identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
03FB87DFD14DDA082ABCFF535EB75368.text	03FB87DFD14DDA082ABCFF535EB75368.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Arcopotamonautes johnstoni (Miers 1885)	<div><p>Arcopotamonautes johnstoni (Miers, 1885)</p><p>(Figs. 1, 3A, 4A–C, 5A–D, 6A, C, E, 7A–F, 8A, B, E, 9A–C, G, 10A, B, E–G)</p><p>Thelphusa depressa var. johnstoni Miers, 1885: 237–239 .</p><p>Telphusa hilgendorfi Pfeffer, 1889: 32 .</p><p>Potamon (Potamonautes) ambiguus Rathbun, 1904: pl. 14, fig. 7.— Rathbun 1905: 171.</p><p>Potamon (Potamonautes) mrogoroensis — Rathbun 1905: 173 (not Hilgendorf 1898).</p><p>Potamon (Potamonautes) Johnstoni — Rathbun 1905: 170 .</p><p>Potamonautes johnstoni — Balss 1929: 343–344.—Balss 1936: 180–182, fig. 17.— Cumberlidge 1997: 580–581.— Cumberlidge 1998: 200.</p><p>Potamonautes johnstoni f. typical — Pesta 1937: 157.</p><p>Potamon johnstoni — Chace 1942: 214.</p><p>Potamon (Potamonautes) hilgendorfi — Rathbun 1933: 256.—Rathbun 1935: 6.— Chace 1942: 186.</p><p>Potamonautes (Lirrangopotamonautes) johnstoni johnstoni — Bott 1955: 265–267, pl. XV, fig. 2a–d, fig. 36a, b.</p><p>Arcopotamonautes johnstoni — Cumberlidge &amp; Daniels 2022: 1274, 1294, 1295.</p><p>Type material examined. Thelphusa depressa var. johnstoni Miers, 1885: Holotype: NHM 1885.2, subadult male (CW 54.5, CL 37.0 mm), Tanzania, Mt. Kilimanjaro (-3.241171, 37.374988, 1,576 m ASL), no collector or dates provided.</p><p>Other material examined. TANZANIA: NMU TRW1966.05, adult male (CW 71.6 mm), adult female (CW 84.0 mm), West Usambara Mountains, Garaya River near Dindila Factory. Specimen collected un a trap from a steep valley with little shade, crab with dark carapace and blue-tinted sternum, coll. J.N. Raybould, 5 September 1964. — NMU TRW1966.13, subadult male (CW 52.3 mm), south slopes of Kilimanjaro, Kondeni River near Marangu, coll. J.N. Raybould, 6 May 1966. — NMU TRW1966.14, subadult male (CW 53.3, CL 36.5 mm), subadult female (CW 39.2, CL 34.4 mm), 16 km east of Arusha, Usa River (tributary of Kikuletwa River, itself a tributary of the Pangani River), crabs with dark carapace and mauve-tinted sternum; carapace with attached larvae of blackfly, Simulium nyasalandicum, coll. J.N. Raybould, 26 May 1966. — NMU TRW-EA62.25, adult female with hatchlings (CW 78.1 mm) caught in trap, East Usambara Mountains, Amani, Dodwe River, coll. T. R. Williams, 1962. — NMU TRW EA62.67, 3 subadult males (CWs 45.9, 49.4, 49.9 mm), Kilimanjaro area, near Taveta, Mue River, Station 2, riverbed with large boulders, gravel &amp; stones embedded in sand. Large crabs caught from beneath large boulders, using yam bait on sticks. Small crabs caught from riffles, coll. T. R. Williams, 3 March 1962. — NMU TRW1968.11, stream on S-SE slopes of Mount Kilimanjaro, 2,134 m ASL, 5 juvenile males (CWs 21.9–38.9 mm), coll. J.E. Hudson, April 1967. — NMU TRW1969.02, adult male (CW 76.3 mm), East Usambara Mountains, Amani, coll. J. N. Raybould, 6 May 1966. — NMU TRW1970.01, subadult female (CW 63.9 mm), 2 subadult males (CWs 61.8, 63.6 mm), East Usambara Mountains, Amani, coll. T. R. Williams, 1970. — NMU TRW1970.02, male (soft-shelled), coll. T.R. Williams, 6 July 1970. — NMU TRW1970.03, subadult male (CW 56.8 mm), East Usambara Mountains, Amani, coll. T. R. Williams, 1970. — NMU TRW1970.05, subadult female (CW 48.0 mm), East Usambara Mountains, Amani, coll. unknown, 27 March 1971. — NMU TRW1971.11, adult male (CW 65.5 mm), adult female (CW 69.4 mm), canal near Taveta, coll. unknown, 1971. — NMU 03.29.1972.1–5, 3 juvenile males (CWs 18.5–36.3 mm), 2 juvenile females (CWs 34.3, 25.5 mm), East Usambara Mountains, coll. unrecorded, 29 March 1972. — NMU 07.2001.c, canal west of Taveta, 4 males (CWs 48.9, 57.0 mm, 2 damaged) 2 subadult females (CW 56.5 mm; 1 damaged), 2 juvenile females (CWs 32.9, 33.2 mm), coll. J. E. Hudson, date unknown . KENYA: NMU TRW1968.10, subadult female (CW 46.0 