European Journal of Taxonomy 182: 1-18

http://dx.doi.org/10.5852/ejt.2016.182

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ISSN 2118-9773

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2016 • Cumberlidge N. & Clark P.F.

Research article

urn:lsid:zoobank.org:pub:C8C08037-C7EA-45C6-B21B-D2AEAC25FEA5

Two new species of freshwater crabs from the highlands of northern

Uganda, East Africa and a redescription of Potamonautes amalerensis

(Rathbun, 1935) stat. rev. from Mount Kadam

(Brachyura: Potamoidea: Potamonautidae)

Neil CUMBERLIDGE 1 * & Paul F. CLARK 2

1 Department of Biology, Northern Michigan University, Marquette, MI, USA.

department of Life Sciences, The Natural History Museum, Cromwell Road, London, SW7 5BD, UK.

* Corresponding author: [email protected]

2 E-mail: p [email protected]

1 um:lsid:zoobank.org:author:05F6365E-D168-4AE3-B511-80FA7E31ACCl

2 um:lsid:zoobank.org:author:BB4A2E90-621A-40BB-A90C-FFDCEE71A4E9

Abstract. Two new species of potamonautid freshwater crabs are described from the Imatong Mountains

and Mount Moroto in northern Uganda, East Africa, and a third highland species, Potamonautes

amalerensis (Rathbun, 1935) stat. rev. from Mount Kadam is re-diagnosed based on examination of

the holotype. All three species are endemic to a different mountain range and their collection localities

indicate a distinct preference for higher altitudes. Diagnoses, illustrations and distribution maps are

provided for these taxa, and they are compared to similar species from the region. The conservation

status of all three species is discussed.

Key words. Potamonautes imatongensis sp. nov., Potamonautes morotoensis sp. nov., Imatong

Mountains, Mount Moroto, Mount Kadam.

Cumberlidge N. & Clark RF. 2016. Two new species of freshwater crabs from the highlands of northern

Uganda, East Africa and a redescription of Potamonautes amalerensis (Rathbun, 1935) stat. rev. from

Mount Kadam (Brachyura: Potamoidea: Potamonautidae). European Journal of Taxonomy 182: 1-18.

http://dx.doi.org/10.5852/eit.2106.182

Introduction

Freshwater crabs from the highland regions of northern Uganda collected by Trefor R. Williams (formerly

University of Liverpool, United Kingdom) and his colleagues in the 1960s were made available to

the authors for examination. This material proved to include two new species that are described here

based on a unique combination of adult male characters including the first gonopod, carapace, thoracic

sternum and chelipeds. The two new species were collected from streams and rivers draining the slopes

of mountain ranges in the Acholi and Karamajo Provinces of northern Uganda during a survey aimed

at a better understanding of the transmission of river blindness (Onchocerciasis) to humans (Barnley &

Prentice 1958; McMahon et al. 1958; Hynes et al. 1961; Williams et al. 1964; Williams 1968, 1991;

European Journal of Taxonomy 182 : 1-18 ( 2016 )

Crosskey 1990). The third species, Potamon ( Geothelphusa ) amalerensis Rathbun, 1935 stat. rev., is from

Mount Kadam in the Karamoja Province of Uganda and was collected by Arthur Loveridge during the

American Natural History Museum Expedition to Kenya and Uganda in 1933-1934. This species is re¬

described here as Potamonautes amalerensis (Rathbun, 1935) stat. rev. and a second locality is recorded.

Recently, Cumberlidge & Clark (2010) reported on four species of freshwater crabs from Mount Elgon,

a highland region in southeast Uganda, south of Mount Kadem, one of the highland ranges included in

the present study. The freshwater crab faunas of Uganda’s northern and eastern highlands include high-

altitude taxa that are typically small-bodied restricted-range species that are endemic to their mountain

ranges, despite the relatively close proximity of some of these localities.

All of the freshwater crabs reported on here belong to Potamonautes MacLeay, 1838. Specimens of

the two new species are deposited in the NHM, London, UK, while the holotype and paratypes of

P. amalerensis stat. rev. are registered in the MCZ, Harvard University, Cambridge, MA, U.S.A. The

re-description of P. amalerensis stat. rev. is based on examination of the type material and is necessary

because it is still difficult for the non-specialist to distinguish between the many Potamonautes species

from Uganda. This is due to an absence of modern taxonomic treatments, not least because the only

available identification keys (Rathbun 1921; Chace 1942; Bott 1955) are insufficient by modern

standards and their systematics is dated. At present, the only way to make reliable identifications of

freshwater crabs from this part of Africa is to refer to the original type series of all relevant taxa but

these are held in different European and North American museums. Unfortunately, molecular data for

the three species reported on here are not available, because all of this material was originally preserved

in formalin. Diagnoses, illustrations, and distribution maps are provided for these taxa, and they are

compared to similar species from the region. The conservation status of all three species is discussed.

