Parathelphusa pardus, Ng & Riady, 2016

Ng, Peter K. L. & Riady, Rikhi, 2016, Parathelphusa pardus, a new species of lowland freshwater crab from swamps in central Sumatra, Indonesia (Crustacea: Brachyura: Gecarcinucidae), Zootaxa 4084 (4), pp. 495-506 : 496-505

publication ID	https://doi.org/ 10.11646/zootaxa.4084.4.2
publication LSID	lsid:zoobank.org:pub:4D0748BC-983F-4D0A-9D72-5A88AC69C60F
DOI	https://doi.org/10.5281/zenodo.6056815
persistent identifier	https://treatment.plazi.org/id/664887AB-9372-3651-FF35-FE50354EFBD3
treatment provided by	Plazi
scientific name	Parathelphusa pardus
status	sp. nov.

Treatment

Parathelphusa pardus View in CoL sp. nov.

( Figs. 1–6 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 )

Material examined. Holotype—male (37.6 × 28.2 mm) ( MZB Cru 4388), tributary of the Kampar River, in swamp, Pekanbaru, Riau Province, in central-eastern Sumatra, Indonesia, coll. R. Riady, 2014. Paratypes: 7 males, 8 females ( MZB Cru 4389), 7 males (largest 41.0 × 30.1 mm [poor condition]), 14 females (largest 46.1 × 34.7 mm), 1 brooding female (41.5 × 31.3 mm, with ca. 38 juveniles) ( ZRC 2015.0451 View Materials ), 1 male (34.9 × 26.6 mm), 1 female (34.7 × 26.9 mm) ( ZRC 2015.0452 View Materials ), same data as holotype.

Diagnosis. Carapace with dorsal carapace surface distinctly convex ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ); postfrontal, postorbital cristae long, sharp, almost straight or gently sinuous ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ); branchial regions distinctly convex; appears gently inflated from lateral view ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ); external orbital tooth broadly triangular, external margin gently curved, with distal two-thirds almost straight, separated from first epibranchial tooth by Ushaped notch; first epibranchial tooth acutely triangular, directed anteriorly; second epibranchial tooth acutely triangular, directed obliquely outwards ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ); surfaces adjacent to posterolateral margin with short striae, otherwise almost smooth ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ); chelae with fingers not pigmented black ( Figs. 1A, C View FIGURE 1 , 2A View FIGURE 2 , 3F, G View FIGURE 3 , 6A View FIGURE 6 ); ambulatory legs relatively short, merus 1–3 with sharp subdistal spine, merus 4 with sharp angle, not spiniform ( Figs. 1A View FIGURE 1 , 2A View FIGURE 2 , 4 View FIGURE 4 , 6A View FIGURE 6 ); suture separating thoracic sternites 2, 3 sinuous, medially concave with lateral parts convex (towards buccal cavity); abdomen with telson slightly longer than broad, somite 6 1.5–2 times as long as broad, lateral margins gently concave ( Figs. 1B View FIGURE 1 , 3C–E View FIGURE 3 ); G1 relatively slender, almost straight, distal part slightly curved laterally, outer margin with distinct cleft on proximal part; distal part tapering to sharp tip, opening distinct, laterally positioned ( Fig. 5A–G View FIGURE 5 ).

