Descripción del cráneo de Bramocharax caballeroi Contreras & Rivera 1985 (Pisces, Characidae), pez endémico del Lago de Catemaco, Veracruz, México.

The Bramocharax genus is distributed from Central America to Mexico. Until now the species known are Bramocharax bransfordi collected in Nicaragua and Costa Rica, B. dorioni and B. baileyi from Guatemala and B. caballeroi from Catemaco Lake, Veracruz, Mexico. The aim of this work is to realize a detailed description of the skull for Bramocharax caballeroi from the analysis of 37 different topotypes. The skull of this species has 58 osteological elements, 49 of them coupled. Shape is oval in lateral view, because the bones of the snout (ethmoid, vomer, lateral ethmoid, dentary, maxillae, premaxillae, ecto and mesopterygoids) and the frontal and circunorbitals are elongated. The dorsal margin is slightly concave and the anterior part is elongated. In specimens less than 80 mm, all the bones are smoother, with more regular edges. With the age increase, they become more robust with more irregular edges. A comparison of the skull between B. caballeroi and Astyanax mexicanus resulted in 25 bones with differences, while with Astyanax fasciatus, main contrasts were the supraoccipital length, the shape of the opercles and the infraorbital 3. In addition there are important differences in the dentition, gill rackers, as well as suspensory pharingeals and pharyngeal plates with respect to Astyanax.El género Bramocharax se distribuye del centro-norte de Centro América a México. Hasta este momento se conoce a Bramocharax bransfordi de Nicaragua y Costa Rica, a B. dorioni y B. baileyi de Guatemala y a B. caballeroi del lago de Catemaco, Veracruz, México. El trabajo tuvo por objetivo estudiar detalladamente el cráneo de Bramocharax caballeroi a partir del análisis de 37 topotipos de diferentes tallas y compararlo con otras especies relacionadas. B. caballeroi presenta 58 huesos en su cráneo, de los cuales 49 son elementos pareados. En vista lateral su perfil es ovalado, debido a los huesos que conforman el hocico (etmoides, vómer, etmoides lateral, mandíbula, maxila, premaxila, ecto y mesopterigoides), así como el frontal y los circunorbitales, son alargados. El margen dorsal es ligeramente cóncavo y la parte anterior alargada. En los ejemplares menores a 80 mm todos los huesos son más lisos y conforme los organismos tienen una talla mayor, se hacen más robustos y los bordes de cada hueso se hacen más irregulares. Al comparar el cráneo de B. caballeroi con el de Astyanax mexicanus se encontraron diferencias en 25 huesos, mientras que al hacerlo con A. fasciatus, los principales contrastes fueron la longitud del supraoccipital, la forma del opérculo y del infraorbital 3. Adicionalmente, se encontraron diferencias importantes en la dentición y en las branquiespinas así, como en las placas y suspensores faríngeos con respecto a los Astyanax

Distributional and Ecological Notes on the Halfbeaks of Eastern Gulf of Mexico, with a Provisional Key for Their Identifification

Several fishes of the halfbeak genus Hyporhamphus occumng in the Mexican Gulf of Mexico and Caribbean Sea have been misidentified or confused in the literature. Most of it has centered around the taxonomic status of H. unifasciatus (including its synonym H. roberti), which is shown to comprise a complex of three species, H. unifasciatus, the recently described H. meeki, from the western Atlantic region, and an undescribed species from the eastern Pacific Ocean. Another eastern Mexico halfbeak is the freshwater form H. mexicanus. Using Banford and Collette (1993), we examined specimens from collections at UANL, UNAM, IPN, and ECOCH and have clarified the Mexican distribution of these species. We here report additional Mexican records of H. meeki, previously known only from United States waters and from the coast of Yucathn, clarify the distribution of H. unifasciatus, and provide the first marine record of the freshwater species H. mexicanus. A distribution map and keys for identification of the eastern Mexican species are provided

