Sesarmops impressus (H. Milne Edwards, 1837 )
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publication ID |
https://doi.org/ 10.6620/ZS.2020.59-27 |
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persistent identifier |
https://treatment.plazi.org/id/03B887C6-FFEB-A122-1349-3EAAFEE5875C |
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treatment provided by |
Felipe |
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scientific name |
Sesarmops impressus (H. Milne Edwards, 1837 ) |
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Sesarmops impressus (H. Milne Edwards, 1837) View in CoL
( Figs. 1–6 View Fig View Fig View Fig View Fig View Fig View Fig , 13A–D View Fig , 14A–C View Fig , 15A–G, 16A–G, N–P)
Sesarma impressa H. Milne Edwards, 1837: 74 View in CoL (no locality); H.
Milne Edwards 1853: 186 (no locality); De Man 1887: 653, 671
( Madagascar); Lenz 1905: 370 ( Zanzibar). Sesarma frontale A. Milne-Edwards, 1869: 27 ( Madagascar). Sesarma frontalis – De Man 1887: 649 ( Madagascar). Sesarma nodulifera – Lenz 1910: 562 ( Comoros).? Sesarma impressa – Lenz 1910: 561 ( Madagascar).
Sesarma (Sesarma) impressum View in CoL – Crosnier 1965: 63, figs. 82, 92, 104 ( Madagascar, Comoros); Serène 1968: 106.
Sesarma (Sesarma) impressa View in CoL – Guinot 1967: 287 (list, Comoros).
Sesarmops impressum View in CoL – Serène and Soh 1970: 401, 406 (part), pl. 7 figs. A, B (no locality data).
Sesarmops impressus View in CoL – Keith et al. 2006: 36 ( Comoros, Mayotte); Ng et al. 2008: 223 (list); Bouchard 2009: 6, 15 ( Mayotte); Bouchard et al. 2013: 24, fig. 19 ( Mayotte); Poupin et al. 2018: 72 ( Mayotte).
Sesarmops impressus View in CoL 1 – Li et al. 2020: fig. 22 ( Mayotte; Madagascar).
Material examined: Lectotype: female (40.6 × 38.0 mm) (MNHN-IU-2000-3959 = MNHN-B 3959) [dried], no locality. 1 male (28.1 × 26.0 mm) (MNHN- IU-2000-3667 = MNHN-B 3667) [dried, lectotype of Sesarma frontale A. Milne-Edwards, 1869 ], Nosy Bé, coll. Boivin (lectotype of Sesarma frontale A. Milne-Edwards, 1869 ); 1 male (29.7 × 25.6 mm), 1 female (26.0 × 22.1 mm) (MNHN-IU-2000-10929 = MNHN-B 10929) [dried, paralectotypes of Sesarma frontale A. Milne-Edwards, 1869 ], same data as lectotype.
Others: Madagascar: 1 young male (MNHN- I U -2 0 1 9 -4 5 1 8 = M N H N -B3 0 3 3 6), A n t a n a m b é, coll. E. Chevreux, October 1896; 5 males, 1 young male, 1 young female (MNHN-IU- 2019 -4524 = MNHN-B 16678), Antongil Bay, coll. E. Chevreux, 1899; 1 male (MNHN-IU-2019-4513 = MNHN-B 16679), Antongil Bay, no other data; 1 ovigerous female (MNHN-IU-2019-4523), Mahomba, coll. E. Chevreux, October 1896; 1 female, 1 ovigerous female (MNHN-IU-2019-4515 = MNHN-B 25740), Marosoroka River, 39 km south of Maroantsetra, coll. 12 September 1965; 2 males (30.2 × 27.8 mm, 24.8 × 22.3 mm) (MNHN-IU-2019-4517 = MNHN-B 25776), Nosy Bé, coll. Millot, autumn 1922; 2 males (MNHN- IU-2019-4520 = MNHN-B 30338), Nosy Bé, coll. Millot, 1920s; 2 males, 1 female (MNHN-IU-2019-4516 = MNHN-B 25743), Lokobe, Nosy Bé, coll. May 1966; 6 males (largest 32.2 × 29.2 mm), 2 females (27.6 × 25.2 mm, 23.8 × 21.5 mm), 3 ovigerous females (28.1 × 25.0 mm, 26.8 × 23.0 mm, 22.3 × 19.7 mm) (MNHNIU-2019-4521 = MNHN-B 30343), Antongil Hiaraka, coll. R. Pereiras, November 1967; 3 small males (largest 21.7 × 19.9 mm) (MNHN-IU-2019-4519 = MNHN-B 30337), Sainte Marie, coll. E. Chevreux, 1897; 1 male (MNHN-IU-2000-3958 = MNHN-B 3958) [dried], west coast of Madagascar, Lanz coll. 1 female (22.1 × 20.8 mm) ( ZRC 2010.302), Masoala Peninsula, eastern Madagascar, coll. W. Emmerson, June 2005. Mayotte: 3 males (largest 39.6 × 36.5 mm) (MNHN- IU-2009-953 = MNHN-B 32034), station 41a, near cultivated mangroves, 12°55'S 45°9'E, coll. J. M. Bouchard, KUW MAYOTTE 2009, 12 December 2008; 1 female (35.0 × 30.2 mm) ( ZRC 2011.4), station 9, Bassin Mro Oua Ourovéni, coll. Tervuren Museum, 11 October 2000; 1 male (36.1 × 33.1 mm) ( ZRC 2011.5), station 9, Bassin Mro Oua Ourovéni, coll. Tervuren Museum, 11 October 2000. Seychelles: 3 males (31.3 × 29.7 mm, 30.7 × 28.5 mm, 27.1 × 25.0 mm), 1 female (28.5 × 25.7 mm) ( ZRC 2009.896), Mahé, coll. 2009; 1 male 1 female (MNHN-IU-2019-4514 = MNHN-B 29630), Mahé Island, coll. P. Keith et al., 14 October 2003; 1 female (MNHN-IU-2019-4522 = MNHN-B 28938), Mahé Island, coll. P. Keith et al., October 2003.
Diagnosis: Male: Carapace almost quadrate; external orbital tooth with outer margin convex, especially along posterior part, separated from lateral margin by distinct cleft ( Figs. 2A View Fig , 3A View Fig , 4 View Fig , 6A, B View Fig , 13A–D View Fig ); epibranchial tooth short but distinct, sometimes with low lobe posterior to it, never dentiform, sometimes undiscernible ( Figs. 13A–D View Fig , 14A View Fig ); outer surface of chela covered with numerous smooth rounded granules; inner surface granulated, with strong transverse median ridge on proximal part, lined with 7–11 tubercles and granules; dorsal margin of dactylar finger with randomly arranged granules, no trace of stridulatory row ( Figs. 2C View Fig , 5F–I View Fig ); ambulatory merus relatively short, wide, propodus and dactylus relatively short, wide ( Figs. 3A, D View Fig , 4 View Fig , 5A–C View Fig , 6A, B View Fig , 14B View Fig ); male pleon transversely wide, somite 6 subtruncate, much wider than long with convex lateral margins; telson wider than long, distinctly inserted into concave distal margin of somite 6 ( Figs. 3C View Fig , 5A–C View Fig , 14C View Fig ); G1 relatively slender, elongate, distal half of stem expanded, inner margin with gentle but obvious subdistal hump, subdistal part of outer margin gently sloping with chitinous distal part long, gently curved to angle of ca. 60° from longitudinal axis ( Figs. 15A–G, 16A–G, N–P). Female: telson inserted into distal margin of somite 6, lateral margins of somite 6 gently convex ( Figs. 2B View Fig , 6C View Fig ); vulvae anterior half of sternite 6, just touching margin with sternite 5, posterior edge forming bilobed sternal vulval cover, operculum low, non-protruding ( Fig. 6D View Fig ).
