Garthambrus poupini (Garth, 1993)

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 : 9-11

Garthambrus poupini (Garth, 1993)

( Figs 5 A, B, 9A)

Parthenope (Platylambrus) poupini Garth, 1993: 782 , figs 1, 2. Garthambrus poupini — Ng 1996: 159. – Ng & Tan 1999: 122.

Type material. HOLOTYPE: male 35.5 x 28.0 mm (MNHN-B22424), French Polynesia, Tuamotu, Fangataufa, SMCB stn 84, 22°11.1’S, 138°45.1’W, 520–570 m, 22 Jul 1988.

PARATYPES: 1 male 37.9 x 28.9 mm (MNHN-B 21364), French Polynesia, Tuamotu, Fangataufa, SMCB stn 135, 22º15.2’S, 138º46.3’W, 720 m, 25 Feb 1989; 1 male 39.4 x 29.9 mm ( MNHN, MP B- 22420), French Polynesia, Tuamotu, Fangataufa, SMCB stn 395, 22°15.3’S, 138°42.9’W, 660 m, 15 Mar 1991; 1 female 25.6 x 19.4 mm ( MNHN, MP B- 21363), Moruroa, SMCB: stn 125, 21°51’S, 138°47’W, 530–630 m, 29 Oct 1988.

Material examined. New Caledonia: CHALCAL II: stn DW74, 24°40.36’S, 168°38.38’E, 650 m, 29 Oct 1986: 1 male 10.0 x 8.0 mm ( MNHN).

SMIB 8: stn DW151, 24°53.0’S, 168°21.4’E, 530–547 m, 27 Jan 1993: 1 female 14.1 x 11.0 mm ( MNHN).

Redescription. Carapace shape pentagonal, wider than long, ratio CW/CL = 1.3, surface covered with mixture of coarse, fine granules. Larger granules fungiform-shaped, all granules bear tiny granules themselves. Rostrum elongate, prominent, horizontal, increasing in thickness near tip. Frontal region concave, dorsal orbital area swollen into 2 convex parts separated by notch. Protogastric region with 2 more densely granular, convex areas. Broad median ridge of denser granules extends across mesogastric, metagastric areas, on to cardiac region. Anterior branchial region bears 2 prominent ridges: anterior diagonal ridge lies at lower level than posterior diagonal ridge, which is more densely granular, ends just behind posterior epibranchial corner. Posterior branchial region with short, densely granular ridge. Branchiocardiac groove contains 3 well marked pits with large paxillate tubercle.

Orbital margin granular, strongly concave posteriorly, supraorbital suture partially obscured by granules. Margin of suborbital region concave, ending bluntly. Posterior corner of hepatic margin with granular swelling followed by small tooth before hepatic notch. Anterior epibranchial margin with 11 truncated teeth decreasing in size posteriorly until reaching large posterior slightly upturned epibranchial tooth. Posterior epibranchial margin slightly concave without teeth. Posterior margin with 3 heavily granular swellings separated by short concave areas.

Epistome T-shaped with central broadly V-shaped depression, shallow concavity at each end. Subhepatic region concave without fissure. Well marked, closely spaced line of granules begins at corner of buccal frame, extending posteriorly across pterygostomial region. After interruption by hepatic notch, line of granules continues on to sub-branchial region. Cheliped-blocking mechanism consists of stout proximal spine on posterior margin of cheliped merus meeting large sub-branchial spine. Deep U-shaped depression on sternites 3, 4 with large tubercle at each corner. Sternites 5–7 have small slightly projecting tuberculate ridges each proceeded by small depression. Sternal sutures 4/5, 5/6, 6/7, 7/8 all interrupted.

Eyes mobile, eyestalks granular, short, diameter same as cornea, margin of orbit incomplete ventrally, orbital fossa deep, formed by lateral, suborbital margin, around 80% of cornea is concealed when eye is folded away.

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

Article 1 of antenna mobile, wider than long, convex; article 2 trapezoidal, convex, fixed to epistome, suborbital margin; articles 3, 4 mobile, longer than wide; flagellum as long as articles 3, 4 combined.

Basis-ischium of third maxilliped with central longitudinal cavity, medial side with edentate knife-like margin. Merus wider than long with 2 concavities separated by ridge. Lateral corner covers distal end of exopod. Carpus forms part of external cover, but propodus, dactylus hidden beneath merus of endopod.

Inner margin of cheliped merus with 11 or 12 well developed granules interspersed with smaller ones; outer margin with similar number, especially large granule mid-way. Surface of carpus granular. Margins of propodus have about 12 granules of varying size, last 3 granules on inner margin curve up towards base of dactylus. Upper margin of dactylus with 3 blunt granules. Right cheliped a crusher with 3 or 4 obsolete distal teeth while left cheliped a cutter with similar number of weakly developed interlocking teeth. Male cheliped length 2.2 x CW or 2.9 x CL.

Length of walking legs decrease posteriorly. Arrangement of tubercles on legs: P2: merus 6/1, none on carpus or propodus; P3: merus 6/3, carpus 0/0, propodus, 1/0; P4: merus 5/(5 + 3), carpus 1/0, propodus 2/2; P5: merus 6/(7 + 5), carpus, 2/0, propodus 3/3. Dactyli unarmed, shorter than propodi.

Abdominal segments 4–6 medially convex with median hooked tubercle on segment 6. Abdominal segments 3–5 fused in male, but sutures still mostly evident. Abdominal locking mechanism of smooth sternal tubercles on sternite 5 fitting into deep sockets on posterior corners of sixth abdominal segment. Telson triangular, wider than long, tip rounded. Telson medial pit present, surrounded by elevated granules.

G1 extends to middle of sternite 5, while G2 extends to middle of sternite 4. Sperm aperture opens medially, tip covered with short, acute spines directed proximally. Spines only on distal 0.14 of G1 length. Ratio of lengths of G2/G1 = 1.22. Flagellum of G2, twisted, 0.48 of length, no notch marking transition from basal section to flagellum.

Distribution. Previously recorded only from type locality, French Polynesia. Reported here for the first time from New Caledonia.

Remarks. Garthambrus poupini can be distinguished from all other species of Garthambrus by the blunt tips of the epibranchial teeth and by the blunt tubercles on the outer margins of the cheliped merus, carpus and manus. In all the other Garthambrus species, the tips of the epibranchial teeth and the teeth on the outer margins of the cheliped are sharp or pointed.

Ng (1996) recorded as a paratype a male specimen (MNHN MP B-22421) from SMCB stn 395. This is in error since this male specimen was not listed as a type specimen (Garth 1993).

Figures

FIGURE 5. Gonopods. Garthambrus poupini (Garth, 1993): A, B, holotype, male 35.5 x 28.0 mm (MNHN B 22424), French Polynesia, Tuamotu Archipelago, Fangataufa (after Garth 1992: figs. 2 d, e) (scale bar not available). — Garthambrus allisoni (Garth, 1993): C, D, holotype, male 23.5 x 17.8 mm (LACM; ex. AHF 645), Easter I. Fracture Zone (after Garth 1992: fig. 5 f) (scale bar = 1 mm). — Garthambrus complanatus (Rathbun, 1906): E, F, lectotype, male 17.3 x 12.7 mm (USNM 29845 a), Hawaiian Is, Kauai (scale bar = 1 mm). A, E, left G 1; B, F, left G 2; C, right G 1; D, right G 2.