The addition of P. imatongensis sp. nov. and P. morotoensis sp. nov., and the recognition of a previously

suppressed taxon, P. amalerensis stat. rev. raises to 13 the number of freshwater crabs known from

Uganda (Cumberlidge & Clark 2010).

Material and methods

Measurements were made with digital calipers and are given in millimeters. The terminology is adapted

from Cumberlidge (1999) and the higher classification used here follows that of Ng et al. (2008). Line

drawings were prepared using a Leica MZ 16 binocular microscope. The habitus photographs were

taken with a digital camera in combination with a Leiz MZ 95 adapter. Post processing was undertaken

using Adobe Photoshop CS5.

Abbreviations

a = abdominal somite

a7/a6 = sutures between abdominal somites

CW = carapace width measured at widest point

CL = carapace length measured along median line from anterior to posterior margin

CH = carapace height measured at maximum height of cephalothorax

e = thoracic episternite

FW = front width measured along anterior frontal margin between orbits

G1 = first gonopod

G2 = second gonopod

IUCN = International Union for the Conservation of Nature

MCZ = Museum of Comparative Zoology, Harvard University, Cambridge, MA, USA

NHM = Natural History Museum, London, UK

NMU = Northern Michigan University, Marquette, MI, USA

CUMBERLIDGE N. & CLARK P.F., New species of Ugandan freshwater crabs

pl-p5 = pereiopods 1-5

s = thoracic sternite

s4/s5 = sternal sulci between adjacent thoracic sternites

s4/e4 = epistemal sulci between adjacent thoracic sternites and episternites

ZSM = Zoologische Staatssammlung, Miinchen, Germany

Results

Infraorder Brachyura Latreille, 1802

Superfamily Potamoidea Ortmann, 1896

Family Potamonautidae Bott, 1970

Subfamily Potamonautinae Bott, 1970

Genus Potamonautes MacLeay, 1838

Potamonautes imatongensis sp. nov.

urn:lsid:zoobank.org:act:3FEF2D5C-9660-4C99-AC96-E9DEE74E1412

Figs 1A-B; 2A-B, G, J; 3A-B, G-H; 4 A-C; 7A-B; 8

Diagnosis

Postfrontal crest faint but complete, lateral ends well defined, meeting epibranchial teeth; exorbital

tooth low, blunt; epibranchial tooth reduced to granule; anterolateral margin posterior to epibranchial

tooth smooth. Third maxilliped ischium lacking vertical groove. Sternal sulcus s3/s4 deep at edges,

faint medially, almost meeting thickened, raised anterior margin of stemoabdominal cavity; margins of

s4 distinctly raised, thickened. Fixed finger (propodus), movable finger (dactylus) of major cheliped of

adult male both slim, elongated, lined by small teeth; movable finger (dactylus) highly arched, enclosing

oval interspace when closed. Cheliped carpus: first tooth medium sized, pointed; second tooth small,

broad, pointed. G1 terminal article short, straight, in line with longitudinal axis, cone-shaped, evenly

tapering, tip narrow, tube-like.

Etymology

The new species is named for the Imatong Mountains on the border between Uganda and South Sudan,

which is the locality where this species was first collected.

Material examined

Holotype

UGANDA: adult 3 , CW 21.5, CL 14.4, CH 7.4, FW 6.5 mm, Imatong Mountains, near border with

South Sudan (3.79° N, 32.87° E), at 2,134 m asl, 11 Aug. 1955, L.C. Beadle (NHM 1955.11.8.26-27).

Paratypes

UGANDA: 5 adult 33 , CWs 19.7, 18.7, 21.5, 18.6, 18.2; 2 adult ??, CWs 20.5, 21.3 mm, Aringa

River, northern Acholi District (3.74° N, 32.90° E), at 1,173 m asl, 11 Aug. 1955, L. C. Beadle (NHM

1955.11.8.20-25).