Description of male: Carapace almost quadrate, widest point at edge of external orbital tooth posterolateral margin near base of third ambulatory legs ( Figs. 2A View Fig , 3A View Fig , 4 View Fig , 13A–D View Fig ); dorsal surface rugose, small flattened granules and striae, regions clearly defined with distinct grooves, with only scattered short stiff setae on margins; not inflated in frontal view ( Figs. 3A, B, D View Fig , 5D View Fig ); surface adjacent lateral margins with distinct oblique striae; median gastro-cardiac groove distinct ( Figs. 3A, B, D–E View Fig , 4 View Fig ). Front deflexed downwards, margin sinuous, bilobed, lobes separated by wide concavity, margin sinuous to gently convex ( Figs. 3A, B, D, E View Fig , 4 View Fig , 5D View Fig ). Supraorbital margin separated from frontal margin by low angle, no lateral tooth, margin entire, strongly convex, confluent with acutely triangular external orbital tooth, outer margin convex, especially along posterior part, separated from lateral margin by distinct cleft, sometimes deep; epibranchial tooth short but distinct, sometimes with low lobe posterior to it, never dentiform, sometimes undiscernible ( Figs. 3A, D View Fig , 4 View Fig ). Antero- and posterolateral margins not demarcated, posterolateral area indicated only by presence of stronger striae, margin entire, gently sinuous to almost straight, gently divergent (sometimes subparallel) towards almost straight posterior carapace margin ( Figs. 3A, D View Fig , 4 View Fig ). Epistome relatively narrow, transversely subtruncate, posterior margin with obtuse low median triangular tooth, lateral margins gently concave ( Figs. 3B, E View Fig , 5D View Fig ). Antennule large, transversely ovate, separated from base of antenna by low tooth, with distinct hiatus between them. Antenna relatively short; basal article subovate; flagellum entering orbit.
Third maxilliped slender; ischium shorter than merus, with oblique submedian sulcus; merus subovate with distinct median ridge extending to anteroexternal angle of ischium; exopod slender, reaching to midlength of merus, with long flagellum, longer than width of merus ( Fig. 5E View Fig ).
Chelipeds subequal, stout in adults ( Figs. 3A, D View Fig , 4 View Fig ). Basis, ischium separated by distinct suture; inner margin with clusters of sharp granules ( Fig. 5A– C View Fig ). Inner margin of merus lined with sharp granules of varying sizes with distal one largest; margins not lamelliform; outer margin gently convex, granulated; inner surface with oblique row of stiff setae ( Fig. 5A– C View Fig ). Outer surface of carpus distinctly squamiform; inner distal angle weakly or not produced, lined with short tubercles or relatively long spines (especially in smaller specimens) ( Figs. 3A, B, E View Fig , 4 View Fig , 5A–C View Fig ). Adult chela high, outer surface prominently covered with numerous smooth rounded granules; inner surface granulated, with strong transverse median ridge on proximal part, lined with 7–11 tubercles and granules ( Figs. 3A–E View Fig , 4 View Fig , 5A– C, F–I View Fig ); dorsal margin of palm granulated ( Figs. 3A– C View Fig , 4 View Fig , 5F, H View Fig ); ventral margin with median part concave, granulated ( Figs. 5F–I View Fig , 3C, E View Fig ); fingers as long as palm, slightly gaping when closed ( Figs. 3E View Fig , 5F–I View Fig ); propodal finger gently curved, cutting margin with 3–5 large teeth on proximal half, usually with 1 subdistal tooth ( Figs. 3E View Fig , 5F–I View Fig ); dactylar finger curved, more slender, dorsal margin distinctly granulated along proximal third, remaining margin with low granules to almost smooth, granules not arranged in stridulatory row ( Figs. 3E View Fig , 5F– I View Fig ); tips of both fingers chitinised, gently excavated on inner surface ( Figs. 3E View Fig , 5F–I View Fig ).
Ambulatory legs relatively short, stout, second pair longest ( Figs. 3A, D View Fig , 4 View Fig ). Outer surfaces of merus, with distinct striae; outer surface of carpus and propodus smooth except for ridges ( Figs. 3A, D View Fig , 4 View Fig ). Meri laterally flattened, dorsal margin gently cristate, gently serrate, with sharp, subdistal dorsal spine ( Figs. 3A, D View Fig , 4 View Fig ). Outer surface of carpus of first to third legs with 2 low carinae; that of fourth leg with distinct carina ( Figs. 3A, D View Fig , 4 View Fig ). Propodi of first to third legs with long, simple setae that partially obscures margins, that on third leg least setose; ventral margin of first propodus with very dense mat of short setae, absent on propodi of other legs; surface of fourth propodus almost glabrous except for scattered short setae ( Figs. 3C View Fig , 4 View Fig , 5A–C View Fig ). Dactylopropodal lock not distinct. Inner surface of coxae of first to third ambulatory legs without tufts of dense short setae, with scattered short setae at most.
Surface, margins of anterior thoracic sternites setose. Sternites 1, 2 completely fused, forming triangular structure ( Figs. 3C View Fig , 5C View Fig ), separated from sternite 3 by suture, median part shallow, concave toward buccal cavity; sternites 3, 4 fused but demarcated by low transverse setose groove ( Fig. 5C View Fig ). No visible pleonal locking tubercle on sternite 5, locking mechanism formed by enlarged rim-like anterior edge of sternopleonal cavity on sternite 4. Sternites 4/5, 5/6, 6/7, 7/8 medially interrupted, with median longitudinal groove on sternites 7 and 8. Sternopleonal cavity deep, reaching to just before margin of fused sternites 3, 4, to imaginary line joining anterior edges of coxae of chelipeds ( Fig. 5A–C View Fig ). Penis long, curved, partially chitinised.
Pleon transversely wide, subtriangular; all somites, telson free ( Figs. 3C View Fig , 5A–C View Fig ). Somites 1–3 widest; somites 4, 5 transversely trapezoidal; somite 6 subtruncate, distinctly wider than long with convex lateral margins; telson wider than long with rounded tip, distinctly inserted into concave distal margin of somite 6 ( Figs. 3C View Fig , 5A–C View Fig ).
G1 relatively slender, elongate, distal half of stem expanded, inner margin with gentle but obvious subdistal hump, subdistal part of outer margin gently sloping with chitinous distal part long, gently curved to angle of ca. 60° from longitudinal axis ( Figs. 15A–C, E, F, 16A, B, C, E). G2 short, about quarter length of G1, without flagellum ( Fig. 16G).
Females: Female specimens are similar to males in most non-sexual characters ( Figs. 2A View Fig , 6A, B View Fig ), the major difference being in the form of the chelae. Female chelae are proportionately much smaller and not swollen, and the fingers not gaping when closed ( Figs. 2C View Fig , 6A, B View Fig ). In smaller specimens, the surfaces are generally smoother, the granules being more scattered, smaller and less distinct, and the fingers not gaping when closed ( Fig. 3F View Fig ). The pleon covers most of the thoracic sternum and the telson is inserted into the distal margin of somite 6 which has the lateral margins gently convex ( Figs. 2B View Fig , 6C View Fig ). The vulvae are on the anterior half of sternite 6, just touching the margin with sternite 5, with low, non-protruding operculum, and the anterior and posterior edges forming a bilobed sternal vulval cover with the posterior lobe more developed ( Fig. 6D View Fig ).
