Morfometría comparada del aparato mandibular en especies de Chirostoma (Atheriniformes : Atherinopsidae) del Lago de Pátzcuaro, Michoacán, México

The genus Chirostoma is a group of fishes endemic to the Mesa Central of Mexico, whose diversification is explained both by processes of allopatric speciation in lotic environments, and by intralacustrine diversification through sympatric speciation. Trying to corroborate the second hypothesis for species of Chirostoma from Lake Pátzcuaro, we evaluated morphometric differences of 11 bones in the mandibular region of C. attenuatum, C. grandocule, C. estor, and C. patzcuaro. In order to identify taxa, we carried out a cluster analysis applying euclidian distances, as well as a principal component analysis on the variance-covariance matrix. The results of the cluster analysis show four groups corresponding to each species, C. grandocule and C. patzcuaro being most similar between themselves and C. attenuatum the most different from the rest. Principal component analysis confirmed the separation of these species, defined by the angle formed by the jaws, the height of the dentary and the length of the post-articulate apophysis. These bones are related to the capture of food. Thus, the species of Chirostoma show clear morphological differentiation in the bony pieces of the mandibular region, a pattern that supports the hypothesis of trophic segregation that allows the coexistence of species in Lake Pátzcuaro.El género Chirostoma es un grupo de peces endémicos de la Mesa Central de México, cuya diversificación se explica tanto por procesos de especiación alopátrica en ambientes lóticos, como por una diversificación intralacustre debida a especiación simpátrica. Tratando de corroborar la segunda hipótesis en especies de Chirostoma en Pátzcuaro, se evaluaron diferencias morfométricas de 11 piezas osteológicas de la región mandibular de C. attenuatum, C. grandocule, C. estor y C. patzcuaro. Con objeto de identificar los taxones se realizó un análisis de agrupación aplicando distancias euclidianas, así como un análisis de componentes principales sobre la matriz de varianza-covarianza. Los resultados del análisis de agrupamiento muestran cuatro grupos que corresponden a cada especie, siendo C. grandocule y C. patzcuaro las más semejantes entre sí y C. attenuatum la más disímil del resto. El análisis de componentes principales confirmó la separación de especies y definió como medidas significativas al ángulo formado por las mandíbulas, la altura del dentario y la longitud de la apófisis post-articular; dichos huesos se relacionan con la captura del alimento. De este modo, las especies de Chirostoma manifiestan una clara diferenciación morfológica en las piezas óseas de la región mandibular, lo cual apoya la idea de una segregación trófica que permite la coexistencia entre especies del Lago de Pátzcuaro

Assessment of aquatic food web and trophic niche as a measurement of recovery function in restored mangroves in the Southern Gulf of Mexico

Mangroves are coastal wetlands with high biodiversity and productivity, with great interaction with coastal environments. In the face of worldwide mangrove loss, restoration projects attempt to recover ecosystem composition and functioning over time. Our objective was to examine and compare the food webs in mangrove areas with different restoration times and in a reference mangrove in Términos Lagoon, Mexico. We estimated the trophic structure, identified the carbon resources that maintain aquatic consumers through the analysis of stable isotopes, and compared the trophic niche of the restored mangroves with the reference mangrove. We analyzed environmental variables, trophic structure, and contributions of resources during three seasons: rainy, dry, and “nortes”. Environmental changes and food structure changed in response to regional seasons. Bayesian mixing models indicated that food webs varied seasonally as a response to the primary productivity developed at Términos Lagoon. As expected, the assimilation of C3 plants in the reference mangrove was highest, as a primary (“nortes” season) and secondary resource (dry and rainy seasons). The restored mangroves depended mainly on allochthonous resources (seagrass, epiphytes, and phytoplankton). The assimilation of these resources highlighted the importance of connectivity and the input of sources of carbon from nearby coastal environments. Trophic niche analysis showed that the area with longer restoration time was more similar to the reference mangrove, which is evidence of the importance and efficacy of the restoration process, as well as the restoration of the ecosystem function over time

Fishes in the lower San Pedro Mezquital River, Nayarit, Mexico

The San Pedro Mezquital River is the seventh largest river in Mexico, and flows through the Sierra Madre Occidental into the Marismas Nacionales Biosphere Reserve, on the coast of the state of Nayarit. The present study is to conform a systematic checklist of fishes in the lower basin of the San Pedro Mezquital River. In total, 52 species were collected from 24 families. Four native species were collected (Atherinella crystallina, Poecilia butleri, Poeciliopsis latidens and Poeciliopsis prolifica) that are federally protected. Five of the collected species were new records for the state of Nayarit. This checklist constitutes a first approximation of the fish fauna present in the San Pedro Mezquital River. However, the construction of the Las Cruces dam upstream, will modify the basin hydrology, worsen the introduction of exotic species and create habitat loss, which can have immediate negative impacts on the fish communities in this region

New report and range extension of invasive suckermouth armored catfishes of the genus Pterygoplichthys (Actinopterygii: Siluriformes: Loricariidae) in the Yucatan Peninsula

Commonly known as suckermouth armored catfishes or pleco, Pterygoplichthys spp. are a group of invasive fishes that are widely distributed in several countries, including Mexico. This paper reports the first records of suckermouth armored catfishes in the Candelaria River, thereby expanding its distribution within the Yucatan Peninsula. Fifteen individuals were collected from three sites in the upper and middle parts of the basin. They represented two phenotypically distinct species of catfishes: (vermiculate) Pterygoplichthys disjunctivus (Weber, 1991) and (spotted) Pterygoplichthys pardalis (Castelnau, 1855). Adults and juveniles were caught in lotic ecosystems in 2023 during the dry and rainy seasons. Results suggest that the invasive process of the Candelaria River is linked to the San Pedro River upper basin, in El Petén, Guatemala, through floodings enhanced by hurricanes, allowing these species to disperse. These records highlight the importance of connectivity between adjacent watersheds for the dispersal and expansion of these invasive fishes, mainly from rivers neighboring Guatemala. However, further research is necessary to explore the dynamics and connectivity between aquatic ecosystems and the possible mechanisms that promote the invasion of these fishes in this region

