Freshwater Crabs (Brachyura : Potamoidea : Potamonautidae) From The Rainforests Of The Central African Republic, Central Africa

14 Pages·2000·11.4 MB·English

by  N Cumberlidge

PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
113(2):406-419. 2000.
Freshwater crabs (Brachyura: Potamoidea: Potamonautidae) from
the rainforests of the Central African Republic, Central Africa
Neil Cumberlidge and Christopher B. Boyko
(NC) Department of Biology, Northern Michigan University, Marquette, Michigan 49855, U.S.A.
(CBB) Division of Invertebrate Zoology, American Museum of Natural History,
Central Park West @ 79th St., New York, New York 10024, U.S.A., and
Department of Biological Sciences, University of Rhode Island,
Kingston, Rhode Island 02881, U.S.A.
—
A
Abstract. collection of freshwater crabs of the family Potamonautidae
from the Central African Republic made recently by the Central African Re-
public Expedition of the American Museum of Natural History, New York,
comprised four species in two genera. The collection included two species of
Potamonautes MacLeay, 1838, P. paecilei A. Milne-Edwards, 1886, and P.
ballayi A. Milne-Edwards, 1886 and two species of Sudanonautes Bott, 1955,
S. africanus A. Milne-Edwards, 1869, and S. sangha, new species. Only six
species of freshwater crabs have been previously reported to occur in the Cen-
tral African Republic. The addition of S. africanus and S. sangha brings to
eight the number of species of freshwater crabs reported from that country.
The freshwater crabs reported on here danonautes Bott, 1955. Both of these genera
were collected during a systematic survey of belong to the exclusively African freshwater
the freshwater and terrestrial Mollusca ofthe crab family Potamonautidae Bott, 1970. The
Central African Republic made by the two species of Potamonautes are P. ballayi
American Museum of Natural History. The (A. Milne-Edwards, 1886) and P. paecilei
survey aimed to document biodiversity, to (A. Milne-Edwards, 1886). Both are little-
catalogue introduced species, and to identify known species and their diagnostic charac-
intermediate hosts that may serve as vectors ters are redescribed here. Additionally, a lec-
of parasite larvae responsible for disease in totype is herein designated for P. paecilei.
humans and domestic animals. The fresh- One of the species of Sudanonautes is
water crab collections were made in the vi- clearly S. africanus (A. Milne-Edwards,
cinity of the village of Bayanga, Central Af- 1869). This is a common and well-known
rican Republic, which lies on the banks of species that was recently redescribed by
the Sangha river in a remote and largely Cumberlidge (1995a, 1999). The second
roadless area close to southern Cameroon, species of Sudanonautes in the collection is
the Republic Populaire du Congo (formerly superficially similar in some respects to S.
French Congo), and Gabon. This region in- africanus, S. chavanesii (A. Milne-Edwards,
cludes an area of tropical forest that supports 1886), S. faradjensis (Rathbun, 1921), S.
elements of both the West African and Zaire floweri (de Man, 1901), S. granulatus
river basin faunas, and consequently has an (Balss, 1929) and S. aubryi (H. Milne Ed-
unusually high biodiversity. wards, 1853). However, the new specimen
The collection of freshwater crabs ob- from the Central African Republic has a
tained included two species of Potamonau- number of important characters that do not
tes MacLeay, 1838, and two species of Su- conform to the descriptions of any of these
VOLUME 1 13, NUMBER 2 407
species (Cumberlidge 1993, 1994, 1995a, s4/s5, s5/s6, s6/s7, s7/s8, sternal sulci be-
1995b, 1995c, 1995d; 1999). Although the tween adjacent thoracic sternites; s4/e4, s5/
specimen is a subadult female, and ideally e5, s6/e6, s7/e7, episternal sulci between ad-
an adult male is needed to make a definitive jacent thoracic sternites and episternites; Pl-
identification, a preliminary description is P5, pereiopods 1-5.