Colour: Carapace bicoloured, anterior half of carapace white or yellowish to dirty white, posterior half dark brown to almost black; chelipeds white to yellowish-brown; ambulatory legs dark brown to almost black; ventral surfaces dirty white with margins purplish ( Fig. 1 View Fig ).
Remarks: Henri Milne Edwards (1837: 74) described S. impressus only briefly: “Bords latéraux de la carapace armés de trois dents (dont la postérieure à peine distincte), droits, un peu divergens postérieurement et se terminant en dessus des pates de la quatrième paire. Front moins large que dans les espèces précédentes, ne dépassant pas notablement le troisième article des antennes externes, presque vertical et profondément quadrilobé en dessus. Deuxième article des pates-mâchoires externes marqué d’une dépression semi lunaire longitudinale. Pinces fortes, surtout du coté gauche. Ressemble beaucoup à la S. tétragone. Longueur, 18 lignes.” [Lateral edges of the carapace armed with three teeth (including the posterior which is barely distinct), straight, a little divergent posteriorly and ending above the legs of the fourth pair. Front less wide than in the preceding species, not exceeding the third section of the external antennae, almost vertical and deeply quadrilobed above. Second article of third maxilliped marked with a semi-lunar longitudinal depression. Strong chelae, especially on the left side. Very similar to Sesarma tetragona . Length, 18 lines (= 40.5 mm).] The single measurement provided suggests he may only have had one specimen, and it matches the width of the present specimen very well (although he cited it as carapace length). As for Sesarma frontale , which is clearly a junior synonym of S. impressa, A. Milne-Edwards (1869: 27) described the species briefly, providing the measurements for one specimen (25.0 × 22.0 mm) from western Madagascar but without recording its sex. He did not indicate how many specimens he had. MNHN has three dried type specimens, all of which should be regarded as syntypes. The measurements of the syntypes do not exactly match those of the MNHN specimens but the differences are not substantial and probably due to how accurately they were measured then. We here select the best male specimen (28.1 × 26.0 mm, MNHN-IU-2000-3667) to be the lectotype of Sesarma frontale . The selection of lectotypes for S. impressa and Sesarma frontale will stabilise the taxonomy of the species involved.
Serène and Soh (1970: pl. 7 figs. A, B) figured two specimens from MNHN and the Natural History Museum in London but did not state where they were from. The carapaces of the two specimens closely match that of S. impressus s. str. So it is likely both were from the western Indian Ocean.
Crosnier (1965: 63) noted that Lenz’s (1910) record of “ Sesarma nodulifera ” from the Comoros is actually S. impressus , and probably also his record of the latter species from Madagascar.
Ecology: Sesarmops impressus is primarily a mangrove species although it can be found further upstream in more freshwater habitats ( Keith et al. 2006; Bouchard 2009). Bouchard et al. (2013: 24) observed that “It lives generally in the upper part of the Mangrove, in cultivated fields and/or in meadows.”
Distribution: Madagascar, Mayotte, Comoros and adjacent areas in the western Indian Ocean.
Sesarmops indicus sp. nov. ( Figs. 7 View Fig , 8 View Fig , 14D–F View Fig , 15H–M, 16H–M) urn:lsid:zoobank.org:act:70D65351-90DD-4E32-8630-D3270E9D10F1
? Sesarma (Episesarma) frontalis – De Man 1895: 172 (Atjeh, northern Sumatra).
? Sesarma (Sesarma) impressa View in CoL – Nobili 1900: 507 (Mentawei Islands, west coast Sumatra).
? Sesarma (Sesarma) frontalis – Nobili 1900: 509 (Engano, west coast Sumatra).
Material examined: Holotype: male (22.7 ×
22.0 mm) ( ZRC 2015.344a), hill streams, evergreen and semi-evergreen forest, Mt. Harriet, South Andaman Islands, 11°42'05"– 11°51'45"N, 92°43'41"– 92°48'13"E, ca. 300–400 m asl, coll. I. Das, 20–30 August 1997. Paratypes: male (19.7 × 18.1 mm), 2 females (10.4 × 9.6 mm, 21.5 × 19.5 mm) ( ZRC 2019.1829), same data as holotype; 1 male (16.0 × 14.4 mm) ( ZRC 2015.345), Saddle Peak, Dumor Nalla, North Andamans, India, coll. P. Biswas, 8 June 1998.
Diagnosis: Male: carapace almost quadrate; external orbital tooth with outer margin convex, especially along posterior part, separated from lateral margin by distinct cleft ( Fig. 7A View Fig ); epibranchial tooth short but distinct, no visible low lobe posterior to it ( Fig. 14D View Fig ); outer surface of chela covered with numerous smooth rounded granules; inner surface granulated, with transverse median ridge on proximal part, lined with 8–10 tubercles and granules; dorsal margin of dactylar finger with randomly arranged granules, no trace of stridulatory row ( Fig. 7C, D View Fig ); ambulatory merus relatively longer, more slender, propodus and dactylus long ( Fig. 14E View Fig ); male pleon transversely narrower, somite 6 subtruncate, just wider than long with strongly convex lateral margins; telson as long as wide, not inserted into straight distal margin of somite 6 ( Figs. 7B View Fig , 14F View Fig ); G1 relatively slender, elongate, stem straight with no obvious expansion along entire length, without subdistal hump along inner margin, subdistal part of outer margin with distinct angular hump, chitinous distal part long, straight, bent at angle of about 45° from longitudinal axis, relatively longer, gently tapering when viewed laterally, with base shorter ( Figs. 15H– M, 16H–M). Female: telson inserted into distal margin of somite 6, lateral margins of somite 6 margins of somite 6 more strongly convex, appears proportionately wider ( Fig. 8C View Fig ); vulvae anterior half of sternite 6, just touching margin with sternite 5, posterior edge forming weakly bilobed sternal vulval cover, operculum low, non-protruding ( Fig. 8D View Fig ).
Colour: Not known.
Remarks: The present series of specimens from the Andamans are superficially similar to S. impressus s. str. and S. imperator sp. nov., but can easily be separated by the proportions of the ambulatory legs, as well as structures of the male pleons and gonopods (see DISCUSSION). Records of “ Sesarma impressa ” and “ Sesarma frontalis ” from northern Sumatra, Mentawei Islands and Engano Islands, all in the eastern Ocean, by De Man (1895) and Nobili (1900) are provisionally referred to this species until the specimens can be re-examined. This pattern of distribution is to be expected for an inland crab species which still have a dispersive phase via their planktonic larvae (see Ng and Shih 2014; Lai et al. 2017).
Ecology: Most of the type specimens were collected from an altitude of 300–400 m asl in freshwater streams in good forest. There are streams flowing to the Indian Ocean, most of which are only 500–1000 m from the sea. Nothing else is known about its ecology. Another freshwater sesarmid, Geosesarma thelxinoe (De Man, 1908) , was found with Sesarmops indicus (see Naruse and Ng 2020). For the ecology and other fauna known from this site, see Das (1997 1998) and Chandramouli et al. (2016).
Distribution: Known only from the Andamans but probably also present in other parts of the eastern Indian Ocean.
Sesarmops imperator sp. nov. ( Figs. 9– 12 View Fig View Fig View Fig View Fig , 13E, F View Fig , 14G–I View Fig , 15N–S, 16Q–S, 17) urn:lsid:zoobank.org:act:6D28BF5B-4BC8-47AC-85AF-F19BE67266B7
? Sesarma atrorubens View in CoL – De Man 1887: 653, 676, 678 (part) (Timor, Ambon and Xulla Besi [ Moluccas], Sanghir [northern Sulawesi]).
