Johngarthia cocoensis, Perger, Robert, Vargas, Rita & Wall, Adam, 2011

Perger, Robert, Vargas, Rita & Wall, Adam, 2011, Johngarthia cocoensis, a new species of Gecarcinidae MacLeay, 1838 (Crustacea, Decapoda, Brachyura) from Cocos Island, Costa Rica, Zootaxa 2911, pp. 57-68 : 58-63

Johngarthia cocoensis n. sp.

( Figs. 1 A, B; 2; 3; 4; 5B; 6D–F)

Type material. Costa Rica, Cocos Island: male, holotype, MZ-UCR-622-01, 13.08.1973, C. Villalobos and D.G. Robinson leg.; 1 male, paratype, same data; Costa Rica, Manuelita Island: 3 males, 1 female, paratypes, MZ-UCR- 623-01, 14.8.1973, N. Scott leg.; Costa Rica, Cocos Island, Bahía Wafer: 10 juveniles, paratypes, MZ-UCR-2401- 0 6, 28.11.2001 M. Montoya leg.

Comparative material examined. Johngarthia planatus : Mexico, Socorro I.: 1 male, MNHN- B13154, A. Anthony leg.; 2 males, LACM, 16 Feb. 1971, J. Garth det.; 1 male USNM 20691, A. Anthony leg.; Mexico, San Benedicto I.: 2 males, LACM-170, J. Garth det.; 1 male, USNM 20690, A. Anthony leg.; Mexico, Lower California: 1 male (most likely holotype of Gecarcinus digueti Bouvier, 1895 ), MNHN-B10951, Diguet leg.; 1 male, 1 female, USNM 12465; Mexico, Tres Marias I., María Cleofas: 1 male, USNM 20650, Nelson & Goldman leg., 30- 05-1897; Clipperton I.: 4 males, LACM, 12.09.1958, Limbaugh leg., J. Garth det.; 1 male, MNHN-B13156, D. Guinot det.; 1 male, 1 female, USNM 19646, J. Arnheim leg; Johngarthia malpilensis : Colombia, Malpelo I.: 3 males, 4 females, LACM, 16.01.1933, Hancock Pacific Expeditions, J. Garth det. Additional high resolution photographs of live J. planatus from Clipperton (provided by Michel Montoya, Fundación Amigos Isla del Coco, Costa Rica, and Julian P. Sachs, University of Washington) and J. malpilensis (provided by Mateo Lopéz-Victoria, Justus Liebig Universität, Giessen, Germany) were also examined.

Remark. We could not locate the type material of J. planatus in the USNM, the Zoological Museum in Copenhagen or the Natural History Museum, London, where some type material of species described by Stimpson has been deposited (see Evans 1967; Vasile et al. 2005; Manning & Reed 2006). The material of J. planatus was most likely destroyed by the Great Chicago Fire of 1871 (see Vasile et al. 2005). The possible holotype of G. digueti Bouvier, 1895 (MNHN-B10951) was labeled as Gecarcinus planatus , but it is the only specimen in the MNHN concordant with the type specimen of G. digueti described by Bouvier (1895) and subsequently reported by Rathbun (1899). Bouvier apparently only had one specimen from “Basse-Californie” (Lower California), which he noted was measuring 67 mm (sex not specified) ( Bouvier, 1898). Rathbun (1899) recognized G. digueti as a distinct species, recording it from María Cleofa Island off Lower California, and apparently examined the type in the Paris Museum which she stated was a male measuring 69.0 by 46.3 mm. Maria Cleofa Island is situated relatively close to Cabo San Lucas (Cape St. Lucas, the most southern tip of Lower California peninsula), the type locality of J. planatus ( Stimpson 1860) . On the basis of the available data, this MNHN specimen is almost certainly the holotype of G. digueti Bouvier, 1895 . Rathbun (1918) later synonymized both G. malpilensis ( Faxon, 1893) and G. digueti (Bouvier, 1895) with G. planatus ( Stimpson, 1860) . Türkay (1970) recognized G. malpilensis as a distinct species but retained G. digueti under the synonymy of G. planatus . The presumptive holotype of G. digueti has all the diagnostic characters which we here identify with J. planatus and we are confident they are conspecific and different from J. cocoensis n. sp.