provided here, based on several unique so-
matic characters of the specimen. This new Systematic Account
taxon is the eleventh species of Sudanon-
Genus Potamonautes MacLeay, 1838
autes to be described (Cumberlidge 1999). —
Characters of the gonopods, male abdomen, Diagnosis. Postfrontal crest completely
and male chelipeds will be described when crossing carapace and meeting anterolateral
more material (including an adult male) be- margins at epibranchial teeth. Anterolateral
comes available. margin always lacking intermediate tooth
Only six species of freshwater crabs have between exorbital angle and epibranchial
been previously reported to occur in the tooth. Mandibular palp always two-seg-
Central African Republic (Bott 1955, Cum- mented. Exopod of third maxilliped always
berlidge 1999). These are: Potamonautes with long flagellum. Terminal article of gon-
ballayi (A. Milne-Edwards, 1886), P. pae- opod 1 short, about one-quarter to one-third
cilei (A. Milne-Edwards, 1886), P. dybowski as long as subterminal segment of gonopod
(Rathbun, 1904), Sudanonautes faradjensis 1. Terminal article of gonopod 2 a long fla-
(Rathbun, 1921), S. flowed (de Man, 1901) gellum about 0.5-0.75 times as long as sub-
and S. granulatus (Balss, 1929). The addi- terminal seg—ment of gonopod 2.
tion of S. africanus and S. sangha new spe- Remarks. Bott (1955) revised Potamon-
cies in the present work brings to eight the autes and included 38 species and 14 sub-
number of species of freshwater crab re- species, and erected 15 subgenera to accom-
ported from the Central African Republic. modate these taxa. Since that work, a num-
ber of other species and subspecies have
Materials and Methods been described. These are Potamonautes
triangulus (Bott, 1959), P. brincki (Bott,
Figures were prepared by capturing an 1960) (Cumberlidge 1994, 1999; Stewart
image with a digital camera and completed 1997a), P. (Isopotamonautes) anchetiae ma-
using the programs Adobe Photoshop® and chadoi Bott, 1964, P. (Lirrangopotamonau-
Adobe Illustrator® (Harvey 1999). The tes) lirrangensis adeleae Bott, 1968, P. (/)
specimens are deposited in the American senegalensis Bott, 1970, P. dentatus Stew-
Museum of Natural History, New York, art, Coke, & Cook, 1995, P. parvispina
U.S.A. (AMNH). Abbreviations: Museum Stewart, 1997b, P. granulans Daniels, Stew-
&
national d'Histoire naturelle, Paris, France art, Gibbons, 1998, and P. reidi Cumber-
(MNHN); Museum royale d'Afrique central, lidge, 1999.
Tervuren, Belgium (MRAC); Biology, Bott (1955) assigned Potamonautes bal-
Northern Michigan University, Marquette, layi and P. paecilei to the subgenus Longi-
Michigan, U.S.A. (NMU); Senckenberg Mu- potamonautes Bott, 1955, which also includ-
seum, Frankfurt, Germany (SMF); cw, dis- ed a number of other species of rainforest
tance across the carapace at the widest point; river crabs from Central Africa in which
cl, carapace length measured along the me- adult males have an elongated, highly arched
dian line, from the anterior to the posterior right cheliped and sharp teeth on the antero-
margin; ch, carapace height (the maximum lateral margins of the carapace: P. vanden-
height of the cephalothorax); fw, front width brandeni (Balss, 1936), P. schubotzi (Balss,
measured along the anterior margin; s, tho- 1914), P. punctatus Bott, 1955, P. ballayi
racic sternite; e, thoracic episternite; s4/s5, acristatus Bott, 1955, and P. ballayi gono-
408 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
cristatus Bott, 1955. Although Bott (1955) curving slightly outward, lacking interme-
recognised numerous subgenera of Pota- diate tooth; anterolateral margin posterior to
monautes including Isolapotmonautes, Pla- epibranchial tooth smooth, raised, curving
typotamonautes, Lirrangopotamonautes and inward over mesobranchial surface of cara-
Longipotamonautes, we prefer here to fol- pace, and not continuous with posterolateral
low Cumberlidge (1999) and use Potamon- margin. Carapace height approximately
autes sensu lato for all species, pending a equal to front width (ch/fw 1.07). Front very
revision of the entire genus. broad, measuring almost one half width of
carapace (fw/cw 0.45) (Fig. IB). Sidewall of
Potamonautes ballayi (A. Milne-Edwards, carapace with distinct vertical sulcus, con-
1886) tinuing downward in pterygostomial region,
Figs. 1, 2 dividing sidewall into four parts. Exopod of
third maxilliped with a long flagellum, is-
Thelphusa Ballayi A. Milne-Edwards, 1886:
chium of third maxilliped smooth lacking
149.—A. Milne-Edwards, 1887:132, pi. 7,
vertical sulcus (Fig. ID). First thoracic ster-
figs. 2, 2a.