Other material examined

UGANDA: adult 3 , CW 21.5, CL 14.7, CH 7.7, FW 6.5 mm (NHM 2016.16); 5 adult 33 , CWs 20.0,

18.0, 19.2, 21.2, 21.3 (NHMUK 2016.17-21); 4 adult??, CWs 23.1, 19.4, 18.2, 19.2 mm (NHMUK

2016.22-25), 2 juveniles CW 12.1, 13.0 mm (NHMUK 2016. 26-27), tributary of the Aringa River at

Lututuru (48 km north of Kitgum), Imatong Mountains, northern Acholi District near border with South

Sudan (3.75° N, 32.90° E), at 1,524 m asl, 22.5 °C, at 4:00 pm, 16 May 1968, A.W.R. McRae (NMU

TRW 1968.03); adult 3 , CW 21.5, CL 14.4, CH 7.4, FW 6.5 mm, Aringa River, northern Acholi District

(3.74° N, 32.90° E), 1,173 m asl, 11 Aug. 1955, L. C. Beadle (NHM 1955.11.8.20-25).

European Journal of Taxonomy 182 : 1-18 ( 2016 )

Type locality

Uganda, Imatong Mountains, near border with South Sudan (3.79° N, 32.87° E), at an altitude of

2,134 m asl.

Description

Based on holotype (adult male CW 21.5). Carapace outline transversely oval, medium height (CH/FW

1.1); front broad, measuring one-third CW (FW/CW 0.30). Postfrontal crest faint but complete, lateral

ends well defined, meeting epibranchial teeth; epigastric crests clear, median sulcus between crests

short, forked posteriorly, semi-circular, urogastric, cardiac, posterior, cervical carapace grooves all

distinct. Exorbital tooth low, blunt; epibranchial tooth reduced to granule; anterolateral margin posterior

to epibranchial tooth smooth; anterolateral margin between exorbital, epibranchial teeth smooth,

curving slightly outward, lacking intermediate tooth; carapace sidewall vertical sulcus faint, incomplete.

Fig. 1. A-B Potamonautes imatongensis sp. nov., holotype, adult S, CW 21.5 mm, from the Imatong

Mountains in northern Uganda (NHM 1955.11.8.26-27). A. Carapace, dorsal view. B. Carapace,

frontal view. — C-D. Potamonautes morotoensis sp. nov., holotype, adult CW 26 mm, from Mount

Moroto in northern Uganda (NHM 2015.3056). C. Carapace, dorsal view. D. Carapace, frontal view. —

E-F. Potamonautes amalerensis (Rathbun, 1935) stat. rev., holotype, adult S, CW 3E5 mm, from

Mount Kadam, northern Uganda (MCZ 8238). E. Carapace, dorsal view. F. Carapace, frontal view.

Scale bar: A-B = 6.3 mm; C-D = 7.3 mm; E-F = 9.1 mm

CUMBERLIDGE N. & CLARK P.F., New species of Ugandan freshwater crabs

Fig. 2. A-B, G, J Potamonautes imatongensis sp. nov., holotype, adult CW 21.5 mm, from the

Imatong Mountains in northern Uganda (NHM 1955.11.8.26-27). A. Carpus and merus of right cheliped,

dorsal view. B. Carpus and merus of right cheliped, ventral view. G. Third maxilliped frontal view.

J. Anterior thoracic sternum. — C-D, H, K. Potamonautes morotoensis sp. nov., holotype, adult S,

CW 26 mm, from Mount Moroto in northern Uganda (NHM 2015.3056). C. Carpus and merus of right

cheliped, dorsal view. D. Carpus and merus of right cheliped, ventral view. H. Third maxilliped, frontal

view. K. Anterior thoracic sternum. — E-F, I, L. Potamonautes amalerensis (Rathbun, 1935) stat. rev.,

holotype, adult $, CW 31.5 mm, from Mount Kadam, northern Uganda (MCZ 8238). E. Carpus and

merus of right cheliped, dorsal view. F. Carpus and merus of right cheliped, ventral view. I. Third

maxilliped frontal view. L. Anterior thoracic sternum. Scale bar: A-B = 3.4 mm; C-D = 3.8 mm; E-F =

5.5 mm ; G = 4.6 mm ; H = 4.9 mm ; I = 7.8 mm ; J = 5.9 mm ; K = 7.3 mm ; L = 9.5 mm.

European Journal of Taxonomy 182 : 1-18 ( 2016 )

Fig. 3. A-B, G-H Potamonautes imatongensis sp. nov., holotype, adult CW 21.5 mm, from the

Imatong Mountains in northern Uganda (NHM 1955.11.8.26-27). A. Right cheliped, frontal view.