Diagnosis. P about half as wide as orbital width; juvenile, subadults (W 20–60 mm) with well developed exorbital carapace tooth, 6–16 anterolateral carapace teeth; ILs mostly separated from each other when resting against buccal cavity ( Fig. 3 ); palp of MXP3 merus partly exposed, epistomial tooth completely exposed ( Fig. 3 ; 6D–F); MXP3 exopodite not reaching ischium-merus joint, terminal setae protruding beyond ischium-merus joint; male first gonopod relatively straight ( Fig. 4 A, B)

Measurements. Males 57.2–112.3 mm; females 21.2 –57.35 mm; W/L = 1.24±0.06; W/H = 2.33±0.06; H/ MXP3 length = 1.52±0.03; MXP3 merus length/width = 1.23±0.05; FO width = 1.353W 0,754 (R² = 0,99); F width = 0.445W 0,751 (R² = 0.99); PL = 0.0894W 1,4957 (R² = 0.98)

Description. Relatively large-size, robust species; carapace transversely ovate, strongly longitudinally, transversely convex, widest in anterior half; gastric region particularly well defined; median, cervical, urogastric grooves very pronounced; median groove reaches posterior height of greatest width of carapace; extremities of cervical grooves reaching pits at orbital angles; P about half as wide as orbital width; pit median, posterior of each cervical groove, smaller than pits at orbital angles, posterior very close to cervical groove, converging with urogastric groove; irregular lines of smaller pits lateral to cervical grooves; epigastric carinae absent, cardiac lobe strongly backward prolonged between bases of posterior legs; postfrontal crest strongly curved downwards, terminating as prominent carina, carina slightly curved medially. Suborbital, pterygostomial regions sparsely granular laterally; surfaces smooth. Subhepatic region with rounded postero-lateral margins, with rows of 3–9 small granules. In juvenile, subadult specimens (20–60 mm) carapace in anterior third with small granules, rest of surface smooth; lateral borders swollen, upper border marked by carapace anterolateral border when seen in frontal view, prominently developed exorbital carapace tooth, carapace anterolateral border lined by 6–16 sharp teeth. In adult specimens (> 60 mm) dorsal surface of carapace smooth; protogastric area, branchial regions conspicuously swollen; exorbital tooth weakly developed, anterolateral border smooth.

Orbit deep, broadly oval, height about 3/4 width, eye not completely filling orbit when folded; dorsal border slightly raised, outer angle distinctly defined, outer ventral, dorsal orbital borders converge with carapace anterolateral border at height of widest width of orbit when seen in frontal view; wide gap in ventral orbital border, border weakly carinate, projected, with row of 5 or 6 teeth, inner angle reaches front, separates antennae from orbit, furnished with 2 or 3 teeth.

Epistome sunken, densely covered with short setae, separated from basal segments of antennules by transverse ridge, ridge aligned with suborbital-border; median with band of setae; epistomial tooth exposed, triangular; antennules folded obliquely; antennae very short, nearly longitudinal, almost concealed by front, inter-antennular septum of moderate width; buccal cavern wide, widest in middle, laterally arched, densely covered with long, thick hairs, setae forming dense brush fitting with lateral border of MXP3, not visible when MXP3 rest against buccal cavern.

MXP3 leaving between them wide rhomboidal gap when closed, mandibles exposed, internal border of ischium laterally lined with setae, ischium with well pronounced vertical sulcus; ILs mostly separated from each other when resting against buccal cavity, considerably narrower, shorter than ischium, longer than wide, not reaching epistome, leaving gap between lateral borders of buccal cavern, exposing epistomial tooth, borders of MXP3 merus relatively straight; apex apically divided by wide, V-shaped fissure, deepest point of emargination lateral, palp articulating at this point, palp partly exposed in resting position; IL longer than OL, rounded; exopod concealed by ischium, apex not reaching ischium-merus joint (size about 80% of ischium), terminal setae protrude from ischium-merus joint, flagellum absent.

Meri and chela of chelipeds allometric, in specimens W ≥ 60 mm slightly surpassing carapace anterolateral border, in large males abnormally elongated, widely surpassing carapace anterolateral border; in specimens ≥ 60 mm surface of merus smooth, anterior proximal border furnished with 6 or 7 distinct teeth increasing in size distally, 3 sub-distal, 2 distal carpal teeth; surface, border of merus smooth in larger specimens.

Specimens <W 100 mm homochelous, males> W 100 mm slightly heterochelous (left palm bigger, biggest difference between palm length 20%), palms elongated, length may exceed W, flattened in height, width, interiorproximal with longitudinal furrow; dactyl, pollex elongated, drop shaped in cross section, gaping moderate in largest chela when closed, not crossing, with triangular teeth, terminal with 7 rows of nearly uniform, oblique conical teeth, arrangement of teeth more diffuse proximally, manus smooth.

Ambulatory legs stout, sparsely furnished with setae; merus triangular in cross section, ventral edges with strongly developed ridges, dentate; carpus pentagonal in cross-section, distal edges with spines; propodus rhomboidal in cross-section, edges strongly dentate; dactylus longitudinally ridged, with 6 rows of spines. Sternum wider than long, S1 triangular, exposed, S2 narrow, S1-S3 fused, indistinct, S2-S3 suture, S3 separated from S4; S4 widest; sulci between S3-S6 distinct, sternites fused at upper border of abdominal cavity, separated medially, fused again near midline; abdominal cavity with longitudinal suture in S6; upper border of abdominal cavity with patches of setae; all abdominal somites and telson distinct, freely articulating; first somite filling space between last pair of ambulatory legs, sixth somite longest, considerably longer than telson, telson sub-triangular, narrow; lateral margins nearly straight, tip rounded.

