Garthambrus pteromerus (Ortmann, 1893)

Mclay, Colin L., 2009, Revision of the crab genus Garthambrus Ng, 1996, with the description of two new genera and discussion of the status of Tutankhamen Rathbun, 1925 (Crustacea: Brachyura: Parthenopidae), Zootaxa 2122, pp. 1-50 : 17-20

Garthambrus pteromerus (Ortmann, 1893) nov. comb.

( Figs 7 A, B, 12C, D, 22E–H)

Lambrus (Parthenopoides) pteromerus Ortmann, 1893: 416 , pl. 17, fig. 1. – Balss 1922: 135; 1924: 61. – Yokoya 1933: 166 (list). – Sakai 1934: 299.

Parthenopoides pteromerus — Flipse 1930: 85 (list). – Sakai 1935: 72, text-fig. 6; 1936: 110, text-fig. 51.

Tutankhamen pteromerus — Sakai 1938: 339, pl. 41 figs 1, 2. – Miyake 1961: 17. – Sakai 1965: 97, pl. 44 fig. 4. – Takeda & Miyake 1969: 473, fig. 1. – Miyake 1983: 53, 211 (list), pl. 18. – Cai et al. 1994: 583. Parthenope (Platylambrus) validus forma intermedius — Dong et al. 1988: 88, fig. 80. Not Lambrus intermedius Miers, 1879 a.

Material examined. China: unknown location, 1 male 19.3 x 13.7 mm ( ZRC).

Taiwan. TAIWAN 1: stn CP58, 24º35.1’N, 122º5.8’E to 24º33.3’N 122º05.6’E, 221–254 m, dense crinoids, 4 Aug 2000: 1 male 22.2 x 15.3 mm ( ZRC 2001.2225); Same data as previous: 1 male 16.4 x 11.6 mm, 1 female 11.4 x 8.4 mm ( MNHN).

TAIWAN 2: stn 2, waters off Kaohsiung, 200 m, 9 Apr 2002: 1 male 13.1 x 10.0 mm, 1 female 20.0 x 14.4 mm (MNHN)

Japan.: unknown location, 17 Mar 1967, 1 female 18.2 x 13.7 mm (SFM) (TS00383); Sagami Bay, Hatsushima bei Atami, Kanagawa Ken, dredge, forschungsschiff der Uni Yokohama, no date: 1 male 20.9 x 15.5 mm.

Albatross: stn 4807, Cape Tsiuka, from Hakodata, Japan to Ebisu, Sado I., Sea of Japan (via Tsugaru Strait), 81 m, 16 Jul 1906: 2 males 19.1 x 14.1, 21.9 x 16.2 mm (USNM 50912); Stn 4894, Ose Sakai Strait, 10 to20 miles SW of Goto Is, Eastern Sea, 174 m, 9 Aug 1906: 1 female, 16.9 x 12.2 mm (USNM 50910).

Danish Pacific Expedition, 1914–1915: 23 miles northwest, 3/ 4 miles west of Goto (or Osesaki), 32º49’N, 128º14’E, 210 m, 14 May 1914: 1 ovig. female 14.0 x 10.3 mm (ZMUC); Off Misaki, 80–100 fm (146-183 m), 19 Jun 1914: 1 male 33.1 x 22.4 m. (ZMUC). Bungo Strait, Shikoku I., Tosa Bay, T. & K. Sakai coll., 16 Nov 1958: 1 male 31.8 x 19.9 mm (USNM 120717); Kii Peninsula, west of Shionomisaki, 33º26.72’N, 135º39.20’E, 180 m, 16 Apr 1997: 2 males 9.8 x 8.1, 15.9 x 11.6 mm, 1 female 18.1 x 12.9 mm (ZRC).

Indonesia. KARUBAR: stn DW32, Kai Is, 05º47’S, 132º51’E, 170–206 m, 26 Oct 1991: 1 female 19.2 x 14.4 mm (MNHN).

Philippines. MUSORSTOM 1, stn 35, 13º59.0’N, 120º18.5’E, 186–187 m, 23 Mar 1976: 1 male 29.5 x 19.0 mm (MNHN-B31873).

MUSORSTOM 2, stn DG32, 13º40’N, 120º54’E, 192–220 m, 24 Nov 1980: 1 female 16.7 x 12.8 mm, 1 ovig. female 22.9 x 14.6 mm (MNHN-B31874).

