Potamonautes entebbe, Cumberlidge & Clark, 2017
Cumberlidge, Neil & Clark, Paul F., 2017, Description of three new species of Potamonautes MacLeay, 1838 from the Lake Victoria region in southern Uganda, East Africa (Brachyura: Potamoidea: Potamonautidae), European Journal of Taxonomy 371, pp. 1-19: 4-7
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Potamonautes entebbe sp. nov.
Postfrontal crest faint but complete, lateral ends meeting anterolateral margins at epibranchial teeth; exorbital, epibranchial teeth each reduced to granule; anterolateral margin posterior to epibranchial tooth smooth ( Figs 1A View Fig , 4A View Fig ). Third maxilliped ischium lacking vertical sulcus ( Figs 1B View Fig , 4A View Fig ); s3/s4 V-shaped, deep at sides, faint in middle; margins of s4 distinctly raised, thickened ( Fig. 1B View Fig ). Propodus, dactylus of major cheliped of adult male slim, elongated, both lined by small teeth, dactylus highly arched, enclosing oval interspace when closed ( Figs 1 View Fig A–B). Cheliped carpus inner margin distal tooth large, pointed, proximal tooth small, broad, pointed ( Figs 1B View Fig , 5 View Fig A–B). G1 terminal article short (0.25 × length of G1), slim, straight, curving gently outward, needle-shaped, evenly tapering, tip straight ( Fig. 6A View Fig ).
The new species is named for the city of Entebbe, Uganda, which lies on the northern shore of Lake Victoria where this species was first collected. The specific epithet is used as a noun in apposition. Vernacular name: the Entebbe crab.
Holotype (here designated)
UGANDA: adult ♂, CW 35.0, CL 23.2, CH 11.6, FW 9.4 mm, Entebbe, N shore of Lake Victoria , 1.04216° N, 30.67056° E, 11 Aug. 1955, Captain C.R.S. Pittman leg. ( NHMUK 19188.8.131.52).GoogleMaps
UGANDA: subadult ♀, CW 8.5 mm, same collection data as for holotype ( NHMUK 19184.108.40.206).
Based on holotype (adult male CW 35 mm). Carapace outline transversely oval, inflated ( CH /FW 1.24; Fig. 1A View Fig ), front broad measuring one-third CW (FW/CW 0.27; Fig. 4A View Fig ). Postfrontal crest faint but complete, lateral ends meeting epibranchial teeth; epigastric crests distinct, median sulcus between crests short, forked posteriorly; semi-circular, urogastric, cardiac, posterior and cervical carapace grooves all faint. Exorbital tooth very low, blunt, epibranchial tooth reduced to granule; anterolateral margin between exorbital, epibranchial teeth smooth, lacking intermediate tooth, anterolateral margin posterior to epibranchial tooth smooth ( Fig. 1A View Fig ). Suborbital margin granular ( Fig. 4A View Fig ). Carapace sidewall vertical sulcus faint, incomplete, meeting longitudinal sulcus, dividing sidewall into three parts. Third maxilliped exopod with long flagellum, ischium lacking vertical sulcus ( Fig. 4A View Fig ). Epistomial tooth large, triangular, edges lined by granules ( Fig. 4A View Fig ). Mandibular palp 2-segmented; terminal segment simple; s2/s3 deep, running horizontally across sternum; s3/s4 V-shaped, deep at sides, faint in middle; margins of s4 distinctly raised, thickened ( Fig. 1B View Fig ); s4/e4, s5/e5, s6/e6 and s7/e7 all visible ( Fig. 1B View Fig ). Chelipeds of adult male unequal; fixed finger (propodus) and movable finger (dactylus) of major cheliped slim, elongated, both lined by small teeth, moveable finger highly arched, encompassing oval interspace when closed ( Fig. 5 View Fig A–B). Two pointed teeth on inner margin of cheliped carpus, distal tooth of medium size, proximal tooth small ( Fig. 1A View Fig ). Inferior margins of merus of cheliped with series of small sharp teeth, distal tooth pointed; superior surface of merus with carinae ( Fig. 1 View Fig A–B). Pleon outline broadly triangular, with straight edges ( Fig. 1B View Fig ). G1 terminal article short (0.25 × length of G1), curving gently outward, broad at base, tapering evenly to straight tip ( Fig. 6 A, D View Fig ). G2 terminal article long (0.5 × length of G2), flagellum-like.