B. Left cheliped, frontal view. G. G1 ventral view. H. G1 dorsal view. — C-D, I-J. Potamonautes

morotoensis sp. nov., holotype, adult CW 26 mm, from Mount Moroto in northern Uganda (NHM

2015.3056). C. Right cheliped, frontal view. D. Left cheliped, frontal view. I. G1 ventral view. J. G1

dorsal view. — E-F, K-L. Potamonautes amalerensis (Rathbun, 1935) stat. rev., holotype, adult CW

31.5 mm, from Mount Kadam, northern Uganda (MCZ 8238). E. Right cheliped, frontal view. F. Left

cheliped, frontal view. K. G1 ventral view. L. G1 dorsal view. Scale bar: A-B = 6.8 mm; C-D =5.1 mm;

E-F = 6.5 mm; G-L = 4.5.

CUMBERLIDGE N. & CLARK P.F., New species of Ugandan freshwater crabs

not meeting anterolateral margin. Suborbital margin smooth. Carapace sidewall pterygostomial region

with distinct granulated vertical sulcus, ending at longitudinal sulcus, dividing sidewall into 3 parts.

Third maxilliped exopod with long flagellum, ischium lacking vertical groove. Epistomial tooth large,

triangular, edges lined by large rounded granules. Mandibular palp 2-segmented; terminal segment

simple. Thoracic sternal sulcus s2/s3 deep, running horizontally across sternum; thoracic sternal sulcus

s3/s4 deep at edges, faint medially, almost meeting thickened, raised anterior margin of sternoabdominal

cavity; margins of s4 distinctly raised, thickened. Thoracic episternal sulci s4/e4, s5/e5, s6/e6, s7/e7 all

visible grooves. Chelipeds of adult male unequal; fixed (propodus) and movable (dactylus) fingers of

adult male slim, elongated, both lined by small teeth, movable finger (dactylus) highly arched, enclosing

oval interspace when closed. Cheliped carpus: first tooth medium size, pointed, second tooth small,

broad, pointed. Inferior margins of merus of cheliped with series of small sharp teeth; distal meral

tooth pointed; superior surface of merus granulated. Abdomen outline broadly triangular with straight

edges. G1 terminal article short, straight, in line with longitudinal axis of gonopod, cone-shaped, evenly

tapering, tip narrow, tube-like. G2 terminal article long, flagellum-like.

Size

Small species, adult size range CW 18.2-23 mm.

Colour

Preserved specimens uniformly light brown.

Distribution

The localities where this species is known to occur are in the Aringa River or its tributaries in northern

Acholi Province of Uganda close to the border with South Sudan. The Aringa River is part of the Nile

River drainage and flows north out of Uganda, eventually meeting the White Nile River in South Sudan

(Fig. 10). The third locality from the ‘Sudan (now South Sudan)/Uganda border at 7,000 feet (= 2,134 m

asiy is vague, but has been estimated here based possible places at that altitude in the Aringa River basin

in the Imatong Mountains.

Ecology

This species is so far known only from high altitude localities, and has been collected from streams at

over 1,500 m asl, and in the Aringa River at 2,134 m asl.

Vernacular name

The Imatong Mountains Crab.

Conservation status

An IUCN conservation assessment of Potamonautes imatongensis sp. nov. has not yet been carried out.

Remarks

Potamonautes imatongensis sp. nov. is superficially similar to several other Potamonautes species that

share the following characters: a small body size at maturity (beginning at CW 18 mm), a complete

postfrontal crest; completely reduced or absent exorbital and epibranchial teeth; smooth anterolateral

margins immediately behind each epibranchial tooth; a third maxilliped ischium that lacks a visible

sulcus; the first tooth on the carpus of the cheliped that is strong and pointed; a distal meral tooth of

the cheliped that is strong and pointed; and a slim, elongated, highly arched dactylus of the male major

cheliped. East African crabs that share this suite of characters include P. mutandensis (Chace, 1942)

European Journal of Taxonomy 182 : 1-18 ( 2016 )

Fig. 4. Potamonautes imatongensis sp. nov., holotype, adult CW 21.5 mm, from the Imatong

Mountains in northern Uganda (NHM 1955.11.8.26-27). A. Whole animal, dorsal view. B. Frontal view.

C. Ventral view, anterior sternum. Scale bars: 21.4 mm

CUMBERLIDGE N. & CLARK P.F., New species of Ugandan freshwater crabs

(southwest Uganda), P berardi (Audouin, 1826) (Nile River basin), P. williamsi Cumberlidge & Clark,

2010 (Mount Elgon, Uganda), P. amalerensis (Rathbun, 1935) stat. rev. and P. morotoensis sp. nov.