Sesarma impressa View in CoL – De Man 1892: 330 (Timor); Bürger 1893: 620, pl. 21 figs. 4, 5 ( Philippines; Palau Islands); Schenkel 1902: 546 (Sulawesi). (not Sesarma impressa H. Milne Edwards, 1837 View in CoL ) Sesarma frontalis – De Man 1892: 334, pl. 19 fig. 13 ( Flores). (not Sesarma frontale A. Milne-Edwards, 1869 View in CoL ).
? Sesarma (Sesarma) impressa View in CoL – Nobili 1900: 507 (Timor).
Sesarma (Sesarma) impressa View in CoL – De Man 1902: 527 ( Ternate, Batjan, Halmahera); Tesch 1917: 158 (Halmahera, Sulawesi, Nias, Papua New Guinea); Balss 1922: 155 (southern Taiwan); Sakai 1939: 685, pl. 110 fig. 1 (Danshuei, Taiwan); Horikawa 1940: 30 ( Taiwan; list); Sakai 1940: 32 ( Taiwan; list); Lin 1949: 30 (southern Taiwan; no new specimens); Shen and Dai 1964: 136, 1 unnumbered fig. (Hainan, China). (not Sesarma impressa H. Milne Edwards, 1837 View in CoL ).
? Sesarma (Sesarma) atrorubens View in CoL – Tesch 1917: 131 (part) (Timor, Ambon and Soela Besi [ Moluccas], Sanghir [northern Sulawesi]).
Sesarma (Parasesarma) impressa View in CoL – Miyake 1939: 226, 244 ( Palau). (not Sesarma impressa H. Milne Edwards, 1837 View in CoL ).
Sesarma (Sesarmops) impressum View in CoL – Dai et al. 1986: 493, pl. 69(7), text fig. 178(1–3) (Taiwan); Dai and Yang 1991: 540, pl. 69(7), text fig. 178(1–3) (Taiwan). (not Sesarma impressa H. Milne Edwards, 1837 View in CoL ).
Sesarmops impressum View in CoL – Serène and Soh 1970: 401, 406 (part), pl. 7 figs. A, B (no locality data); Sakai 1976: 660, text fig. 360 (Taiwan); Wang and Liu 1996: 123, figs. 161–162 (Taiwan); Liu 1999: 88 (Taiwan); Cai and Ng 2001: 691, fig. 19 (Halmahera, Indonesia); Lee 2001: 134, 2 unnumbered figs. (Taiwan); Ng et al. 2001: 43 (Taiwan); C.-H. Jeng and M.-F. Wang 2002: 85, 2 unnumbered figs. (Taiwan); Ho 2003: 9, 34, 2 unnumbered figs. (Taiwan). Liu 2009: 57, fig. 18 (Taiwan); Li and Chiu 2013: 56, 3 unnumbered figs. (Taiwan); Li and Chiu 2019a: 89; Li and Chiu 2019b: 45 (Taiwan); Ng et al. 2017: 106; Shao et al. 2007: 207, 1 unnumbered fig. (not Sesarma impressa H. Milne Edwards, 1837 View in CoL ).
Parasesarma pictum View in CoL – Y.-H. Chen 2001: 222, 1 unnumbered fig. [lower]. (not Grapsus (Pachysoma) pictus De Haan, 1835 View in CoL )
Sesarma impressum View in CoL – W.-J. Chen and Lo 2014: 144, 2 unnumbered figs. (Taiwan). (not Sesarma impressa H. Milne Edwards, 1837 View in CoL )
Sesarmops impressus View in CoL – Fukui et al. 1989: 230 (Taiwan); Yu et al. 1996: 15, figs. 75–76 (Taiwan); Jeng 1997: 18 (Taiwan); Jeng 1998: lower image on p. 81, upper image on p. 82 (Taiwan); Ng et al. 2008: 223 (part); C.-H. Jeng et al. 2010: 72, 5 unnumbered figs. (Taiwan); Li et al. 2010: 6 (Taiwan); Liu and Wang 2010: 61, 3 unnumbered figs. (Taiwan); Maenosono and Naruse 2016: 7 (Ryukyus, Japan; Lanyu, Taiwan); Maenosono and Saeki 2016: 9 (Ryukyus, Japan). (not Sesarma impressa H. Milne Edwards, 1837 View in CoL ).
Sesarmops impressus View in CoL 2 – Li et al. 2020: fig. 22 ( Taiwan; Philippines; Sulawesi, Indonesia).
Material examined: Holotype: male (37.7 × 36.3 mm) (NCHUZOOL 15068), Beiguan Tidal Park, outside Beiguan Crab Museum, 24°54'42.0"N, 121°52'38.0"E, Dasi, Yilan, coll. P.K.L. Ng, 4 June 2009. Paratypes: Taiwan: 2 males (32.3 × 31.4 mm, 34.9 × 35.0 mm) ( ZRC 2009.670), same data as holotype; 1 male ( ZRC 2009.694), Siangjiaowan, Hengchun, Pingtung, coll. P.K.L. Ng, June 2009; 1 male (38.0 × 36.3 mm), 1 female (36.7 × 34.8 mm), 1 ovig. female (36.1 × 35.7 mm) (NCHUZOOL 15870), Gangkou R. estuary, Manjhou, Pingtung, coll. H.-T. Shih, 2 July 2001; 2 males (37.6 × 33.7 mm, 35.4 × 32.3 mm), 1 female (23.0 × 20.7 mm) (NCHUZOOL 15069), lower reaches of Gangkou R., Manjhou, Pingtung, coll. J.-J. Li, 6 July 2017; 1 male (46.9 × 43.1 mm) (NCHUZOOL 15070), lower reaches of Gangkou R., Manjhou, Pingtung, coll. J.-J. Li, 4 April 2018; 2 females (29.0 × 26.3 mm, 28.9 × 26.8 mm) (NCHUZOOL 15071), lower reaches of Gangkou R., Manjhou, Pingtung, coll. J.-J. Li, 18 May 2019; 1 male (40.1 × 38.0 mm) ( ZRC 2001.32), Kenting National Park, Pingtung, coll. P.K.L. Ng, 7 November 2000; 1 male ( ZRC 1998.400), Hengchun Peninsula, Pingtung, coll. H.-C. Liu, 19 May 1998; 1 male ( ZRC 2000.1858), Lanyu Island, Taitung, coll. C.D. Schubart et al., 20 September 1999; 1 male (35.2 × 34.6 mm) (NCHUZOOL 15869), Lanyu, Taitung, 7 April 2002; 1 male ( ZRC 1999.1276), near Nanliao Fishport, Lyudao (= Green Island), Taitung, coll. P.K.L. Ng, 6 June 1993; 1 female ( ZRC 2002.427), at night, Changbin, Taitung, 23°18'22"N, 121°24'14"E, coll. P.K.L. Ng and H.-C. Liu, 22 June 2002; 1 male ( ZRC 2017.0984), near shore, along banks, Nioushan, Hualien, coll. J.-J. Li and P.Y.C. Ng, 14 June 2017; 5 males (13.7 × 12.7 mm, 15.5 × 14.8 mm, 18.2 × 17.3 mm, 20.3 × 19.4 mm, 30.3 × 29.6 mm), 4 females (12.6 × 11.4 mm, 13.1 × 12.0 mm, 21.8 × 20.8 mm, 31.6 × 30.4 mm) (NCHUZOOL 15868), Meilun R. estuary, Hualien, 29 July 2014; 8 males, 2 females ( ZRC 2017.0985), near shore, along banks, Meilun River estuary, Hualien City, Hualien, coll. J.-J. Li and P.Y.C. Ng, 14 June 2017.
