Afrithelphusa afzelii ( Colosi, 1924 )

Cumberlidge, Neil, Mvogo Ndongo, Pierre A., Clark, Paul F., Salieu, Sankoh & von Rintelen, Thomas, 2023, A revision of the West African freshwater crab genus Afrithelphusa Bott, 1969 (Brachyura: Deckeniidae: Deckeniinae) based on new morphological and genetic data, Journal of Natural History 57 (13 - 16), pp. 924-946 : 934-938

Afrithelphusa afzelii ( Colosi, 1924)

( Figures 1 , 2 (a), 3(a), 4(a,d,h), 5(a,b,i,m), 6(a,b,c,m), 7(a,c,e), 8; Tables 1–3 )

Afzeli̍s freshwater crab Parathelphusa (Barythelphusa) afzelii Colosi, 1924: 19–21 , fig. 14a–b.

Para-Barythelphusa afzelii Balss, 1936: 200 .

Parathelphusa afzelii Chace, 1942: 226 ; Bott 1955: 213.

Afrithelphusa afzelii Bott, 1970: 27 ; Monod 1977: 1210; 1980: 380; Cumberlidge 1996a: 690–692, table 1; 1999: fig. 46B, 47B, 49B, 50B, 54–57, 62B, 68C, table IX, pl. 2; Mvogo Ndongo et al. 2022: fig. 2, P 3030.

Material examined

Type material. Lectotype: Sierra Leone: adult ♂ (CW 29.5 mm), ′Sierra Leone̍, ~1796, coll. Adam Afzelius, ca. 1796 ( SMNH 168 ).

Paralectotype: Sierra Leone: adult ♀ (CW 29.5 mm), ′Sierra Leone̍, coll. Adam Afzelius, ca. 1796 ( SMNH 168 ) .

Other material. Sierra Leone: 3 adult ♂♂ (CW 25.0, CL 18.8,CH 13.9, FW 8.5 mm; CW 22.6,CL 18.0, CH 12.5, FW 8.0 mm; CW 19.6, CL 15.7, CH 11.3, FW 7.8 mm), 6 subadult ♂♂ (CW 19.0, CL 14.6, CH 10.2, FW 6.2; CW 18.9, CL 15.0, CH 10.8, FW 6.5 mm; CW 18.0, CL 14.8, CH 11.1, FW 7.2 mm;CW 17.6,CL 14.4,CH 9.7, FW 6.7 mm; CW 17.0,CL 14.2,CH 9.8,FW 6.5 mm; CW 15.8,CL 12.5, CH 8.8, FW 5.5 mm); 3 adult ♀♀ (CW 23.7, CL 18.1, CH 13.2, FW 8.2 mm; CW 23.1, CL 18.3, CH 13.3,FW 8.7 mm; CW 20.50, CL 17.14,CH 12.80,FW 7.90 mm); 3 subadult ♀♀ (CW 18.00,CL 15.00, CH 10.80, FW 6.50 mm; CW 17.6, CL 14.4, CH 9.7, FW 6.7 mm; CW 17.3, CL 14.0, CH 10.0, FW 5.8 mm), Moyamba District, Kombora Chiefdom , Southern Province, 20 – 80 m from a permanent stream, in forest near farm land close to Tungie Village (8.1993°N, − 12.5489°W), 33 m ASL, coll. P. A. Mvogo Ndongo, 23–24 January 2021 ( ZMB Crust. 34,607; ACCRHa-01 ).