Description of male. Carapace hexagonal; transversely wider than long; dorsal carapace surface distinctly convex, smooth; regions poorly demarcated; cervical groove broad, shallow; median H-shaped gastro-cardiac depression distinct ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ). Frontal margin broad, contiguous with supraorbital margin, cristate, appearing almost straight from dorsal view, sinuous from frontal view; frontal median triangle distinct, broad ( Figs. 2A View FIGURE 2 , 3A View FIGURE 3 ). Postfrontal cristae sharp, almost straight separated from each other medially by short, narrow Y-shaped fissure; postorbital cristae long, sharp, almost straight or gently sinuous, contiguous with postfrontal cristae, cristae ending before of base of first epibranchial tooth ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ). Branchial regions distinctly convex; appears gently inflated from lateral view ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ). Orbits large, ovate; eyes well developed with pigmented cornea, completely filling orbit ( Figs. 1A View FIGURE 1 , 2 View FIGURE 2 , 3A View FIGURE 3 , 6A View FIGURE 6 ). Supraorbital margin concave, entire; confluent with frontal margin; suborbital margin concave, entire ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ). Pterygostomian region covered with scattered low granules, short striae; suborbital, subhepatic regions with low striae, granules ( Figs. 2C View FIGURE 2 , 3A View FIGURE 3 ). External orbital tooth broadly triangular, external margin gently curved, with distal two-thirds almost straight; inner angle triangular, extending to level of frontal margin, separated from first epibranchial tooth by U-shaped notch; first epibranchial tooth sharp, acutely triangular, directed anteriorly; second epibranchial tooth sharp, acutely triangular, directed obliquely outwards ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ). Posterolateral margin gently concave, without visible crista, lateral surfaces with short striae, otherwise almost smooth; posterolateral margins converging towards almost straight posterior carapace margin ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ). Posterior margin of epistome sinuous; median tooth triangular with rounded tip, lateral margins convex ( Figs. 2C View FIGURE 2 , 3A View FIGURE 3 ).

Third maxilliped elongated, completely covering buccal cavity when closed; merus subquadrate, as wide as long, median part gently depressed, anterolateral margin slightly auriculiform, rounded; ischium rectangular, with deep submedian oblique sulcus; exopod relatively stout, reaching to median part of merus, with distinct subterminal tooth on inner margin, flagellum long ( Fig. 3B View FIGURE 3 ).

Chelipeds asymmetrical in adult males; merus relatively short; with distinct subdistal spine; carpus subovate, outer surface rugose, inner distal angle with prominent, elongated spine, inner margin gently serrated; chelae enlarged, outer surface smooth or almost so; fingers not pigmented black, those on major chela of larger males gently curved, subequal or slightly longer than palm, forming basal gap when closed; cutting edges with small and large rounded teeth, denticles ( Figs. 1A, C View FIGURE 1 , 2A View FIGURE 2 , 3F, G View FIGURE 3 , 6A View FIGURE 6 ).

Ambulatory legs relatively short, stout; second leg longest; merus subrectangular, margins cristate, dorsal margins of meri 1–3 with sharp subdistal spine or angle, that of merus 4 with sharp angle, not spiniform; carpus unarmed, with cristate dorsal margin, subparallel crista on outer median surface; propodus with dorsal margin cristate, ventral margin gently serrated; outer surface with shallow submedian longitudinal depression; dactylus gently curved with corneous tip, quadrate in cross-section, margins with 4 rows of strong sharp spines ( Figs. 1A View FIGURE 1 , 2A View FIGURE 2 , 4 View FIGURE 4 , 6A View FIGURE 6 ).

Thoracic sternum evenly pitted to smooth; sternites 1, 2 completely fused forming triangular structure, relatively narrow longitudinally; suture separating sternites 2, 3 sinuous, medially concave with lateral parts convex (towards buccal cavity); sternites 3, 4 completely fused; sternoabdominal cavity extending to just before suture between sternites 2, 3, reaching imaginary line jointing anterior edges of coxae of chelipeds ( Fig. 3C, D View FIGURE 3 ). Tubercle of press-button male abdominal locking mechanism rounded, on anterior edge of sternite 5.

Abdomen distinctly T-shaped; telson triangular, slightly longer than broad, lateral margins gently sinuous, tip rounded; somite 6 rectangular, 1.5–2 times as long as broad, lateral margins gently concave; somites 3–5 trapezoidal; lateral margins of somites 4, 5 concave; somite 3 broad, proximal edge reaching to coxae of last ambulatory legs, lateral margins convex; somites 1, 2 longitudinally narrow, wide, reaching to bases of coxae of last pair of ambulatory legs ( Figs. 1B View FIGURE 1 , 3C–E View FIGURE 3 ).

