Potamonautes karooensis, Daniels & Busschau & Gullacksen & Marais & Gouws & Barnes, 2023

Daniels, Savel R., Busschau, Theo, Gullacksen, Graeme, Marais, Hannes, Gouws, Gavin & Barnes, Aaron, 2023, Cryptic and widespread: a recipe for taxonomic misidentification in a freshwater crab species (Decapoda: Potamonautidae: Potamonautes sidneyi) as evident from species delimitation methods, Zoological Journal of the Linnean Society 197 (4), pp. 1005-1033 : 1019-1022

POTAMONAUTES KAROOENSIS SP. NOV.

( FIGS 2 , 4 , 5 A–C , 6A, B , 7A–D; TABLE 3)

Zoobank registration: urn: lsid: zoobank. org:act: 220C7F3B-1829-42AB-81C7-322F8464CBE2.

Holotype: Erasmuskloof farm, Eastern Cape Province, 32°16 ′ 44.0 ″ S, 24° 47 ′ 44.0 ″ E, 1326 m above sea level (a.s.l.) South Africa, SAM MB-A094477 ; one male. Collected by A. Barnes and S. R. Daniels, 2 May 2021 in a flowing stream ( Fig. 3A, B ).

Paratype: Asante Sana , Waterkloof hike, Eastern Cape Province, 32° 16 ′ 12.3 ″ S, 24° 57 ′ 25.4 ″ E, 1090 m a.s.l., South Africa, SAM MB-A094478 ; one male. Hand collected by A. Barnes and S. R. Daniels, 1 May 2021. Collected in a forested stream under rocks

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Additional material examined: Asante Sana , Waterkloof hike, 32° 16 ′ 12.3 ″ S, 24° 57 ′ 25.4 ″ E, 1090 m a.s.l., Eastern Cape Province, South Africa, SAM MB-A094479 ; four males and two females. Collected by A. Barnes and S. R. Daniels, 1 May 2021 in a flowing stream along the mountain side. Langfontein farm, 32° 11 ′ 8.12 ″ S, 24° 09 ′ 9.05 ″ E, 976m a.s.l., Eastern Cape Province, South Africa, SAM MB-A094480 ; four females. Collected by A. Barnes and S. R. Daniels, 2 May 2021. Hand collected in a flowing stream under boulders. Ouberg Pass, 32° 04 ′ 0.93 ″ S, 24° 21 ′ 4.20 ″ E, 1178 m a.s.l., Eastern Cape Province, South Africa, SAM MB-A094481 , four females. Collected by A. Barnes and S. R. Daniels, 4 May 2021. Hand collected in stagnant water under a bridge.

Diagnosis: Carapace very flat ( CH /CL = 0.43) ( Table 3 ); postfrontal crest well-defined, complete, lateral ends meeting anterolateral margins; epigastric crests faint, median sulcus between crests short, not forked posteriorly; exorbital, epibranchial teeth reduced to granules; anterolateral carapace margin with small epibranchial tooth ( Fig. 5A–C ). Third maxilliped: ischium with distinct vertical sulcus; s3/s4 complete, V-shaped, deep, midpoint almost meeting anterior margin of sternopleonal cavity; margins of s4 low, not raised ( Fig. 5B ). Cheliped: dactylus (moveable finger) slim, highly arched, enclosing oval interspace, with three larger teeth interspersed by smaller teeth along length; propodus (fixed finger) with four larger teeth interspersed by smaller teeth along length ( Fig. 6A, B ); carpus inner margin distal tooth large, pointed, proximal tooth reduced to granules; medial inferior margin of merus lined with series of small granules terminating distally at small, low distal meral tooth, lateral inferior margin smooth. G1 terminal article: one-third length of subterminal segment; first-third straight in line with longitudinal axis of subterminal segment, middle part directed outward at 45°, widened by raised rounded ventral lobe, tip curving sharply upward ( Fig. 6A, B ).