Diagnosis

Carapace outline transversely oval, highly arched ( CH /FW = 1.4); pterygostomial region of carapace branchiostegite smooth, lacking setal patches ( Figure 4 (a)). Mandibular palp consisting of basis followed by two articles; terminal article (MPTA) bilobed, MPAL/ MPTA = 0.6 ( Figure 4 (h); Table 3 ). Cheliped carpus smooth-textured ( Figure 5 (k)), ambulatory legs P2–5 long, slender (ΣP2–5/CW = 6.4) ( Figure 2 (a), 7(a,c); Table 3 ). G1TA medium length (G1TA/G1SA = 0.4), slim, straight, broadest proximally ( Figure 6 (a,c); Table 3 ); G1SA with raised rounded shoulder on external margin near G1TA-G1SA junction ( Figure 6 (a,c)); dorsal membrane (DM) narrow ( Figure 6 (c)). G2TA medium length (G2TA/G2SA = 0.4), flagellum-like, ending in rounded tip ( Figure 6 (b); Table 3 ). For detailed description see Colosi (1924), Bott (1955, 1970), Monod (1977, 1980) and Cumberlidge (1996a, 1999).

Size

The adult size range is CW 22–29.5 mm.

Colour

When alive ambulatory legs orange, carapace purple, sternum and underside cream.

Type locality

The type locality of the A. afzelii syntypes simply states ′ Sierra Leone ̍, a vague and nonspecific location. The only known specific locality is Moyamba District in Southern Province, Sierra Leone, where the species was rediscovered in 2021 ( Figure 1 ; Mvogo Ndongo et al. 2022). This locality is approximately 90 km from Freetown where Adam Afzelius received the original specimens in 1796 ( Lindroth 1955). It would have taken ca. 2 days to walk that distance, and probably even less time if the type material had been collected from a location closer to Freetown.

Distribution

Afrithelphusa afzelii is restricted to the Upper Guinea forests of West Africa in the forest zone of southern Sierra Leone ( Figure 1 ). No specimens of A. afzelii were found in surveys in lowland forests of the Northern or Eastern Provinces, or in the Western Area of Sierra Leone, but large parts of this country have yet to be surveyed for freshwater crabs. The rest of the forest zone in Sierra Leone (which originally occupied about 2/3 of the land area of this country between its borders with Guinea and Liberia) offers similar conditions to those of the Southern Province, so there is no obvious reason for the apparent absence of A. afzelii from this region.

Habitat

This species was collected from an unknown locality, and from a single specific locality in disturbed rainforest near farmland in Moyamba District in southern Sierra Leone, which lies in the Northern Upper Guinea Ecoregion (FEOW 511).

Conservation

Afrithelphusa afzelii is considered a critically endangered species in danger of extinction under the International Union for Conservation of Nature (IUCN) Red List guidelines ( Cumberlidge and Daniels 2020b). The newly collected material from Sierra Leone, and the additional data on its ecology, habitat preferences, and threats, will allow a reassessment of this species, although further population and distribution studies are needed to compile conservation options for the protection of this threatened species and its habitat ( Mvogo Ndongo et al. 2022).

Remarks

The type material of A. afzelii (an adult male and adult female) were collected in 1796 from an unspecified locality in Sierra Leone and were presented to Swedish naturalist Adam Afzelius who was based in Freetown. Afzelius subsequently deposited these specimens in the Swedish Museum of Natural History in Stockholm. Until recently, A. afzelii was only known from the type material, but its taxonomic history has changed several times over the years. It took 127 years after they were collected for these museum specimens to be described, when Colosi (1924) named them Parathelphusa (Barythelphusa) afzelii Colosi, 1924 . Balss (1936) then treated this species as Para-Barythelphusa afzelii , while Chace (1942); Bott (1955) referred to it as Parathelphusa afzelii . Bott 1970 finally placed this species in its current genus, Afrithelphusa , and designated the male syntype as the lectotype and the female syntype as the paralectotype. In the absence of any new material, the vague notes on the museum label for these two specimens have represented the total sum of our knowledge of the biology of this species for the past 225 years. After a hiatus of more than two centuries, the recent discovery of a population of A. afzelii living in the lowland rainforest of Sierra Leone ( Mvogo Ndongo et al. 2022) has enabled the present preliminary account of the biology of this species, based on the examination of 14 A. afzelii specimens from the only known specific location for this species in Sierra Leone. These new specimens are conspecific with the types of A. afzelii , based on their key diagnostic characters (eg of the carapace, chelipeds, mandibles, pleon, G1, G2, and ambulatory legs) that all correspond closely to the types.