Visayas, Bohol, Panglao I., off Panglao town, Balicasag I.: about 200–300 m, tangle nets, Dec 2000: 1 male 27.6 x 18.3 mm (ZRC). – about 200–300 m, tangle nets, Dec 2000: 1 male 20.1 x 14.1 mm (ZRC). – about 50–500 m, in tangle nets, 28 Nov 2001: 10 males (ZRC).

Redescription. Carapace sub-pentagonal, wider than long, CW/CL = 1.35–1.55, surface finely granular with some eroded/pitted areas, especially on prominent parts of carapace. Median rostral tooth blunt, narrowing anteriorly, horizontal; lateral teeth hardly produced, edge eroded to accommodate antennules. Frontal region concave, dorsal orbital region slightly elevated with small mid-way eroded area. Protogastric area elevated, pitted, eroded, with pair of faint rounded tubercles. Mesogastric region with broad pitted median ridge topped by prominent tubercle. Ridge continues through metagastric area at lower level, faint tubercle sometimes present. Cardiac region has narrow median ridge with prominent rounded tubercle, weak tubercle present in intestinal area as ridge descends towards posterior margin. Anterior branchial region with diagonal ridge ending in low rounded tubercle behind posterior epibranchial corner. Posterior branchial region with distinct narrow tubercle which overhangs posterior epibranchial margin. Three pits in branchiocardiac groove, also faint tubercle. Total number of carapace tubercles 10.

Orbital margin finely granular, strongly concave posteriorly to well marked supraorbital suture. Suborbital concave margin ends in sub-acute tooth with large gap between tooth, lateral rostral tooth. Posterior corner of hepatic margin produced, with small tubercle on posterior edge. First anterior epibranchial tooth immediately above hepatic notch followed by 8–10 distinct teeth. Anterior epibranchial margin laciniate, posterior epibranchial corner flange-like, with, small tooth. All anterior epibranchial teeth tend to be curved upwards. Posterior epibranchial margin with 2 teeth posterior to epibranchial corner, first larger. Posterior margin with 3 blunt teeth, lateral ones larger.

Epistome T-shaped, central region with adjacent circular concavities separated by ridge; lateral concavities lack complete encircling ridge. Subhepatic region concave with hepatic fissure extending forward towards corner of buccal frame. Fissure surrounded by tubercles. Strong ridge begins at corner of buccal frame, below hepatic fissure, after interruption by distinct notch beneath first anterior epibranchial tooth, extends posteriorly on to sub-branchial region. Cheliped-blocking mechanism consists of proximal meral spine on cheliped meeting strong sub-branchial spine. Surface of sternites 3, 4 have U-shaped depression with large tubercle at each corner. Sternites 5 –7 with small slightly projecting tuberculate ridges each preceded by small depression. Only sternal suture 6/7 complete in both sexes.

Eyes mobile, eyestalks granular, short, diameter same as cornea, articulate at right angles to body axis; margin of orbit incomplete ventrally, orbital fossa deep, formed by lateral, suborbital margin, approximately 80% of cornea concealed when eye folded away.

Antennule article 1 mobile, 6-sided; article 2 much longer than wide, inserted medially, folded away at an oblique angle; article 3 much longer than wide; articles 3, 4 normally kept folded away in antennular fossa.

Antennal article 1 (“urinal article”) mobile, wider than long, convex; article 2 (“basal article”) trapezoidal, convex, fixed to epistome, suborbital margin; articles 3, 4 mobile, longer than wide; flagellum as long as articles 3, 4 combined.

Third maxilliped basis-ischium with longitudinal central depression, blade-like medial margin. Merus with dense coarse granules obscuring adjacent depressions. Distolateral corner of merus covers distal end of exopod. Carpus, propodus, dactylus of endopod decrease in size distally, last 2 articles folded under merus.

Cheliped length in males 2.7 x CW or 4.0 x CL. Corresponding ratios for females 1.9, 2.6. Inner margin of merus with 17 well developed subacute tubercles, with many smaller ones interspersed. Outer meral margin with 10 or 11 similar tubercles with, mid-way, a group of 4 tubercles curving down from dorsal to ventral surface, but these are not involved with the cheliped-blocking mechanism. Carpus with 7 tubercles of varying size on inner margin, 3 or 4 on the surface. Outer margin of propodus with 8 to 10 tubercles (4 larger evenly spaced tubercles with smaller ones in between), outer margin with 12 tubercles of various sizes, last 5 curving up toward base of dactylus. Upper surface of dactylus with 3 or 4 tubercles decreasing in size distally. Right cheliped (crusher) with essentially obsolete teeth, left (cutter) with 3 very weak teeth.

