Longipotamonautes bolobo Cumberlidge & Krajenka 2023, n. sp.
Creators: name: Cumberlidge, Neil
name: Krajenka, Grace E.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Potamonautidae
Longipotamonautes
Longipotamonautes bolobo

description: Longipotamonautes bolobo n. sp.
(Figs. 1–3, 7)
Holotype. RMCA _ CRUST _50940, adult male (CW 38.8, CL 27.8, CH 13.4, FW 13.2 mm; length of propodus of major chela = 41.7 mm); Democratic Republic of the Congo, Bulobo (= Bolobo) (2.168828°S, 16.225909°E), 1959, coll. N. Kele.
Diagnosis. Carapace surface smooth, widest in anterior third (CW/FW = 2.9), medium height (CH /FW 1.01) (Fig. 1B), semi-circular, urogastric, cardiac, transverse branchial grooves, posterior grooves deep; cervical grooves short, faint (Fig. 1A); frontal width about 1/3 carapace width (FW/CW = 0.34); frontal margin straight (Fig. 1A, B); exorbital tooth small, pointed, directed forward; epibranchial tooth reduced to granule; postfrontal crest sharply defined, complete, traversing entire carapace; straight part consisting of fused epigastric, postorbital crests; meeting carapace lateral margins at epibranchial teeth; carapace lateral margin posterior to epibranchial tooth smooth (Fig. 1A, B). Branchiostegite with longitudinal (epimeral), vertical sutures, dividing carapace sidewall into suborbital, subhepatic, pterygostomial regions, each with smooth surface (Fig. 1B); pterygostomial region divided into two parts by additional sulcus continuous with vertical sulcus reaching down to third maxilliped basis (Fig. 1B). S3/4 complete, deep, U-shaped, middle meeting anterior margin of sternopleonal cavity; outer margins of S4 low, not raised (Fig. 1B). Third maxilliped ischium smooth, vertical sulcus very faint (Fig. 1B). Major cheliped propodus elongated, inferior margin length (41.7 mm) greater than CW (38.8 mm). Movable finger (dactylus) of right chela slim, distinctly arched, enclosing broad oval interspace when closed; dactylus with two large rounded teeth proximally with two small teeth in between, distal half with small even-sized teeth; fixed finger (pollex of propodus) of right chela with two very large rounded teeth proximally, distal half with small even-sized teeth (Fig. 2B, C). Distal tooth on cheliped carpus inner margin large, slim, pointed, proximal tooth reduced to granule, followed by series of granules along margin (Fig. 2F). Cheliped merus lower margins both completely smooth, distal meral tooth obscure (Fig. 2D). Telson bell-shaped with deeply indented side margins, apex rounded. G1 TA short (G1 TA/SA = 0.33), basal half angled slightly outward at 50 ° to longitudinal axis of G1 SA, distal 1/3 curved upwards, tapering to pointed tip; G1 TA slim, not widened in midsection (Fig. 3A, B); longitudinal groove of G1 TA visible along proximal 2/3. G2 TA long, flagellum-like (G2 TA/SA = 0.5) (Fig. 3C).
Description. Male holotype. Carapace with moderate width (CW/FW = 2.9), length (CL/ FW 2.1), height (CH / FW = 1.01); carapace surface smooth, semi-circular, urogastric, cardiac, transverse branchial grooves, posterior grooves deep; cervical grooves short, faint (Fig. 1A). Front width about 1/3 carapace width (FW/CW = 0.34); frontal margin straight (Fig. 1A, B); exorbital tooth small, pointed, directed forward; epibranchial tooth reduced to granule; epigastric crests low, separated by clear, short, forked mid-groove; postfrontal crest sharply defined, complete, traversing entire carapace; straight part consisting of fused epigastric, postorbital crests; meeting carapace lateral margins at epibranchial teeth; carapace lateral margin posterior to epibranchial tooth smooth (Fig. 1A, B). Branchiostegite with longitudinal (epimeral), vertical sulci, dividing carapace sidewall into suborbital, subhepatic, pterygostomial regions, each with smooth surface (Fig. 1B), pterygostomial region divided into two parts by additional sulcus continuous with vertical sulcus reaching down to third maxilliped basis (Fig. 1B).
Mandibular palp consisting of basis followed by 2 articles; terminal article simple.