Ecomorfología de los Cíclidos en la Selva Lacandona (Rebima), Chiapas, México

San Cristóbal de Las Casas, Chiapas, México : El Colegio de la Frontera Sur, 2009

Morfometría de las especies de Vieja (Cichlidae) en ríos de la cuenca del Usumacinta, Chiapas, México

We evaluated and compared morphological characteristics among the 6 species of Vieja Fernández-Yépez, 1969 from Usumacinta River. We analyzed 20 adults by specie, obtaining 33 measurements, which were standardized and analyzed with a discriminant analysis. We also performed a comparison of body shape among species, using the geometric morphometric analysis from digitalized images. Traditional and geometric morphometrics allowed distinguishing each taxa. We found 10 discriminants measures, related with the head region and length of fins, only mouth position was different among more taxa. In both analyses, similarity relationships showed 2 groups, being V. bifasciata (Steindachner, 1864) and V. synspila (Hubbs, 1935) the most similar species. Thin plate spline showed greater variation in the cephalic region, specifically in eyes and mouth position. Morphometrics differences can be used for taxonomic identification in future works. The variation found in cephalic and trophic morphology can be a mechanism that promotes coexistence of species and explain the diversity of the group in this region.Se evaluaron y compararon diversas características morfológicas de 6 especies de Vieja Fernández-Yépez, 1969 del río Usumacinta. Se emplearon 20 organismos adultos por especie y 33 medidas corporales que fueron estandarizadas y examinadas con un análisis discriminante. Además se comparó la forma del cuerpo entre las especies, mediante el análisis de morfometría geométrica a partir de imágenes digitalizadas. El análisis con la morfometría tradicional y geométrica permitió diferenciar los seis taxones. Se encontraron 10 medidas discriminantes, que expresan diferencias significativas en la longitud de las aletas y la región cefálica, de las cuales la posición de la boca diferenció estadísticamente más taxones. Las relaciones de similitud con ambos análisis mostraron 2 grupos, siendo V. bifasciata (Steindachner, 1864) y V. synspila (Hubbs, 1935) las especies más parecidas. Las gradillas de deformación mostraron que la mayor variación está en la región cefálica, específicamente en la posición de la boca y los ojos. Las diferencias morfométricas encontradas pueden servir para la determinación taxonómica en trabajos futuros. La variación encontrada en la morfología cefálica y trófica puede ser un mecanismo que favorece la coexistencia de las especies y la diversidad del grupo en la región

Análisis morfométrico de los peces del grupo labialis, género Profundulus (Cyprinodontiformes: Profundulidae), en Chiapas, México Morphometric analysis of the fish included in the labialis group, genus Profundulus (Cyprinodontiformes: Profundulidae), in Chiapas, Mexico

Se presentan los resultados de la comparación morfométrica de las especies del "complejo labialis", del género Profundulus, basada en 11 medidas tradicionales y 21 cruzadas. Mediante el análisis de componentes principales y agrupamiento se demostró que Profundulus labialis y P. candalarius muestran un patrón morfológico semejante, caracterizado por mayor altura del cuerpo, menor longitud del hocico, y menor longitud y ancho de la boca; mientras que P. hildebrandi presenta características diferentes. El análisis de varianza mostró 14 medidas morfométricas estadísticamente significativas que permiten separar, por lo menos, a una de las tres especies y además corroboran su validez taxonómica. Las relaciones de similitud establecidas en este análisis concuerdan con las relaciones filogenéticas propuestas por otros autores. Las diferencias encontradas en medidas relacionadas con estructuras tróficas y de la altura del cuerpo podrían estar relacionadas con aspectos ecológicos o asociaciones con distintos hábitats.Results of morphometrical comparison of the species of the "labialis complex", of the genus Profundulus, based on 11 traditional and 21 crossed measures, are herein presented. Through the principal components and cluster analyses we have found that Profundulus labialis and P. candalarius show a similar morphological pattern, characterized by the greater altitude, the shorter snout, and the shorter length and width of the mouth; while P. hildebrandi has the opposite characteristics. The analysis of variance showed 14 statistically different measures that allow to recognize at least one of the three species, and they also corroborate their taxonomical validity. The results of the present analyses of similarities are congruent with the phylogenetic relationships proposed by other authors. Some measurements associated to trophic structures seem to vary according to ecological conditions

Análisis morfométrico de los peces del grupo labialis, género Profundulus (Cyprinodontiformes: Profundulidae), en Chiapas, México

Se presentan los resultados de la comparación morfométrica de las especies del "complejo labialis", del género Profundulus, basada en 11 medidas tradicionales y 21 cruzadas. Mediante el análisis de componentes principales y agrupamiento se demostró que Profundulus labialis y P. candalarius muestran un patrón morfológico semejante, caracterizado por mayor altura del cuerpo, menor longitud del hocico, y menor longitud y ancho de la boca; mientras que P. hildebrandi presenta características diferentes. El análisis de varianza mostró 14 medidas morfométricas estadísticamente significativas que permiten separar, por lo menos, a una de las tres especies y además corroboran su validez taxonómica. Las relaciones de similitud establecidas en este análisis concuerdan con las relaciones filogenéticas propuestas por otros autores. Las diferencias encontradas en medidas relacionadas con estructuras tróficas y de la altura del cuerpo podrían estar relacionadas con aspectos ecológicos o asociaciones con distintos hábitats