G1 relatively slender, terminal, subterminal segments not differentiated; entire structure almost straight, distal part slightly curved laterally; outer margin almost straight, entire along distal two-thirds, with distinct cleft on proximal part; lateral margins of proximal part with dense, long plumose setae; outer margin of distal quarter with long and short simple setae; subdistal surface with very short simple setae, scale-like setae; distal part tapering to sharp tip, opening distinct, laterally positioned ( Fig. 5A–G View FIGURE 5 ). G2 much longer than G1; distal segment elongated, almost as long as basal segment ( Fig. 5D, H View FIGURE 5 )

Variation in males. The male chelipeds are asymmetrical in large males in excess of about 35 mm in carapace width. In smaller adult males, the major chela is relatively less inflated with the fingers less elongated and curved ( Fig. 3G View FIGURE 3 ) when compared to those of larger males (e.g., Fig. 1C View FIGURE 1 ). The suture between thoracic sternites 2, 3 varies slightly in males less than 30 mm in carapace width, from sinuous to almost straight or gently evenly concave towards the buccal cavity. In adult males larger than 35 mm carapace width, it is constant (see description). The male abdominal somite 6 varies in shape slightly. In smaller males (e.g., 34.9 × 26.6 mm, ZRC 2015.0452), somite 6 is more quadrate with the length only about 1.5 times the length ( Fig. 3D View FIGURE 3 ). In larger males (e.g., holotype 37.6 × 28.2 mm, MZB Cru 4388), this ratio is about two times ( Fig. 1B View FIGURE 1 ). This is typical for many gecarcinucids in which somite 6, the telson are proportionately longer in large males.

Female. Females are similar to males in most non-sexual features. The chelipeds are symmetrical, not inflated and relatively slender, even in large females ( Fig. 6A View FIGURE 6 ). The abdomen is almost round and covers most of the surface of the thoracic sternum; with all the somites and telson free; telson broadly triangular with gently convex lateral margins. Female specimens less than 35 mm in carapace width (e.g., female 30.2 × 23.8 mm, ZRC 2015.0451) have more subovate abdomens and are not mature. The vulvae are relatively large, on surface of thoracic sternite 6 closer to suture between sternites 5 and 6; posterior part of vulva convex, anterior part with a soft, semilunate operculum ( Fig. 6B View FIGURE 6 ).

Colour in life. The carapace and pereopods have a spotted and reticulated pattern in live and freshly preserved specimens ( Figs. 1A View FIGURE 1 , 2A View FIGURE 2 , 6A View FIGURE 6 ).

Etymology. The name is derived from the Latin pardus for “leopard”, alluding to the pattern of spots on the carapace. The name is used as a noun in apposition.

Remarks. The colour pattern of Parathelphusa pardus sp. nov. is distinctive, and the large series of specimens examined shows it is relatively constant character, even in small specimens. In Sumatra, this is a colour pattern shared with P. maindroni and P. batamensis (cf. Ng 1992, 1993). This colour pattern is also observed in P. reticulata Ng, 1990 (from Singapore) and P. oxygona Nobili, 1901 (from western Sarawak) (cf. Ng 1990b, 2004, 2014). Like P. pardus sp. nov. these species are also usually associated with freshwater and peat-swamp habitats. Non swamp dwelling species like P. convexa and P. maculata sometimes also have an unevenly patterned carapace but it is never as distinctly patterned or brightly coloured as the above species.

The swelling of the dorsal carapace surface of P. pardus sp. nov. is most like P. maindroni (cf. Ng 1993: pl. 1A, B, pl. 2A, pl. 3A, C, pl. 4; Ng 1990b: fig. 6A), but the suture between sternites 2 and 3 are more sinuous, with the median part gently concave and the lateral parts convex towards the buccal cavity ( Fig. 3C View FIGURE 3 ) (evenly concave toward the buccal cavity in P. maindroni , cf. Ng 1990b: fig. 7C; Ng 1993: fig. 1G); and most significantly, the outer margin of the proximal part of the G1 has a distinct cleft ( Fig. 5A–D, E–G View FIGURE 5 ) (outer margin of the proximal part of the G1 is entire in P. maindroni , cf. Ng 1990b: fig. 8A–D; Ng 1993: figs. 1B, C, E, F, 2). The type locality of P. pardus sp. nov., Pekanbaru, is more than 100 km southwest of Bengkalis, the type locality of P. maindroni (cf. Rathbun 1902), with the latter species also present in Peninsular Malaysia ( Ng 1993).