mm), Kibalwa, near Taveta, canal from Lumi River, coll. J. E. Hudson, 1 February 1967. — NMU TRW1968.12, subadult male (CW 53.4 mm), Kibalwa, near Taveta, canal from Lumi River, coll. J. E. Hudson 1 February. — NMU TRW1971.13, 3 subadult males (CWs 42.0– 63.7 mm), stream above Kibo Safari Camp, Amboseli National Park, northern slopes of Mt. Kilimanjaro (-2.796749, 37.371512, 2,134 m ASL), J. E. Hudson, date unknown. — NMU TRW1971.14, 22 juveniles, stream above Kibo Safari Camp, Amboseli National Park (-2.796749, 37.371512, 2,134 m ASL), coll. J. E. Hudson, February 1967. — USNM 32297, subadult male (CW 47.4 mm), Bura, Taita Hills (-3.450708, 38.313286, 1,400 m ASL), coll. C. H. Alluaud, 1904. — USNM 70913, male, Mount Mbololo (-3.360735, 38.455903, 1,096 m ASL) near Voi, coll. A. Loveridge, April 1934 .</p><p>Rediagnosis. Postfrontal crest sharp-edged, completely traversing carapace, meeting anterolateral margins at epibranchial teeth; exorbital tooth small, low; epibranchial tooth small, distinct; carapace lateral margins lined by small teeth, posterior end continuous with carapace posterolateral margin (Figs. 3A, 4A, B, 5A); all three regions of carapace branchiostegite smooth; thoracic sternal sulcus S3/4 deep, completely traversing sternum (Figs. 4A, C, 5B, D); sternite S4 lacking raised marginal ridges at points where chelipeds articulate (Figs. 4C, 5B, C); episternal sulci S4/E4, S5/E5, S6/E6, S7/E7 all clearly marked (Fig. 5C); ischium of third maxilliped with faint shallow vertical sulcus (Fig. 9A); male right (major) chela dactylus broad, curving but not arched leaving long narrow gap when fingers touching, cutting edge lined by medium rounded teeth, tips pointed; lower margin of chela propodus straight; propodus granulated on posterior portion (Fig. 7A, C, E); major cheliped carpus dorsal surface with carinae; cheliped carpus inner margin distal tooth large, sharp, proximal tooth small, pointed (Fig. 8E); cheliped merus medial inferior margin lined by small rounded teeth; distal meral tooth large, pointed; lateral inferior margin lined by granules (Fig. 8A, B); inner margin of cheliped ischium lined by small granules (Fig. 8A, B); anterior margin of P3, P5 carpus completely smooth (Fig. 6C, E); P2 dactylus length equal to P2 propodus length (Fig. 6C, E); G1 TA first half straight, second half bent outward at 90° angle to longitudinal axis of gonopod, tapering to pointed, upcurved tip (Fig. 10A, B); G1 TA widened in mid region by ventral, dorsal lobes, with wide gutter in between lobes running almost to tip, ventral lobe low throughout (Fig. 10E); dorsal lobe in two parts divided by a shallow groove, outer part low, inner part with wafer-thin D-shaped rounded crest (Fig. 10B, F). In dorsal view, distal end of G1 SA with slim elongated U-shaped dorsal membrane (Fig. 10F).</p><p>Size. Large, with an adult size range between CWs 69.0–84.0 mm.</p><p>Type locality. Mt. Kilimanjaro, Tanzania. In 1884 H. H. Johnson led the six-month expedition to Kilimanjaro by the Royal Geographic Society and British Association that was based at Moshi on the southern slopes of Mt. Kilimanjaro in Tanzania. The type locality of this species is probably in the vicinity of Johnston’s base camp near Moshi.</p><p>Distribution. Southeast Kenya and northeast Tanzania in the vicinity of Mt. Kilimanjaro, east to the Usambara Mountains. Other records in Cumberlidge (1998) that report this species to occur in Nekona, Mrogoro, Tanzania, and in Malawi and the D. R. Congo are now doubtful.</p><p>Conservation status. This species is Least Concern (LC) on the IUCN Red List because it is known from more than 10 locations and its extent of occurrence (EOO) is approximately 40,000 km ². This wide distributional range covers a large area spanning two countries, but the area of occupancy (AOO) is much less given that it is only found in streams and rivers and surface waters that flow year-round in the higher altitude forested areas but these waters are seasonal in the savanna areas with an arid climate and low annual rainfall. There is no evidence of an immediate threat that would cause a decline in the extent and quality of the habitat of A. johnstoni, although there are long-term threats to its habitat from disturbance associated with growing human populations in the region. This species is not found in a protected area.