Lepidothelphusa menneri Ng & Wowor 2024, n. sp.
Creators: name: Ng, Peter K. L.
name: Wowor, Daisy
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Gecarcinucidae
Lepidothelphusa
Lepidothelphusa menneri

description: Lepidothelphusa menneri n. sp.
(Figs. 1–4)
Material examined. Holotype: male (12.7 × 11.5 mm) (MZB Cru 5713), Gunung Kelam, ca. 20 km east of Sintang, Sintang Regency, Kalimantan Barat Province, ca. 0.07ºN 111.7ºE, Indonesia, Borneo, coll. locals, April 2022. Paratypes: 1 female (12.0 × 11.0 mm) (MZB Cru 5714), 2 females (8.7 × 7.7 mm, 10.9 × 10.1 mm) (ZRC 2023.0028), same data as holotype; 13 males (10.9 x 9.8 mm –14.1 × 12.6 mm), 30 females (10.7 × 9.5 mm –14.3 × 12.9 mm), 1 ovigerous female (10.5 × 9.7 mm) (MZB Cru 5715), 7 males (10.7 × 9.6 mm –3.5 × 11.9 mm), 17 females (10.0 × 8.8 mm –14.1 × 12. 6 mm) (ZRC 2023.0317), same locality as holotype, coll. locals, 20–22 May 2023. Others: 1 male (9.7× 8.9 mm), 1 female (10.7 × 9.8 mm) (MZB Cru 5716), from aquarium trade in Bekasi— Indonesia, from around Gunung Kelam, Sintang Regency, Kalimantan Barat Province, coll. locals, don. A.R. Dietra, 29 May 2023; 6 males (largest 12.2 × 11.3 mm), 4 females (largest 11.8 × 10.5 mm) (ZRC 2023.0039), from aquarium trade in Singapore, almost certainly from Gunung Kelam, ca. 20 km east of Sintang, Kalimantan Barat, ca. 0.07ºN 111.7ºE, Indonesia, Borneo, from aquarium in Singapore, Z.W. Tan, 13 May 2023.
Diagnosis. Carapace almost quadrate with weakly convex lateral margins (Figs. 1E–H, 2A, C, 3H), width to length ratio 1.08–1.13; dorsal surface gently convex, weakly rugose; anterolateral margin short, almost smooth; antero- and posterolateral regions slightly rugose, lateral surfaces with distinct low striae; epibranchial tooth barely discernible as a low angle, marked by lateral edge of postorbital crista; epigastric crista distinct but not sharp; frontal margin almost straight in dorsal view, margin weakly serrated, with very low median concavity; lateral lobe of front low but clearly demarcated by cleft; cervical and H-grooves shallow, not confluent (Figs. 2A, C–E, 3H); posterior margin of epistome with distinct median triangular lobe, adjacent lateral margins straight, parallel to frontal margin in frontal view (Fig. 2D, E). Third maxilliped ischium rhomboidal, much longer than broad, sulcus undiscernible (Fig. 2B). Inner margin of merus of adult cheliped serrate, not expanded or lobiform (Fig. 2F); carpus of chelipeds smooth, inner angle with low angle but not clearly dentiform (Fig. 2F); fingers of adult major male chela weakly gaping (Fig. 2G). Ambulatory legs relatively long, merus of P5 shorter than length of carapace (Figs. 2A, 3D, H). Male pleon triangular, somite 6 with distal margin about half width of proximal margin, lateral margins weakly convex to almost straight (Fig. 3A); G1 almost straight in both ventral and dorsal views, outer margins of terminal and subterminal segments forming a straight line, terminal segment distinctly elongate, with distal half sharply tapering towards long, narrow tip (Figs. 3E, F, 4A–C); G2 with long distal segment, about half length of basal segment (Figs. 3G, 4D). Vulvae subovate, without vulvar cover or operculum, positioned obliquely on anterior half of sternite 6 (Fig. 3J).
Morphological variation. The degree of morphological variation is minor. Smaller males and females have relatively smaller and almost symmetrical chelipeds, but their carapaces are similar and there are no visible differences in the ambulatory leg proportions. The smallest female (10.0 × 8.8 mm, ZRC 2023.0317) is almost adult, with the pleon ovate and the pleopods already setose. The only ovigerous female (10.5 × 9.7 mm, MZB Cru 5715) we examined has 21 large round eggs, (eyes not yet visible), with an average diameter of 1.3 mm.
Colour in life. The colour of the species is distinctive, with a tri-coloured carapace. The frontal third of the carapace is a bright yellow to orange, with the median part dark brown to purplish-black, and the posterior third is pale to bright blue (Fig. 1A, F, G, H). In one specimen, the median dark band is narrower in width with the lateral parts pale blue and there is a dark spot on the left side (Fig. 1E). The anterior margin of the dark band usually has a blue rhomboidal spot on the median part (Fig. 1A, F, H), but in some specimens, there is an additional triangular blue spot on each side of the median one as well (Fig. 1G). The chelipeds are pale yellow with the ambulatory legs are reddish to orangish-brown (Fig. 1). The ventral surfaces are a dirty white. The sexes do not differ in colour.
