Gecarcinus quadratus De Saussure 1853
Creators: name: Toledano-Carrasco, Ia Atzimba
name: Villalobos, José Luis
name: Álvarez, Fernando
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Gecarcinidae
Gecarcinus
Gecarcinus quadratus

description: Gecarcinus quadratus De Saussure 1853
(Figs. 1B; 2E–H; 3B, C, E)
Gecarcinus quadratus De Saussure 1853: 360. Rathbun 1918: 358. Garth 1948:58.
Gecarcinus (Gecarcinus) lateralis quadratus.— Türkay 1970: 338. von Prahl & Manjarrés 1984: 155.
Gecarcinus quadratus.— Ng et al. 2008: 215. Arzola-González et al. 2010: 187.
Gecarcinus lateralis.— Perger & Wall 2014: 97.
Gecarcinus quadratus.— Guinot et al. 2018: 568-570. Toledano-Carrasco 2019: 22-26. Ng et al. 2019: 99-100.
Material examined. MEXICO. Sinaloa: 8 males, 2 females, CNCR 362, Municipality Mazatlán, Isla Venados, May 30, 1974, colls. M.C. Chávez, C.A. Martínez.– Nayarit: 2 males, CNCR 33941, Municipality Bahía de Banderas, Punta de Mita, Apr 21, 2017, Coll. Anonymous; 1 male, CNCR 34012, Municipality Bahía de Banderas, Playa Higuera Blanca, Jul 07, 2017, coll. J.L. Villalobos. – Jalisco: 1 female, CNCR 3514, Municipality La Huerta, Playa La Rosada, Bahía de Chamela, Jun 16, 1984, coll. A. Cantú; 1 female, CNCR 3517, Municipality La Huerta, Salinas, Bahía de Chamela, Jun 15, 1984, colls. J.C. Nates, J.L. Villalobos, A. Cantú; 1 male, CNCR 34846, Municipality La Huerta, Estación de Biología Chamela, Instituto de Biología, UNAM, no date, coll. anonymous.– Michoacán: 1 male, CNCR 11736, Municipality Aquila, Playa de Maruata, Jun 20, 1990, coll. M.S. García; 2 females, CNCR 25629, Municipality Lázaro Cárdenas, Río Popoyuta, cerca desembocadura, Jul 12, 1986, coll. A. Raz Guzman; 3 males, 2 females, CNCR 6158, Municipality Aquila, Monte del Oro, km 175 carretera Tecomán-Playa Azul, Mar 03, 1986, coll. R. Lamothe, L.J. Rangel.– Guerrero: 1 male, 1 female, 1 juvenile, CNCR 19003, Municipality La Unión de Isidoro Montes de Oca, Playa Troncones, N of Zihuatanejo, Jan 01, 2001, coll. C. Candelaria. – Oaxaca: 1 male, 1 female, CNCR 34013, Municipality Santa María Tonameca, Playa Aragón, Jan 01, 2017, coll. anonymous; 1 male, 1 female, CNCR 3031, Municipality Santa María Colotepec, Playa El Carrizalillo, Puerto Escondido, Sep 08, 1983, coll. A. Cantú. – Chiapas: 2 males, CNCR 34630, Municipality Tonalá, Barra de Boca del Cielo, Mar 08, 2018, colls. J.L. Villalobos, I. Toledano, E. Moreno.
Diagnosis. Male abdomen triangular; telson triangular, lateral margins straight continuous with those of sixth abdominal somite, slightly marked, tip moderately rounded. Sixth somite with posterior margin as broad as telson or slightly wider, lateral margins forming continued straight margin with telson (Fig. 2F). Female abdomen subcircular, not covering thoracic sternum completely; telson triangular, narrower than posterior margin of sixth somite, lateral margins slightly concave with faint vertical suture at middle (Fig. 3E). Antero-lateral margins of sternites 3-4 widely convex at junction of third maxillipeds, gently concave at level of articulation of first pereiopods (Figs. 2F, 3E). Endostomial ridges (Davie et al. 2015) delimiting efferent branchial channel. Third maxilliped with merus not reaching epistome.