Potamonautes imatongensis sp. nov. differs from P. mutandensis in that the second tooth on the carpus of

the cheliped is weak, low and blunt (vs pointed and as large as the first carpal tooth in P. mutandensis ), the

outer margins of sternal segment s4 are distinctly thickened (vs slim and not thickened in P. mutandensis ;

see Chace 1942; Cumberlidge & Meyer 2011), and the G1 terminal article of P. imatongensis sp. nov.

is straight and cone-shaped and not directed only slightly outward (vs s-shaped, widened medially, and

angled outward at a 45° angle to the longitudinal axis of the gonopod in P. mutandensis).

Potamonautes imatongensis sp. nov. differs from P. berardi in that the G1 terminal article is straight,

cone-shaped and not directed outward (vs straight at first, then bent sharply outward at 45° to the

longitudinal axis in the mid-section in P. berardi) and the outer margins of thoracic sternite s4 are

distinctly thickened (vs slender and not thickened in P. berardi ; see Chace 1942; Cumberlidge & Meyer

2011 ).

Potamonautes imatongensis sp. nov. differs from P. williamsi from Mount Elgon, Uganda, in that the

first tooth on the carpus of the cheliped is strong and pointed (vs small and low in P. williamsi ), thoracic

sternal sulcus s3/s4 is deep at the edges and medially faint (vs s3/s4 is reduced to two short notches

on the external margins of the sternite in P. williamsi) and the outer margins of thoracic sternite s4 are

distinctly thickened (vs slender and not thickened in P. williamsi ; see Cumberlidge & Clark 2010).

As for the species described here, P. imatongensis sp. nov. differs from P. morotoensis sp. nov. in that

the G1 terminal article is straight, cone-shaped and tapering, with a long tube-like tip (vs straight at

first, bent outward at 45° to the longitudinal axis, and cone-shaped, tapering evenly to a down-turned

tip in P. morotoensis sp. nov.), the first tooth on the carpus of the cheliped is medium sized and pointed,

and the second carpal tooth is small, broad and pointed (vs both teeth small and low in P. morotoensis

sp. nov.) and the dactylus of the cheliped is highly arched, enclosing a widely oval interspace when

closed (vs a cheliped dactylus that is only slightly arched and enclosing a long narrow interspace when

closed in P. morotoensis sp. nov.).

Potamonautes imatongensis sp. nov. differs from P. amalerensis stat. rev. in that the G1 terminal article

is straight and cone-shaped with a long tube-like tip (vs straight at first, bent outward at 45° to the

longitudinal axis and cone-shaped, tapering evenly to a pointed tip in P. amalerensis stat. rev.), the

first tooth on the carpus of the cheliped is medium sized and pointed, and the second carpal tooth is

small, broad and pointed (vs a small first carpal tooth and reduced granule-sized second carpal tooth

in P. amalerensis stat. rev.), and the dactylus of the cheliped is highly arched, enclosing a widely oval

interspace when closed (vs a cheliped dactylus that is only slightly arched and encloses a long narrow

interspace when closed in P. amalerensis stat. rev.).

Potamonautes morotoensis sp. nov.

urn:lsid:zoobank.org:act:C751A933-6705-487F-9FEF-4584DC0DA4B7

Figs 1C-D; 2C-D, H, K; 3C-D, I-J; 5A-C; 7C-D; 8

Diagnosis

Based on holotype (adult male CW 26). Carapace outline transversely oval, medium height (CH/FW 1.0);

exorbital tooth low, blunt, epibranchial tooth reduced to granule, postfrontal crest complete faint medially,

lateral ends well defined meeting epibranchial teeth; anterolateral margin posterior to epibranchial

tooth smooth; carapace sidewall vertical sulcus meeting anterolateral margin. Third maxilliped ischium

lacking vertical groove. Sternal sulcus s3/s4 deep, completely crossing sternum, meeting thickened.

European Journal of Taxonomy 182 : 1-18 ( 2016 )

Fig. 5. Potamonautes morotoensis sp. nov., holotype, adult $, CW 26 mm, from Mount Moroto in

northern Uganda (NHM 2015.3056). A. Whole animal, dorsal view. B. Frontal view. C. Ventral view,

anterior sternum. Scale bars: 21.4 mm

CUMBERLIDGE N. & CLARK P.F., New species of Ugandan freshwater crabs

raised anterior margin of sternoabdominal cavity; margins of s4 distinctly raised, thickened. Chelipeds

of adult male unequal; movable finger (dactylus) and fixed finger (propodus) of major cheliped of adult

male slim, elongated, fixed finger (propodus) with 2 large teeth proximally followed by series of small

teeth; movable finger (dactylus) slightly arched, enclosing narrow rectangular interspace when closed.