nal sulcus sl/s2 absent; second sulcus s2/s3
Potamon {Potamori) ballayi: Rathbun, 1904:
deep, running horizontally across sternum;
294, pi. 12, fig. 9.—Rathbun, 1921:419-
third sternal sulcus s3/s4 absent so that ster-
422, pi. 27-28, figs. 1, 10. num in this region completely smooth (Fig.
Potamon {Potamonautes) ballayi: Balss,
1C). Thoracic episternal sulci s4/e4, s5/e5,
1936:174-177, figs. 9, 12-13. — s6/e6 and s7/e7 smooth, none marked by
Potamon ballayi: Chace, 1942:206. Ca-
visible groove. Major cheliped of adult
part, 1954:827, fig. 3.
males distinct, with widely arched dactylus
Potamonautes {Longipotamonautes) ballayi
and propodus longer than carapace width
ballayi: Bott, 1955:244-245, pi. VII, figs.
(Fig. 1G). First carpal tooth of inner margin
2a-Ki, figs. 23, 73.
of carpus of cheliped large, slender, pointed;
—
Type material and type locality. Female second carpal tooth pointed, half size of first
holotype, Ngancin (=Nganchu = Ngabe), tooth. Lateral inferior margin of merus of
Republic Populaire du Congo (formerly cheliped lined by small teeth, medial inferior
French Congo), 03°18'S, 16°6'E, on oppo- margin of merus of cheliped smooth, with
site bank to Kwamouth, Democratic Repub- single large pointed distal meral tooth at dis-
lic of Congo (formerly Zaire), coll. Apr tal end (Fig. 1J); superior surface of merus
MNHN.
1884, — ridged by rows of short carinae (Fig. II).
Material examined. Central African Re- Terminal article of gonopod 1 short (about
public. 1 adult male, cw 18.8 mm (AMNH one-third as long as subterminal segment),
17826), about 19 km from the village of longitudinal groove visible on dorsal and su-
Bayanga, Yobei (Yobe) river, depth 0.1 m, perior sides (but not on ventral side); entire
sandy shore near large dam made entirely of terminal article slim, tubular, and directed
closely interwoven branches and vines, coll. outward at 45° angle to vertical, ending in
J. Cordeiro, 1—8 Jun 1998. wide tip forming distinct pointed process on
Diagnosis. Postfrontal crest not com- medial side; lateral and medial folds on ter-
plete, epigastric lobes significantly separated minal article of gonopod 1 approximately
from postorbital crests, and lateral ends of equal (Figs. 2A-C). The adult size range of
postorbital crests not quite meeting antero- P. ballayi is be—tween cw 28-30 mm.
lateral margins (Fig. 1A). Exorbital angle Description. For a detailed description
produced into small pointed tooth; epibran- and additional illustrations see Rathbun
chial tooth large, sharp, and pointing for- (1921) and Bott (1955). For a brief descrip-
ward; anterolateral margin between exorbital tion of the t—ype, see Capart (1954, fig. 3).
angle tooth and epibranchial tooth smooth, Remarks. Rathbun (1921) recorded the
VOLUME 113, NUMBER 2 409
Fig. 1. Potamonautes ballayi (A. Milne-Edwards, 1886). Male, cw 17.3 mm, AMNH 17826. A, carapace
and eyes, dorsal view; B, cephalothorax, carapace and eyes, frontal view; C, anterior sternum; D, left third
maxilliped; E, left mandible; F, abdomen; G, right cheliped, frontal view; H, left cheliped, frontal view; I, carpus
and merus of right cheliped, lateral view; J, carpus and merus of right cheliped, mesial view; K, left second
pereiopod, lateral view. Scale = 1.6 mm (E), 3.3 mm (D, G-J), and 4.4 mm (A-C, F, K).