Others: Philippines: 2 females ( ZRC 2013.1337), Luyang Cave Park, Catanduanes Island, Catanduanes Province, San Andres, coll. 9 July 2004; 1 young male ( ZRC 2017.308), Dagubdub River, Sibuyan Island, San Fernando town, España Barangay, coll. E.Y. Sy, 11 February 2013; 1 male (35.9 × 34.7 mm) ( ZRC 2017.477), under rocks, downstream from falls, Ambakan Falls, Jordan Town, Barangay Poblacion, Guimaras Island, coll. J.C. Mendoza and L. Ganancial, 1 June 2017; 8 males (largest 41.8 × 41.1 mm), 1 female, 3 ovigerous females ( ZRC 2001.307), Kawasan Falls, Matutinao, Cebu, coll. P.K.L. Ng et al., 20 December 2000; 4 males, 1 ovigerous female ( ZRC 2001.2318), Kawasan Falls, Matutinao, Cebu, coll. P.K.L. Ng, 25 November 2001; 2 males, 1 female ( ZRC 2019.1822), base of Kawasan Falls, Matutinao, Cebu, coll. P.K.L. Ng, 30 July 2003; 1 male (29.2 × 29.2 mm) (NCHUZOOL 15871), Camiguin I., coll. H.-T. Shih, 30 August 2003. Indonesia: 2 males, 2 females, 1 juvenile female ( ZRC 2019.1821), station THH 03-04, near Murex Resort, Manado, northern Sulawesi, coll. H. H. Tan, 24–27 May 2003; 1 male (24.7 × 23.4 mm) ( ZRC 2019.1816), rocky area in front of Murex Resort, Manado, Sulawesi, coll. N.K. Ng and H.H. Tan, 16 July 2003; 2 males, 2 females ( ZRC 2019.1820), 1 male (34.8 × 32.7 mm) ( ZRC 2016.252) near Murex Resort, Manado, northern Sulawesi, coll. P.K.L. Ng, 17 July 2003; 1 female ( ZRC 2019.1057), Bitung, Pulau Lembeh, Mawali Bay, area near to NAD Resort, Manado, Sulawesi, coll. H.H. Tan December 2018; 1 juvenile male (MNHN- IU-2019-4512 = MNHN-B 16680), Saluta, Halmahera, coll. W. Kükenthal, 1893–1894; 2 males (42.9 × 40.0 mm, 39.0 × 37.8 mm) ( ZRC 2012.412), Sungei Okito, Wasile, northern Halmahera, Moluccas, coll. P. Robb, August 1994; 1 male ( RMNH 26603), in office of Land Office, Hollandia harbour, Djayapura, ca. 500 m from sea, Indonesian Papua, coll. J. Ham and H.W. Moll, 19 October 1954. Papua New Guinea: 1 female ( ZRC 2019.1819), Ioa Cave, Pomio District, New Britain, coll. F. Brehier, 25 February 2002. Vanuatu: 1 male (27.9 × 26.2 mm) ( ZRC 2019.1818), Santo, coll. Santo Expedition 2006; 1 female (with moult, 38.1 × 34.1 mm) ( ZRC 2019.1817), Riorua, Santo, coll. L. Deharveng and A. Bedos, 17 September 2006.
Diagnosis: Male: carapace subtrapezoidal, longer than wide in adults; external orbital tooth with outer margin gently convex to almost straight, separated from lateral margin by cleft ( Figs. 10A View Fig , 11A, B View Fig , 13E, F View Fig ); epibranchial tooth short, may possess barely discernible very low lobe posterior to it but never distinct or dentiform ( Figs. 13 View Fig , E, F, 14G View Fig ); outer surface of chela covered with numerous smooth rounded granules; inner surface granulated, with strong transverse median ridge on proximal part, lined with 7–11 tubercles and granules; dorsal margin of dactylar finger with randomly arranged granules, no trace of stridulatory row ( Figs. 10D, E View Fig , 11E, F View Fig ); ambulatory merus relatively short, wide, propodus and dactylus relatively short, wide ( Fig. 14H View Fig ); male pleon transversely wide, somite 6 subtruncate, much wider than long with convex lateral margins; telson wider than long, distinctly inserted into concave distal margin of somite 6 ( Figs. 10C View Fig , 11C, D View Fig , 14I View Fig ); G1 relatively slender, elongate, stem straight with no obvious expansion along entire length, without subdistal hump along inner margin, subdistal part of outer margin with distinct angular hump, chitinous distal part long, straight, bent at angle of about 45° from longitudinal axis, relatively shorter, proximal and distal parts subequal in width when viewed laterally, with base longer ( Figs. 15N–S, 16Q–S). Female: telson inserted into distal margin of somite 6, lateral margins of somite 6 more strongly convex, structure appears proportionately wider ( Fig. 12C View Fig ); vulvae anterior half of sternite 6, intrudes into margin with sternite 5, posterior edge forming weakly bilobed sternal vulval cover, operculum low, non-protruding ( Fig. 12D View Fig ).
Colour: Carapace reddish-brown to purplishbrown, lateral and frontal margins yellow to orange; chelipeds usually purple, sometimes dark red, with tubercles white; ambulatory legs light brown; ventral surfaces dirty white ( Fig. 9 View Fig ). This species (as Sesarmops impressus or S. impressum ) has been well figured in many Taiwanese books (e.g., Lee 2001: 134; Liu and Wang 2010: 61; Li and Chiu 2019a: 89; Li and Chiu 2019b: 45).
Etymology: The name is derived from the Latin for emperor, with which the colour purple has always been associated with in European culture. The name alludes to the colour of the species as well as the relatively large size when compared to the other sesarmids that occur in its habitat. The name is used as a noun.
Remarks: The species is superficially similar to S. impressus s. str. with which it has long been confused. The differences, notably in the G1, however, are marked and leave no doubt it is a distinct species (see DISCUSSION).
On the basis of the specimens examined, S. imperator sp. nov., has a very wide range from Sundaic Southeast Asia to the Ryukyus and Vanuatu in the western Pacific. We have also examined photographs of specimens from various parts of the Indonesian Moluccas and Papua New Guinea, and they are all S. imperator . On the basis of the distribution, we provisionally refer old records of “ S. impressus ”, “ S. frontalis ” and “ S. atrorubens ” from Flores and Timor by De Man (1887 1892), Nobili (1900) and Tesch (1917) to S. imperator as well.
Ecology: Sesarmops imperator is a freshwater species, typically found among rocky areas in riverine habitats, usually with clean faster flowing water, often at the bases of waterfalls. They can be found near the shore where there is tidal influence all the way to several kilometres inland, even in highland sites (see also Liu 2009; Li et al. 2010; Liu and Wang 2010; Li and Chiu 2013; personal observations). In the central Philippines in particular, it can be found with two other species, S. mindanaoensis and S. mora Li, Shih & Ng, 2020 . They have also been found near limestone caves in the Philippines (unpublished data), and one specimen ( ZRC 2019.1817) from Riorua in Vanuatu was collected from next to a cave (see Lips et al. 2011). They are not known from mangroves.
Distribution: Southeast Asia to Taiwan and Japan (Ryukyus), Palau, Indonesia ( Moluccas, Lesser Sunda Islands, Sulawesi), Papua New Guinea and Vanuatu. Surprisingly, not yet known from Guam, other Mariana Islands and New Caledonia (cf. Paulay et al. 2003; Ng and Richer de Forges 2007).