Bott (1969, 1970) did not illustrate A. afzelii . The G1 and mandible of A. afzelii were described briefly by Cumberlidge (1999, fig. 52D) and are photographed and described here in detail based on the new material. Bott (1969, 1970) and Monod (1977, 1980) distinguished between A. afzelii and A. gerhildae based on differences in the length and width of the ambulatory legs P2–5. The ambulatory legs of A. afzelii are long and slender, while those of A. gerhildae are medium length and wider ( Table 3 ). This difference in ambulatory limb lengths between these species was also observed by Cumberlidge (1991). The description of A. afzelii by Bott (1970) noted that the third maxilliped had a flagellum on the exopod, but it is doubtful that he was working with specimens of A. afzelii because the exopod of the third maxilliped has no flagellum in this species ( Cumberlidge 1996a, 1996b, 1999).

Figures

Figure 1. Distribution map of West Africa showing the known localities of all Afrithelphusa Bott, 1969 species in Guinea and Sierra Leone. Afrithelphusa afzelii (Colosi, 1924) (black triangle, not shown to scale); A. leonensis (Cumberlidge, 1987) (black circles, not shown to scale); A. monodosa (Bott, 1959) (black squares, not shown to scale); A. gerhildae Bott, 1969 (black diamond, not shown to scale). For exact localities see text. Scale bar = 111 km.

Figure 2. Afrithelphusa afzelii (Colosi 1924), adult ♂, CW 25.0 mm, ZMB Crust. 34,607, from Moyamba District, Sierra Leone: a, whole animal, dorsal view. Afrithelphusa gerhildae Bott, 1969, adult ♂ CW 22.5 mm, SMF 2619a, Le Voile de la Mariée, Kindia, Guinea: b, whole animal, dorsal view. Afrithelphusa leonensis (Cumberlidge, 1987), adult ♂, CW 26.4 mm, ZMB Crust. 34,606, from Guma Lake, Sugar Loaf Mountain, Sierra Leone: c, whole animal, dorsal view. Afrithelphusa monodosa (Bott, 1969), adult ♂, CW 24.3 mm, NMU 24.IV.2005, Sarabaya, Guinea: d, whole animal, dorsal view. Photographs a, c by PAMN; b by Michael Türkay; d by N. Cumberlidge and M. Lorenz. Scale bar: a = 17.2 mm; b = 15.5 mm; c = 18.9 mm; d = 15.7 mm. CW = carapace width, ZMB = Museum für Naturkunde, Berlin, Germany, SMF = Senckenberg Museum, Frankfurt, Germany, NMU = Northern Michigan University,USA,PAMN = Pierre Armand Mvogo Ndongo.

Figure 4. Afrithelphusa afzelii (Colosi 1924), adult ♂ CW 25.0 mm, ZMB Crust. 34,607, from Moyamba District, Sierra Leone: a, carapace, frontal view; d, thoracic sternum, h, mandible frontal view. Afrithelphusa gerhildae Bott, 1969, adult ♂ CW 22.5 mm, SMF 2619a, Le Voile de la Mariée, Kindia, Guinea: e, thoracic sternum, i, mandible frontal view (Cumberlidge 1999, fig. 48A). Afrithelphusa leonensis (Cumberlidge, 1987), adult ♂, CW 26.4 mm, ZMB Crust. 34,606, from Guma Lake, Sugar Loaf Mountain, Sierra Leone: b, carapace, frontal view; f, thoracic sternum, j, mandible frontal view. Afrithelphusa monodosa (Bott, 1969), adult ♂, CW 24.3 mm, NMU 24.IV.2005, Sarabaya, Guinea: c, carapace,frontal view; g, thoracic sternum, k, mandible, frontal view. Photographs a, c by P. A. Mvogo Ndongo; d by Neil Cumberlidge and Margaret Lorenz; e by Michael Türkay. Scale bar: a = 8.9 mm; b = 9.6 mm; c = 11.6 mm; d–g = 8.0 mm; h–k = 3.1 mm. CW = carapace width, ZMB = Museum für Naturkunde, Berlin, Germany, NMU = Northern Michigan University, USA.