410 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
Fig. 2. Potamonautes ballayi (A. Milne-Edwards, 1886). Male, cw 17.3 mm, AMNH 17826. A, left gonopod
1, cephalic view; B, left gonopod 1, caudal view; C, distal portion of left gonopod 1, superior view; D, left
gonopod 2. Scale = 0.80 mm (C), and 1.67 mm (A, B, D).
mandibular palp as three-segmented. This is (now Kisangani). Lang wrote that it is prob-
an error, for it is clearly two-segmented (Fig. able that P. ballayi can live out of water and
IE), as is the case for all members of the that it is only dependent on a certain amount
genus, and, indeed all potamonautid African of moisture. When disturbed, crabs were re-
freshwater crabs (Cumberlidge 1999). Be- ported to instantly cover themselves with
cause the type of P. ballayi is a female, the mud and secure protection beneath any ob-
gonopods were not illustrated in the first de- ject. —
scriptive works on the species. Gonopod 1 Distribution. Republic Populaire du
of P. ballayi was subsequently illustrated by Congo (formerly French Congo), Democrat-
Rathbun (1921) who used a male (cw 26 ic Republic of Congo, and Gabon. The type
AMNH
mm, 3356) from Stanleyville (now locality of P. ballayi at Ngabe, Republic Po-
Kisangani, Democratic Republic of Congo) pulaire du Congo lies on the banks of the
and by Bott (1955), who used a male (cw Zaire river opposite Kwamouth, Democratic
33 mm, MRAC 17413) from Karawa, Uban- Republic of Congo. The present study
gi, Democratic Republic of Congo. Gono- showed that P. ballayi is present in the Yobe
pod 1 of the male from the Central African river, a tributary of the Sangha river which
Republic is shown here in more detail (Figs. drains into the Zaire river in a broad marshy
2A-C), and gonopod 2 of P. ballayi is il- area at Mossaka, Republic Populaire du
lustrated fo—r the first time (Fig. 2D). Congo. For more localities see Rathbun
Ecology. The specimen from the Central (1921), Balss (1936), and Bott (1955).
African Republic was caught in shallow wa-
ter (only 0.1 m deep) near a dam made en- Potamonautes paecilei (A. Milne-Edwards,
1886)
tirely of closely interwoven branches and
vines. Herbert Lang's field notes (in Rathbun Fig. 3
1921) record that P. ballayi is common in Thelphusa paecilei A. Milne-Edwards,
shallow forest streams around Stanleyville 1886:149
VOLUME 1 13, NUMBER 2 411
Parathelphusa paecilei: A. Milne-Edwards, um of third maxilliped smooth, lacking ver-
1887:143, pi. 7, figs. 1, la; Ortmann, tical sulcus (Fig. 3D). First thoracic sternal
1897:300. sulcus sl/s2 absent; second sulcus s2/s3
Potamon {Parathelphusa) paecilei: Rath- deep, running horizontally across sternum;
bun, 1905:257, fig. 167. — third sternal sulcus s3/s4 absent; sternum in
Potamon paecilei: Chace, 1942:208. Ca- this region completely smooth. Episternal
part, 1954:841-842, figs. 34, 37. sulci s4/e4, s5/e5, s6/e6 and s7/e7 smooth,
Potamonautes (Longipotamonautes) paeci- none marked by visible groove. Major che-
lei: Bott, 1955:242-243, pi. VI, figs. 2a- liped of adult males distinct, with widely
d, text figs. 21, 71. arched dactylus and a propodus longer than
— carapace width. First carpal tooth of inner
Type material and type locality. Adult
mm margin of carpus of cheliped large, slender,
male lectotype, cw 32 (MNHN-B263),
pointed; second carpal tooth half size offirst.
