left chelae elongated (inferior margin 55.1 mm, 50.3 mm respectively), almost as long as CW (55.3 mm); palms of right, left chelae not enlarged (height 18.2 mm, 15.5 mm respectively). Cheliped carpus inner margin with large pointed distal tooth, smaller pointed proximal tooth ( Fig. 5H ); cheliped merus lower margins both lined by large granules; distal meral tooth large, pointed; superior surface of cheliped merus granulated ( Fig. 5G ). P2–5 slender, long. For additional characters and photographs of this species see Bott (1968: pl. 1, figs. 1–4).

Size. Large species, adult at CW 55.0 mm.

Type locality. Angola. Province of Lunda Norte, Cuango River, Cafunfo (-8.808363, 17.97665) ( Fig. 8 ) .

Habitat. Potamonautes adeleae is a large species that is endemic to Angola. It is known only from a single locality in the forested Lunda Norte Province. It was collected from the Cuango River, a northward-flowing tributary of the Congo River which is part of the central African region ( Fig. 8 ).

Colour. The colour of living specimens is unknown, but specimens preserved in ethanol are light brown.

Distribution. This species is only known from a single locality in Angola in the Province of Lunda Norte, Cuango River, Cafunfo (-8.808363, 17.97665) ( Fig. 8 ).

Conservation status. Potamonautes adeleae was listed in the IUCN Red List of Threatened Species as Data Deficient ( Cumberlidge 2008a) because it is known to occur in just one locality and there is very little information available on its population trends, habitat, or threats. This makes it a rare species of high research interest. The diamond mines at Cafunfo have resulted in a great deal of habitat disturbance and pollution of the Cuango River, that may prove to be threats to this species.

Remarks. Bott (1968) described P. adeleae as a subspecies of P. lirrangensis ( Rathbun, 1904) from Liranga, Republique du Congo, in the middle Congo basin but Cumberlidge & Tavares (2006), Cumberlidge (2008c), and Ng et al. (2008) recognised P. adeleae as a valid species. Cumberlidge & Tavares (2006) cited morphological differences between the adult male paratype of P. adeleae from Angola and the dried adult female type of Potamon (Potamonautes) lirrangensis Rathbun, 1904 (CW 53.9 mm) which was photographed by Rathbun (1904: pl. XIV, fig. 8), and illustrated by Capart (1954: fig. 28). Potamon (Potamonautes) lirrangensis was recently redescribed by Cumberlidge et al. (2021: figs. 1, 4A, 7A) as Potamonautes lirrangensis s.s. who restricted that species to the type specimen from Liranga, Republique du Congo, in the middle Congo basin. Unfortunately, the fact that the female holotype of this species is poorly preserved excludes most of the taxonomic characters that are useful to distinguish between species. Despite this, differences in the anterolateral margin of P. adeleae ( Fig. 1A, B ) and P. lirrangenis s.s. (cf. Cumberlidge et al., 2021: fig. 4A) can be used to separate these two taxa. Potamonautes adeleae shares a number of characters (e.g., a complete postfrontal crest, a reduced epibranchial tooth, a granulated anterolateral margin, and the general form of the G1 TA) with species from the middle Congo River basin (such as P. dybowskii ( Rathbun, 1904)) , and the affinities of this Angolan species lie with the Congo basin fauna rather than with the southern African regional fauna.

Figures

FIGURE 1. Potamonautes adeleae Bott, 1968, paratype, adult ♂ CW 55.3 mm, from Lunda Norte Province, Angola (SMF 4444). Whole animal, dorsal view (A), whole animal, ventral view (B). Scale bars: A = 10.17 mm, B = 10 mm.

FIGURE 4. Frontal view of carapace. (A) Potamonautes adeleae Bott, 1968, paratype, adult ♂ CW 55.3 mm, from Lunda Norte Province, Angola (SMF 4444); (B) Potamonautes kensleyi Cumberlidge & Tavares, 2006, adult male CW 35.4 mm, from the Cuanza River, Soxujwa, Kekere, Malanje Province, Angola (AMG GEN 1887A); (C) Potamonautes macrobrachii Bott, 1953, paratype, adult ♂ CW 32.9 mm, from Huamba Province, Angola (SMF 1892). Photograph B by Theo Busschau, University of Stellenbosch, South Africa. Scale bar: A = 10.4 mm; B = 5.7 mm; C = 4.7 mm.