Figure 5. Afrithelphusa afzelii (Colosi 1924), adult ♂ CW 25.0 mm, ZMB 34607, from Moyamba District, Sierra Leone: a, right cheliped, frontal view;b, left cheliped, frontal view;i, right cheliped carpus superior view; m, right cheliped merus superior view. Afrithelphusa gerhildae Bott, 1969, adult ♂ CW 22.5 mm, SMF 2619a, Le Voile de la Mariée, Kindia, Guinea: c, right cheliped, frontal view (Cumberlidge 1999, fig. 50A); d, left cheliped, frontal view (Cumberlidge 1999, fig. 50A); j, right cheliped carpus superior view; n, right cheliped merus superior view. Afrithelphusa leonensis (Cumberlidge, 1987), adult ♂, CW 26.4 mm, ZMB Crust. 34,606, from Guma Lake, Sugar Loaf Mountain, Sierra Leone: e, right cheliped, frontal view; f, left cheliped, frontal view; k, right cheliped carpus superior view; o, right cheliped merus superior view. Afrithelphusa monodosa (Bott, 1969), adult ♂, CW 24.3 mm, NMU 24.IV.2005, Sarabaya, Guinea: g, right cheliped, frontal view; h, left cheliped, frontal view; l, right cheliped carpus superior view; p, right cheliped merus superior view. Photographs a, b, e, f, i, k, m, o by P. A. Mvogo Ndongo; g, h, l, p by Neil Cumberlidge and Margaret Lorenz; j, n by Michael Türkay. Scale bar: a–h = 11.2 mm; i–p = 5.6 mm. CW = carapace width, ZMB = Museum für Naturkunde, Berlin, Germany, SMF = Senckenberg Museum, Frankfurt, Germany, NMU = Northern Michigan University, USA.

Figure 6. Afrithelphusa afzelii (Colosi 1924), adult ♂ CW 29.5 mm, SMNH 168, Sierra Leone: a, G1 ventral view; b, G2 ventral view; c, G1 dorsal view; m, third maxilliped, frontal view. Afrithelphusa gerhildae Bott, 1969, adult ♂ CW 22.5 mm, SMF 2619a, Le Voile de la Mariée, Kindia, Guinea: d, G1 ventral view; e, G2 ventral view (Cumberlidge 1999, fig. 53AA); f, G1 dorsal view (Cumberlidge 1999, fig. 52B); n, third maxilliped, frontal view (Cumberlidge 1999, fig. 49A). Afrithelphusa leonensis (Cumberlidge, 1987), adult ♂, CW 26.4 mm, ZMB Crust. 34,606, from Guma Lake, Sugar Loaf Mountain, Sierra Leone: g, G1 ventral view; h, G2 ventral view; i, G1 dorsal view; o, third maxilliped, frontal view.Afrithelphusa monodosa (Bott, 1969), adult ♂, CW 24.3 mm, NMU 24.IV.2005, Sarabaya, Guinea: j, G1 ventral view; k, G2 ventral view; l, G1 dorsal view; p, third maxilliped,frontal view. Photographs a–c, g–i, m, o by P. A. Mvogo Ndongo; j–l, p by Neil Cumberlidge and Margaret Lorenz;d by Michael Türkay.Scale bar:a, c, d, f, g, i, j, l = 10.0 mm; b, e, h, k = 5.8 mm; m–p = 2.4 mm. CW = carapace width, SMNH = Swedish Museum of Natural History, Stockholm,Sweden,G1 = gonopod 1, G2 = gonopod 2, ZMB = Museum für Naturkunde,Berlin,Germany, SMF = Senckenberg Museum, Frankfurt, Germany, NMU = Northern Michigan University, USA.