Central Africa, Republic Populaire du Con-
Lateral and medial inferior margins ofmerus
go (formerly French Congo), Lateke (=Lek-
of cheliped lined by small teeth; single large
eti), Alima river (14°56'E, 1°36'S), coll. M.
pointed distal meral tooth at distal end (Fig.
de Brazzae.
— 3J); superior surface of merus ridged by
Material examined. Central African Re-
public. adult female, cw 18.6 mm, rows of short carinae (Fig. 31). Terminal ar-
1
(AMNH 17827), 17.3 km from the village ticle of gonopod 1 short (about one-third as
long as subterminal segment), longitudinal
of Bayanga (02°45'43"N, 16°14'12"E), Lossi
groove visible on superior side, but not on
creek, depth 1-2 m, bottom of the fine sand
dorsal and ventral sides; entire terminal ar-
and mud, caught in net in swiftly moving
black water, coll. J. Sullivan, 19 Jun 1998.— ticle slim, tubular, curved; directed outward
1 adult male, cw 20.7 mm (AMNH 18032), at an approximately 45° angle to vertical;
17.3 km from the village of Bayanga ending in broadened upcurved tip; lateral
and medial folds on terminal article of gon-
(02°45'43"N, 16°14'12"E), Lossi creek,
depth 1-2 m, bottom of fine sand and mud, opod 1 approximately equal size. The adult
caught in net in swiftly moving black water, size range of P. paecilei is between cw 28-
30 mm.
coll. M. Lawrence, J. Sullivan, and local res- —
idents, 30 Jun 1998. Description. See Bott (1955), and Ca-
—
Diagnosis. Postfrontal crest either com- part (1954).—
Remarks. One of us (NC) has examined
plete or almost complete, wherein lateral
ends of postorbital crests not quite meeting an adult male syntype (cw 32 mm) of P.
anterolateral margins (Fig. 3A). Exorbital paecilei (MNHN-B 263) from the Alima riv-
angle produced into small, pointed, sharp er, Lateke French Congo collected by M. de
tooth; epibranchial tooth large, pointed, di- Brazzae. We designate this specimen here as
A
rected forward; anterolateral margin be- the lectotype. different male syntype (now
tween exorbital angle tooth and epibranchial paralectotype) of P. paecilei (cw 22.7 mm)
tooth smooth, curving outward, lacking in- was figured by Capart (1954). The charac-
termediate tooth; anterolateral margin pos- ters of this species (Fig. 3) include a large
terior to epibranchial tooth with two sharp, forward-pointing epibranchial tooth; a large
forward-pointing teeth; margin otherwise tooth (or two teeth) behind the epibranchial
smooth, continuous with posterolateral mar- tooth on the anterolateral margin; an en-
gin. Front very broad, measuring almost larged major cheliped in adult males with a
one-half width of carapace (fw/cw 0.45) widely arched dactylus and a propodus that
(Fig. 3A, B). Carapace height approximately is longer than the carapace width; a long
equal to front width (ch/fw 1.07). Exopod of sharp distal meral spine on the merus of the
third maxilliped with long flagellum, ischi- cheliped; and the ischium of the third max-
412 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
Fig. 3. Potamonautes paecilei (A. Milne-Edwards, 1886). Female, cw 18.6 mm, AMNH 17827. A, carapace
and eyes, dorsal view; B, cephalothorax, carapace and eyes, frontal view; C, anterior sternum; D, left third
maxilliped; E, left mandible; F, abdomen; G, right cheliped, frontal view; H, left cheliped, frontal view; I, carpus
and merus of right cheliped, lateral view; J, carpus and merus of right cheliped, mesial view; K, left second
pereiopod, lateral view. Scale = 2.2 mm (E), 3.3 mm (D, I, J), 4.4 mm (A, B, F-H, K), and 5.9 (C).
