Eugerres castroaguirrei, González-Acosta & Rodiles-Hernández, 2013

González-Acosta, Adrián F. & Rodiles-Hernández, Rocío, 2013, New species of Eugerres from the Usumacinta Province, México and Guatemala with a redescription of E. mexicanus (Steindachner, 1863) (Teleostei: Gerreidae), Neotropical Ichthyology 11 (2), pp. 307-318 : 309-311

Eugerres castroaguirrei , new species

( Fig. 3a )

Diapterus mexicanus (not of Steindachner). Chávez Lomelí et al., 1989: 89 (description). Rodiles- Hernández et al., 1999: 460 (list; distribution) [in part et non] Gerres mexicanus Steindachner, 1863 .

Eugerres mexicanus (not of Steindachner). Rodiles-Hernández, 2005: 204 (list; distribution; ecological notes) [in part et non] Gerres mexicanus Steindachner, 1863 .

Holotype. ECOSC 775, 184.3 mm SL, México, Chiapas, Marqués de Comillas, Lacandona Rainforest, río Lacantún , between Reforma Agraria and Galaxia, 16º14’35’’N 90º51’30’’W, 25 Mar 1997, R. Rodiles-Hernández.

Paratypes. All collected with the holotype: AMNH 239190 , 1, 221.6 mm SL ; UABC 2665 , 1, 226.3 mm SL ; FMNH 117268 , 1, 228.5 mm SL ; IBUNAM 11436 , 1, 213 mm SL ; NMW 95100 , 1, 202.1 mm SL; and UMMZ 247665 , 1, 194.3 mm SL .

Diagnosis. Eugerres castroaguirrei is distinct from its congeners (except E. mexicanus ) by their body oblong and laterally ticker (vs. deep and laterally compressed) and the dorsal-fin origin posterior to the insertion of the pectoral and pelvic fins (vs. anterior to the insertion of the pectoral and pelvic fins). Differs from E. mexicanus by the combination of the following characteristics: length of second dorsal-fin spine 23.2-34.2% SL (vs. 18.9-43.3% SL); depressed second dorsal-spine extends to base of third or fourth dorsal-fin rays; length of second anal-fin spine 11.1- 20.6% SL (vs. 16.7-30.2% SL); depressed second anal-fin spine extends to base of third or fourth anal fin-rays and not reaching the distal point of last anal-fin ray; orbit diameter 23.3-31.5% HL (vs. 26.5-45.3% SL); pelvic-fin spine 49.7- 65.0% SL (vs. 42.3-78.2% SL) in the length of first pelvic-fin ray. Lower lips ventrally extending to midpoint of eye (vs. ventrally not reaching the anterior margin of eye).

Description. Dorsal-fin rays IX,10; anal-fin rays III,8; pectoral-fin rays iii,12,i; pelvic-fin rays I,5; pored lateral-line (LL) scales 43-51 (mode 46); scales between base of dorsal-fin and LL 3.5-4 (mode 4); scales between LL and anal-fin base 8-9 (mode 9); gill rakers on lower limb of first arch 12-15 (mode 13). Predorsal margin sharply convex. Interorbital space with a wide and central oval depression; premaxillary groove without scales. Maxillary extending to posterior margin of pupil. Dorsal fin origin inserts behind anterior margin of pectoral and pelvic fins; posterior margin of dorsal fin, nearly straight. Second dorsal-fin spine thicker than third dorsal-fin spine, but equal in length. Second anal-fin spine hooked, thicker than third and equal in length. Pectoral fins lanceolate, frequently extend past vent but not reaching the anal fin origin. Caudal-fin deeply forked, lobes equal in length (thicker than in E. mexicanus ); lower lobe thicker than upper. Mouth protractile and terminal; upper and lower lips enlarged, the lower lips ventrally flattened and extending to midpoint of eye. Pharyngeal teeth granular, serially arranged. Posterior and lower preopercle margins with conspicuous serrations. Lower margins of preorbital 1 and jugal serrated. Subopercular and infraorbital margins frequently serrated. Head covered by small cycloid scales; ctenoid scales on trunk. Morphometric and meristic data are presented in

Tables 1 and 4, respectively.

Coloration. Coloration in life specimens yellowish-silver; four dark, wide stripes on sides; lower dark stripes discontinuous (vs. 9-11 continuous dark stripes in other Eugerres species); dorsal and caudal fins with blackish margins; pectoral, pelvic and anal fins yellowish-white. Ground color on preserved specimens silvery brown back; four well-defined longitudinal dark stripes on sides of the body; belly silver to yellowish-white; ventral stripes not well-defined; fins yellowish to brownish-white; black margin on first dorsal fin.

Size. Largest specimen examined 242.0 mm SL, 312.2 mm TL, and weight 347.0 g (ECOSC 1742).

