New species of Eugerres from the Usumacinta Province, México and Guatemala with a redescription of E. mexicanus (Steindachner, 1863) (Teleostei: Gerreidae)

Abstract

Eugerres castroaguirrei, new species is described from the río Grijalva-Usumacinta basin of southeastern Mexico and northern Guatemala. Eugerres castroaguirrei and E. mexicanus are distinguishable from their marine estuarine congeners by the dorsalfin origin posterior to the insertion of the pectoral and pelvic fins, a shorter and broad based supraoccipital crest, and a distinct geographic distribution restricted to freshwater habitats. Eugerres castroaguirrei differs from E. mexicanus by diagnostic characters of the body skeleton: anterior process of supraoccipital convex, infraorbital 1 with foramen, premaxillary ascending process developed with margins curved, pharyngeal plate granular and not serially arranged, and dorsal and anal fin-rays reduced. Likewise, E. castroaguirrei is characterized by an oblong and laterally thicker body (37.6-58.5% HL); greater body depth (33.8-42.1% SL), and eye diameter (23.3-31.6% HL); in addition to 16 significant morphometric characters: length of the second dorsal-fin spine 23.2-34.2% SL; depressed second dorsal-fin spine (extending to base of third to fourth dorsal-fin rays); length of second anal-fin spine 11.1-20.6% SL, depressed second anal-fin spine extending to the base of third to fourth anal-fin rays not reaching the distal point of last anal-fin ray; pelvic-fin spine length 49.7-65.0% in the first pelvic-fin ray length.Eugerres castroaguirrei, es descrita como especie nueva de la cuenca del sistema de ríos Grijalva-Usumacinta, en el sureste de México y norte de Guatemala. Eugerres castroaguirrei y E. mexicanus se distinguen de sus congéneres marino estuarinos por el origen de su aleta dorsal que es posterior a la inserción de las aletas pectorales y pélvicas, así como por su cresta supraoccipital de longitud corta y base amplia, además de una distribución restringida a ambientes dulceacuícolas. Eugerres castroaguirrei se distingue de E. mexicanus mediante caracteres óseos diagnósticos como: proceso anterior del supraoccipital convexo, presencia de un foramen en el infraorbital 1, proceso ascendente del premaxilar desarrollado y con márgenes curvos, las placas faríngeas con dientes granulares desarreglados y los soportes de las aletas dorsal y anal reducidos. Asimismo, E. castroaguirrei se caracteriza por tener un cuerpo alargado y lateralmente comprimido cuyo grosor representa 37.6-58.5% de la longitud cefálica [LC]; la altura del cuerpo comprendida entre 33.8-42.1% de la longitud patrón [LP] y el diámetro ocular 23.3-31.6 % de la LC; además de 16 caracteres de tipo morfométrico: longitud de la segunda espina dorsal que representa 23.2-34.2% de la LP; segunda espina dorsal que cuando esta plegada se extiende hasta la base del tercer y cuarto radio dorsal; longitud de la segunda espina anal que comprende 11.1-20.6% de la LP; segunda espina anal que plegada se extiende hasta la base del tercer y cuarto radio anal, aunque no alcanza la porción distal del último radio anal; y la longitud de la espina de la aleta pélvica que comprende 49.7-65.0% de la longitud del prime...

Eugerres castroaguirrei González-Acosta et Rodiles-Hernández, 2013 is a junior synonym of Eugerres mexicanus (Steindachner, 1863) (Actinopterygii: Perciformes: Gerreidae)

“…Biometric data were analysed as proportions of standard length (%SL; fi ve body proportions), body depth (%BD; two body proportions), head length (%HL; fi ve body proportions), and three other body proportions, as suggested in the original description of E. castroaguirrei. In addition to the fi sh sample described above, comparisons also include the data set of 42 specimens of E. castroaguirrei (six type specimens, plus 35 non-type specimens; SL: 114.6 to 241.7 mm; mean = 201.0 mm) and 125 specimens of E. mexicanus (three type specimens, plus 122 non-type specimens; SL: 43.7 to 193.0 mm; mean = 146.4 mm), that were reported in the description of the new species by González-Acosta and Rodiles-Hernández (2013;Pp. 309-310).…”

“…The collected fi sh are held in the Ichthyological Collection (CI) from Centro Interdisciplinario de Ciencias Marinas (CICIMAR-CI 8810-11). The taxonomic determination of fi eld-collected and museum specimens was carried out under a stereomicroscope according to the morphological characteristics described in the reference diagnosis for both species by Deckert and Greenfi eld (1987) and González-Acosta and Rodiles-Hernández (2013), and also to additional criteria established by Castro- Aguirre et al (1999) for the species Eugerres mexicanus. It should be emphasized that González-Acosta and Rodiles-Hernán-dez (2013) did not include a dichotomous key for species identifi cation, and that all of the measurable diagnostic characters fi gured for Eugerres castroaguirrei are overlapped with those of E. mexicanus (see Introduction section herein, and González-Acosta and Rodiles-Hernández 2013; Pp.…”

“…The measured fi sh include the holotype of the Lacandon mojarra, Eugerres castroaguirrei, that belongs to the Coleccion de Peces de El Colegio de la Frontera Sur, Unidad San Cristóbal, Chiapas, México (ECOSC 775; Fig. 1a), the non-type specimens listed by González-Acosta and Rodiles-Hernández (2013;ECOSC 750,110, 694, 1570ECOSC 750,110, 694, , 704, 689, 641, 2191, and the lectotype (NMW 72289; Fig. 1b), and two paralectotypes (NMW 78820-1, NMW 78820-2) of the Mexican mojarra, Eugerres mexicanus, belonging to the Museum of Natural History, Wien, Austria (NHM).…”

“…Additionally, other specimens of the Mexican mojarra were included (ECOSC 047,380,431,587,398,048,302; and aforementioned CICIMAR-CI 8810-11), thus, a total of 44 specimens were considered for the analysis. Defi nitions of measurements, proportions, and their abbreviations are shown by González-Acosta and Rodiles-Hernández (2013;Pp. 308-309).…”

“…Recently, a new freshwater species, the Lacandon mojarra, Eugerres castroaguirrei González-Acosta et Rodiles-Hernández, 2013 from the Grijalva-Usumacinta River basin of south-eastern Mexico and northern Guatemala was described (González-Acosta and Rodiles-Hernández 2013).…”