Sesarmops atrorubens ( Hess, 1865) View in CoL ( Figs. 18–21 View Fig View Fig View Fig View Fig , 23A–G View Fig , 24A–F)
Sesarma atrorubens Hess, 1865: 149 View in CoL , pl. 6 fig. 12 (Sydney); Haswell 1882: 108 (list); De Man 1887: 653, 676, 678 (part) (Sydney); De Man 1890: 95 ( Fiji); Ortmann 1894: 724 ( Fiji).
Sesarma (Sesarma) atrorubens View in CoL – Tesch 1917: 131 (part) ( Fiji).
Sesarmops impressum View in CoL – Serène and Soh 1970: 401, 406 (list). (not Sesarma impressa H. Milne Edwards, 1837 View in CoL ).
Sesarma (Sesarmops) impressum View in CoL – McLay and Ryan 1990: 108, figs. 1A–G ( Fiji). (not Sesarma impressa H. Milne Edwards, 1837 View in CoL ).
Sesarmops impressus View in CoL – Ng et al. 2008: 223 (part; list). (not Sesarma impressa H. Milne Edwards, 1837 View in CoL ).
Material examined: Neotype (here designated): male (31.9 × 32.4 mm) ( ZRC 2019.1069 View Materials ), fast flowing stream with large boulder rocks, stream of Twin waterfall, near Naba Village along Lavena Coastal Walk, Taveuni Island, 16°52'15.3"S, 179°54'06.6"W, Fiji, coll. B.Y. Lee, et al., 24 July 2019. GoogleMaps
Others: 1 male (26.1 × 26.6 mm), 1 female (26.8 × 26.5 mm) ( ZRC 2019.1070) second waterfall, approx. 30–40 min hike along trail, Tavoro waterfalls, Bouma National Park, Taveuni Island, Fiji, coll. B.Y. Lee, S. Choy and B. Rashni, 25 July 2019.
Diagnosis: Male: carapace subtrapezoidal, longer than wide in adults; external orbital tooth with outer margin convex, especially along posterior part, separated from lateral margin by distinct cleft ( Figs. 19A View Fig , 20A, B View Fig ); epibranchial tooth short, may possess barely discernible very low lobe posterior to it but never distinct or dentiform ( Fig. 20B View Fig ); outer surface of chela covered with small number of large round tubercles; inner surface with several large rounded granules, that on subdorsal surface largest, without transverse median ridge; dorsal margin of dactylar finger lined with stridulatory row of 26–30 granules, most transversely rectangular with median transverse depression, proximal ones more rounded, similar to surrounding rounded granules, distal ones low, poorly formed ( Figs. 19C View Fig , 20F–I View Fig ); ambulatory merus relatively longer, more slender, propodus and dactylus long ( Figs. 19 View Fig , 20A View Fig ); male pleon transversely narrower, somite 6 subtruncate, just wider than long with gently convex lateral margins; telson as long as wide, not inserted into straight distal margin of somite 6 ( Figs. 19B View Fig , 20E View Fig ); G1 relatively short, stout, stem with distal part distinctly wider than median parts, outer margin distinctly concave, with subdistal hump along inner margin, subdistal part of outer margin with distinct angular hump, chitinous distal part short, straight, subtruncate, spatuliform, bent at angle of about 45° from longitudinal axis ( Figs. 23A– G View Fig , 24A–F). Female: telson inserted into distal margin of somite 6, lateral margins of somite 6 convex ( Fig. 21B View Fig ); vulvae anterior half of sternite 6, distinctly intrudes into margin with sternite 5, posterior edge forming low bilobed sternal vulval cover with prominent, protruding operculum ( Fig. 21C View Fig ).
Colour: McLay and Ryan (1990: 110) noted that in life, the “Dorsal surface of carapace and limbs dark purple, ventral surface pale creamy yellow. Fingers and tubercles on outer face of cheliped propodus pale yellow against a dark purple background.” The present specimens agree in general with this description, though we would add the following: the lateral margins of the carapace are white, the ventral margins of the ambulatory meri are white, the palm of the chela is evenly purple except for the white tubercles, with the pollex completely white to pale yellow, the dactylar finger has the upper part of the proximal third purple with white tubercles, the carpus of the cheliped is dark purple with white granules, the ventral surfaces are dirty white to pale yellow, and the eyes bright yellow ( Figs. 18 View Fig , 19 View Fig ). The two sexes do not differ in colour.
Remarks: Hess (1865: 149) described the species relatively briefly as follows: “Der Cephalothorax ist fast quadratisch, die Seiten fast grade mit drei Zähnen bewaffnet, von denen der letzte nur sehr klein ist. Die senkrecht nach abwärts gerichtete Stirn ist ausgeschweift und von vier sehr stark geschiedenen Loben fast überragt. Die Ischia sind gekörnelt und ziemlich lang, die übrigen Fussglieder büschelförmig behaart, besonders stark am oberen und unteren Rande. Die Klauenglieder sind grade und scharf zugespitzt. Der Carpus ist gross, gekörnelt, die Hand mit grossen Tuberkeln bedeckt. Die Finger sind am Innenrande stark gezähnt. Am Daumen befinden sich drei, am Zeigefinger zwei grössere Zähne. Der Aussenrand des Zeigefingers ist glatt, der des Daumens gerippt. Länge 3,8 Cm., Breite 3,5 Cm. Farbe dunkelviolet.” [The carapace is almost square, the sides almost armed with three teeth, the last of which is very small. The front, which is directed vertically downwards, is swept out and almost obscured by four very strongly separated ridges. The meri are granular and fairly long, the rest of the segments hairy, being particularly strong on the upper and lower edges. The dactyli are straight and sharply pointed. The carpus is large, granular, the hand covered with large tubercles. The fingers are heavily serrated on the inner edge. There are three larger teeth on the pollex and two larger teeth on the dactylar finger. The outer edge of the dactylar finger is smooth, that of the pollex is ribbed. Length 3.8 cm, Width 3.5 cm. Dark purple colour.] A figure of the overall specimen was provided ( Hess 1865: pl. 6 fig. 12).
Davie (2002: 226) commented that the syntypes in the Göttingen University “appear to be lost as they were not found when collection was transferred to SMF”. We have since confirmed this but note that Hess (1865) only had one male specimen anyway. The type locality for S. atrorubens is wrong, and has already been shown for several of Hess’ (1865) species (see also Ng 2012). Davie (2002: 226) noted that “the Australian distribution for this species is based on the type locality of ‘Sydney’, and this is certainly in error; extensive field collecting across northern Australia has so far failed to recollect S. atrorubens ; most probably it was collected from the islands of the south-west Pacific and sent to Hess via Sydney; however, as the northern coast of Australia is within the latitudinal range of the species, I will not yet exclude its possible occurrence.”
De Man’s (1887: 671–675) examined the type male and his detailed comparisons leave no doubt that the present material of S. atrorubens from Fiji is identical with the type male. Most significantly, De Man (1887: 675) notes that “Die nahe verwandte Sesarma atrorubens Hess lässt sich von der impressa leicht durch ihre schmälere, mehr hervorragende Stirn sowie durch den Bau der Scheerenfüsse und ihre schlankeren Lauffüsse unterscheiden, indem die Scheeren des Männchens an der Aussenseite nur mit einer beschränkten Zahl grosser Tuberkeln besetzt sind, während der bewegliche Finger auf seinem Oberrande eine Längs reihe von 25–30 kleinen, glatten Querrippchen trägt.” [The closely related Sesarma atrorubens Hess can be differentiated from impressa easily by its narrower, more pronounced front as well as the structure of the chelae, with the male palm slimmer and fewer large tubercles while the upper margin of the dactylar finger has a longitudinal row of 25–30 small, smooth transverse tubercles.] His observations agree completely with the specimens of the two species on hand.
