Un caso de leucismo en el Juil de Jamapa, Rhamdia laticauda (Siluriformes, Heptapteridae) en el noreste del estado de Oaxaca, México

Se reporta la primera observación de un espécimen leucístico en el Juil de Jamapa, Rhamdia laticauda en el noreste del estado de Oaxaca. En un estudio ictiológico de la Reserva de la Biosfera Tehuacán-Cuicatlán en el río Xiquila de la cuenca alta del río Papaloapan, el pez se capturó con pesca eléctrica y se fotografió. El bagre vivo mostró una reducción de pigmentos en la piel, manchas blancas y ojos negros normales. Esto contribuye al conocimiento de la variabilidad intraespecífica y la historia natural de R. laticauda. Se discuten las causas potenciales de esta anomalía de color

Trophic ecology and niche overlap of two sympatric species of Rhamdia (Siluriformes, Heptapteridae) from northeast Oaxaca, Mexico

The trophic ecology of fishes in the genus Rhamdia remains poorly reported. Here, we aim to describe the diet composition and infer the trophic levels, niche breadth, and niche overlap between Rhamdia guatemalensis and Rhamdia laticauda in northeast Oaxaca, Mexico. Fishes were sampled using an electrofishing device between 2016 and 2017. We calculated the Quotient index and the diet composition was analyzed using the percentage of the Index of Relative Importance (%IRI) to analyze possible ontogenetic and sexual differences on feeding ecology. We then calculated the trophic niche breadth using the Levins´ standardized index (BA). Trophic levels (TLk) of each species were calculated using the trophic index and trophic niche overlap using Pianka´s index (Ojk). The results indicate that both species are carnivorous and tend to prey on aquatic insects, with R. guatemalensis feeding on nine different orders of animals and R. laticauda displaying a broader diet spectrum, encompassing 19 orders. Our data showed ontogeny and sex differences in the trophic ecology of R. guatemalensis. They were secondary consumers (TLk > 3) and showed a specialized diet (BA < 0.4). We found evidence of trophic niche partitioning between adults (Ojk = 0.40) and females (Ojk = 0.42). Our results highlight the fundamental role of this species in the area as a carnivorous/insectivorous, predatory fishes, secondary consumers, and biological control for Diptera, Ephemeroptera, and Megaloptera. Both species minimize the trophic overlap through food resource partitioning mediated by fish body size. Additionally, adults and females consume different prey, which allows the coexistence of closely related species. Our findings regarding trophic ecology could be crucial for devising conservation and management plans for these particular Rhamdia species

Registros notables de Panthera onca y Taxidea taxus (Carnivora: Mammalia) en Oaxaca, México

On October 23, 2015, traces of a large feline were found (Figure 1A) during a tour along the banks of the Sabino River, Municipality of Santa María Tecomavaca, District of Teotitlán (17 ° 51'52 ”N and 97 01'50.6 "W; 615 masl; Figure 2). Photographs and measurements (length and width) were taken from each footprint. It was determined that the footprints belong to a jaguar by a set of qualitative and quantitative characteristics: they were wider than long, almost round; the upper part of the plantar bearing is not concave and the fingers were not pointed, as in the puma; the lower lobes of the plantar bearing are not marked; the bearings tend to have lower lobes that are better defined and less wide; the proportion of the first third of the fingers was greater than its lengthEl 23 de octubre de 2015, se encontraron huellas de un felino grande (Figura 1A) durante un recorrido a lo largo de la ribera del río Sabino, Municipio de Santa María Tecomavaca, Distrito de Teotitlán (17°51’52” N y 97°01’50.6” W; 615 msnm; Figura 2). De cada huella se tomaron fotografías y medidas (largo y ancho). Se determinó que las huellas pertenecen a un jaguar por un conjunto de características cualitativas y cuantitativas: fueron más anchas que largas, casi redondas; la parte superior del cojinete plantar no es cóncavo y los dedos no fueron puntiagudos, como en el puma; los lóbulos inferiores del cojinete plantar no están marcados; los cojinetes tienden a presentar lóbulos inferiores mejor definidos y menos anchos; la proporción del primer tercio de los dedos fue mayor que su longitu