Etymology. The species is named after Jochen K. Menner who first alerted the authors about the presence of this species in Kalimantan, and then facilitated the collection of the specimens with the locals in Sintang for the second author.
Remarks. Lepidothelphusa menneri n. sp. is arguably the most distinctive species in the genus in life, with its distinctive tricoloured carapace (Fig. 1). Morphologically, it can immediately be distinguished from all congeners in the form of its epistome. In L. menneri n. sp., the posterior margin of the epistome has a distinct median triangular lobe which is distinctly separated from the adjacent lateral margins which are straight and parallel to the frontal margin (Fig. 2D, E). In all its congeners, the posterior margin of the epistome forms a wide triangular structure with the median lobe not demarcated and the adjacent lateral margins are sloping downwards (cf. Grinang & Ng 2015: figs. 3D, 5D, 7D, 9D, 11D).
The ischium of the third maxilliped of L. menneri n. sp. is relatively long and rhomboidal in shape (Fig. 2B), and is similar to that in L. cognettii, L. limau, L. loi and L. padawan (cf. Grinang & Ng 2015: figs. 1F, 5F, 7F, 9F). In contrast, the third maxilliped ischia of L. flavochela and L. sangon are proportionately shorter (Grinang & Ng 2015: figs. 3F, 11F).
The weakly gaping fingers of the adult major male chela of L. menneri n. sp. (Fig. 2F, G) is a character shared with L. flavochela, L. limau, L. loi and L. sangon (cf. Grinang & Ng 2015: figs. 3G, 5H, 7H, 11H); in L. cognettii and L. padawan, the fingers are strongly curved forming a wide gape (cf. Grinang & Ng 2015: figs. 1H, 9G, H). In L. cognettii, L. limau, L. padawan and L. sangon, the merus of the adult male cheliped is expanded along the inner margin, forming a prominent serrated flange (cf. Grinang & Ng 2015: figs. 1G, 5G, 9G, 11G). In L. menneri n. sp., the inner margin of the merus is not expanded at all (Fig. 2F), more like the condition in L. flavochela and L. loi where the margin is slightly expanded (cf. Grinang & Ng 2015: figs. 3I, 7G).
The male pleonal somite 6 of L. menneri n. sp. is distinctive in that it is most triangular in shape, with the distal margin only about half the width of the proximal margin with the lateral margins only slightly convex (Fig. 3A). In the other congeners, pleonal somite 6 has a different shape, with the distal margin is distinctly wider than half the width of proximal margin and the lateral margins are more convex (cf. Grinang & Ng 2015: figs. 1C, 3C, 5C, 7C, 9C, 11C).
The G1 structures of all the species are very distinct, with those of L. menneri n. sp., L. flavochela, L. limau and L. loi being almost straight (in either ventral or dorsal views), with the outer margins of terminal and subterminal segments forming a straight line or almost so (cf. Grinang & Ng 2015: figs. 4A, 6A, D, 8A, D). The terminal segment of L. menneri n. sp., however, is distinctly more elongate, with the distal half sharply tapering towards a long, narrow tip (Figs. 3E, F, 4A–C) compared to those of L. flavochela, L. limau and L. loi (cf. Grinang & Ng 2015: figs. 4A, B, D, E, 6A, B, D, E, 8A, B, D, E). The G1 of L. sangon is relatively straight overall, but the outer margins of the terminal and subterminal segments are distinctly sinuous (cf. Grinang & Ng 2015: fig. 12A, D); in contrast to the straight margins in L. menneri n. sp. (Figs. 3E, F, 4A–C). The G1s of L. cognettii and L. padawan are quite different, with the terminal segments curved (cf. Grinang & Ng 2015: figs. 2A, B, D, E, 10A, B, D, E).
Notes on habitat. This new species prefers to live at the edge of creeks in very shallow water with mixture of gravel and stone substrates, usually among leave litter and roots.
Distribution. So far, Lepidothelphusa menneri n. sp. is known only from the Gunung Kelam area in Sintang Regency, Kalimantan Barat Province, Indonesian Borneo.
Conservation. It is hard to assess the conservation status of this species as its precise distributional range is not known. It is, however, now collected in large numbers from the type locality by local collectors for the trade as has been exported to Singapore, China and Europe. Considering that most Lepidothelphusa species have a relatively small brood size (the only ovigerous specimen of L. menneri n. sp. has only 21 eggs) and their very restricted distributions, we expect the pet trade to potentially pose a serious threat to the species; so the species should at least be regarded as vulnerable (cf. Cumberlidge et al. 2009).
description: Published as part of Ng, Peter K. L. & Wowor, Daisy, 2024, Lepidothelphusa menneri n. sp. (Crustacea: Brachyura: Gecarcinucidae), first record of the genus from Kalimantan, Indonesia, pp. 218-224 in Zootaxa 5397 (2) on pages 219-224, DOI: 10.11646/zootaxa.5397.2.3, http://zenodo.org/record/10468612