FIGURE 5. (A–F) Frontal view of right and left chela; (G–L) cheliped merus and carpus. (A, B) Potamonautes adeleae Bott, 1968, paratype, adult ♂ CW 55.3 mm, from Lunda Norte Province, Angola (SMF 4444); (C, D) Potamonautes kensleyi Cumberlidge & Tavares, 2006, adult male CW 35.4 mm, from the Cuanza River, Soxujwa, Kekere, Malanje Province, Angola (AMG GEN 1887A); (E, F) Potamonautes macrobrachii Bott, 1953, holotype, adult ♂ CW 32.9 mm, from Huamba Province, Angola (SMF 1892); (G, H) Potamonautes adeleae Bott, 1968, paratype, adult ♂ CW 55.3 mm, from Lunda Norte Province, Angola (SMF 4444); (G) ventral view of right chela merus; (H) dorsal view of right chela carpus and merus; (I, J) Potamonautes kensleyi Cumberlidge & Tavares, 2006, adult male CW 35.4 mm, from the Cuanza River, Soxujwa, Kekere, Malanje Province,Angola (AMG GEN 1887A) (I) ventral view of right chela merus; (J) dorsal view of right chela merus and carpus; (K, L) Potamonautes macrobrachii Bott, 1953, holotype, adult ♂ CW 32.9 mm, from Huamba Province, Angola (SMF 1892): (K) ventral view of right chela merus; (L) dorsal view of right chela merus and carpus;. Photographs C, D, I, J by Theo Busschau, University of Stellenbosch, South Africa. Scale bar: A = 18.4 mm; B = 17.9 mm; C, D = 8.9 mm; E = 8.33 mm; F = 5.81 mm; G = 17.9 mm; H = 7.3 mm; I = 8.9 mm; J = 5.9 mm; K = 5.81 mm; L = 5.6 mm.

FIGURE 6. Right G1, ventral view (A–C) and dorsal view (D, F). (A, D) Potamonautes adeleae Bott, 1968, paratype, adult ♂ CW 55.3 mm, from Lunda Norte Province, Angola (SMF 4444); (B, E) Potamonautes kensleyi Cumberlidge & Tavares, 2006, adult male CW 35.4 mm, from the Cuanza River, Soxujwa, Kekere, Malanje Province, Angola (AMG GEN 1887A); (C, F) Potamonautes macrobrachii Bott, 1953, holotype, adult ♂ CW 32.9 mm, from Huamba Province, Angola (SMF 1892). Photo- graphs B and E by Theo Busschau, University of Stellenbosch, South Africa. Scale bar: A= 6.7 mm; B = 2.3 mm; C = 1.13 mm; D = 2.7 mm; E = 2.3 mm; F = 1.2.

FIGURE 7. Right G2 ventral view (A–C); (A) Potamonautes adeleae Bott, 1968, paratype, adult ♂ CW 55.3 mm, from Lunda Norte Province, Angola (SMF 4444); (B) Potamonautes kensleyi Cumberlidge & Tavares, 2006, adult male CW 35.4 mm, from the Cuanza River, Soxujwa, Kekere, Malanje Province, Angola (AMG GEN 1887A); (C) Potamonautes macrobrachii Bott, 1953, holotype, adult ♂ CW 32.9 mm, from Huamba Province, Angola (SMF 1892). Photograph C by Theo Busschau, University of Stellenbosch, South Africa. Scale bar: A = 5.6 mm; B = 2.3 mm; C = 1.2 mm.

FIGURE 8. Map of the Angola showing the known localities of Potamonautes adeleae (black square, not shown to scale), P. kensleyi (black circles, not shown to scale), and P. macrobrachii (black diamond, not shown to scale). Scale bar = 520 km. See text for exact locality coordinates.