Pseudolitochira taiwang Ng & Lin 2023, n. sp.
Creators: name: Ng, Peter K. L.
name: Lin, Chia-Wei
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Pilumnidae
Pseudolitochira
Pseudolitochira taiwang

description: Pseudolitochira taiwang n. sp.
(Figs. 1D, 6, 7)
Type material. Holotype: female (11.2 × 8.1 mm) (NMMBCD5627), Badouzi, Keelung County, Taiwan, coll. SCUBA, C.-W. Lin, 27 July 2016.
Other material examined. 1 female (11.0 × 7.6 mm) (RUMF-ZC-7770), Sesoko Island, Okinawa Island, Ryukyus, Japan, ca. 1.0 m, coll. T. Maenosono, 25 December 2022; 1 male (8.5 × 5.9 mm) (ZRC 2023.0031, ex RUMF-ZC-7523), subtidal, off Kudaka island, Nanjo, Okinawa Island, Ryukyus, Japan, coll. Okinawa Prefecture Environment Center, T. Saito, 21 May 2021.
Diagnosis. Carapace transversely ovate, width 1.38 times length (Fig. 6A, B); surface covered with short fine pubescence, frontal and anterolateral margins with dense, long silk-like pubescence, those lining postfrontal ridge relatively shorter, plumose (Figs. 1D, 6A, C); external orbital tooth low, barely separated from very low first anterolateral tooth, margin appears granulate, second anterolateral tooth distinct but short, lateral margins lined with denticles, last anterolateral tooth small, directed laterally (Fig. 6B); posterior margin of epistome with median lobe low, broadly triangular, lateral margin gently concave (Fig. 6C, E). Third maxilliped with short, subquadrate ischium, merus quadrate, subdistal margin with low granules (Fig. 6D). Chelipeds homochelous, chela with fingers about three-quarters length of palm, outer surface covered with granules and long setae obscuring margins (Fig. 6A, G). Ambulatory legs with merus and propodus distinctly short, stout, lined with dense long silk-like setae (Fig. 6A, H). Vulvae large, ovate, on proximal half of sternite 6, positioned close to median part of sternite 6, opening obliquely (Fig. 6F).
Colour in life. Carapace, chelipeds and ambulatory legs orangish-red with long setae bright yellow; distal twothirds of fingers black (Fig. 1D).
Etymology. The name is an arbitrary combination of the name Taiwan with Wang Chia-Hsiang. Chia-Hsiang, who passed away in 2022, was the first author’s oldest friend in Taiwan, and a valued colleague beyond measure. He encouraged many generations of young people to pursue carcinology and bring the community in the island together. That the species is found in Taiwan and Okinawa is also providence, it was there where Chia-Hsiang and the first author first met a lifetime ago. The name is used as a noun in apposition.
Remarks. With regards to the dense and long silk-like setae on the carapace and armature of the anterolateral carapace teeth, Pseudolitochira taiwang n. sp. most closely resembles P. lanuginosus (Klunzinger, 1913) from the Red Sea, but P. taiwang n. sp. is a distinctly larger species with the adult holotype female measuring 11.2 × 8.1 mm (adult females of P. lanuginosus already mature at 5.4 × 3.5 mm and ovigerous at 5.1 × 3.5 mm); the carapace is higher with the dorsal surface prominently convex (Fig. 6A, C) (carapace relatively lower in P. lanuginosus; Ng & Clark 2022b: fig. 1A, B); and the merus of the third maxilliped is proportionately smaller (Fig. 6D) (distinctly larger in P. lanuginosus; Ng & Clark 2022b: fig. 2D).
