REDESCRIPTION OF AFRICAN FRESH-WATER CRAB 



117 



of chelipeds and pereiopods light brown, ventral surface light 

 brown. Specimens from the Ogoue river, in the Fang forest, 

 Gabon, with brown-pink carapace, shading into neutral 

 orange in middle; walking legs orange-vermillion. 



Variation. The anterolateral margin is raised, marked by a 

 series of granules or small teeth in some specimens (from 

 Juba, Shambe, and Kojo-Kaji, Sudan; Ituri forest, Banana, 

 and Faradje, Zaire; and Ogoja, Kaduna, and Bendel State, 

 Nigeria). In other specimens (Poko, Zaire; Fernando Po, and 

 Luali, Angola) the anterolateral margin is completely 

 smooth. In specimens from Oban, Nigeria, the anterolateral 

 margin is smooth except for the epibranchial tooth (which is 

 the size of a large granule), followed by two smaller granules. 

 It is possible that the above variations of the anterolateral 

 margin are due to changes associated with growth. For 

 example, the adult male (CW 53.5 mm) from Juba, Sudan 

 (FMC) was the only one in which the anterolateral margin 

 was smooth out of 25 specimens of all sizes. This margin was 

 toothed or serrated in all the other specimens which mea- 

 sured CW 48 mm or less. A similar observation was made in 

 the series of specimens from Cameroon (RCM 53.389), 

 where the anterolateral margin of a large male (CW 60.4 mm) 

 was completely smooth, but that of smaller specimens was 

 granulated. Some specimens from Juba, Sudan, had serra- 

 tions on the dorsal surface of the dactylus of the cheliped 

 while other specimens from Juba, and from Nepoko, Zaire, 

 lacked these serrations. 



ECOLOGICAL NOTES 



Sudanonautes flowed is a common species of fresh-water crab 

 widely distributed in Nigeria and Central Africa. It is found in 

 the moister regions of the woodland and guinea savanna 

 zones from central Nigeria to southern Sudan. This species is 

 also found in the humid tropical rain forest habitats in 

 south-east Nigeria, south Cameroon, Bioko, Central African 

 Republic, Zaire, Congo, and Gabon. In Nigeria, 5. floweri 

 occurs in the drainage basins of the lower Niger, Benue and 

 Cross rivers. Specimens collected from Yankari Game 

 Reserve, Bauchi State, Nigeria were dug from holes at the 

 base of tufts of tall grass clumps in a marsh at the confluence 

 of rivers Yashi and Gaji, an area heavily trampled by big 

 igame, especially elephants. Many specimens of S. floweri 

 ('were caught on land during heavy tropical rain. 



In Sudan, 5. floweri lives both in the Yei river basin (a 

 tributary of the Nile), in the mountainous watershed between 

 the Nile and the Zaire rivers, and in the level papyrus swamps 

 (Flower, 1931). In Zaire, 5. floweri has been reported from 

 the lower and middle reaches of the Zaire river, and in the 

 Ubangi and Uele rivers (Rathbun, 1921). The habitat of 5. 

 floweri in Zaire has also been described by Rathbun (1921), 

 who summarised the field notes of Herbert Lang. 5. floweri 

 iwas often found in heaps of rotting vegetation in water 

 icourses, and Lang speculated that this habit may carry the 

 crabs downstream, explaining (at least in part) the wide 

 jdistribution of this species. Predators of S. floweri in the rain 

 jforests of Zaire include crocodiles, monitor lizards (Varanus 

 niloticus), insectivorous otter shrews (Potamogale velox) and 

 several small carnivores, chiefly species of mongooses and the 

 African civet (Viverra civetta). 



Sudanonautes floweri is common in shallow streams, rivers, 



and ponds, and digs burrows near waterways. This species is 

 also found on land either next to water or some distance 

 away, since it is capable of breathing air, and functions well 

 for long periods out of water. The widened and highly arched 

 carapace, and the lack of teeth on the anterolateral margins 

 of the carapace of S. floweri are features often associated with 

 air-breathing and burrow-living. This body shape contrasts 

 with the more flattened, deep-grooved, and spiny carapace of 

 the more aquatic river-living species such 5. faradjensis 

 (Rathbun, 1921). 



TAXONOMIC REMARKS 



The difficulties in distinguishing between 5. aubryi and 5. 

 floweri date back to the work of Rathbun (1904, 1905). 

 Although Rathbun (1905) described S. floweri and S. aubryi 

 as separate species, her description of P. (P.) aubryi was 

 based largely on specimens of 5. floweri. Specimens from 

 Cabinda (MNHN B5048) and Zaire (BP 5049) used by 

 Rathbun (1905) to describe S. aubryi have been examined in 

 the present study and found to be S. floweri. This opinion is 

 supported by the photographs of the specimens from Zaire 

 and Gabon provided by Rathbun (1904: TVI, plate IX, figs 5, 

 8) which closely resemble S. floweri, and which are clearly 

 different from the photograph of the female type of 5. aubryi 

 (Rathbun, 1904: TVI, plate IX, fig. 3). Unfortunately, Rath- 

 bun's (1905) ideas were accepted by later workers with the 

 result that the descriptions of 5. aubryi in Balss (1914, 1929), 

 Capart (1954), Bott (1955) and Monod (1977, 1980) all refer 

 to S. floweri rather than to S. aubryi sensu H. Milne Edwards 

 (1853). 



Comparisons. Six species of Sudanonautes are sympatric 

 with S. floweri in Nigeria and Central Africa, viz. 5. granula- 

 ns (Balss, 1929), S. kagoroensis Cumberlidge, 1991, S. 

 orthostylis Bott, 1955, S. monodi (Balss, 1929), 5. aubryi, and 

 S. africanus. These taxa can be distinguished from 5. floweri 

 as follows. The small hard flap on the mandibular palp at the 

 junction between the two segments (Fig. 2 a-c), and the 

 conspicuous raised ridges on the sternum at the points where 

 the chelipeds insert (Fig. 1 c), distinguish S. floweri from all 

 other species of Sudanonautes, which lack these features. 



In addition, the raised lobe on the cephalic part of the 

 terminal segment of gonopod 1, separated from the caudal 

 part by a conspicuous longitudinal groove in S. floweri (Fig. 2 

 d,f) is also shared, in varying degrees, by S. monodi, S. 

 kagoroensis and S. granulatus. These three species can be 

 further distinguished from 5. floweri by the following charac- 

 ters. The raised lobe on the cephalic part of the terminal 

 segment of gonopod 1 of S. monodi (Cumberlidge, 1991) is 

 considerably higher than that of S. floweri. In addition, the 

 carapace of S. monodi is significantly (P <0.001) flatter 

 (CH/CL 5. monodi = 0.52, S. floweri = 0.61), and less wide 

 (CW/CL 5. monodi = 1.37, S. floweri = 1.51) than that of 5. 

 floweri (Table 1). Sudanonautes monodi has patches of 

 granules on the anterior corners of the carapace behind the 

 postfrontal crest, while S. floweri lacks these granules. 

 Finally, S. monodi is found in dry sudan savanna from 

 Nigeria to Sudan, while S. floweri is absent from this region; 

 and S. monodi is absent from woodland savanna and rain 

 forest where 5. floweri is abundant. 



Sudanonautes kagoroensis was described by Cumberlidge 