Inferior margins of merus of cheliped lined by series of small granules, distal meral tooth small pointed;

superior surface of merus granulated. Cheliped carpus first and second teeth small, low, equal-sized. G1

terminal article short, straight, in line with longitudinal axis, cone-shaped, evenly tapering to pointed tip.

Etymology

The new species is named for Mount Moroto in Karamoja District, Uganda which is the only locality

where this species has been collected.

Material examined

Holotype

UGANDA: adult <S, CW 26, CL 17, CH 8.4, FW 8.4 mm (photographed), Lipath River, Mt. Moroto, near

Matheniko Game Reserve, Karamoja District (2.54° N, 34.73° E), extreme headwaters, about 2,438 m

asl, in grassland, 9 Jul. 1963, T.R. Williams (NHM 2015.3056, formerly TRW collection 9 Jul.1963).

Type locality

Uganda, Lipath River, Mt. Moroto, near Matheniko Game Reserve, Karamoja District (2.54° N,

34.73° E), extreme headwaters, about 2,438 m asl, in grassland.

Description

Carapace medium height (CH/FW 1.0); front broad, measuring one-third CW (FW/CW 0.32). Semi¬

circular, urogastric, cardiac, posterior, cervical carapace grooves all distinct. Postfrontal crest complete,

faint medially, lateral ends well defined meeting epibranchial teeth; exorbital tooth low, blunt. Epigastric

crests clear, median sulcus between crests short, forked posteriorly. Epibranchial tooth reduced to

granule; anterolateral margin between exorbital, epibranchial teeth smooth, curving slightly outward,

lacking intermediate tooth; anterolateral margin posterior to epibranchial tooth smooth; carapace

sidewall vertical sulcus faint, incomplete, not meeting anterolateral margin. Suborbital margin smooth.

Carapace sidewall with distinct granulated, vertical sulcus, ending at longitudinal sulcus, dividing

sidewall into 3 parts. Third maxilliped exopod with long flagellum, ischium lacking vertical groove.

Epistomial tooth large, triangular, edges lined by large round granules. Mandibular palp 2-segmented;

terminal segment simple. Thoracic sternal sulcus s2/s3 deep, running horizontally across sternum;

thoracic sternal sulcus s3/s4 deep at edges, faint in middle, almost meeting thickened, raised anterior

margin of sternoabdominal cavity; margins of s4 distinctly raised, thickened. Thoracic episternal sulci

s4/e4, s5/e5, s6/e6, s7/e7 all visible grooves. Chelipeds of adult male unequal; movable finger (dactylus)

and fixed finger (propodus) of major cheliped of adult male slim, elongated, propodus with 2 large teeth

proximally followed by series of small teeth, dactylus slightly arched, enclosing narrow rectangular

interspace when closed. Inferior margins of merus of cheliped with series of small granules, distal meral

tooth small pointed; superior surface of merus granulated. Cheliped carpus first, second teeth small,

low, equal-sized. Abdomen outline broadly triangular with straight edges. G1 terminal article short,

straight, in line with longitudinal axis, cone-shaped, evenly tapering to broad tip. G2 terminal article

long, flagellum-like.

Size

Small species, adult at CW 26 mm.

European Journal of Taxonomy 182 : 1-18 ( 2016 )

Colour

Preserved specimens uniformly light brown.

Distribution

Mount Moroto (2,438 m asl) in Karamoja Province, northern Uganda.

Ecology

This species is so far known only from a single high altitude locality, and was collected from a mountain

stream at 2,438 m asl.

Conservation status

An IUCN conservation assessment of Potamonautes morotoensis sp. nov. has not yet been carried out,

but given the fact that this species is known from a single specimen from a single locality it would

probably be regarded as Data Deficient.

Vernacular name

Mount Moroto Crab

Remarks

Potamonautes morotoensis sp. nov. is superficially similar to several other Potamonautes species that

share the following characters: a small body size at maturity, a complete postfrontal crest; completely

reduced or absent exorbital and epibranchial teeth; smooth anterolateral margins immediately behind each

epibranchial tooth; a third maxilliped ischium that lacks a visible sulcus; a first tooth on the carpus of the

cheliped that is strong and pointed; a strong and pointed distal meral tooth; and a slim, elongated, highly

arched dactylus of the cheliped. East African crabs that share these characters include Potamonautes

imatongensis sp. nov., P. mutandensis (Chace, 1942) (southwest Uganda), P. berardi (Audouin, 1826)

(Nile River basin), and P. williamsi Cumberlidge & Clark, 2010 (Mount Elgon, Uganda).