Wild-caught Hybrids Between Sailfin and Shortfin Mollies (Poeciliidae, Poecilia): Morphological and Molecular Verification

This study documents four wild-caught, interspecific hybrids between sailfin mollies (Poecilia velifera or P. petenensis) and shortfin mollies (P. mexicana or P. orri) from the Yucatán peninsula and Isthmus of Tehuantepec regions of México. In canonical discriminant analysis of morphological data all four putative hybrid males were intermediate in shape between shortfin and sailfin molly species, falling well outside 95% confidence ellipses for those putative parental species. For two of the four hybrid individuals, we used allele size differences at the nuclear Xsrc gene between sailfin and shortfin species to determine that one was a first (F1) or early generation (F2, BC1) hybrid and the other was a later generation (>F1) hybrid. Sequences of the mtDNA control region (483 bp) and Xsrc nuclear gene (636 bp) indicated that the female parent of the early generation hybrid individual was P. mexicana and the male parent was P. velifera. Thus, while rare in the wild, interspecific hybridization and introgression between sailfin and shortfin mollies does occasionally occur despite the existence of behavioral pre-mating isolating mechanisms

Freshwater ecoregions of the world: A new map of biogeographic units for freshwater biodiversity conservation

We present a new map depicting the first global biogeographic regionalization of Earth's freshwater systems. This map of freshwater ecoregions is based on the distributions and compositions of freshwater fish species and incorporates major ecological and evolutionary patterns. Covering virtually all freshwater habitats on Earth, this ecoregion map, together with associated species data, is a useful tool for underpinning global and regional conservation planning efforts (particularly to identify outstanding and imperiled freshwater systems); for serving as a logical framework for large-scale conservation strategies; and for providing a global-scale knowledge base for increasing freshwater biogeographic literacy. Preliminary data for fish species compiled by ecoregion reveal some previously unrecognized areas of high biodiversity, highlighting the benefit of looking at the world's freshwaters through a new framework.La lista completa de autores que integran el documento puede consultarse en el archivo.Facultad de Ciencias Naturales y Muse

Freshwater ecoregions of the world: A new map of biogeographic units for freshwater biodiversity conservation

We present a new map depicting the first global biogeographic regionalization of Earth's freshwater systems. This map of freshwater ecoregions is based on the distributions and compositions of freshwater fish species and incorporates major ecological and evolutionary patterns. Covering virtually all freshwater habitats on Earth, this ecoregion map, together with associated species data, is a useful tool for underpinning global and regional conservation planning efforts (particularly to identify outstanding and imperiled freshwater systems); for serving as a logical framework for large-scale conservation strategies; and for providing a global-scale knowledge base for increasing freshwater biogeographic literacy. Preliminary data for fish species compiled by ecoregion reveal some previously unrecognized areas of high biodiversity, highlighting the benefit of looking at the world's freshwaters through a new framework.La lista completa de autores que integran el documento puede consultarse en el archivo.Facultad de Ciencias Naturales y Muse

Freshwater ecoregions of the world: A new map of biogeographic units for freshwater biodiversity conservation

We present a new map depicting the first global biogeographic regionalization of Earth's freshwater systems. This map of freshwater ecoregions is based on the distributions and compositions of freshwater fish species and incorporates major ecological and evolutionary patterns. Covering virtually all freshwater habitats on Earth, this ecoregion map, together with associated species data, is a useful tool for underpinning global and regional conservation planning efforts (particularly to identify outstanding and imperiled freshwater systems); for serving as a logical framework for large-scale conservation strategies; and for providing a global-scale knowledge base for increasing freshwater biogeographic literacy. Preliminary data for fish species compiled by ecoregion reveal some previously unrecognized areas of high biodiversity, highlighting the benefit of looking at the world's freshwaters through a new framework.La lista completa de autores que integran el documento puede consultarse en el archivo.Facultad de Ciencias Naturales y Muse

Skull osteology of the characid fish Astyanax mexicanus (Teleostei: Characidae)

Volume: 116Start Page: 341End Page: 35