Description. Carapace transversely oval, wider anteriorly, strongly arched at level of branchial regions, anterolateral margin thin. Regions well-defined, delimited by shallow grooves. Branchial regions prominent. Fronto-orbital margin about half of maximum carapace width (Fig. 1B). Front about 1/4 length of carapace, deflexed, surface slightly concave; inferior margin lightly granulated, not raised from surface, straight, leaving visible basal segments of antennules; frontal lobes poorly defined (Fig. 2E).
Orbits delimited by well defined, smooth, superior border. Infra-orbital margin granulated, interrupted by deep notch, continued as subrectangular or low subtriangular plate forming mesial lobe; area of contact between internal angle of front and mesial lobe of infraorbital margin of variable width (Perger & Wall 2014), reaching superior border of epistome. Suborbital ridge softly marked, short, extending laterally from superior border of epistome, not reaching subhepatic suture. Third maxillipeds not closing completely, leaving rhomboidal gap; merus not reaching epistome, anterior border straight, occasionally with shallow emargination or discontinuity; ischium with scattered setae on mesial margin, subequal in width to merus, but longer than it (Fig. 2E). Palp short, hidden, articulated behind merus, directed laterally. Exognath hidden behind ischium, without flagellum, not reaching ischium-merus articulation.
Chelipeds in both sexes subequal or similar, evident heterochely in largest males. Chelae with fingers longer than palm, with corneous tips, surface with longitudinal rows of pits and granules, more evident dorsally; cutting margins with distinct subacute tubercles along fingers length, dactyl slightly curved inwards, with 8-10 irregularly spaced small blunt teeth, largest tooth on proximal half; fixed finger with 11-12 irregularly spaced small blunt teeth, largest tooth on distal half; fingers gapping (Fig. 2H). Palm with internal surface smooth, swollen, without tuberculated longitudinal ridge, internal depression next to articulation with carpus. Carpus subtriangular, dorso-mesial margin smooth in large organisms or with spinules in small ones. Merus elongated, subtriangular, inner surface striated, used as stridulatory plectrum.
Pereiopods long, slender with short setae; merus elongated, surface striated, dorsal ridge distally spinulated; carpus subtriangular, shorter than propodus, or almost of same length in fifth pair, distal half of dorsal ridge spinulated; propodus shorter than dactyl, dorsal, ventral and lateral ridges armed with short, thin spines; dactyli armed with 6 rows of spines (Fig. 2G), 5 rows in juveniles.
Male and female abdomen as in species diagnosis.
Male G1, as in genus diagnosis (Fig. 3B, C).
Coloration. Dorsal surface of carapace dark purple, posterior and postero-lateral margins yellow or slightly orange, as well as the ambulatory appendages. Yellow or light orange patches above orbits, and on lower part of front. Chelipeds purple, carpus and merus darker (Fig. 1B).
Measurements. Males: 35.8–54.3 mm CL; 44.9–71.7 mm CW. Females 33– 51.8 mm CL; 38.7–63.9 mm CW.
Remarks. With the resurrection of G. quadratus as a distinct species and geminate analogue from the western Atlantic of G. lateralis, new morphologic and genetic analyses including the eastern Pacific G. nobilii are necessary. According to Perger & Wall (2014), G. nobilii is distinguished from G. lateralis because the former has a particular coloration: carapace without lighter anterolateral and posterior patches on the light lateral margin, carpus and palm of chelipeds homogeneously red or white. Additionally, the frontal width is distinctly greater than the distance between the mesial ends of the suborbital cristae. Also, the width of the mesial lobe of the infraorbital margin at point of contact with the carapace front is longer than the shortest distance between the carapace front and the mesial end of the suborbital crista (Perger & Wall 2014).
description: Published as part of Toledano-Carrasco, Ia Atzimba, Villalobos, José Luis & Álvarez, Fernando, 2021, A morphological, phylogenetic and phylogeographic reappraisal of the land crabs Gecarcinus quadratus De Saussure, 1853, and G. lateralis Fréminville in Guérin 1832 (Decapoda: Gecarcinidae). Are they different species?, pp. 215-236 in Zootaxa 5048 (2) on pages 228-229, DOI: 10.11646/zootaxa.5048.2.4, http://zenodo.org/record/5552003