Platymaia alcocki Rathbun, 1918

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 : 35

Platymaia alcocki Rathbun, 1918

( Figure 9G )

Material examined. M07,Stn. 1,449m, ♀ 53.8× 53.9mm; ♂ 68.2× 68.2mm (IEO-CD-MZ07/1920), 16S( MZ 424953 ) , COI ( MZ 434797 ) ; M08, Stn. 68, 244m, ♂ (IEO-CD-MZ08/1789); M09, Stn. 19, 542m, ♂ 84.2× 73.5mm (IEO-CD-MZ09/1854-2), 16S ( MZ 424954 ) , COI ( MZ 434798 ) .

Habitat and distribution. This species has an IP distribution, Andaman Sea, Great Nicobar, East African coast (Griffin & Trander 1986), East China Sea and Hong Kong ( Sasaki 2019) and has been cited by Emmerson (2016c) in Mozambican waters, between 210– 655m.

Results and remarks. The four studied specimens of Platymaia alcocki were collected in M07 and M09, at depths between 449 and 542m. The specimens were identified following Guinot & Richer de Forges (1986) and Griffin & Tranter (1986a,b). Although P. alcocki and P. wyvillethomsoni Miers were confused in the past, some features described mainly by Griffin & Tranter (1986a) allowed us to confirm the identification of our specimens as P. alcocki , among them: similar length of the interantennular spines in relation to the rostral spines; rostral spines curved inward; margins of the supraorbital eave gently tuberculated in males and sharply tuberculated and swollen in females; gastric regions strongly elevated and protogastric ridges tuberculated without spines; and apex of the tip of the first pleopod of the male curved up.

Colouration observed. Colour of carapace and legs bright orange, with some white parts as tips of quelipeds, dactyli and spines, basi-ischium and deeper areas of carapace.

DNA barcodes: There are not 16S sequences available for this species in Genbank. There is only a short (400 bp) and incomplete 16S sequence of Platymaia remifera , deposited in Genbank by Tsang et al. (2014) that probably correspond with the version of the sequence after alignment and removal of hypervariable positions, for example after application of GBlocks. Therefore, it is not possible a real comparison without the complete sequence. There is a COI sequence ( MDECA 062-10) in BOLD, corresponding to a specimen identified by Chan as Platymaia sp. that was collected in Mozambique by the MB-exp in 2009 (date collection: 2009-04-09) and deposited at the MNHN ( MNHN _IU200810370). However, the COI haplotype of the two specimens of P. alcocki present a similarity of 83.5% respect to that of Platymaia sp. , representing distances expected at intergeneric level.

Figures

FIGURE 9. A, Oxypleurodon difficilis, ♂ IEO-CD-MZ08/1774; B, Naxioides robillardi, ♀ IEO-CD-MZ07/1892; C, Samadinia galathea, ♂ IEO-CD-MZ09/1802-1; D, Samadinia pulchra, ♂ IEO-CD-MZ07/1893; E,F, Cyrtomaia gaillardi, ♂ IEO-CD- MZ08/1788; G, Platymaia alcocki, ♂ IEO-CD-MZ08/1789. Scale bars: 1cm.