VOLUME 113, NUMBER 2 413
illiped is smooth and a vertical sulcus is article of gonopod 1 very long (at least two-
lacking. thirds as long as subterminal segment). Ter-
The sidewall of the carapace of the spec- minal article of gonopod 1 either slim and
imens from the Central African Republic has needle-like (where longitudinal groove not
a distinct vertical sulcus which continues visible) or broadened in middle (the result
downward across the pterygostomial region, of a higher medial fold) with longitudinal
dividing the carapace sidewall into four groove visible at least for part of length. Ter-
parts. This contrasts with the type from the minal article of gonopod 2 very short, one-
Republic Populaire du Congo where the fifteenth length of subterminal segment.
—
sidewall of the carapace is divided into only Distribution. The genus is present in
three parts.— Cote-dTvoire, Ghana, Togo, Benin, Nigeria,
Ecology. The specimens from the Cen- Cameroon, Gabon, Bioko (Fernando Po),
tral African Republic were netted in a small Central African Republic, Congo, Zaire,
m
stream (1-2 deep), with swiftly moving northern Angola, and southwest Sudan. The
black water flow—ing over fine sand and mud. eleven species of Sudanonautes are found in
Distribution. Republic Populaire du the inland waters of West and Central Africa
Congo, and Democratic Republic of Congo. in a region bounded by Cote-dTvoire, south-
The Yobe river is a tributary of the Sangha west Sudan, and northern Angola. This area
river which drains southwestern Central Af- includes the Upper Guinea rainforests, the
rican Republic and forms part of the border Lower Guinea forest together with the sa-
between the Central African Republic and vannas of the eastern part of West Africa,
Cameroon, and then between Cameroon and and the offshore island of Bioko. In Central
Republic Populaire du Congo, beforejoining Africa seven species of Sudanonautes {S. af-
the Zaire river in a broad marshy area at ricanus, S. aubryi, S. floweri, S. granulatus,
Mossaka, Republic Populaire du Congo. The S. chavanesii, S. faradjensis, and S. sangha)
type locality lies on the Alima river which share the rivers and forests with species of
flows into the Zaire river just to the south of Potamonautes and Erimetopus A. Milne-Ed-
Mossaka and contributes to the same ex- wards, 1886 (Bott 1955, Cumberlidge 1999).
panse of marsh and wetlands as the Sangha
river. Sudanonautes africanus (A. Milne-
Edwards, 1869)
Sudanonautes Bott, 1955
— Thelphusa africana A. Milne-Edwards,
Sudanonautes Bott, 1955:295. Cumberlid-
1869:186, pi. XI, figs. 2, 2a,b.—A. Milne-
ge, 1999:172-176.
— Edwards, 1887:124-126, pi. IV, fig. 8.
Diagnosis. Intermediate tooth on antero- Potamon {Potamonautes) africanus: de
lateral margin between epibranchial tooth Man, 1903:41, pi. IX, figs. 7-9.—Rath-
and exorbital angle. Postfrontal crest prom- bun, 1904, pi. 16, fig. 6.—Rathbun, 1905:
inent, almost horizontal, complete, with lat- 188-190, fig. 47.—Balss, 1929:124-125,
eral ends meeting anterolateral margins. Car- figs. 5-7.—Balss, 1936:166.
apace sidewall divided by two sulci into Potamon {Potamonautes) africanum: Colo-
three parts. Mandibular palp two-segmented; si, 1920:34.—Colosi, 1924:21, fig. 16.—
terminal segment consisting of large oval Roux, 1927:237.
—
posterior lobe (in three species there a small Potamon africanus: Chace, 1942:204. Ca-
but distinct anterior process at junction be- part, 1954:824, figs. 1, 6.
tween segments). Long, plumose flagellum Sudanonautes {Sudanonautes) africanus af-
on exopod of third maxilliped in all species. ricanus: Bott, 1955:295-298, figs. 61, 93-
Sternal sulcus s3/s4 represented only by two 95, 103 a-d, pi. 24, figs. 2a-c, 3.—Bott,
short notches at sides of sternum. Terminal 1959:1004-1005.—Monod, 1977:1216
414 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
(not figs. 93-95, 102).—Monod, 1980: (AMNH 18036), about 5 km from the village
384, pi. V, fig. 27. of Bayanga, Mobeya [Moubia?] creek, up-
Sudanonautes africanus: Cumberlidge, stream of mouth, depth 0.5-1 m, sandy,
1995a:588-598, figs. 1-3, table 1.—Cum- gravely and muddy pools, in burrows in over-
berlidge, 1999:181-184, figs. 30B, 32B, hanging banks, among roots, under logs, coll.