Length of ambulatory legs decreases posteriorly. Formula for leg tubercles: P2: no tubercles on any articles; P3: merus 0/(0 + 3), none on carpus, propodus; P4: merus 0/(3 + 3), none on carpus, propodus; P5: merus 0/(3 + 3), carpus 0/0, propodus 0/3. Most leg margins have continuous crest except for meral segments where crests interrupted to produce teeth-like features. Dactyli of P2–P5 shorter than propodi.

Abdominal segment 3 with lateral ridge on each side, central depression, while segments 4-6 have low central median ridge. Segments 3-5 fused in male, sutures only indicated by marginal notches. Acute medial hook present on segment 6. Abdominal locking mechanism complete, working in males, females. Telson triangular, wider than long, tip narrowly rounded. Tip more pointed in female with telson occupying most of fourth sternite.

Male G1 reaches mid-way of sternite 5 in situ, sub-terminal sperm aperture opens medially, surface minutely spinose over distal 27% of length. G2 reaches mid-way of sternite 4 in situ, tip acute, twisted. G2 made up of two sections, proximal calcified section followed by horny flexible, twisted flagellum 0.48 of length. Beginning of flagellum marked by presence of small notch, sudden reduction in diameter of gonopod. Ratio of G2/G1 = 1.4. Female gonopore in middle of sternite 6, only slightly raised above sternal surface, subcircular in shape, covered by flexible layer.

Distribution. Japan and China, and now for the first time from. Taiwan, Philippines and Indonesia.

Remarks. The generic placement of Lambrus (Parthenopoides) pteromerus Ortmann, 1893 , has been the subject of considerable debate. This species is certainly not related to Parthenopoides Miers, 1879 b (type species: Lambrus massena Roux, 1830 ), due to the very different carapace shape and the considerably longer chelipeds. Sakai (1938) placed it in Tutankhamen Rathbun, 1925 (type species: Mesorhoea cristatipes A. Milne-Edwards, 1878 ), based mainly on the carapace shape and the size of the basal antennal segment (antennal article 2) and synonymised G. lacunosus with it. Garth (1993) refuted the synonymy because G. lacunosus does not possess a lamellar ridge that lines the afferent respiratory channels, which is present in L. (P.) pteromerus . Ng (1996) pointed out that the restriction of Tutankhamen to the Atlantic Ocean, the different carapace dimensions and gonopod structure makes it very unlikely that the two species are congeneric. He noted that it is very close to Garthambrus but due to a lack of specimens hesitated to place it in Garthambrus . The examination of specimens of L. (P.) pteromerus and of the type species of T. cristatipes allowed us to conclusively place it in Garthambrus . Some generic characters were also clarified.

Balss (1922) commented that G. pteromerus is “scheint der L. (Parthenolambrus) exilipes Rathbun, 1893 von Californien und den Galapagos-Inslen zu sein” [i.e. G. pteromerus “appears to be the same as L. (Parthenolambrus) exilipes from California and the Galapagos Islands”]. Sakai (1935) identified his material as Parthenopoides pteromerus but commented that they were similar to G. lacunosus . It is clear from his figure, however, that they belonged to G. pteromerus .

The identification by Dong et al. (1988) of Parthenope (Platylambrus) validus forma intermedius from the East China Seas is incorrect and should be referred to G. pteromerus .

All three specimens from the Albatross Expedition were originally identified by M. Rathbun as Parthenope (Platylambrus) stellata lacunosa Rathbun, 1906 . These old records were apparently never published by Rathbun.

Figures

FIGURE 7. Gonopods. Garthambrus pteromerus (Ortmann, 1893): A, B, male 31.8 x 19.9 mm (USNM 120717), Japan, Buno Straits, Shikoku I. — Garthambrus stellatus (Rathbun, 1906): C, D, holotype, male 48.6 x 32.8 mm (USNM 29839), Hawaiian Is, south coast, Oahu. A, C, left G 1; B, D, left G 2. Scale bar = 1 mm.