</p><p>Remarks. The subadult male holotype of T. depressa var. johnstoni Miers, 1885 (CW 57.0 mm) (NHM 1885.2) from Mt. Kilimanjaro in Tanzania was collected by the East Africa-Kilimanjaro Expedition (in 1884) and was named by Miers (1885) for Sir Harry Hamilton Johnston who headed the expedition. All specimens of A. johnstoni, including the adult male from the West Usambara mountains illustrated here (NMU TRW 1966.05, Fig. 3A) were identified based on comparisons of the carapace, mouthparts, sternum, pleon, and gonopods of the male holotype of T. depressa var. johnstoni Miers, 1885 . Bott (1955) synonymized A. johnstoni with seven different taxa, but Cumberlidge (1997, 1998), Reed &amp; Cumberlidge (2006), Ng et al. (2008), and Cumberlidge &amp; Daniels 2022 did not recognize any of these synonymies and their opinions are followed here.</p></div>	https://treatment.plazi.org/id/03FB87DFD14DDA082ABCFF535EB75368	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		MagnoliaPress via Plazi	Cumberlidge, Neil;Daniels, Savel R.;Kipyegon, John K.;Galaszewski, Taylor	Cumberlidge, Neil, Daniels, Savel R., Kipyegon, John K., Galaszewski, Taylor (2026): On the taxonomic status of two large species of East African freshwater crabs: Arcopotamonautes johnstoni (Miers, 1885) from Mount Kilimanjaro and A. platycentron (Hilgendorf, 1897) from Lake Chala (Brachyura: Potamoidea: Potamonautidae). Zootaxa 5748 (3): 369-386, DOI: 10.11646/zootaxa.5748.3.3, URL: https://doi.org/10.11646/zootaxa.5748.3.3
03FB87DFD14BDA1C2ABCFC4459B55408.text	03FB87DFD14BDA1C2ABCFC4459B55408.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Arcopotamonautes platycentron (Hilgendorf 1897)	<div><p>Arcopotamonautes platycentron (Hilgendorf, 1897)</p><p>(Figs. 2, 3B, 4D, 6B, D, F, 7G, H, 8C, D–F, 9D–F, H, 10C, D, H, I, 11A–D)</p><p>Telphusa platycentron Hilgendorf, 1897: 81–85 .— Hilgendorf 1898: 11–12, pl. fig. 4, 4a–c.</p><p>Potamon platycentron — de Man 1898: 437.— Chace 1942: 220.</p><p>Potamon (Potamonautes) platycentron — Rathbun 1905: 173.</p><p>Potamonautes (Lirrangopotamonautes) johnstoni platycentron — Bott 1955: 267–268, pl. XVI, fig. 1a–d, fig. 37a, b.</p><p>Potamonautes platycentron — Balss 1929: 349.— Reed &amp; Cumberlidge 2006: 3, 4, 7, 9–11, 14, 17, 30, 31, 58–60, 136, figs. 82–92, 161–162, 181, plate IX.— Ng et al. 2008: 171.</p><p>Type material examined. Holotype: ZMB 9656, subadult male (CW 46.0, CL 34.0, CH 22.0, FW 13.0 mm); Tanzania, <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=37.68845&amp;materialsCitation.latitude=-3.309695" title="Search Plazi for locations around (long 37.68845/lat -3.309695)">Lake Chala</a>, southeast slope of Mt. Kilimanjaro (-3.309695, 37.688448, 880 m ASL), coll. Kretschmer and O. Newmann, no dates provided . Paratypes: ZMB 9655, adult male (CW 59 mm), same details as holotype .— ZMB 9657, subadult female (CW 40 mm), same details as holotype .</p><p>Other material examined. KENYA: NHM 2002.910-911, adult male, (CW 50.0 mm), Lake Chala, southeast slope of Mt. Kilimanjaro, common along shore, 0–5 m depth, coll. M. Richmond, 3 February 2002 .— NMU TRW 1968.09, adult female (CW 57.0, CL 39.4, CH 15.6, FW 15.3 mm), adult female (CW 48.6; CL 33.2; CH 14.6, FW 13.7 mm), adult male (CW 49.2, CL 34.3, CH 15.6, FW 14.5 mm), Lake Chala, southeast slope of Mt. Kilimanjaro, coll. J. E. Hudson, 1 July 1967 .