SIZE. Medium-sized species, adult at CW 35 mm.
COLOUR. Preserved specimens uniformly light brown.
This species is known only from two specimens collected from a single locality at Entebbe, Uganda in the Lake Victoria drainage basin ( Fig. 7 View Fig ). Although only sparse details of the habitat were provided by the collector, the inference is that this species was either collected on the Lake Victoria shoreline itself, or in a stream or river close to where it joins the lake.
Little is known about the ecology of this species. Potamonautes entebbe sp. nov. is not found in a protected area and was collected from a locality that is either in or near Lake Victoria, adjacent to the city of Entebbe. At the time the specimens were collected (1955) this area was relatively undisturbed, but it is now under increasing pressure from anthropogenic pollution and disturbance.
An IUCN extinction risk assessment of P. entebbe sp. nov. has not yet been carried out, but given the fact that this species is known for only two specimens from a single locality, it would probably be regarded as Data Deficient.
Potamonautes entebbe sp. nov. is superficially similar to several other species in this genus from Uganda that all share the following characters: a medium body size at maturity (CW 30 mm and above); a complete postfrontal crest; reduced or absent exorbital and epibranchial teeth; a smooth anterolateral margin behind the epibranchial tooth; and a male major cheliped with a slim, elongated, highly arched dactylus. Ugandan crabs that share this suite of characters include four species from southeastern Uganda ( P. loveni (Colosi, 1924) , P. elgonensis Cumberlidge & Clark, 2010 , P. williamsi (Cumberlidge & Clark, 2010) and P. amalerensis (Rathbun, 1935)) , two from northern Uganda ( P. morotoensis Cumberlidge & Clark, 2016 , and P. imatongensis Cumberlidge & Clark, 2016 ), and two from western Uganda ( P. aloysiisabaudiae (Nobili, 1906) and P. rukwanzi Corace, Cumberlidge & Garms, 2001 ).
Potamonautes entebbe sp. nov. differs from P. loveni and P. williamsi in that the proximal tooth on the inner margin of the cheliped carpus of P. entebbe sp. nov. is pointed and subequal to the distal tooth ( Fig. 1A View Fig ) (vs both teeth weak, low and blunt in P. loveni and P. williamsi ). Potamonautes entebbe sp. nov. differs from P. aloysiisabaudiae , P. busungwe sp. nov., P. elgonensis and P. kantsyore sp. nov. in that the G1 terminal article of P. entebbe sp. nov. has a straight tip ( Fig. 6A, D View Fig ) (vs a G1 terminal article that has either a slightly or distinctly upcurved tip in these other species) ( Chace 1942; Bott 1955; Cumberlidge & Clark 2010a). Potamonautes entebbe sp. nov. differs from P. williamsi as follows: the distal tooth on the inner margin of the carpus of the cheliped is strong and pointed ( Fig. 1A View Fig ) (vs small and low in P. williamsi ) and s3/s4 is deep at the edges and faint medially ( Fig. 1B View Fig ) (vs not visible except for two short notches on the external margins of the sternite in P. williamsi ) ( Cumberlidge & Clark 2010a). Potamonautes entebbe sp. nov. differs from P. rukwanzi by the third maxilliped ischium, which has a faint, barely visible sulcus ( Fig. 1B View Fig ) (vs a distinct and complete sulcus in P. rukwanzi ) ( Corace et al. 2001).
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