33B, 34B, 35C, 36E, 37C, 53P, 54-57, M. Lawrence, J. Sullivan, and J. B. Kindi-
60B, 67A, table IX. moungo, 28 Jun 1998.
—
— Type locali—ty. Gabon.
Type material. The holotype used by A. Diagnosis. Carapace relatively flat (ch/
Milne-Edwards (1869) to describe Thelphu- fw 1.06). Postfrontal crest smooth almost
sa africana was a small juvenile (MNHN)
straight; spanning entire carapace, meeting
(cw 17 mm) collected from Gabon by M. anterolateral margins at epibranchial teeth;
A
Aubry-Lecomte. more detailed descrip- posterior surface of carapace in cardiac and
tion by A. Milne-Edwards (1887) was based branchial regions with patches of raised cir-
on a larger, but still subadult female cular blisters, lateral parts with fields of
(MNHN) (cw 53 mm) collected from the
raised short lines (carinae); semi-circular,
river Ogoue, Congo (=Gabon). Because nei- cardiac, urogastric grooves very deep. Prox-
ther of these specimens was suitable to re- imal region of pollex of propodus of major
describe the species (one is a juvenile and cheliped of adult with large, conspicuously
the other a subadult female), and because no
flattened tooth. Exorbital angle tooth large,
topotypes were available, the species was re- triangular; intermediate tooth large, triangu-
described by Cumberlidge (1995a) from an lar blunt, as big as exorbital angle tooth. Epi-
adult male (cw 83 mm) from Cross River branchial tooth small, about half size of in-
(NMU
State, Nigeria 9.IV.1983), and an termediate tooth and exorbital angle tooth.
adult female (cw 108 mm) from a tributary Anterolateral margin behind epibranchial
of the Ikpan river, Cross River State, Nigeria tooth smooth. Terminal article of gonopod 1
(NMU
5.IV.1983). — thin, needle-like, subterminal segment of
Material examined. Central African Re- gonopod 1 slim. This is the largest species
public. Ten specimens, sub-adults and juve- of freshwater crab in Africa. Adult sizes
(AMNH km
niles (no adults) 18033), 19.5 range from the size at the pubertal molt (cw
from the village of Bayanga (03°05'27"N, 70-75 mm) to largest the known specimen
16°16'40"E), Mapoyo (Mboye) creek, depth (cw 113 mm).
—
1—1.5 m, either on muddy bottom, or in bur- Description. For a detailed description
rows in overhanging banks, coll. M. see Cumberlidge (1995a, 1999). For a brief
Lawrence, J. Sullivan, and local residents, 17 description of the type see Capart (1954,
Jun 1998. Four specimens, 1 adult male and figs. 1, 6). —
3 juveniles (AMNH 18034), about 5 km from Remarks. Sudanonautes africanus is a
the village of Bayanga, Mobeya [Moubia?] common and well-known species that was
creek, upstream of mouth, depth 0.5-1 m, recently redescribed (Cumberlidge 1995a,
sandy, gravely and muddy pools, in burrows 1999).
—
in overhanging banks, among roots, under Ecology. This species is restricted to the
logs, coll. M. Lawrence and local residents, more humid areas of the coastal rainforest
26 Jun 1998. One subadult male (AMNH belt from south-east Nigeria to the mouth of
18035), 19.5 km from the village of Bayanga the Zaire river. Sudanonautes africanus oc-
(03°05'27"N, 16°16'40"E), Mapoyo (Mboye) curs in a range of permanent aquatic habitats
creek, depth 1-1.5 m, on muddy bottom, or from large rivers and small streams (with
in burrows in overhanging banks, coll. M. both fast and slow flowing water) to ponds.