Sexual dimorphism. Not observed.

Distribution and habitat. Eugerres castroaguirrei inhabits the ríos Grijalva-Usumacinta basin in the highlands of Chiapas and Tabasco, Mexico and northern Guatemala ( Fig. 4 ). This species has a sympatric distribution with its congener E. mexicanus .

Ecological notes. Eugerres castroaguirrei has not yet been studied; thus, biological and ecological data are lacking. Specimens of the new species are fished by local communities and consumed as food. Further studies are necessary to obtain additional data. The holotype was captured using a seine net 90 cm bellow surface in channel with sandy-slime bottom, pH 8.0, conductivity 478 μS/cm, dissolved solids 242 mg /l, dissolved oxygen 6.9 mg /l, and 26 ºC.

Etymology. The name proposed ( castroaguirrei ) honors the late Dr. José Luis Castro Aguirre, who made several important contributions to our understanding of Mexican fish fauna.

Proposed common name. The proposed English common name is “Lacandon mojarra”, after its principal area of distribution. The proposed Spanish common name is “mojarra lacandona”.

Remarks. Here we establish that Eugerres castroaguirrei was a previously overlooked species in the literature on the Family Gerreidae and freshwater ichthyofauna of CentralAmerica (e.g., Meek & Hildebrand, 1925; Jordan & Evermann, 1927; Deckert & Greenfield, 1987; Castro-Aguirre et al., 1999; Miller et al., 2006). The distinctive characters of the new species are based on meristic, morphometric, and osteological analyses (see formal descriptions), comparison of the external morphology with ‘ Gerres ’ mexicanus syntypes [sic] (NMW 72289 [165.6 mm SL] and NMW 78820 [142.8-152.5 mm SL]), and specimens assigned to the nominal species (see material examined section).

Material examined. México: Chiapas, La Venta-Mal Paso, ECOSC 4560, 1, 171.0 mm SL. Tabasco-Chiapas, río Tulijá, ECOSC 4372, 1, 187.4 mm SL. México (Chiapas) and Guatemala, arroyo Negro, ECOSC 1570, 1, 231.6 mm SL. Río Lacanjá-Lacandona Rainforest, ECOSC 641, 1, 203.5 mm SL; ECOSC 694, 1, 199.7 mm SL; ECOSC 704, 2, 141.6- 237.4 mm SL; ECOSC 1272, 1, 179.2 mm SL; ECOSC 1411, 1, 220.4 mm SL; ECOSC 1490, 1, 223.6 mm SL. Río Tzendales - río San Pedro mouth, ECOSC 1848, 3, 192.8- 223.9 mm SL. Arroyo Cantabal, mouth of río Chixoy, UMMZ 189974, 1, 202.1 mm SL. Reforma Agraria - río Lacantún, ECOSC 110, 2, 188.2- 219.5 mm SL. Arroyo El Bravo - río Lacantún, ECOSC 689, 1, 193.7 mm SL. Arroyo El Salado - río Lacantún, ECOSC 2191, 1, 184.6 mm SL. Playón La Gloria - río Lacantún, ECOSC 750, 3, 184.5- 201.9 mm SL. Galaxia - río Lacantún, ECOSC 775, 6, 184.3- 228.5 mm SL. Boca Chajul - río Lacantún, ECOSC 1658, 1, 204.2 mm SL; ECOSC 2347, 1, 233.5 mm SL. López Mateos - río Lacantún, ECOSC 1687, 2, 215.8- 227.3 mm SL. Playón de la Mula - río Lacantún, ECOSC 1418, 1, 204.3 mm SL; ECOSC 1840, 2, 199.1- 222.9 mm SL; ECOSC 2503, 1, 215.0 mm SL. Playón 21 - río Lacantún, ECOSC 2326, 1, 214.1 mm SL. Playa Chavín - río Lacantún, ECOSC 1742, 1, 241.7 mm SL; ECOSC 2170, 1, 181.8 mm SL. El Tigre-Boca Lacantún, ECOSC 1749, 1, 203.3 mm SL. Boca Chajulillo - río Lacantún, ECOSC 2606, 2, 167-195.1 mm SL.

Figures

Fig. 3. a) Eugerres castroaguirrei new species, ECOSC 775, holotype, 184.3 mm SL. México, Chiapas, río Lacantún, Selva Lacandona, Marqués de Comillas, ReformaAgraria and Galaxia; b) Eugerres mexicanus, NMW 72289, lectotype, 165.6 mm SL. México, Tabasco, Flus (río) Teapa.

Fig. 4. Distribution of freshwater species of Eugerres in drainages along southeastern Mexico and northern Guatemala: E. castroaguirrei new species (black dots) and E. mexicanus (white dots), type locality (star).