Pseudolitochira taiwang n. sp. is also close to P. crinita Ng & Clark, 2022a, from Papua New Guinea. It can, however, easily be separated by the setae on the carapace and legs being much denser (Figs. 1D, 6A) (setae less dense in P. crinita; Ng & Clark 2022a: fig. 2b); the carapace is more hexagonal with the posterolateral margins slightly concave to almost straight (Fig. 6A, B) (carapace transversely ovate with the posterolateral margins gently convex in P. crinita; Ng & Clark 2022a: figs. 2b, 5e); the dorsal surface of the carapace is distinctly higher and more convex in frontal view (Fig. 6A, C) (dorsal surface relatively lower in P. crinita; Ng & Clark 2022a: fig. 5f, g); the anterolateral carapace margin has the first anterolateral spine low, with the next two spines more prominent, the junction with the posterolateral margin marked by a spine (Fig. 6B) (with only two very low spines, the junction with the posterolateral margin being rounded in P. crinita; Ng & Clark 2022a: fig. 5e); the merus of the third maxilliped is proportionately smaller (Fig. 6D) (larger in P. crinita; Ng & Clark 2022a: figs. 5h, 7c); and the merus of the fourth ambulatory leg is proportionately shorter (Fig. 6H) (merus distinctly longer in P. crinita; Ng & Clark 2022a: fig. 6g).
Pseudolitochira taiwang n. sp. closely resembles H. setosus (A. Milne-Edwards, 1873) from New Caledonia, especially with regards to the pattern of setation (cf. A. Milne-Edwards 1873: 267–268). The latter species is poorly known and although often reported from various parts of the Pacific and Indian Oceans (e. g., see Poupin 2010; Trivedi et al. 2018), it has never been redescribed to modern standards. The figures of the species are relatively accurate, and the first author has examined photographs of four dried syntypes in the Muséum national d’Histoire Naturelle, Paris. The species was originally described in Carcinoplax H. Milne Edwards, 1852, but was referred to Heteropilumnus by Balss (1933). The figure of the frontal part of the cephalothorax of H. setosus by A. Milne-Edwards (1873: pl. 12 fig. 2a) is diagnostic and shows the posterior margin of the epistome entire, without any lateral clefts or lobes: a diagnostic character of Pseudolitochira. As such, Carcinoplax setosa A. Milne-Edwards, 1873, is here also transferred to Pseudolitochira. Pseudolitochira taiwang n. sp. can be distinguished from P. setosa by its relatively narrower carapace (width to length ratio 1.38 versus 1.50; Fig. 6A, B versus A. Milne-Edwards, 1873: pl. 12 fig. 2); the last anterolateral carapace tooth is spiniform (Fig. 6B) (dentiform in P. setosa; A. Milne-Edwards 1873: pl. 12 fig. 2); the posterolateral margins are more convergent towards the posterior carapace margin (Fig. 6A, B) (more divergent in P. setosa; A. Milne-Edwards 1873: pl. 12 fig. 2); the median lobe of the posterior margin of the epistome is relatively lower (Fig. 6C, E) (more produced in P. setosa; A. Milne-Edwards 1873: pl. 12 fig. 2a); and the merus of the fourth ambulatory leg is distinctly shorter (Fig. 6A, H) (more elongate in P. setosa; A. Milne-Edwards 1873: pl. 12 fig. 2).
The specimen identified as “ Heteropilumnus longisetum Davie & Humpherys, 1997 ” (type locality Western Australia) by Maenosono (2023: 165) (RUMF-ZC-7770) from Sesoko Island, Okinawa, Ryukyus, Japan, is clearly identical to P. taiwang n. sp. The figures of the specimen (Maenosono 2023: figs. 1, 2) agree with the type female in all aspects. There is also a male specimen (ZRC 2023.0031) from Okinawa that agrees with the rest of the material in all non-sexual aspects; its male pleon and gonopods are here figured (Fig. 7E–I). Compared to P. maenosonoi, the only congener in which males are known, the G1 is distinctly more sinuous with the distal part more elongate and directed laterally (Fig. 7F–H) (G1 less sinuous with the distal part gently curved and not elongate in P. maenosonoi; cf. Ng & Clark, 2022a: fig. 7e–g).
Biology. The type specimen was found under a rock with a soft, muddy substrate.
description: Published as part of Ng, Peter K. L. & Lin, Chia-Wei, 2023, Two new species of hairy crabs (Pilumnidae) and the first record of Crinitocinus alcocki (Borradaile, 1900) (Acidopsidae) (Crustacea: Brachyura) from Taiwan, pp. 101-114 in Zootaxa 5297 (1) on pages 106-111, DOI: 10.11646/zootaxa.5297.1.5, http://zenodo.org/record/7989367