Lawrence, J. Sullivan, and local residents, 17 In the Central African Republic S. africanus
m
Jun 1998. Four specimens, all juveniles is found in creeks up to 1.5 deep with a
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VOLUME 113, NUMBER 2 415
sand, gravel or mud bottom. Specimens pointed; second carpal tooth reduced to
were also taken from burrows in overhang- small granule. —
ing banks, among roots and under logs. Else- Description. Carapace (Figs. 4A, B).
where in its range, this species is also com- Ovoid, widest in anterior third (cw/fw 3.79),
mon in streams and rivers draining mature medium height (ch/fw = 1.16), semi-circu-
forest, and has been reported to dig burrows lar, urogastric, transverse branchial grooves
near waterways. This crab also occurs in very deep, regions smooth; cardiac region
temporary water sources such as drainage weakly marked, cervical grooves present but
culverts and ditches. For more details see weak. Front slightly bilobed, anterior margin
Cumberlidge (19—95a, 1999). indented, relatively narrow, about one-quar-
Distribution. Sudanonautes africanus ter carapace width (fw/cw = 0.26) (Fig. 4B).
occurs in the coastal rainforest regions ofNi- Postfrontal crest smooth, spanning entire
geria and Central Africa. In Central Africa carapace, straight part consisting of fused
S. africanus occurs in south Cameroon, the epigastric, postorbital crests, then curving
Republic Populaire du Congo, and Gabon backward behind intermediate teeth to meet
(in the San Benito, Ogoue and Alima rivers), anterolateral margins at epibranchial teeth.
and in the lower reaches of the Zaire River Anterolateral margin smooth posterior to
basin. For more details see Cumberlidge epibranchial tooth. Exorbital tooth large,
(1995a, 1999). The present record is the first sharp, pointed forward. Epibranchial tooth
report of the presence of S. africanus in the low, small, set back behind mid-point of
Central African Republic. postfrontal crest.
Carapace sidewalls mostly smooth, with
Sudanonautes sangha, new species faint granules in suborbital regions. Each
Fig. 4 sidewall with two sutures, one longitudinal,
one vertical, dividing sidewall into three
—
Type material and type locality. Central parts. Longitudinal (epimeral) suture divid-
African Republic. Holotype: 1 subadult fe- ing suborbital, subhepatic regions from pter-
mm
male, cw 40.5, cl 29.7, ch 12.5, fw 10.7 ygostomial region, beginning medially at
(AMNH 17825), a few km upstream from lower margin of orbit, curving backward
the village of Bayanga (02°45'43"N, across flank. Short vertical suture dividing
16°14'12"E), Sangha river, depth 1-2 m, in suborbital region from subhepatic region;
fish trap, eating worm, coll. J. Sullivan and vertical suture meeting intermediate tooth.
J. B. Kindimo—ungo, 18 Jun 1998. First transverse groove on sternum, between
Diagnosis. Exorbital tooth large, point- sternal segments s2 and s3, complete; sec-
ed; intermediate tooth small, low; epibran- ond groove, between sternal segments s3
chial tooth small, low, not directed outward, and s4, consisting of two small notches at
set back behind mid-point of postfrontal sides of sternum. Third maxillipeds filling
crest. Postfrontal crest spanning entire cara- entire oral field, except for transversely oval
pace, crest curving backward before meeting efferent respiratory openings at superior lat-
epibranchial tooth, anterolateral margin pos- eral corners; long flagellum on exopod of
terior to epibranchial tooth raised, lined by third maxilliped; ischium of third maxilliped
small granules. Semi-circular, urogastric, smooth, with clear vertical groove (Fig. 4C).
transverse branchial grooves very deep. Ver- Mandibular palp two-segmented; terminal
tical suture on carapace sidewall meeting in- segment single, undivided, with hair but no
termediate tooth. Carapace medium height hard flap at junction between segments (Fig.
(ch/fw = 1.16). Mandibular palp two-seg- 4D). Segments 1-6 of female abdomen four-
mented; terminal segment single, undivided, sided, last segment a broad rounded triangle,
with hair at junction between segments. First sides forming a smooth curved, rounded
carpal tooth on carpus of cheliped large, margin; segments 5-6 broadest (Fig. 4E).