Potamonautes perparvus ( Rathbun, 1921 )

Meyer, Kirstin S. & Cumberlidge, Neil, 2011, A revision of the freshwater crabs (Crustacea: Decapoda: Brachyura: Potamonautidae) of the Lake Kivu drainage basin in Central and East Africa, Zootaxa 3011, pp. 45-58 : 46-48

Potamonautes perparvus ( Rathbun, 1921)

( Fig. 1 , 2 , Table 1 , 2)

Potamon (Geothelphusa) perparvus Rathbun 1921: 425 , fig. 12, plate 28, fig 2; plate 30, fig. 1–3. Potamon (Geothelphusa) perparvus— Rathbun 1935: 24.

Potamon perparvus— Chace 1942: 219.

Potamonautes (Lobopotamonautes) perparvus perparvus— Bott 1955: fig. 47; plate 21, fig. 1 a–d. Potamonautes perparvus perparvus— Ng et al. 2008: 171.

Potamonautes perparvus— Cumberlidge et al. 2009: appendix item 942.

Type material examined. DR CONGO: Affluent of Tschopo River near Kisangani, adult male holotype (CW 19.6, CL 13.6), adult female (CW 17.2, CL 12.6) 21 Aug 1909 (J. Chapin and H. Lang) ( AMNH 3383).

Other material. DR CONGO: Kalima (R. Laurent) ( SMF 2425); Kisangani (formerly Stanleyville), 1915 (J. Chapin and H. Lang) ( MRAC 1.056, ex AMNH); Kisangani, April 1915 (J. Chapin and H. Lang) ( MRAC 1.688 ex AMNH). RWANDA: Rukarara River, southeast of Lake Kivu, southwest Rwanda, Aug 1907 ( ZSM 1204/1).

Diagnosis. Carapace highly arched ( CH /FW 1.6), surface smooth, postfrontal crest weak but complete, lateral ends curving forward; exorbital tooth small, epibranchial tooth absent, anterolateral margin smooth; ischium of third maxilliped with distinct vertical sulcus; first carpal tooth on carpus of cheliped large, pointed; second carpal tooth smaller, pointed; distal meral tooth of P1 merus large, rounded; fixed finger of propodus of major cheliped lined by small, rounded teeth, two of which are prominent; dactylus of major cheliped lined by small, rounded teeth, dactylus curving, fingers enclosing wide interspace; sternal sulcus s2 / s3 deep, completely crossing sternum; s3 / s4 deep at sides, faint in middle, not meeting top of sternoabdominal cavity; terminal article of G1 significantly widened in middle, tapering to slim, upturned tip, medial fold higher than lateral fold ( Fig. 1 , Rathbun 1921).

Size. Small species, adult size range from CW 19–20 mm.

Color. The carapace is dark brown, lighter toward the abdomen, with a tinge of red; chelipeds brown-purple; abdomen white-grey.

Type locality. Affluent of Tschopo River near Kisangani, DR Congo ( Fig. 2 ).

Conservation status. Potamonautes perparvus was listed as “least concern” ( IUCN 2003; Cumberlidge et al. 2009) because there is no evidence of a decline in the extent and quality of its habitat and there are no long-term threats to its habitat from disturbance and pollution ( Cumberlidge 2008a).

Distribution. This species is found in the tributaries of the Congo River and Lake Kivu drainage basins in the DR Congo and Rwanda ( Fig. 2 ; Table 2).

Remarks. This species is superficially similar to P. emini from northwest Tanzania ( Reed and Cumberlidge 2006). Both species are small in size and have smooth carapace margins. The most important difference between the two species is that the front width of P. perparvus is greater than that of P. e m i n i. In addition, the postfrontal crest is distinct in P. emini but weak in P. perparvus and sternal sulcus s3/s4 meets the top of the sac in P. p e r p a r v u s but not in P. emini . The two species can also be distinguished by the terminal article of the first gonopod, which in P. e m i n i is straight and not widened in the middle, whereas in P. perparvus the terminal article is slightly widened in the middle, tapering to a slim, upturned tip. Rathbun (1921) provided good notes on the habitat and natural history of P. perparvus .

East Africa. See Methods for abbreviations used.

P. perparvus P. minor P. gonocristatus P. semilunaris

Adult size range 19–20 21–22 19–23 21–22

(CW, mm)

examined in present work, Rathbun (1921, 1935) and Bott (1955).

Country Locality Latitude/longitude Species of Potamonautes

Democratic Republic of Affluent of Tschopo River near 0 31’48”N/25 12’40”E P. perparvus

the Congo Kisangani

Bunyakiri 2 4’0”S/28 34’0”E P. semilunaris Kahuzi-Biega National Park 2 30’0”S/28 45’0”E P. minor , P. gonocristatus Kalima 5 30’0”S/28 12’0”E P. perparvus Kasiki 2 55’42”S/28 32’14”E P. gonocristatus Kiandjo 3 23’43”S/28 39’26”E P. gonocristatus Kisangani (Stanleyville) 0 31’0”N/25 12’0”E P. perparvus Luika 4°58’0”S /26 57’0”E P. gonocristatus Lubile 2 54’39”S/26 45’14”E P. perparvus Matale 2 39’17”S/28 21’55”E P. m i n o r

Muenga, Kamituga 3 4’0”S/28 11’0”E P. gonocristatus Miki 3 23’46”S/28 41’41”E P. perparvus Terifwazi, Kahuzi 2 15’0”S/28 41’0”E P. semilunaris Shubanda, Kigulube 2 36’0”S/28 1’0”E P. gonocristatus Utu 1 24’0”S/27 49’0”E P. gonocristatus Mongbwalu 1 57’0”N/30 2’0”E P. minor , P. perparvus

Rwanda Rukarara River 2 18’5”S/29 36’52” E P. perparvus

Figures

FIGURE 1. Potamonautes perparvus. A, dorsal view; B, frontal view. Adult male holotype (AMNH 3383), CW 19.6 mm. Modified from Rathbun (1921).

FIGURE 2. Potamonautes perparvus distribution. = type locality, = other localities. Scale bar = 249 km. Localities are shown for material examined in this study, as well as those provided by Rathbun (1921, 1935) and Bott (1955).

Tables

TABLE 1. Comparison of diagnostic characters of species of Potamonautes from the Lake Kivu drainage basin, Central and

Anterolateral margin	smooth	smooth	lined by granules	smooth
Horizontal sulcus on carapace sidewall	smooth	smooth	lined by granules	smooth
Mandibular palp	simple, no hard ledge at junction between segments	simple, with small hard ledge at junction between segments	simple, with small hard ledge at junction between segments	simple, no hard ledge at junction between segments
s2/s3	deep	deep	faint depression	deep
s3/s4	deep at sides, faint in middle, meeting top of sac	faint in middle, meeting top of sac	missing in middle, not meeting top of sac	missing in middle, not meeting top of sac
G1 terminal article	slightly widened in middle, medial fold higher than lateral fold	significantly widened in middle, lateral fold higher than medial fold	significantly widened in middle, lateral fold higher than medial fold	not widened in middle, lateral and medial folds low, even
Dorsal membrane of G1	data unavailable	margins of equal width	medial margin wider than lateral margin	margins of equal width