Carcinoplax longimanus (De Haan, 1833 )

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 : 25-26

Carcinoplax longimanus (De Haan, 1833)

( Figure 8D,E )

Material examined. M07, Stn. 106, 259m, ♀ 54.3×43.9 (IEO-CD-MZ07/1919); M08, Stn. 68, 244m, ♂ 59.2× 48mm; ♂ 58.5× 46.5mm; ♂ 66× 52.4mm; ♂ 55.2× 44.1mm (IEO-CD-MZ08/1787); M08, Stn. 69, 277m, ♀ 44.2× 36.6mm; ♂ 65.4× 51.2mm; ♂ 67.5× 52.6mm; ♂ 52× 42mm; ♂ 49.2× 49mm; ♂ 54.8× 45.7mm; ♂ 50× 41.1mm (IEO-CD-MZ08/1786); M08, Stn. 74, 336m, ♀ 52.4× 41.2mm (IEO-CD-MZ08/1851), 16S ( MZ 424935 ) , COI ( MZ 434781 ) ; M08, Stn. 75, 256m, ♀ 51.2× 41.2mm, ♀ 50.6× 40.9mm (IEO-CD-MZ08/1826); M09, Stn. 83, 299m, ♂ 62× 47.7mm (IEO-CD-MZ09/1828); M09, Stn. 84, 254m, ♀ 51.2× 41.4mm (IEO-CD-MZ09/1829-1), COI ( MZ 434782 ) , ♂ 24.2× 18.1mm, ♂ 50.66× 40.2mm (IEO-CD-MZ09/1829-2), 16S ( MZ 424936 ) , COI ( MZ 434783 ) .

Habitat and distribution. Wide distribution from South and East Africa to the western Pacific Ocean ( Korea and Japan to Indonesia) from 6 to 377m depth ( Castro 2013). In waters of Mozambique, it was cited between 66–377m ( Emmerson 2016c) and between 80 and 120m ( Sasaki 2019). It is a very abundant species in a wide depth range and quite common in the bycatch of shrimper trawl fisheries ( Oh et al. 2009; Sobrino et al. pers. comm.). They are benthic crabs, which inhabits mud or sand bottoms where they build burrows ( Castro 2007; Hsueh & Hung 2009; Kensley 1981; Ng 1998).

Results and remarks. Our specimens agree well with the descriptions and figures by Castro (2007). We checked 19 specimens of C. longimanus collected in M07, M08 and M09 surveys, at depths between 244 and 336m.

There is great size-related morphometric variability in this species. The antero-lateral teeth are polished over time and become smaller in relation to the specimen size with growing, in a way that the carapace edge seems to be unarmed in the biggest individuals. Moreover, there is also a certain sexual dimorphism, as the females and juvenile males have short chelipeds, while the chelipeds are exceptionally long in adult males (see Figure 8D ), the merus and propodus being almost three times longer than in juveniles and females while the carpus remains practically the same length (see Figure 8E ). These features were also illustrated by Yamashita (1965), Guinot (1989) and Ikeda (1998).

Colouration observed. Specimens looked polished, the carapace being orange-brown, the chelipeds bright orange with the fingers, the spines and the knobs at the beginning of the propodus, bright white. The pereiopods were orange with the junction between merus-carpus and carpus-propodus white. Dactyli were brown, partly due to their dense tomentum. After preservation in ethanol or formalin, females and juveniles acquire a uniform bone colour, while the carapace of big males turns to brown.

DNA barcode. The two 16S sequences obtained for specimens from M08 and M09 fit 100% with an incomplete sequence of C. longimanus of 406 bp (hypervariable parts deleted) from Taiwan (?) ( NTOU B00091, Genbank code KJ132525 ) included in the study by Tsang et al. (2014). Respect to COI sequences, each specimen presents a different haplotype (differing in just one mutation). These sequences show a similarity between 98.89 and 99.21% with three unpublished (private) sequences of specimens of Carcinoplax longimanus (as C. longimana ) from South Korea deposited in BOLD. However, they present a similarity of 84.4% with C. ischurodous (99 mutations) that underline the above-mentioned differences of this species with congeneric ones, supporting the possibility of a different genus for C. ischurodous .

Figures

FIGURE 8. A, Platepistoma guezei, ♀ IEO-CD-MOZ07/279; B, Dairoides margaritatus, ♀ IEO-CD-MZ07/1911 (preserved); C, Carcinoplax ischurodous, ♂ IEO-CD-MZ08/1824; D, Carcinoplax longimanus, ♂ IEO-CD-MZ08/1787; E, Carcinoplax longimanus, ♀ IEO-CD-MZ08/1851; F, Tanaoa pustulosus, ♀ IEO-CD-MZ08/1776; G, Euclosiana exquisita, ♀ IEO-CD- MZ08/1757. Scale bars: 1cm.