Third maxillipeds filling entire oral field, except for transversely oval efferent respiratory openings. Ischium smooth, vertical sulcus very faint (Fig. 1B). Exopod with long flagellum, ischium vertical sulcus faint (Fig. 1B).
Thoracic sternal sutures S1/2, S2/3 deep, completely traversing sternum; S3/4 complete, deep, U-shaped, middle meeting anterior margin of sternopleonal cavity; outer margins of S4 low, not raised (Fig. 1B); episternal sulci S4/E4, S5/E5, S6/ E6, S7/E7 each distinct.
Chelipeds unequal, right (major) longer, higher than left (minor) (Fig. 2B, C). Major chela propodus inferior margin length (41.7 mm) greater than CW (38.8 mm). Movable finger (dactylus) of right chela slim, distinctly arched, tips touching when closed, enclosing broad oval interspace; propodus palm swollen. Dactylus proximal half with two large, rounded teeth, two small teeth in between, distal half with small even-sized teeth; fixed finger (pollex of propodus) of right chela with two very large, rounded teeth proximally, distal half with small even-sized teeth (Fig. 2B, C). Distal tooth on cheliped carpus inner margin large, slim, pointed, proximal tooth reduced to granule followed by series of granules along margin (Fig. 2F). Cheliped merus lower margins both completely smooth, distal meral tooth obscure (Fig. 2D).
Ambulatory legs (P2–5) slender, P5 shortest; dactyli P2–5 tapering to point, each bearing rows of downwardpointing sharp bristles (Fig. 1A).
Male pleon, telson together forming triangle with convex margins, broadest at base; telson bell-shaped with deeply indented side margins, apex rounded; pleomeres PL1–6 rectangular, wider than long, PL 6 longest, more than 1/2 as long as wide (Fig. 1B); remaining pleomeres short, more than 1/4 as long as wide. G1 TA short (G1 TA/SA = 0.33), basal half angled outward at 50 ° to longitudinal axis of G1 SA, distal 1/3 curved upwards, tapering to pointed tip; G1 TA slim, not widened in midsection (Fig. 3A, B); longitudinal groove of G1 TA visible along proximal 2/3. G1 SA widest at base, narrowest at G1 TA/SA junction; G1 SA ventral side mesial margins with tuft of conspicuous long setae; lateral margin with short sparse setae; G1 SA ventral side with broad setae-lined fold partly covering SA basally, completely covering SA at TA-SA junction; G1 SA dorsal side with broad dorsal membrane at TA-SA junction. G2 SA widest at base, tapering sharply inward about 1/3 along length, distal 2/3s forming long, thin, tapering, upright process supporting long, flagellum-like G2 TA (G2 TA/SA = 0.33) (Fig. 3C). Medium-sized species, adult at CW 38.8 mm.
Colour. The colour of living specimens is unknown, but the specimen preserved in ethanol is light brown.
Type locality. Democratic Republic of the Congo, Bolobo (= Bulobo), on the Congo River in Mai-Ndombe Province (2.168828°S, 16.225909°E), 281.33 m ASL (Fig. 7).
Etymology. The species is named for Bolobo, which is a town on the Congo River in Mai-Ndombe Province in the western part of the D. R. Congo where it was collected. The species epithet is used as a noun in apposition.
. Distribution. Longipotamonautes bolobo n. sp. is known only from just one locality on the Congo River (2.168828°S, 16.225909°E) 281.3 m ASL, in Mai-Ndombe Province in the D. R. Congo (Fig. 7).
Habitat. Bolobo lies in the Kasai Ecoregion (FEOW 546) in the catchment of the Kasai River, which occupies a vast area (900,000 km 2) within southwestern D. R. Congo and the northeast corner of Angola. The type locality is in the low-lying central Congo basin (the Cuvette Centrale).
Conservation status. Very little information is available on the distributional range, population size and trends, or habitat of L. bolobo n. sp. which is considered here as Data Deficient until more field data can be collected.
Remarks. The genus Longipotamonautes (Bott, 1955) currently comprises nine species from the D. R. Congo, the Republic of the Congo, Gabon, Cameroon, and Nigeria (Cumberlidge & Daniels 2022). Longipotamonautes bolobo n. sp. is assigned to this genus because it conforms to the diagnosis provided by Cumberlidge & Daniels (2022: 1291). For example, L. bolobo n. sp. has a third maxilliped whose ischium is smooth and lacks a distinct vertical sulcus; the G1 TA is medium long (G1 TA length 0.33 × G1 SA length) and slim, with low medial and low lateral folds and a blunt (not pointed) tip (Fig. 1A, B); the telson is bell-shaped with indented lateral margins; the pleon is broadly triangular, with subequal sides and base; the lower margin of the major chela propodus is longer than the carapace width; and the major chela dactylus is slim and highly arched (Fig. 1D–F).