— NMU TRW1971.12, adult male (CW 50.8, CL 35.1, CH 18.8, FW 14.8 mm), 4 adult females (CW 52.7, CL 37.4 mm; CW 55.3, CL 38.8 mm; CW 49.3, CL 35.2 mm; CW 52.9, CL 36.7 mm), 2 adult males (CWs 51.7, 50.8 mm), <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=37.698532&amp;materialsCitation.latitude=-3.323402" title="Search Plazi for locations around (long 37.698532/lat -3.323402)">Lake Chala</a>, near Taveta, from the littoral zone of the eastern shore, lake-bed stony (-3.323402, 37.698534, 762 m ASL), coll. J. E. Hudson, July1967 .</p><p>Diagnosis. Postfrontal crest sharp-edged meeting anterolateral margins at epibranchial teeth; exorbital tooth sharp, triangular; epibranchial tooth small, granular; carapace lateral margins granulated, posterior end curving inward over carapace (Fig. 3B, 4D); all three regions of carapace branchiostegite smooth (Fig. 6B); thoracic sternal sulcus S3/4 completely traversing sternum; lateral margins of S4 low, not raised; episternal sulci S4/E4, S5/E5, S6/E6, S7/E7 all clearly marked (Fig. 11B, C); ischium of third maxilliped with vertical sulcus (Fig. 9D); male left (major) chela dactylus broad, robust, straight, not curved; closed chela cutting edges meshing with those of propodus fixed finger leaving no gap, tips rounded (Fig. 7H); lower margin of chela propodus straight; proximal part of propodus granulated (Fig. 6G); major cheliped carpus dorsal surface with low carinae (Fig. 8F); cheliped carpus inner margin distinctly broadened by large, blunt, wide tooth formed by fusion of expanded distal tooth with smaller proximal tooth, inner margin smooth except for small granules proximally (Fig. 8F); cheliped merus medial inferior margin lined by large pointed teeth, lateral inferior margin lined by granules (Fig. 8C, D); distal meral tooth large, sharp (Fig. 8C, D); inner margin of cheliped ischium lined by large teeth (Fig. 8C, D); anterior margin of P3 carpus lined by small distinct spines distally (Fig. 6D, F); P3 dactylus length shorter than P3 propodus length (Fig. 6D, F); G1TA first half straight, second half bent outward at 45° angle to longitudinal axis of gonopod, tapering to pointed tip (Fig. 10H, I); G1TA widened in mid region by ventral, dorsal lobes, separated by wide gutter running almost to tip (Fig. 10H, I); ventral lobe low throughout; dorsal lobe broadest, in two parts, outer part low, inner margin raised slightly by long, wafer-thin crest shaped like crescent moon (Fig. 10H, I); in dorsal view, dorsal membrane at distal end of G1SA sub-circular, shaped like wine glass, distal margin formed by G1SA-G1TA junction (Fig. 10D, H).</p><p>Size. A large-bodied species. The adult size range is estimated to be between CW 48.0–57.0 mm.</p><p>Colour. The carapace and pereiopods of living specimens are red-brown, the thoracic sternum is mostly creamyellow, with olive green and violet in places. Specimens preserved in ethanol are uniformly light brown.</p><p>Type locality. Tanzania, Lake Chala, southeast slope of Mt. Kilimanjaro (-3.309695, 37.688448, 880 m ASL). The original collection notes did not provide an exact locality, date, or even which country the first specimens were taken from, but it is likely that the type specimen was collected on the Tanzanian side of <a href="https://tb.plazi.org/GgServer/search?materialsCitation.longitude=37.68845&amp;materialsCitation.latitude=-3.309695" title="Search Plazi for locations around (long 37.68845/lat -3.309695)">Lake Chala. Although</a> the exact collection date is unknown, it was probably after 1891 (when the Germans declared the region a protectorate as part of German East Africa) and before 1897 (the year when the species was described), at a time when Tanzania (as Tanganyika) formed part of German East Africa. Further support for a Tanzanian type locality is provided by the fact that the German collectors (Kretschmer and O. Newmann) deposited their type specimens in the ZMB, Berlin.</p><p>Distribution. Tanzania and Kenya. Arcopotamonautes platycentron is endemic to Lake Chala. The border between Kenya and Tanzania crosses the northeastern slopes of Mt. Kilimanjaro and passes through Lake Chala, and this species has been collected from both sides of this crater lake in Tanzania (Rombo District of the Kilimanjaro Region), and in Kenya (Taita-Taveta District) (Fig. 10).