De Man (1887: 678) commented that S. atrorubens was close to Sesarma trapezoidea H. Milne Edwards, 1837 (at present in Labuanium Serène & Soh, 1970 ), noting they differed only in the proportions of the carapace that is also more convex dorsally, and the relatively longer ambulatory legs. Both species have the distinctive pattern of transverse tubercles on the dactylar finger of the male chela (see also Jeng et al. 2003). The similarities are indeed marked, and the G1 of L. trapezoideum , although longer and slenderer than that of S. atrorubens , has the same general shape (cf. Jeng et al. 2003: fig. 4H, I), including the distinctive bulge on the distal part of the subterminal segment ( Figs. 23A–D, F View Fig , 24A, B, D). Although both occur in freshwater habitats, their habits are quite different, with L. trapezoideum known to be a climber, occuring on steep walls, while S. atrorubens lives on the forest floor.
De Man (1887: 678) also reported specimens of S. atrorubens from Timor, Ambon and Xulla Besi in the Moluccas, as well as Sanghir in northern Sulawesi, but this material needs to be re-examined. The only species known from this area thus far is S. imperator sp. nov., and as such, his records from these sites are provisionally referred there. This also applies to Tesch’s (1917) record who lists De Man’s (1887 1890) material (spelling Xulla Besi as Soela Besi instead). It is also possible that De Man (1887) confused his material from these areas with another species, Sesarmops weberi which was described only later by himself (De Man 1892) (see Naruse and Ng 2020, for redescription of types). Sesarmops weberi and S. atrorubens have similar carapace features and longer proportions of the ambulatory legs and have the same pattern of transverse tubercles on the dactylar finger of the male chela; although their G1s are very different in structure (see Naruse and Ng 2020, for redescription of types). Interestingly, when De Man (1892: 338–341) described S. weberi , he compared it at length with Labuanium trapezoideum but not with S. atrorubens although he said they were very close a few years earlier (De Man 1887: 678).
McLay and Ryan (1990) recorded a female specimen from Taveuni Island in Fiji, redescribed the species and figured the carapace, cheliped, ambulatory leg and pleon. Their description as well as colour notes agree well with the present specimens.
A s d is cu s s ed ear lier, th e ty p e o f S es a r m a atrorubens Hess, 1865 , is no longer extant. We here select a freshly collected male (31.9 × 32.4 mm) ( ZRC 2019.1069) from Fiji as the neotype of the species. This action will stabilise the name and allow for a more effective revision of the genera in Sesarmidae in the future.
Ecology: McLay and Ryan (1990: 110) observed that “This crab is known locally as the ‘blue’ land crab and the present specimen came from a dried creek bed, 1.5 km from the sea at an altitude of approx. 100 m. Here a crab was observed during the day sitting on a boulder in among mosses and ferns. On a previous occasion one of us (P.A. R.) observed a cast exoskeleton of S. (S.) impressum in a creek bed in Taveuni rainforest at an altitude of approx. 1200 m. Clearly this crab is capable of living far from the sea.” The present specimens were collected only a few hundred metres from the sea and were hiding under rocks at the base of the waterfall (BY Lee, personal communication). The local communities protect the crab from over exploitation as its popular with tourists and locals.
Distribution: Known for certain only from Fiji.
Sesarmops similis ( Hess, 1865) View in CoL ( Figs. 22 View Fig , 23H–Q View Fig , 24G–L)
Sesarma similis Hess, 1865: 150 View in CoL (“Sydney”); Haswell 1882: 108 (list). Sesarma impressa View in CoL – Ortmann 1894: 723 ( Samoa). (not Sesarma impressa H. Milne Edwards, 1837 View in CoL ).
Material examined: Neotype (here designated): male (32.5 × 30.0 mm) ( ZRC 2017.8 View Materials ), Upolu, Samoa, coll. Wroblewsky (Museum Godeffroy), 1800s.
Diagnosis: Male: carapace almost quadrate; external orbital tooth with outer margin convex, separated from lateral margin by distinct cleft ( Fig. 22A, B View Fig ); epibranchial tooth short but distinct, sometimes without lobe posterior to it ( Fig. 22B View Fig ); outer surface of chela covered with numerous smooth rounded granules; inner surface granulated, with transverse median ridge on proximal part, lined with 17 tubercles and granules; dorsal margin of dactylar finger with randomly arranged granules, no trace of stridulatory row ( Fig. 22G, H View Fig ); ambulatory merus relatively short, wide, propodus and dactylus relatively short, wide ( Fig. 22A View Fig ); male pleon transversely wide, somite 6 subtruncate, wider than long with gently convex lateral margins; telson slightly longer than wide, not inserted into straight distal margin of somite 6 ( Fig. 22E View Fig ); G1 short, stout, stem with distal part distinctly wider than median parts, outer margin distinctly concave, subdistal part of outer margin with rounded hump, chitinous distal part short, beak-like, very wide ( Figs. 23H–Q View Fig , 24G–K). Female: not known.
Colour: The female holotype was described as “dark yellow-red” by Hess (1865: 150).
Remarks: Hess (1865: 150) described Sesarma similis as follows: “Der Cephalothorax ist wie bei Ses. atrorubens . Die Stirn ist gleichfalls in vier Loben getheilt, die jedoch nicht so weit vorragen. Die Beine wie bei der vorigen Species, nur sind die Ischia breiter und kürzer. Die Scheerenfüsse des Weibchens sind sehr klein. Die Hände sind nicht mit Tuberkeln besetzt. Jeder Finger trägt drei grössere Zähne. Länge 3.5 Cm., Breite 3.3 Cm. Farbe dunkelgelbroth.”, noting that “Vielleicht nur Weibchen des vorigen, was ich um so mehr vermuthe, da von den Exemplaren der Samm lung die ersteren nur Männchen, die letzteren nur Weibchen sind.” [The carapace is like Ses. atrorubens . The front is likewise divided into four ridges, which, however, does not protrude as far anteriorly. The legs as in the previous one species, only the meri are wider and shorter. The chelae of the female are very small. The palms are not covered with tubercles. Each finger carries three bigger teeth. Length 3.5 cm, Width 3.3 cm. Colour dark yellow-red… Maybe only females of the previous one { Ses. atrorubens }, which is likely, as from the collection, the former there are only males, the latter only females.]. No figures were provided. We do not agree with Hess that Sesarma similis is a female of S. atrorubens because we now have females of the latter, and its colour is like of males (purple and white), the postfrontal lobes still protrude prominently anteriorly like in males, the outer surface of the chelae is still covered with distinct large tubercles, and the ambulatory meri are not distinctly wider and shorter. As Hess specimen measures 33 mm in carapace width, it is quite large and not a juvenile.
The type locality for S. similis is probably incorrect (see above discussion for S. atrorubens ). Davie (2002: 226) commented that “(the Australian distribution for this species is based on the type locality of ‘Sydney’ for Sesarma similis Hess , and this is certainly erroneous; extensive field collecting across northern Australia has so far failed to recollect S. impressus ; most probably it was collected from the islands of the south-west Pacific and sent to Hess via Sydney; however, as the northern coast of Australia is within the latitudinal range of the species. I will not yet exclude its possible occurrence.)”
De Man’s (1887) comparisons of S. similis with S. impressus were made difficult by the fact that S. similis is known only from a female. On the basis of the present material we refer to these two species, we agree that they are superficially very similar. As noted by De Man, the carapaces are very close, with the shape, dorsal surface, lateral teeth, frontal margin and postfrontal lobes all similar. The ambulatory leg proportions, notably in the merus and dactylus, are also the same. Without a male of S. similis and relying only on carapace and pereopod features, it is not surprising De Man believed both species were synonymous. We believe; however, that they are separate species.