Longipotamonautes bolobo n. sp. is closest to L. acristatus (Bott, 1995) and L. adentatus (Bott, 1955) in that the epibranchial tooth is reduced to a granule, the carapace lateral margins are smooth (Fig. 1A), and the adult male major cheliped is longer than the CW in all three species (Fig. 2A). In addition, the holotype of L. acristatus (as Potamonautes (Longipotamonautes) ballayi acristatus (RMCA_CRUST_32018)) was also collected from Bolobo, D. R. Congo (Bott 1955). Longipotamonautes bolobo n. sp. can be distinguished from L. acristatus and L. adentatus by the exorbital tooth, which is distinct and pointed in L. bolobo n. sp. (Fig. 1A) (vs a low or absent exorbital tooth in L. acristatus (Bott 1955: pl. VIII, fig. 2a; fig. 75) and L. adentatus (Bott 1955: pl. VIII, fig. 1a; fig. 74)), and by the dentition on the major chela, where the movable and fixed fingers each have two large teeth spaced apart on the cutting edges in L. bolobo n. sp. (Fig. 2A) (vs a major chela whose movable and fixed fingers lack teeth in L. acristatus (Bott 1955: pl. VIII, fig. 2a; fig. 75) and L. adentatus (Bott 1955: pl. VIII, fig. 1a; fig. 74)). In addition, the size at maturity is different in these species: L. bolobo n. sp. is adult at CW 38.8 mm, whereas both L. acristatus and L. adentatus are adult at CW 29 mm. Longipotamonautes bolobo n. sp. can be further distinguished from L. adentatus by the strong distinct postfrontal crest (vs a weak and poorly defined postfrontal crest in L. adentatus).
Longipotamonautes bolobo n. sp. can be distinguished from the seven other species in this genus as follows. The epibranchial tooth is lacking and the carapace lateral margin is smooth and lacks teeth in L. bolobo n. sp. (Fig. 1A) (vs a large pointed epibranchial tooth and a carapace lateral margin that has two teeth behind the epibranchial tooth in L. nheenae Cumberlidge, 2017 from Gabon (Cumberlidge 2017: fig. 1A, 4B), a large pointed epibranchial tooth and a carapace lateral margin that has three teeth behind the epibranchial tooth in L. paecilei (A. Milne-Edwards, 1886) from the D. R. Congo (Bott 1955; Cumberlidge 2017); a large pointed epibranchial tooth and a carapace lateral margin that has one tooth behind the epibranchial tooth in both L. schubotzi (Balss, 1936) from the D. R. Congo and L. reidi (Cumberlidge, 1999) from Nigeria and Cameroon (Bott 1955; Cumberlidge 1999: 15 D, 2017); and a large pointed epibranchial tooth and a carapace lateral margin that is smooth and lacks teeth behind the epibranchial tooth in L. ballayi (A. Milne-Edwards, 1886)).
Longipotamonautes bolobo n. sp. can be distinguished from L. punctatus (Bott, 1955) by the lack of a proximal tooth on the cheliped carpus inner margin (Fig. 2F) (vs a small acute proximal tooth on the cheliped carpus inner margin in L. punctatus (Bott 1955: fig. 72). Finally, L. bolobo n. sp. can be distinguished from L. semilunaris (Bott, 1955) by the deep S3/4 that completely traverses the sternum and meets the anterior margin of the sternopleonal cavity, and by the outer margins of S4 that are low and not raised (Fig. 1B) (vs an incomplete S3/4 that is deep only at the margins and faint in the middle and does not meet the anterior margin of the sternopleonal cavity, and outer margins of S4 that are raised in L. semilunaris (Bott 1955: pl. XXIV fig. 2b)).
description: Published as part of Cumberlidge, Neil & Krajenka, Grace E., 2023, Description of two new species of Central African freshwater crabs from the Democratic Republic of the Congo and Rwanda (Brachyura: Potamoidea: Potamonautidae), pp. 379-391 in Zootaxa 5293 (2) on pages 380-385, DOI: 10.11646/zootaxa.5293.2.11, http://zenodo.org/record/7959937