</p><p>Habitat. Lake Chala is a 90 m deep oligotrophic crater lake located on the lower south-eastern slope of Mt. Kilimanjaro in Tanzania, East Africa. The border between Kenya and Tanzania runs through Lake Chala. This small steep-sided caldera lake (4.2 km 2) has a raised crater rim, and a rocky shoreline lined by moist evergreen forest. The lake is meromictic, because its water layers remain in place and do not intermix. The bottom layer is anoxic and very few organisms are found there, while the surface waters are relatively well-oxygenated so this is where most of the lake’s plants and animals live. Interestingly, there are no surface rivers or streams draining into or out of Lake Chala, so the lake’s year-round waters derive mainly from the strong-flowing underground streams that are fed by the heavy rains that fall on the montane forest zone (1,800–2,800 m ASL) of Mt. Kilimanjaro. The constant flow of these underground streams maintains lake levels, keeps the lake waters clear, and accounts for most of the water supply of the lake. Only a small part of the lake’s water is contributed by the low annual rainfall, (about 565 mm) which is seasonal and alternates with a prolonged dry season from June to August when many of the nearby surface streams dry out.</p><p>Lake Chala is a geologically young lake that formed approximately 250,000 years ago. Crabs may have first reached the lake via the surface streams and rivers that may have existed then in this part of Africa. There is no evidence that crabs can reach Lake Chala via the underground streams that currently feed into, and drain out of, the lake. The absence of any surface connections with the lake today indicate that it has been isolated for a long time, and there is no evidence of new recruitment of crabs to Lake Chala from the surrounding area.</p><p>Crab populations that entered the lake in the past would have become geographically isolated from their nonlake parent population. This may have driven ecological speciation and a cessation of gene flow resulting in geneticisolation and rapid speciation of crab populations in the lake. Lake Chala lies within the distributional range of A. johnstoni so it is likely that this species is similar to the ancestral populations that entered the lake and gave rise to A. platycentron . Since then, these two crab taxa have been isolated by their different habitats (adapting to lotic stream and lentic lake conditions respectively) and have diverged over time. The morphological evolutionary changes to the carapace, chelipeds, and gonopods of A. platycentron summarized in this work are presumably associated with the changed demands of lake-living compared to a life in streams and rivers.</p><p>Arcopotamonautes platycentron (whose local name is ‘Kaa’) is reportedly common in Lake Chala along the lake’s littoral zone down to about 8 m, where it scavenges between rocks and boulders for dead organisms (e.g., fish) and other organic matter that has fallen to the bottom. There are no reports of crabs living either in the lake’s deeper waters (where there is a severe lack of oxygen) or of crabs swimming in the open waters of the lake. This species is caught on lines with baited hooks, and is also a frequent by-catch of the artisanal gill-net fishery, although it is not the intended target of the fishermen who consider it a nuisance because it can become tangled in their nets.