Male first gonopod ( Fig. 4 A, B) slightly sinuous from lateral view, relatively straight from mesial view, slen- der, stiff, heavily chitinized, surfaces concave, mesial suture indistinct, margin distinctly developed; cephalic surface with band of sparse setae, apical border lined with stiff setae, caudal process shorter than mesial process, close-fitting to mesial process from lateral view, separated by emargination in mesial view; mesial process of first gonopod prominently developed, end piece on a level with terminal setae; diagonal, triangular, convex, amber-colored, aperture sub terminal, opening in an external-longitudinal channel.

Color. In adults, carapace reddish brown, carapace pits creamy white. In juvenile specimens, carapace dark brown-purple, carapace pits white, chelipeds and ambulatory legs reddish, tips of fingers white ( Fig. 1 A, B).

Type locality. Costa Rica, Cocos Island, Manuelita Island.

Etymology. The species is named after the type locality (Cocos Island).

Comparisons. In Johngarthia cocoensis n. sp. the shape of the third maxilliped merus more closely resembles that of J. malpilensis than J. planatus . In J. cocoensis n. sp. and J. malpilensis , the V-shaped emargination of the third maxilliped merus is positioned laterally and the outer apical lobe is shorter than the inner apical lobe ( Fig. 5 B, C; 6D–I).

Johngarthia cocoensis n. sp. is distinguished from J. planatus by having the third maxilliped merus considerably longer than wide ( Fig. 3 ; 5B; 6D–F), in J. planatus the third maxilliped merus is as long as wide or slightly longer ( Fig. 5 D; 6A–C). In J. planatus the carapace is more flattened than in J. cocoensis n. sp. ( Tab. 1 ). In J. cocoensis n. sp., the third maxilliped meri are so short that the inner apical lobes are mostly not overlapping in resting position and the third maxilliped palp is partly exposed ( Fig. 3 ; 5B; 6D–F), while in J. malpilensis , these lobes are enlarged, mostly overlapping and conceal the third maxilliped palp ( Fig. 5 C; 6G–I). In J. malpilensis and J. planatus the base of the male first gonopod is relatively more compact and the apex relatively more slender from mesial and lateral views, the opposite condition is discerned when viewed from the caudal and cephalic views. In J. cocoensis n. sp. the male first gonopod is relatively much straighter ( Fig. 4 A, B). In J. malpilensis and J. planatus the surfaces of the are considerably more concave and the apex of the end piece is longer in relation to the male first gonopod than in J. cocoensis n. sp.

Figures

FIGURE 1. Live color, A, Johngarthia cocoensis n. sp., male (Cocos I., Costa Rica, photo by Michel Montoya); B, idem, female, juvenile (Cocos I., Costa Rica), photo by Michel Montoya); C, Gecarcoidea lalandii, male (Taiwan, photo by Hung- Chang Liu, Providence University, Taiwan); D, idem, female (Taiwan, photo by Hung-Chang Liu, Providence University, Taiwan); E, Johngarthia planatus (Clipperton Island, March 2008, photo by Julian P. Sachs, University of Washington); F, idem (Puerto Escondido, Oaxaca, Mexico).

FIGURE 3. Frontal view, A, Johngarthia cocoensis n. sp., holotype male, W 89.85 mm, MZ-UCR- 622 - 01 (Cocos I., Costa Rica), preserved in alcohol 70 %, dorsal view; B, idem, paratype female, W 57.35 mm, MZ-UCR- 623 - 01, preserved in alcohol 70 %.

FIGURE 4. Johngarthia cocoensis n. sp., holotype male, MZ-UCR- 622 - 01, A, left male first gonopod, lateral view; Scale bar = 5 mm. B, same, mesial view; C, abdomen (segments 3 – 7), male, Scale bar = 10 mm; D, idem, female, Scale bar = 10 mm; E, right male cheliped (MZ-UCR- 623 - 01, W 112.3 mm); Scale bar = 10 mm.

FIGURE 5. Frontal view (P, pit at orbital angle; M, merus of third maxilliped; OL, outer apical lobe of M; IL, inner apical lobe of M), A, Gecarcoidea lalandii, female, LACM, JWK- 326 (Marshall Islands, Enewetak Atoll, Igurin I.); B, Johngarthia cocoensis n. sp., paratype, female, MZ-UCR- 623 - 01 (Manuelita I., Costa Rica); C, Johngarthia malpilensis, female, LACM (Malpelo I., Colombia); D, Johngarthia planatus, female, LACM (Clipperton I., Mexico).