Effects of temperature and water turbulence on vertebral number and body shape in Astyanax mexicanus (Teleostei: Characidae).

Environmental changes can modify the phenotypic characteristics of populations, which in turn can influence their evolutionary trajectories. In ectotherms like fishes, temperature is a particularly important environmental variable that is known to have significant impacts on the phenotype. Here, we raised specimens of the surface ecomorph of Astyanax mexicanus at temperatures of 20°C, 23°C, 25°C, and 28°C to examine how temperature influenced vertebral number and body shape. To increase biological realism, specimens were also subjected to two water turbulence regimes. Vertebral number was counted from x-rays and body shape variation was analysed using geometric morphometric methods. Temperature significantly impacted mean total vertebral number, which increased at the lowest and highest temperatures. Fish reared at lower temperatures had relatively more precaudal vertebrae while fish reared at higher temperatures had relatively more caudal vertebrae. Vertebral anomalies, especially vertebral fusions, were most frequent at the extreme temperature treatments. Temperature significantly impacted body shape as well, with fish reared at 20°C being particularly divergent. Water turbulence also impacted body shape in a generally predictable manner, with specimens reared in high turbulence environments being more streamlined and having extended dorsal and anal fin bases. Variation in environmental variables thus resulted in significant changes in morphological traits known to impact fish fitness, indicating that A. mexicanus has the capacity to exhibit a range of phenotypic plasticity when challenged by environmental change. Understanding the biochemical mechanisms underlying this plasticity and whether adaptive plasticity has influenced the evolutionary radiation of the Characidae, are major directions for future research

Presencia de actividad antimicrobiana en el mucus del pez chame (dormitator latifrons).

El presente trabajo describe la presencia de actividad antimicrobiana del mucus del pez chame (Dormitator latifrons) ante la presencia de diferentes bacterias de tipo Gram (+) y Gram (-). De esta forma, se demostró un efecto inhibitorio del mucus de chame sobre 2 de 3 cepas de tipo bacilo analizadas (Bacilo sp.1, Bacilo sp.2 y Bacilo sp.3). Además, se determinó la existencia de un fuerte efecto inhibitorio del mucus de chame sobre cepas de Vibrio vulnificus y Vibrio harveyi. También se observó en menor magnitud efecto inhibitorio sobre una cepa de Vibrio anguillarum. La información preliminar obtenida en este estudio sugiere la presencia de agentes antibacterianos en el mucus del pez chame, los cuales podrían ser utilizados en un futuro con una aplicación en salud animal y humana