Description: Based on male holotype (holotype CWW 63.95 mm, Table 3 ). Carapace with small distinct tooth on the anterolateral margins; widest anteriorly, narrowest posteriorly (CWP/CL 0.50); flattened (CH/ CL 0.43) ( Fig. 5C ); front broad, one-third CWW (FW/ CWW 0.35); urogastric, cardiac grooves distinct, other grooves faint or missing; postfrontal crest complete, anterolateral margin posterior to epibranchial tooth granulated, meeting epibranchial teeth; epigastric crests faint, median sulcus between crests short, forked posteriorly; exorbital, epibranchial teeth each reduced to granule; anterolateral margin between exorbital, epibranchial teeth faintly granulated, curving slightly outward, lacking intermediate tooth ( Fig. 5A–C ); branchiostegal wall vertical, sulcus faint, meeting longitudinal sulcus, dividing branchiostegal wall into three parts, suborbital, dorsal pterygostomial regions granulated, hepatic region smooth; suborbital margin faintly granulated. Third maxilliped: filling entire buccal frame, except for respiratory openings; exopod with long flagellum, ischium with faint vertical groove ( Fig. 7D ). Epistomial tooth large, triangular, margins lined by large granules. Mandible: palp two-segmented; terminal segment simple; tuft of setae at junction between segments. Sternum: s1, s2 fused; s2/s3 deep, completely crossing sternum; s3/s4 complete, V-shaped, deep, midpoint almost meeting anterior margin of sternopleonal cavity; margins of s4 low, not raised. Cheliped: dactylus (moveable finger) slim, arched, enclosing oval interspace, with three larger teeth interspersed by smaller teeth along length; propodus (fixed finger) with four larger teeth interspersed by smaller teeth along length ( Fig. 6A, B ); carpus distal tooth large, pointed, proximal tooth small but distinct, followed by granule; both inferior margins of merus lined by series of small granules, distal meral tooth small, pointed. Pereopods: walking legs slender, pereopod 3 longest, pereopod 5 shortest; dorsal margins of pereopods with fine sharp bristles, dactyli of walking legs ending in sharp point, with rows of spine-like bristles along segment. Pleon: outline broadly triangular with straight margins. G1 terminal article: short (one-third length of subterminal segment), curving away from midline, first-third straight in line with longitudinal axis of subterminal segment, middle part directed outward at 45°, widened by low raised rounded ventral lobe, tip curving gently upward. G1 subterminal segment broad at base, tapering to slim junction with terminal article distally where these two parts have same width, ventral side of segment with heavily setose margins; with setae-fringed flap covering lateral half of segment; dorsal side of segment smooth, no flap, with broad membrane on the dorsal side of suture marking junction between terminal, subterminal parts ( Fig. 7A, B ). G2: terminal article long, flagellum-like, 0.5 times length of subterminal segment ( Fig. 7C ).

Molecular diagnosis: 16S rRNA GenBank accession numbers: O L 6 8 5 3 9 5 –O L 6 8 5 3 9 8, O L 6 8 5 4 0 1– OL685411, OL685504. COI GenBank accession numbers: OL660552–OL660566, OL660588.

Distribution: Known from the Great Karoo Basin around the town of Graaff-Reinet, Eastern Cape Province, South Africa.

