Afrithelphusa afzelii
Creators: name: Cumberlidge, Neil
name: Mvogo Ndongo, Pierre A.
name: Clark, Paul F.
name: Salieu, Sankoh
name: von Rintelen, Thomas
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Deckeniidae
Afrithelphusa
Afrithelphusa afzelii

description: 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).
description: Published as part of 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, pp. 924-946 in Journal of Natural History 57 (13 - 16) on pages 934-938, DOI: 10.1080/00222933.2023.2216908, http://zenodo.org/record/8221731