</p><p>Conservation status. Arcopotamonautes platycentron is listed on the IUCN Red List as endangered (EN) because it has a very limited geographic range and individuals are in a single location in the small isolated Lake Chala, where it is endemic. For example, it’s extent of occurrence (EOO) is very small (4.2 km ²), and its area of occupancy (AOO) is even smaller (Fig. 2). Although both the EOO and the AOO are below the thresholds for CR, unless immediate threats can be established, EN would still be justified. The population size of A. platycentron was estimated at fewer than 2,500 mature individuals over the entire range. Interestingly, a four-month study by the second author in 2021 (unpublished) deployed crab traps at different depths in different parts of Lake Chala and found A. platycentron to be abundant, with estimates of over 4,500 individuals, indicating an increasing trend in population levels. Potential threats to this species would include increased habitat disturbance by growing human populations (including development projects), and additional traffic due to ecotourism in the area. Recent changes to the conservation status of Lake Chala include its designation as an Alliance for Zero Extinction (AZE) protected site in part due to the presence of A. platycentron, a threatened species that is a lake endemic listed as endangered (EN) on the IUCN Red List. The original reports of A. platycentron date back to the late 19 th century, and it’s continued presence in the lake is verified by its frequent encounters with fishermen and in recent studies.</p><p>Arcopotamonautes platycentron faces potential new threats from a proposed project to upgrade the road between the towns of Taveta and Illasit in Kenya. The road would pass close to the lake and through the buffer zone of the AZE site. All road work would, therefore, take place inside the AZE protected area and may involve habitat disturbance, so it is important to establish whether any of the endangered species of fish or crabs in the lake itself or in the larger AZE site that includes the lake and its environs would be affected.</p><p>Our recent preliminary survey of Lake Chala and the area surrounding the lake within the AZE site has confirmed that A. platycentron is indeed endemic to Lake Chala and is not found outside of the lake. This is important because the absence of any surface waters feeding into, and draining out of, the lake makes it unlikely that any nearby road work would disturb the lake endemics. This is because their aquatic environment is fed by groundwater catchments and seasonal rainfall that would not be directly impacted by anthropogenic activities on the surface. If the construction work or other activities in the buffer zone related to the roadworks were to affect Lake Chala itself, then this would become a problem because the combination of immediate threats and the very small size of the lake would justify reassessing the threat category of A. platycentron from the present EN to critically endangered (CR). The distributional range of the river and stream species A. johnstoni (least concern, LC) comprises localities associated with the area around Mt. Kilimanjaro including the area around Lake Chala in both Kenya and Tanzania (Fig. 1), but the range does not include the lake itself, so it is possible that this species might be affected by the proposed road works. If the threats to this species were to increase then an extinction risk reassessment would be justified.</p><p>Comparisons. The detailed morphological and molecular study of A. platycentron and A. johnstoni presented here supports the continued recognition of these two taxa as valid species whose distributional ranges are updated here (Figs. 1, 2). Arcopotamonautes platycentron shares several morphological characters with A. johnstoni . These characters include a medium to large body size, an epibranchial tooth that is small and granular, a postfrontal crest that is sharp-edged and completely traverses the carapace, meeting the carapace margins at the epibranchial teeth (Figs. 3A, B, 4A, D, 5A, D, 6A, B, 11A, D), episternal sulci S4/E4–S7/E7 that are all clearly marked and deep, a sternite S4 that lacks raised marginal ridges where the chelipeds articulate (Figs. 5B,C, 11B, C), and a cheliped merus inner margin with a large, pointed distal tooth (Fig. 8A–D). In addition, these species have geographically adjacent distributional ranges in northeast Tanzania near the border with southeast Kenya (Figs. 1, 2).