Odontothelphusa apicpac Villalobos, García & Velázquez, 2010, sp. nov.
Creators: name: Villalobos, José Luis
name: García, Anelli J.
name: Velázquez, Ernesto
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Pseudothelphusidae
Odontothelphusa
Odontothelphusa apicpac

description: Odontothelphusa apicpac sp. nov.
(Figs. 1–3)
Holotype. Male, cw 51.0 mm, cl 32.5 mm; Apic-Pac stream, 100 m of Malpaso Dam (17°03'27" N, 93°28'04" W; altitude 176 m), Nature Reserve Selva El Ocote, Municipio de Ocozocoautla de Espinoza, Chiapas; 11 August 2008, coll. A. García-López, M. Anzueto-Calvo; CNCR 25446.
Other material examined. Paratype. Male, cw 83.0 mm, cl 52.5 mm; same locality as holotype; 20 September 2009, coll. A. García-López; CNCR 25962.
Description of holotype. Dorsal surface of carapace slightly convex. Superior frontal border thick, with low, rounded granules, divided by median groove. Inferior frontal border strong more projected anteriorly than superior one. Median groove narrow, shallow anteriorly, disappearing between postfrontal lobes. Postfrontal lobes well formed, indicated anteriorly by shallow depressions; area between postfrontal lobes and superior frontal margin flat. Cervical grooves shallow, straight, ending before reaching anterolateral margin; area surrounding cervical grooves deep. Carapace regions delimited by shallow grooves; surface of cardiac region flat, urogastric region depressed, gastric region somewhat swollen, branchial region clearly inflated (Fig. 1 c). Anterolateral margin formed by low granules between orbit and cervical groove, posterior to cervical groove granules are directed anteriorly, increasing in size, becoming more acute posteriorly. Posterior margin of carapace between coxae of fifth pereiopods straight. Merus of third maxilliped with external margin broadly rounded, with rounded shallow notch on anterior margin; ischium trapezoidal, becoming broader distally, ratio exopod/ischium 0.73 (Fig. 1 d). Major chela left, fingers not gaping, fixed finger with largest tooth on middle portion (Fig. 1 f). Opening of branchial efferent channel square in section. Pterygostomial region covered with pubescence on adjacent area of exopod of third maxilliped (Figs. 1 d, e).
Gonopod straight, proximally thick, with apical portion latero-mesially compressed as a rectangular plate transverse to main axis of gonopod, distally delimited by mesial, lateral crests (Fig. 1 b). In mesial view (Fig. 2 a), main axis of gonopod with fringe of short setae extending on cephalic border, just below angle with apical portion. Apical portion of mesial plate with cephalic margin ending in large proximomesial spine, in some projected, subacute distal angle. Superior margin of mesial crest slightly convex in the middle of its length. Proximomesial spine conical, acute, oriented cephaloproximally, with strong, rounded tubercle at base, with small, acute spine near sharp tip. In cephalic view (Fig. 2 b), distal crest of mesial surface rolled over distal margin of lateral surface. Proximomesial spine conical, laterally inclined; basal tubercle prominent, rounded, spine near sharp end, small, acute. Distal angle of cephalic margin of lateral plate ending in narrow digitiform projection, partially concealed by distomesial angle of mesial plate. Spines of lateral plate of different sizes, proximal one as small, triangular, subacute tubercle. Distal spine oriented laterally, conical, acute, forming straight angle with respect to principal axis of gonopod. Distal hump on caudal portion of lateral surface evident, rounded. In lateral view (Fig. 2 c), spines placed in center of apical plate, proximal one like small triangular tubercle, situated near angle formed by apical plate and principal axis of gonopod; distal one strong, conical, acute, located just below distal crest of lateral surface. Distal angle of cephalic margin of lateral plate ending in narrow digitiform projection. In caudal view (Fig. 2 d), marginal suture not fused along gonopod length. Marginal plate narrowly rectangular, with fringe of setae on proximal third, distally reaching almost same height as lateral and mesial crests. Distolaterally, marginal plate ending in drop-like apical notch. Caudal suture well marked on proximal two thirds, disappearing on distal third, where marginal plate and lateral surface are fused. In distal view (Fig. 2 e), crest of mesial surface covering cephalic half of distal margin of lateral surface. Apical cavity narrow, limited caudally by distal crest of marginal plate, opening of spermatic channel in caudal position, with acute spines rising from internal surface of lateral plate. Distal crest of marginal plate straight, slightly below apical cavity. Hump on caudal portion of lateral surface rounded, forming lateral border of drop-like apical notch of marginal plate.
Etymology. The new species is named after the type locality, the Apic-pac stream, which is used as a noun in apposition. Apic-pac means “chayote seed” in the Zoque dialect.
Remarks. Odontothelphusa apicpac can be easily distinguished from its congeners by the ornamentations in the proximomesial spine of the male first gonopod, in the form of a strong, rounded tubercle at the base and a small, acute spine near the sharply pointed end (Fig. 2). The other species of Odontothelphusa do not have spines, teeth or any ornamentations on the surface of the large proximomesial spine. Odontothelphusa apicpac resembles O. lancandona and O. lacanjaensis in the orientation of the proximomesial spine which forms a 45° angle with respect to the main axis of the gonopod. The new species differs from O. maxillipes, O. monodontis and O. palenquensis, in that the proximomesial spine forms a 90° angle with respect to the main axis of the gonopod, and from O. toninae in that the proximomesial spine is completely oriented proximally, parallel to the main axis of the gonopod.
The paratype showed some morphological differences with respect to the holotype. The major chela has a moderate gap between the fingers that is occupied by two strong teeth on the fixed finger (Fig. 1 f). In the gonopod, the ornamentations of the proximomesial spine are closer to each other, the tubercle is triangular, and the spine little bigger.
The presence of O. apicpac in the tributaries of the Malpaso Dam and Grijalva River represents the southwestern limit of the genus in Chiapas (Fig. 3). The geographic distribution of its congeners concurs well within the Usumacinta province (Miller, 1966, 1982, 1986; Huidobro et al., 2006), four of them in the lowlands adjacent to the Sierra Norte de Chiapas: O. monodontis and O. palenquensis occur in the south, while O. lancandona and O. lacanjaensis are found in the east. The distribution of the latter four species along with the new record of O. apicpac, is associated with the Usumacinta-Grijalva subprovince (Miller, 1966). Only O. toninae is located in the highlands of the central portion of the Sierra Norte de Chiapas, at an altitude of 1000 meters, a region more related to the highlands of southeastern Mexico, Guatemala and Honduras. The occurrence of O. maxillipes in Los Tuxtlas, Veracruz, places this species in the Papaloapan-Coatzacoalcos subprovince and represents the northwestern limit of the genus (Miller, 1966). The distribution pattern of the species of Odontothelphusa is similar to the distribution and diversification patterns shown by other freshwater decapods in the southeastern Mexico, such as species of Macrobrachium, Procambarus (Austrocambarus) and Avotrichodactylus (Alvarez et al., in press). Other aquatic organisms such as fishes or terrestrial like snakes show also similar distributions, all of them resulting from the geological evolution of the Tehuantepec isthmus in the Mexican transition zone (Huidobro et al., 2006; Daza et al., in press).
description: Published as part of Villalobos, José Luis, García, Anelli J. & Velázquez, Ernesto, 2010, A new species of freshwater crab of the genus Odontothelphusa Rodríguez, 1982, (Crustacea: Decapoda: Pseudothelphusidae) from Chiapas, Mexico, pp. 52-58 in Zootaxa 2414 on pages 53-56, DOI: 10.5281/zenodo.293269