Potamonautes morotoensis sp. nov. differs from P. amalerensis stat. rev. in that the second tooth

on the carpus of the cheliped is small and low (vs the second carpal tooth is reduced to a granule in

P. amalerensis stat. rev.) and the G1 terminal article tapers evenly to a broad tip (vs G1 terminal article

tapering evenly to a pointed tip in P. amalerensis stat. rev.).

For comparisons ofR morotoensis sp. nov. with P. imatongensis sp. nov., see above.

Potamonautes amalerensis (Rathbun, 1935) stat. rev.

Figs 1E-F; 2E-F, I, L, 3E-F, K-L, 6A-C, 7E-F, 8

Potamon (Geothelphusa) amalerensis Rathbun, 1935: 25, pi. 2.

Potamonautes amalerensis Ng et al ., 2008: 170 (in catalogue).

Potamon amalerensis - Chace 1942: 204, fig 8.

Potamonautes amalerensis - Cumberlidge et al. 2009, appendix 1: 894 (in list).

Rediagnosis

Carapace medium height (CH/FW 1.1); exorbital tooth low, blunt, epibranchial tooth reduced to

granule, postfrontal crest complete, faint medially, lateral ends well defined, meeting epibranchial

teeth; anterolateral margin posterior to epibranchial tooth finely serrate, almost smooth; carapace

sidewall vertical sulcus meeting anterolateral margin. Third maxilliped ischium lacking vertical groove.

Sternal sulcus s3/s4 deep, completely crossing sternum, meeting thickened, raised anterior margin of

CUMBERLIDGE N. & CLARK P.F., New species of Ugandan freshwater crabs

Fig. 6. Potamonautes amalerensis (Rathbun, 1935) stat. rev. A, C. Holotype, adult CW 31.5 mm,

from Mount Kadam, northern Uganda (MCZ 8238). B. Adult S, CW 31.5 mm, from north side of

Mt. Kadam northern Uganda (NMU TRW 1962.04). A. Whole animal, dorsal view. B. Frontal view.

C. Ventral view, anterior sternum. Scale bars: 21.4 mm.

European Journal of Taxonomy 182 : 1-18 ( 2016 )

sternoabdominal cavity; margins of s4 distinctly raised, thickened. Inferior margins of meras of cheliped

with series of small granules, distal meral tooth pointed; first cheliped carpal tooth small, second cheliped

carpal tooth reduced to small granule. Fixed finger (propodus) and movable finger (dactylus) of major

cheliped of adult male each with larger teeth interspersed with small teeth, dactylus slightly arched.

Fig. 7. A-B Potamonautes imatongensis sp. nov., holotype, adult <f, CW 21.5 mm, from the Imatong

Mountains in northern Uganda (NHM 1955.11.8.26-27). A. G1 ventral view. B. G1 dorsal view. —

C-D. Potamonautes morotoensis sp. nov., holotype, adult S, CW 26 mm, from Mount Moroto in

northern Uganda (NHM 2015.3056). C. G1 ventral view. D. G1 dorsal view. — E-F. Potamonautes

amalerensis (Rathbun, 1935) stat. rev., holotype, adult S, CW 31.5 mm, from Mount Kadam, northern

Uganda (MCZ 8238). E. G1 terminal article ventral view. F. G1 terminal article dorsal view. Scale bars:

A-B = 2.34 mm, C-D = 3.1 mm, E-F = 3.3 mm

CUMBERLIDGE N. & CLARK P.F., New species of Ugandan freshwater crabs

enclosing long narrow interspace when closed. G1 terminal article short cone-shaped, directed outward

at 45° angle to longitudinal axis of gonopod, evenly tapering to pointed tip.

Material examined

Holotype

UGANDA: adult CW 26, CL 17.4, CH 8.4, FW 8.4 mm, Amaler River, Mt. Kadam (formerly Mt.

Debasien), KaramojaDistrict (1.72° N, 34.72° E), at 1,524 m asl, Sep. 1933, A. Loveridge (MCZ 8238).

Paratypes

UGANDA: adult 4 $$, adult 5 55, 1 juvenile, Amaler River, Mt. Kadam (formerly Mt. Debasien),

Karamoja District (1.72° N, 34.72° E), at 1,524 m asl, Sep. 1933, A. Loveridge (MCZ 8237).

Other material examined

UGANDA: adult CW 31.5 mm, north side of Mt. Kadam (formerly Mt. Debasien), Karamoja District

(1.81° N, 34.71° E) (NMU TRW 1962.04).