Remarks: Morphologically, Potamonautes karooensis , is most likely to be confused with P. sidneyi , P. barbarai , P. barnardai , P. granularis and P. perlatus . Geographically, P. karooensis is confined to the Great Karoo Basin, Eastern Cape Province, South Africa where it is present in small, temporary, high-lying mountain streams (Supporting Information, Fig. S3A ). Potamonautes karooensis , is brown-coloured with orangetipped chelipeds (Supporting Information, Fig. S3B ). Potamonautes perlatus is also a large riverine species that is flat ( CH /CL = 0.69) and wide (CWW = 60.5 mm) ( Phiri & Daniels, 2014). The species occurs along the interior and coastal margins of the Western Cape Province where it is common in large rivers and streams at low altitude, such as the Berg, Bot, Eerste, Olifants and Doring rivers ( Phiri & Daniels, 2014). Potamonautes granularis is present only in the lower Olifants River, Western Cape and is a large-bodied riverine species, with a granulated anterolateral carapace margins and orange-tipped chelipeds ( Daniels et al., 1998). In addition, two additional large-bodied riverine species are present in the Western Cape extending into the Eastern Cape provinces, South Africa. Potamonautes barbarai is present in the Gamtoos and Gourits river systems (in the Western and Eastern Cape provinces), the species is large (CWW = 63 mm) and has a swollen carapace ( CH / CL = 0.58), while P. barnardai is present in the Breede River system, and is large-bodied (CWW = 54.6 mm) and flat ( CH /CL = 0.61). Potamonautes sidneyi s.s. occurs in rivers, streams and wetlands in southern KwaZulu-Natal, Gauteng, Mpumalanga, Limpopo and the Northern Cape provinces of South Africa into Mozambique. The latter species is flat ( CH / CL = 0.54) and wide (CWW = 52.4 mm) ( Peer et al., 2017). Geographically, the other large-bodied riverine species that P. karooensis occurs in close geographic proximity to is P. danielsi , despite being phylogenetically distantly related. Potamonautes danielsi is confined to the coastal forest rivers and streams in the Eastern Cape and southern KwaZulu-Natal provinces (Daniels et al., 2022). Potamonautes danielsi is smaller-bodied (CWW = 25.8 mm) and flat ( CH /CL = 0.49). Four described small-bodied, mountain-stream living crabs with highly arched dactyli are present in first and second order streams along the Cape Fold Mountains; these include P. parƲicorpus (Cape Peninsula and Table Mountain, Jonkershoek, Helderberg Mountains), P. parƲispina (Cederberg Mountains) , P. brincki (Hottentots Holland Mountains), P. tuerkayi (Overberg Mountains) , while an undescribed mountain-stream potamonautid crab is known from Hogback (N. Peer, pers. comm.).

Etymology: Named after the Great Karoo Basin of South Africa. A semi-desert region in the interior of South Africa.

Figures

Figure 2. Maximum likelihood phylogenetic tree topology derived from the combined 16S rRNA + COI sequence data, demonstrating the evolutionary relationships within the P. sidneyi s.l. species complex. Statistical support for nodes is provided as posterior probability values above nodes (> 0.95 PP) and bootstrap values below nodes (> 75%). An * or # denotes nodal relationships that were not supported (<0.95 PP/ <75%). Potamonautes sidneyi s.s. (clade 3) localities are marked with a dark blue triangle, while P.danielsi (clade 5) localities are marked by an orange square. The two new species, P. karooensis, (clade 2) and P.Ʋalles (clade 4), are marked by a light-blue circle and a green diamond, respectively. Specimens of P. barbarai are confined to clade 1.

Figure 3. Ultrametric BEAST tree phylogeny of the COI sequence data for the four Afrotropical genera: A, Potamonautes; B, Liberonautes; C, Nesonautes; D,

Figure 4. BEAST chronogram of the three concatenated mtDNA loci (16S rRNA, 12S rRNA + COI) dataset for all the described southern African Potamonautes species. Node bars show 95% highest posterior distributions for each divergence date estimate. The terminal labelled P. sp. nov., represents a yet undescribed species from Hogsback. Posterior probability values> 0.95 (PP) together with bootstrap values> 75% are shown above and below branches, respectively.

Figure 5. Potamonautes karooensis sp. nov., male holotype (CL = 47.48 mm) (SAM-MB A094477) Erasmuskloof, EasternCape Province, SouthAfrica.A,whole animal dorsal aspect; B, whole animal ventral aspect; C, cephalothorax, frontal aspect. Scale bar represents 10 mm.

Figure 6. Potamonautes karooensis sp. nov., male holotype (SAM-MB A094477) A, major right cheliped; B, minor left cheliped. Scale bar represents 10 mm.

Figure 7. Potamonautes karooensis sp. nov., male holotype (SAM-MB A094477) A, left gonopod 1, anterior view; B, left gonopod 1 posterior view; C, left gonopod 2 anterior view; D, right third maxilliped. Scale bar represents 10 mm.