</p><p>Despite these similarities, these two taxa can be distinguished as follows. The major cheliped dactylus of A. platycentron is very broad with a rounded tip (Fig. 7G, H) (whereas that of A. johnstoni is slim with a pointed tip; Fig. 7A–F); the cheliped carpus distal tooth of A. platycentron is extremely broad and blunt (Fig. 8F) (whereas that of A. johnstoni is slim and pointed; Fig 8E); the medial inferior margin of the cheliped ischium and merus of A. platycentron is lined by sharp teeth (Fig. 8C, D) (whereas these margins in A. johnstoni are granulated or lined by small teeth; Fig. 8A, B); the G1 dorsal membrane on the dorsal face between G1TA and G1SA of A. platycentron is rectangular (Fig. 10D, H, I) (whereas this membrane in A. johnstoni is rounded; Fig. 10B, F); and the G1TA ventral lobe of A. platycentron is uniformly thin and low (Fig. 10C, D, G–I) (whereas that of A. johnstoni is raised in the mid-section; Fig. 10B, E–G). For these reasons, we follow the opinions of Reed &amp; Cumberlidge (2006) and Ng et al. (2008) and treat these two taxa as two valid species.</p><p>Bott (1955) treated A. platycentron as a subspecies of A. johnstoni based on shared characters that included a large body size and traits of the carapace and postfrontal crest. On the other hand, there can be no doubt, based on the evidence presented here, that the freshwater crab populations of A. platycentron found in Lake Chala are morphologically distinct from A. johnstoni based on several contrasting traits, and the number of these traits has been increased by the present findings. This study provides additional support for the recognition of these two taxa as two separate species. For example, A. platycentron can be distinguished from A. johnstoni by the carapace lateral margins that are lined by low granules and curved inward at their posterior ends in A. platycentron (Figs. 3B, 4D, 11A) (versus carapace lateral margins lined by rounded distinct teeth that are continuous with the posterolateral margins in A. johnstoni; Figs. 3A, 4A, B, 5A); by an exorbital tooth that is low and blunt, and an epibranchial tooth that is reduced to a small granule in A. platycentron (Figs. 3B, 4D, 11A) (versus an exorbital tooth that is small and pointed, and by an epibranchial tooth that is a small, but distinct in A. johnstoni; Figs. 3A, 4A, B, 5A); by the lateral ends of the postfrontal crest that are smooth in A. platycentron (Fig. 11A) (versus a postfrontal crest whose lateral ends are lined by small distinct granules in A. johnstoni; Fig. 5A); and by the epistomial tooth margins that are distinctly granulated in A. platycentron (Fig. 11D) (versus epistomial tooth margins that are smooth in A. johnstoni; Fig. 5D).</p><p>Other contrasting characters involve differences between the chelipeds of the two species such as the cutting edges of the fixed and movable fingers of the major cheliped that are straight and almost touching along their entire length when closed in A. platycentron (Fig. 7G, H) (versus cutting edges of the fixed finger of the major cheliped that are curved and leave a long narrow interspace when closed in A. johnstoni; Fig. 7A–F); the distal third of the movable and immovable fingers of the major chela lack black pigmentation in A. platycentron (Fig. 7G, H) (versus both major chela fingers have distinct black pigmentation in A. johnstoni; Fig. 7A–F); the distal tooth on the inner margin of the cheliped carpus is extremely broad and blunt in A. platycentron (Fig. 8F) (versus slim, pointed, and spine-like in A. johnstoni; Fig. 8E); the proximal tooth on the inner margin of the cheliped carpus is fused with the expansion of the distal tooth in A. platycentron (Fig. 8F) (versus