Type locality

Uganda, Amaler River, Mt. Kadam (formerly Mt. Debasien), Karamoja District (1.72° N, 34.72° E).

Size

Small species, adult size range between CW 26.0-31.5 mm.

Colour

Preserved specimens uniformly light brown.

Distribution

Uganda, Am aler River, Mt. Kadam (formerly Mt. Debasien), Karamoja District in Karamoja Province,

northern Uganda. This species is known from only two localities: Amaler River (1.72° N, 34.72° E), and

the north side of Mt. Kadam (1.81° N, 34.71° E).

Ecology

This species was collected from high altitude mountain streams at 1,524 m asl.

Vernacular name

Mount Kadam Crab.

Conservation status

This species is known only from two localities both on Mount Kadam in Uganda, and from a total

of 11 specimens collected in 1935 and 1962. Potamonautes amalerensis stat. rev. was listed as Data

Deficient (IUCN 2003; Cumberlidge et al. 2009) in view of the absence of further information on its

extent of occurrence, ecological requirements, population size, population trends, and long-term threats

(Cumberlidge 2008). The addition of a second locality on Mount Kadam would probably not warrant a

change in assessment category.

Remarks

The type material was collected during the AMNH 1933-1934 Expedition to the then colonies of

Kenya and Uganda led by Mr. Arthur Loveridge, a Fellow of the Guggenheim Memorial Foundation.

Potamon ( Geothelphusa ) amalerensis Rathbun, 1935 stat. rev., is redescribed here as the valid species

European Journal of Taxonomy 182 : 1-18 ( 2016 )

Potamonautes amalerensis stat. rev., because Bott (1955) erroneously treated this taxon as a junior

synonym of Potamonautes ( Rotundopotamonautes ) didieri (Rathbun, 1904) from the D.R. Congo

(Cumberlidge & Clark 2012). This opinion of Bott (1955) is further undermined by the fact that he

re-described P. didieri based on a non-type museum specimen from ‘Ethiopia’ using photographs of

the carapace and illustrations of the gonopods of this (unidentified) specimen (ZSM, CW 37 mm). As

a result, a number of subsequent authors (Cumberlidge 1997, 1998; Ng et al. 2008; Cumberlidge et al.

2009) did not accept the opinion of Bott (1955), and recognized P. didieri and P. amalerensis stat. rev.

as valid Potamonautes species. Illustrations and photographs of the holotype of P. amalerensis stat. rev.

Fig. 8. Distribution map showing the known localities of Potamonautes imatongensis sp. nov. (black

circles, not shown to scale), Potamonautes morotoensis sp. nov. (black star, not shown to scale) and

Potamonautes amalerensis (Rathbun, 1935) stat. rev. (black squares, not shown to scale) in Uganda.

East Africa. For exact localities see text.

CUMBERLIDGE N. & CLARK P.F., New species of Ugandan freshwater crabs

were provided by Rathbun (1935: 25, plate 2) as Potamon ( Geothelphusa ) amalerensis stat. rev. and by

Chace (1942: 204, fig. 8) as Potamon amalerensis stat. rev.

Potamonautes amalerensis stat. rev. is superficially similar to several other species of African freshwater

crabs in that they share the following characters: a small body size at maturity (beginning at CW 18 mm);

a complete postfrontal crest; completely reduced or absent exorbital and epibranchial teeth; smooth

anterolateral margins immediately behind each epibranchial tooth; a third maxilliped ischium that lacks

a visible sulcus; a cheliped merus with a strong and pointed distal meral tooth; and a slim, elongated,

arched dactylus of the male major cheliped that when closed encloses either a wide oval interspace or

a long narrow interspace. For comparisons of P. amalerensis stat. rev. with P. morotoensis sp. nov. and

P. imatongensis sp. nov. see above.

Acknowledgements

We would like to acknowledge support from an NMU Faculty Grant Award, and the contributions of

NMU biology student Wesley S. Bos for assisting in part of this work.

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Manuscript received: 13 August 2015

Manuscript accepted: 17 November 2015

Published on: 17 March 2016

Topic editor: Rudy Jocque

Desk editor: Kristiaan Hoedemakers

Printed versions of all papers are also deposited in the libraries of the institutes that are members of the

EJT consortium: Museum national d’Histoire naturelle, Paris, France; Botanic Garden Meise, Belgium;

Royal Museum for Central Africa, Tervuren, Belgium; Natural History Museum, London, United

Kingdom; Royal Belgian Institute of Natural Sciences, Brussels, Belgium; Natural History Museum of

Denmark, Copenhagen, De nm ark.