In the ZRC is an old specimen from Samoa which the late Raoul Serène in 1970 had labelled as a new species, “ Sesarmops samoaensis ”. The name has never been published. The specimen is distinct species, with a very diagnostic G1 ( Figs. 23H–Q View Fig , 24G–K). The specimen was the property or obtained by “Wroblewsky”, who is almost Johannes Julius Wroblewsky (or Wroblewski) (1820–1888). He was a Danish physician associated with several Danish zoologists such as Mørch and Steenstrup ( MacGregor 2008: 236, 237) and probably purchased the specimen from the Museum Godeffroy (see also Schleisner 1889: 19).
We here argue that Serène’s “ Sesarmops samoaensis ” is the same taxon as what has been described as Sesarma similis Hess, 1865 . The carapace and ambulatory characters match in all respects. More significantly, most Sesarmops species, even S. atrorubens , have the outer surface of the female chelae granulated. It is less prominently granulated compared to males but still distinct. Hess (1865) described the chela as smooth, and this is for a large adult specimen. Li et al. (2020) showed that only in adult female S. mindanaoensis are the outer surfaces of the chelae almost smooth or with only few low granules. S. mindanaoensis (known from Philippines, Taiwan and Sulawesi), however, has distinctly more elongate ambulatory legs and a more slender G1 (see Li et al. 2020).
In recognizing the synonymy of S. similis with S. impressus, Davie (2002: 226) noted that the zoological collections of the Göttingen University had two female specimens (catalogue number ZMG 602) which have been transferred to Senckenberg Museum. A search in the Senckenberg collections failed to uncover this material. This is clearly incorrect data as Hess (1865) himself had only one female specimen. As the type of Sesarma similis Hess, 1865 is lost and no longer extant, we here select the present male (32.5 × 30.0 mm) ( ZRC 2017.8) from Samoa to be the neotype of the species. This will stabilise the taxonomy of these species names and allow the necessary generic revisions to be done in the future (see DISCUSSION).
Ecology: Not known.
Distribution: Known for certain only from Samoa.
Molecular analyses
A phylogenetic tree of the combined 16S and COI markers was reconstructed using BI and ML analyses ( Fig. 25 View Fig ). Both Sesarmops imperator and S. impressus are well supported, and sister to each other, although the support values are low. The above two species, as well as Bresedium eurypleon Li, Shih & Ng, 2020 and B. brevipes (De Man, 1889) , form a strongly supported clade, which is sister to S. mora Li, Shih & Ng, 2020 . Both S. mindanaoensis and S. atrorubens are not closely related to the other species.
The mean pairwise nucleotide divergence of K2P distances and bp differences of haplotypes of the four closely related species, Sesarmops impressus , S. imperator , Bresedium eurypleon and B. brevipes , are shown in table 1. The intraspecific nucleotide divergences of the four species were all ≤ 1.23% (8 bp difference). The interspecific divergences among the four species were all ≥ 2.65% (17 bp difference). The interspecific divergence was at least 2.7-fold greater than intraspecific values (between B. brevipes and B. eurypleon ), supporting our hypothesis that the four species are distinct.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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Sesarmops impressus (H. Milne Edwards, 1837 )
| Ng, Peter K. L., Li, Jheng-Jhang & Shih, Hsi-Te 2020 |
Sesarma impressum
| Chen WJ & Lo LC 2014: 144 |
Sesarmops impressus
| Ng PKL & Guinot D & Davie PJF 2008: 223 |
Sesarmops impressus
| Poupin J & Cleva R & Bouchard JM & Dinhut V & Dumas J. 2018: 72 |
| Bouchard JM & Poupin J & Cleva R & Dumas J & Dinhut V. 2013: 24 |
| Bouchard JM 2009: 6 |
| Ng PKL & Guinot D & Davie PJF 2008: 223 |
| Keith P & Marquet G & Valade P & Bosc P & Vigneux P. 2006: 36 |
Parasesarma pictum
| Chen YH 2001: 222 |
Sesarma (Sesarmops) impressum
| McLay CL & Ryan PA 1990: 108 |
Sesarmops impressus
| Maenosono T & Naruse T. 2016: 7 |
| Maenosono T & Saeki T. 2016: 9 |
| Jeng CH & Wang MF & Lai SL & Hsu HL 2010: 72 |
| Li JJ & Ko FC & Li JJ 2010: 6 |
| Liu HC & Wang CH 2010: 61 |
| Ng PKL & Guinot D & Davie PJF 2008: 223 |
| Jeng MS 1997: 18 |
| Yu HP & Jeng MS & Chan TY & Ho PH & Shy JY 1996: 15 |
| Fukui Y & Wada K & Wang CH 1989: 230 |
Sesarma (Sesarmops) impressum
| Dai AY & Yang SL 1991: 540 |
| Dai AY & Yang SL & Song YZ & Chen GX 1986: 493 |
Sesarmops impressum
| Serene R & Soh CL 1970: 401 |
Sesarmops impressum
| Li JJ & Chiu YW 2019: 89 |
| Li JJ & Chiu YW 2019: 45 |
| Li JJ & Chiu YW 2013: 56 |
| Liu HC 2009: 57 |
| Shao KT & Chen CY & Tsai CY & Chiu YW & Yeh JC & Hsieh LY 2007: 207 |
| Ho PH 2003: 9 |
| Cai YX & Ng PKL 2001: 691 |
| Lee JH 2001: 134 |
| Ng PKL & Wang CH & Ho PH & Shih HT 2001: 43 |
| Liu HC 1999: 88 |
| Wang CH & Liu HC 1996: 123 |
| Sakai T. 1976: 660 |
| Serene R & Soh CL 1970: 401 |
Sesarmops impressum
| Serene R & Soh CL 1970: 401 |
Sesarma (Sesarma) impressa
| Guinot D. 1967: 287 |
Sesarma (Sesarma) impressum
| Serene R. 1968: 106 |
| Crosnier A. 1965: 63 |
Sesarma (Parasesarma) impressa
| Miyake S. 1939: 226 |
Sesarma (Sesarma) atrorubens
| Tesch JJ 1917: 131 |
Sesarma (Sesarma) atrorubens
| Tesch JJ 1917: 131 |
Sesarma (Sesarma) impressa
| Shen CJ & Dai AY 1964: 136 |
| Lin CC 1949: 30 |
| Horikawa Y. 1940: 30 |
| Sakai T. 1940: 32 |
| Sakai T. 1939: 685 |
| Balss H. 1922: 155 |
| Tesch JJ 1917: 158 |
| Man JG De 1902: 527 |
Sesarma (Sesarma) impressa
| Nobili G. 1900: 507 |
Sesarma (Sesarma) frontalis
| Nobili G. 1900: 509 |
Sesarma (Sesarma) impressa
| Nobili G. 1900: 507 |
Sesarma (Episesarma) frontalis
| Man JG De 1895: 172 |
Sesarma impressa
| Schenkel E. 1902: 546 |
| Burger O. 1893: 620 |
| Man JG De 1892: 330 |
| Man JG De 1892: 334 |
Sesarma atrorubens
| Man JG De 1887: 653 |
Sesarma atrorubens
| Ortmann AE 1894: 724 |
| Man JG De 1890: 95 |
| Man JG De 1887: 653 |
| Haswell WA 1882: 108 |
| Hess W. 1865: 149 |
Sesarma similis
| Ortmann AE 1894: 723 |
| Haswell WA 1882: 108 |
| Hess W. 1865: 150 |
Sesarma impressa H. Milne Edwards, 1837: 74
| Milne Edwards H. 1837: 74 |