The dorsal surface of the carapace of P. pardus sp. nov. is more convex and swollen ( Figs. 1A View FIGURE 1 , 2 View FIGURE 2 , 6A View FIGURE 6 ) than P. batamensis (cf. Ng 1992: fig. 4A); the suture between sternites 2 and 3 are more sinuous, with the median part gently concave and the lateral parts convex towards the buccal cavity ( Fig. 3C View FIGURE 3 ) (evenly concave toward the buccal cavity in P. batamensis , cf. Ng 1992: fig. 2H); the lateral margins of the male abdominal somite 6 are gently concave ( Fig. 3D View FIGURE 3 ) (gently convex in P. batamensis , cf. Ng 1992: fig. 2G); and the G1 has the distalmost part slightly curved and the outer margin of the proximal part has a distinct cleft ( Fig. 5A–D, E–G View FIGURE 5 ) (distal half more prominently curved laterally and the outer margin of the proximal part is entire in P. batamensis , cf. Ng 1992: fig. 4B, C, E, F).

The dorsal surface of the carapace is relatively less swollen in P. pardus sp. nov. ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ) than in P. reticulata from Singapore (cf. Ng 1990b: figs. 1, 2); the suture between sternites 2 and 3 are more sinuous, with the median part gently concave and the lateral parts convex towards the buccal cavity ( Fig. 3C View FIGURE 3 ) (evenly concave toward the buccal cavity in P. reticulata , cf. Ng 1990b: fig. 7I); the ambulatory legs are relatively shorter and stouter ( Figs. 1A View FIGURE 1 , 2A View FIGURE 2 , 4 View FIGURE 4 , 6A View FIGURE 6 ) than in P. reticulata (cf. Ng 1990b: figs. 1, 2); the distalmost part of the G1 is gently curved and relatively stouter, with the outer margin of the proximal part possessing a distinct cleft ( Fig. 5A–D, E– G View FIGURE 5 ) (almost straight and slender, with the outer margin of the proximal part possessing a more shallow cleft in P. reticulata , cf. Ng 1990b: fig. 8F–I);

The degree of swelling and spotted carapace pattern of P. pardus sp. nov. is also similar to another species, P. oxygona , from western Sarawak, Borneo. Parathelphusa pardus sp. nov. is easily distinguished from P. oxygona by having the outer margin of the external orbital almost straight ( Figs. 1A View FIGURE 1 , 2A, B View FIGURE 2 , 6A View FIGURE 6 ) (distinctly sinuous in P. oxygona , cf. Ng 2014: figs. 1A, 2E), and the G1 is relatively stouter with only the distal part gently curved ( Fig. 5A–D, E–G View FIGURE 5 ) (more slender with the distal part more strongly curved in P. oxygona , cf. Ng 2014: fig. 4A, B)

The cleft on the outer margin of the proximal part of the G 1 in P. pardus sp. nov. is a character also present in P. maculata from Sumatra and Peninsular Malaysia, and P. convexa from southern Sumatra and Java (cf. Ng 1990a: figs. 4A, B, F, I, 5A, B, E, F, H; Ng 1990b: fig. 8K, L). Adults of both P. maculata and P. convexa do not have a spotted or reticulated colour pattern ( Ng 1990a; unpublished data). While the carapace of P. maculata has a much flatter carapace than P. pardus sp. nov. (cf. Ng 1990a: figs. 1, 2), that of P. convexa is more inflated (cf. Bott 1970: pl. 23 fig. 69).

Ecology. All the specimens of P. pardus sp. nov. were collected from various tributaries of the Kampar River in Riau Province, Sumatra. Their preferred habitat is swampy areas along the river, often living in well-shaded areas under the vegetation ( Fig. 7 View FIGURE 7 ). The main aquatic plant in these areas is a species of Barclaya Wallich, 1827 (= Hydrostemma Wallich, 1827 ) (family Nymphaeaceae ) (see Lok et al. 2009). The crabs are mainly nocturnal, coming out to forage only after dark, the same habit for swamp species like P. reticulata (see Ng 1990b, c). For more details of the biology of the species, see Riady et al. (2014).