Tehuana col, Moreno-Juárez & Villalobos & Álvarez, 2022

Moreno-Juarez, Eric G., Villalobos, Jose Luis & Alvarez, Fernando, 2022, Revision of the freshwater crabs of the genus Tehuana Rodriguez & Smalley in Smalley 1970 (Decapoda, Pseudothelphusidae), with the descriptions of two new species, ZooKeys 1117, pp. 1-35 : 1

Tehuana col sp. nov.

Figs 6 , 7

Type material.

Holotype: Mexico - Veracruz • 1 ♂, CL 30.4 mm, CW 50.3 mm; Municipality of San Andrés Tuxtla, Col River at Cascadas Park; 18°38'29"N, 95°09'00"W; alt. 416 m; 25 Apr. 2017; J.L. Villalobos, I.A. Toledano, E.G. Moreno leg; CNCR 33928. Paratype: 1 ♂, CL 13.6 mm, CW 20.8 mm; same data as for holotype; CNCR 36325.

Additional material examined.

Mexico - Veracruz • 1 ♀, CL 19.6 mm, CW 29.5 mm; same data as for holotype; CNCR 36325 .

Description.

Carapace dorsal surface slightly concave, finely punctate, frontal and anterolateral surfaces with minute granulations; gastric and branchial regions slightly inflated; postfrontal portion depressed, almost horizontal, continued anteriorly to reach superior frontal border. Postfrontal lobes low, delimited anteriorly by shallow depressions, separated by narrow, deep median groove. Cardiac region hardly discernible. Cervical groove shallow, curved posteriorly, anterior ¼ straight, becoming obsolete before anterolateral margin, not reaching it. Anterolateral margin prominent, armed with 21-23 conical granules of similar size; portion between orbit and cervical groove granulated, with shallow notch next to orbit. Posterolateral area of carapace with short setae; posterior margin widely concave (Fig. 6A ). In frontal view, superior frontal border inclined towards central portion, formed by low tubercles, divided by moderately deep, narrow V-shaped, median notch; inferior frontal border continuous, sinuous, thinner, more projected than superior one (Fig. 6B ). Orbits with external angle slightly granulated, with shallow basal notch; internal orbital tooth triangular, well developed, extending to interior of orbit floor as high keel. Basal article of antennal peduncle separated from front by orbital hiatus. Antennules and antennular fossae partially visible, slightly wider in the middle; interantennular septum concealed by inferior frontal border. Operculum of antennal gland as ovoidal, flat plate, with middle constriction, tuft of short bristles on lateral third. Epistome, area around buccal cavity and pterygostomian region with short setae; epistomal tooth covered by patch of short setae, triangular, directed downwards. Opening of branchial efferent channel subcircular, longer than wide, width/length ratio 0.68. Third maxilliped with ischium subrectangular, slightly longer than wide, anterior margin of merus rounded; ratio exopod/ischium length 0.81.

Chelipeds moderately heterochelous in both sexes, more evident in males. Major chela right, merus subtriangular in cross section, superior margin rounded with short transversal rows of low granules; lower inner margin with longitudinal row of conical tubercles increasing in size distally (Fig. 6C ).

G1 slender, proximal half cylindrical, becoming compressed distally, meso-distal lobe on mesial surface conical, well developed; principal axis with medial constriction on lateral surface, twisted mesially. In mesial view (Fig. 7B ), distal half inclined towards cephalic surface. Caudo-marginal projection with distal lobe well developed, subrectangular, cephalic margin rounded, separated from proximal lobe by an incision; proximal lobe well developed, ax-shaped, higher than long. Distal crest of MP, partially visible, some rounded and higher than apical cavity. Meso-distal lobe arising from caudal angle of mesial surface, well developed, conical, with subacute apex. In caudal view (Fig. 7C ), distal third straight, apical cavity distally directed, caudal surface ending distally in a wide and shallow concavity. Caudo-marginal projection with distal crest of mesial surface as high or higher than lateral one. Mesial process as a longitudinal plate, caudally undulated, partially visible; subdistal circular scar on the base of the plate partially visible. In cephalic view (Fig. 7A ), mesial process in longitudinal position relative to principal axis of G1, with an incipient rounded tooth on lateral margin, laying over carina of inner surface of proximal lobe of caudo-marginal projection; cephalic border bilobed, internal lobe pyramidal, rounded not touching internal face of the distal lobe of caudo-marginal projection, lateral lobe rounded, semicylindrical, projected anteriorly beyond internal one. Field of apical setae visible, cephalo-caudally elongated, setae brownish, shorter than distal crest of lateral surface. Lobes of caudo-marginal projection cephalically directed, separated, slightly curved mesially; proximal one oval shaped, lateromesially inclined, inner surface carina not visible. Distal crest of lateral surface sharp, smooth, with few short setae; subdistal circular scar on principal axis partially visible. In lateral view (Fig. 7D ), distal lobe of caudo-marginal projection partially visible, separated from proximal one by long incision; inner surface of proximal lobe with circular or semicircular strong carina, extending over basal third of proximal surface. Mesial process as a longitudinal plate that close the apical cavity; lateral margin of smooth, superior angle rounded, median portion with an incipient rounded tooth, continued proximally to end in a subcircular scar. In distal view (Fig. 7E ), Apical cavity U-shaped, opening cephalically, field of apical setae delimited by central and lateral crests; 20-60 apical setae; aperture of spermatic channel in caudal position; central crest ending cephalically in acute, triangular internal lobe of mesial process. Meso-distal lobe (MDL) well developed, conical, distal tip curved mesocephalically.

Distribution.

Only known from type locality.

Etymology.

The name of this species is taken from the River Col, Los Tuxtlas region of Veracruz, where the specimens were collected. We declare the specific epithet as noun in apposition.

Remarks.

Tehuana col sp. nov. is morphologically similar to T. poglayenorum which occurs in the same area in Los Tuxtlas region, with both exhibiting partially overlapping lobes of the caudo-marginal projection; however, they can be easily separated by the mesial process, irregular shape with a sinuous lateral margin in the former, versus a widely rounded plate with a proximal triangular tooth in the latter. Consistent with the morphology, T. col sp. nov. and T. poglayenorum are also genetically closely related (Fig. 3 ), and in turn they are related to T. diabolis and T. veracruzana . It is interesting to highlight that four clearly defined species of Tehuana together with Smalleyus tricristatus Alvarez, 1989 and Pseudothelphusa parabelliana Alvarez, 1989 occur in Los Tuxtlas region which is small mountain range occupying an 80 × 33 km area in the coastal plain of southern Veracruz.

Figures

Figure 3. Phylogenetic tree obtained for the genus Tehuana based on the concatenated analysis of three genes (H 3, 16 S, COI), using maximum likelihood and Bayesian inference. Branch supports values are posterior probability / bootstrap. Only clades with branch support above 50 % indicated. Clades a, b, and c are labelled for discussion purposes.

Figure 6. Tehuana col sp. nov., male holotype A total dorsal view B frontal view of carapace C left chela. Scale bars: 4 cm (A); 3 cm (B); 2 cm (C).

Figure 7. Tehuana col sp. nov., left G 1 of male holotype A cephalic view B mesial view C caudal view D lateral view E distal view. Abbreviations: cdc, caudal distal crest; dl, distal lobe; dmp, distal border of mesial process; ic, internal carena of the proximal lobe; imp, internal angle of the mesial process; mc, middle constriction; mdl, meso-dital lobe; mp, mesial process; ms, marginal suture; pl, proximal lobe; sp, spermatic pore. Scale bars: 1 mm (A-D); 0.5 mm (E).