Wolffogebia inermis Sakai, 1982

(Fig. 8)

Wolffogebia inermis Sakai, 1982: 81, figs. 17c, 18g, 19a, b, 20e, pl. G6 [type locality: Indonesia: Java].— Sakai, 1993: 109, figs. 12–14; 2006: 148.— Ngoc-Ho, 1994b: 213, figs. 10a-c (questionabl e).— Ngoc-Ho et al., 2001: 108.— Dworschak & Anker, 2022: 130.

Wolffogebia phuketensis .— Marin, 2021b: 372, fig. 1c.

Not Wolffogebia inermis .— Ngoc-Ho, 1994b: 213, figs 10e-f, 11.

Material examined. 1 ♂ (cl. 7.5 mm, tl. 26 mm), ZMMU Ma-6225— VIETNAM, Ho Chi Minh District, Cần Gi ớ Mangrove Biosphere Reserve, 10°27’10.8”N 106°53’39.6”E, in burrows in the mud banks of canals located deep in mangroves, yabby-pump, coll. I. Marin & S. Sinelnikov, 25 April 2020 .

Brief description. Rostrum (Fig. 7 a, b) short, about 1.5 times as long as broad at base, reaching the distal margin of antennal peduncle of article 3, bluntly rounded distally in dorsal view, straight in lateral view; dorsal surface fringed with dense mat of short setae; ventral surface rounded, unarmed. Maxilliped 1 with 3-articulated flagellum of exopod. Maxilliped 2 without flagellum of exopod. Maxilliped 3 with 1-segmneted articulated flagellum of exopod. Telson (Fig. 7 g) subquadrate, slightly longer than broad, with shallow longitudinal median groove, reaching the distal margin; posterior margin slightly concave, without median triangular tooth. Pereopod 1 (cheliped) in males (Fig. 7 c, e) moderately stout, subchelate; ischium armed with 1 strong sharp spine distoventrally; merus armed with 1 strong sharp spine on proximal ventral margin, and slender sharp subdistal spine; carpus trigonal, without any groove or carina, with 1 strong long spine at ventrodistal angle and 2 strong long spines at dorsomesial margin; palm (Fig. 7 d, f) with well-marked dorsal ridge, distodorsal margin with large triangular spine and blunt projection, distoventral margin armed with large curved spine resembling the fixed finger; dactylus slender, long, lateral margin with median blunt spine (tubercle). Uropod (Fig. 7 g) exceeding posterior margin of telson; exopod with 2 dorsal and 1 lateral carinae; endopod with 1 lateral and 1 median carinae, anterolateral angle bluntly produced; posterior margin straight.

GenBank accession numbers. OP379708 .

Taxonomic remarks. The specimen corresponds completely to the original description of the species presented by Sakai (1982). The specimens from the Cần Giớ (NMHNTh1279) described by Ngoc-Ho (1994b) do not belong to this species because of the great differences in the morphology of pereopods 1; it obviously belongs to Wolffogebia cangioensis sp. nov. (see below).

Similar to Wolffogebia cangioensis sp. nov., W. inermis belongs to the group of species having a dorsally smooth rostrum (see above Fig. 8 a, b)) and a small fixed finger of pereopod 1 in females (Sakai, 1993: Fig. 14a, b). Within the group, the species can be separated from the related species by 1) exopods of maxillipeds 1 and 3 with 2–4-articulated flagellum; 2) the presence of 1 strong spine and 1 blunt projection at the dorsomesial margin of the propodus of pereopod 1 (chelipeds) in males (Fig. 7 c–f); and 3) a relatively large fixed finger at the distoventral margin of propodus of pereopod 1 (chelipeds) (Fig. 7 c–f), which is much smaller in other species of these group of species.

Habitat and ecology. The single collected male specimen of this species was found during the hand excavations of a mound of the large mud lobster Thalassina sp. (host was not found) within mangroves. Therefore, the specimen was initially identified as Wolffogebia phuketensis K. Sakai, 1982 (see Marin, 2021b), which is often found in large mounds of Thalassina spp. ( Decapoda: Gebiidea: Thalassinidae) (e.g., Ming, 1988; Ng & Kang, 1988). Unfortunately, no details on the burrow structure or the ecology of this species could be gathered. At the same time, in the locality where the individual of W. inermis was found, no specimens of Wolffogebia cangioensis sp. nov. were observed, which suggests that these species prefer different habitats and probably have different ecological preferences.

Distribution. The species is known from South Vietnam (Cần Giớ Mangrove Biosphere Reserve) (present record), Singapore (Dworschak & Anker, 2022), Indonesia (Java, Mocara Tangerang) (the type locality) (Sakai, 1982) and Northern Australia (Port Darwin) (after Sakai, 1993). The latter record is questionable (after Ngoc-Ho, 1994b).