a proximal tooth on the cheliped carpus that is small and pointed, followed by a smooth inner margin in A. johnstoni; Fig. 8E)); the medial inferior margin of the cheliped merus is lined by large, sharp teeth in A. platycentron (Fig. 8C, D) (versus a margin lined by large granules in A. johnstoni; Fig. 8A, B); the lateral inferior margin of the cheliped merus is lined by small, sharp teeth in A. platycentron (Fig. 8C, D) (versus a margin lined by faint granules in A. johnstoni; Fig. 8A, B); the cheliped ischium inner margin is lined by large teeth in A. platycentron (Fig. 8C) (versus a cheliped ischium inner margin lined by small granules in A. johnstoni; Fig. 8B). In addition, the dorsal membrane of the G1SA is subcircular like a round wine glass in A. platycentron (Fig. 10F) (versus a slim, elongated and U-shaped membrane in A. johnstoni; Fig. 10H).</p><p>Finally, there are distinct ecological differences between these two species: A. johnstoni is found in rivers and streams and never found either in Lake Chala or in any other lakes, while A. platycentron is only found in Lake Chala.</p><p>Molecular results. Sequenced specimens collected recently from the Lumi River in Kenya, just a few kilometers from Lake Chala were identified here as A. johnstoni, while other specimens sampled from the Kenyan shores of Lake Chala were identified as A. platycentron . The Lumi River in Kenya flows south close to Lake Chala but makes no connection with the lake. Interestingly, the crabs sequenced from the Lumi River ( A. johnstoni) and from the Kenyan shores of Lake Chala ( A. platycentron) are both genetically similar to each other (low uncorrected CO1 ‘p’ distance values), but both are highly divergent (high uncorrected CO1 ‘p’ distance) from specimens identified as A. platycentron collected from the Tanzanian shores of Lake Chala.</p><p>These preliminary molecular findings would normally indicate that the low uncorrected CO1 ‘p’ distances between A. platycentron and A. johnstoni of 1.51% from Kenya imply that the two taxa are conspecific, because these values for two allopatric species of African freshwater crabs would normally be expected to be between 4% and 8% (Daniels et al. 2023). In other words, the low genetic distance between A. platycentron from the lake in Kenya and A. johnstoni from rivers outside the lake in Kenya (1.51%) would not normally be considered enough to warrant the recognition of these taxa as two separate species. However, their widely different exclusive habitats (lakes and streams) may in part, explain this genetic finding. This is because similar cases of low uncorrected CO1 ‘p’ distances between two closely-related and morphologically distinct species of freshwater crabs have been reported between species of African freshwater crabs, one living in the rivers flowing into Lake Malawi, and the other living exclusively in the lake itself (Layfield et al. 2024). The radical ecological change brought about by switching from riverine to lacustrine environmental conditions may have led to the evolution of a new species by rapid ecological speciation. Further, speciation in stream and cave-adapted species of Asian freshwater crabs may have been prompted by the switch from an epigean to a hypogean environment (Klaus et al. 2013).</p></div>	https://treatment.plazi.org/id/03FB87DFD14BDA1C2ABCFC4459B55408	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		MagnoliaPress via Plazi	Cumberlidge, Neil;Daniels, Savel R.;Kipyegon, John K.;Galaszewski, Taylor	Cumberlidge, Neil, Daniels, Savel R., Kipyegon, John K., Galaszewski, Taylor (2026): On the taxonomic status of two large species of East African freshwater crabs: Arcopotamonautes johnstoni (Miers, 1885) from Mount Kilimanjaro and A. platycentron (Hilgendorf, 1897) from Lake Chala (Brachyura: Potamoidea: Potamonautidae). Zootaxa 5748 (3): 369-386, DOI: 10.11646/zootaxa.5748.3.3, URL: https://doi.org/10.11646/zootaxa.5748.3.3
