Charybdis (Gonioneptunus) africana Shen, 1935

Muñoz, Isabel, García-Isarch, Eva & Cuesta, Jose A., 2021, Annotated and updated checklist of marine crabs (Decapoda: Brachyura) of Mozambique supported by morphological and molecular data from shelf and slope species of the “ MOZAMBIQUE ” surveys, Zootaxa 5056 (1), pp. 1-67 : 44

Charybdis (Gonioneptunus) africana Shen, 1935

( Figure 14D )

Material examined. M07, Stn. 123, 184m, ♂ 84.4× 57.5mm (IEO-CD-MZ07/1915); M08, Stn. 77, 290m, ♂ 24.3× 16.7mm, ♂ 23.4× 15.9mm (IEO-CD-MZ08/1813-1), 16S ( MZ 424971 ) , COI ( MZ 434818 ) , ♂ 24.1× 17.1mm; ♂ 21× 14.5mm, ♂ 24.3× 16.7mm, ♂ 27× 18.9mm (IEO-CD-MZ08/1813-2), 16S ( MZ 424972 ) , COI ( MZ 434819 ) ; M09, Stn. 45, 322m, ♂ 41.2× 29mm (IEO-CD-MZ09/1816), 16S ( MZ 424973 ) , COI ( MZ 434820 ) .

Habitat and distribution. Charybdis (Gonioneptunus) africana occurs between 48 and 126m, off South Africa ( Barnard 1950; Shen 1935) and Mozambique ( Kensley 1981).

Results and remarks. These specimens were identified at genus level following Crosnier (1962), at subgenus level following Leene (1938) and at species level following Shen (1935) and Barnard (1950). A total of eight individuals were collected during the three surveys (M07, M08 and M09), at depths between 184 and 322m. This is the second record in Mozambican waters, which expands the species depth range from 126 up to 322m. Charybdis africana and Charybdis bimaculata have been considered synonyms ( Sakai 1939), although WoRMS currently considers them as valid species. The similarity between the characters used by Shen (1935) and Barnard (1950) to separate both species might have justified that they were considered synonyms by Sakai (1939). However, Shen (1935) established differences in the relationship CW / CL, this being 1.46 for C. africana and 1.55 for C. bimaculata . Considering this as a distinctive character for both species, our specimens with CW / CL ratios between 1.42-1.47 are closer to C. africana . The tip shape of G1 could be a distinctive character between the species, only described so far for C. bimaculata ( Leene 1938) but not for C. africana . The G1 shapes of the specimens (all males) are similar to those described for C. bimaculata , although their tips are more elongated and pointed (see Figure 15B ).

Colouration observed. The common name of C. bimaculata , “two-spot swimming crab”, makes reference to the two spots located on the mesobranchial region of the carapace. No information on the presence or absence of these spots on C. africana is available. These eight specimens also had two spots, although they were not as remarkable as observed in the images available of C. bimaculata . Our specimens showed a white spot on the cardiac region of the carapace, which was also observed in the images of C. bimaculata , although in this case they were much more elongated, even reaching the edge of the carapace. General colouration was also different as C. bimaculata is brown and beige colour, marble-like, while our specimens had a reddish-brown carapace with red granules. Legs and chelae were beige, with very scattered red granules, with bigger size and presence on the chelae. Dactyli were yellowish dorsally and white ventrally.

DNA barcodes. The three 16S sequences present only one haplotype that fits 99.22–99.41% (three–four mutations) with four sequences of C. bimaculata from Taiwan ( KX 060391 ), South Korea ( MG 787408 , NC_ 037695), and Vanuatu ( KT 365596 ), deposited at Genbank by Negri et al. (2018), Liu et al. (2018), Kim et al (2018) and Evans (2018), respectively. The three different haplotypes found for COI sequences, differ in 11–12 mutations respect to several COI sequences of C. bimaculata (similarity ranging from 97.47 to 98.25%). As occurs for Ovalipes iridescens , these values fall just in the limit between inter or intraspecific variability.

Figures

FIGURE 14. A, Chaceon macphersoni, ♀ IEO-CD-MZ09/1812; B, Ovalipes iridescens, ♀ IEO-CD-MZ07/1921. C, Scylla serrata, ♀ IEO-CD-MZ08/2238 (preserved); D, Charybdis africana, ♂ IEO-CD-MZ08/1813; E, Charybdis feriata, ♂ IEO-CD- MZ07/1902 (preserved); F, Charybdis smithii, ♂ IEO-CD-MZ08/1813; G, Monodaeus tuberculidens, ♂ IEO-CD-MZ07/1803. Scale bars: 1cm.

FIGURE 15. Charybdis africana ♂ IEO-CD-MZ08/1813-2. A. Carapace; B, G1; C, Telson. Scale bar: 1cm.