Larval Development in Tropical Gar (Atractosteus tropicus) Is Dependent on the Embryonic Thermal Regime: Ecological Implications under a Climate Change Context

In ectotherm species, environmental temperature plays a key role in development, growth, and survival. Thus, determining how temperature affects fish populations is of utmost importance to accurately predict the risk of climate change over fisheries and aquaculture, critical to warrant nutrition and food security in the coming years. Here, the potential effects of abnormal thermal regimes (24, 28 and 32 °C; TR24, TR28, and TR32, respectively) exclusively applied during embryogenesis in tropical gar (Atractosteus tropicus) has been explored to decipher the potential consequences on hatching and growth from fertilization to 16 days post-fertilization (dpf), while effects on skeletal development and body morphology were explored at fertilization and 16 dpf. Egg incubation at higher temperatures induced an early hatching and mouth opening. A higher hatching rate was obtained in eggs incubated at 28 °C when compared to those at 24 °C. No differences were found in fish survival at 16 dpf, with values ranging from 84.89 to 88.86%, but increased wet body weight and standard length were found in larvae from TR24 and TR32 groups. Thermal regime during embryogenesis also altered the rate at which the skeletal development occurs. Larvae from the TR32 group showed an advanced skeletal development, with a higher development of cartilaginous structures at hatching but reduced at 16 dpf when compared with the TR24 and TR28 groups. Furthermore, this advanced skeletal development seemed to determine the fish body morphology. Based on biometric measures, a principal component analysis showed how along development, larvae from each thermal regime were clustered together, but with each population remaining clearly separated from each other. The current study shows how changes in temperature may induce craniofacial and morphological alterations in fish during early stages and contribute to understanding the possible effects of global warming in early development of fish and its ecological implications.

Programación nutricional en el pejelagarto (Atractosteus tropicus): efecto del almidón de maíz sobre la bioquímica sanguínea

El pejelagarto es una especie carnívora, en la que se ha demostrado una mejora en el crecimiento durante el larvicultivo al incluir almidón de maíz en su dieta, así como una eficiencia en la ruta de la gluconeogénesis al utilizar hasta 23% de carbohidratos en sus dietas. El objetivo de esta investigación fue determinar si el uso de almidón de maíz en el larvicultivo puede producir un afecto de programación metabólica, determinado mediante la bioquímica sanguínea durante la etapa juvenil. Los peces fueron divididos en 3 grupos, los cuales se alimentaron durante 73 días con las dietas experimentales, que tenían diferente porcentaje de inclusión de almidón de maíz (13.8, 22.5 y 28.9 % de carbohidratos). Posteriormente, los peces de los 3 grupos fueron sometidos a una prueba de tolerancia a la glucosa y se midió la concentración de glucosa, triglicéridos y colesterol a las 0, 1.5, 3 y 5 h después de aplicar una descarga de dextrosa intraperitonealmente. Los resultados demuestran que la concentración de carbohidratos y lípidos suministrada mediante la dieta durante la etapa temprana de crianza puede modificar de forma permanente las concentraciones de glucosa y triglicéridos en plasma de los pejelagartos juveniles.

Dietary live yeast (Debaryomyces hansenii) provides no advantages in tropical gar, Atractosteus tropicus (Actinopterygii: Lepisosteiformes: Lepisosteidae), juvenile aquaculture

Tropical gar, Atractosteus tropicus Gill, 1863, is an ancient freshwater fish that is commercially cultivated in southern Mexico. Currently, there is a specific diet for its culture; however, the addition of probiotics has not been investigated. The objective of this study was to evaluate the supplementation of live yeast Debaryomyces hansenii for A. tropicus juveniles on growth, productive parameters, survival, somatic index, digestive enzyme activity, and immune system gene expressions (interleukin 10, il-10, Transforming growth factor β1, tgf-β1, and β2 microglobulin, b2m). Three experimental diets increased the dose of live yeast (0.5, 1.0, and 1.5%; 1014, 1015, and 1016CFU g diet–1, respectively) and a control diet (CD; without yeast) were designed. Daily weight gain and specific growth rate were higher in fish fed with CD and 0.5% D. hansenii. High activities of trypsin, chymotrypsin LAP, and α-amylase, as well as overexpression of il-10 in the spleen, were detected in fish feed 0.5% D. hansenii. The inclusion of D. hansenii had no positive effect on aquaculture for A. tropicus, lower doses should be tested to optimize the diet.

Dietary live yeast (Debaryomyces hansenii) provides no advantages in tropical gar, Atractosteus tropicus (Actinopterygii: Lepisosteiformes: Lepisosteidae), juvenile aquaculture

Tropical gar, Atractosteus tropicus Gill, 1863, is an ancient freshwater fish that is commercially cultivated in southern Mexico. Currently, there is a specific diet for its culture; however, the addition of probiotics has not been investigated. The objective of this study was to evaluate the supplementation of live yeast Debaryomyces hansenii for A. tropicus juveniles on growth, productive parameters, survival, somatic index, digestive enzyme activity, and immune system gene expressions (interleukin 10, il-10, Transforming growth factor β1, tgf-β1, and β2 microglobulin, b2m). Three experimental diets increased the dose of live yeast (0.5, 1.0, and 1.5%; 1014, 1015, and 1016CFU g diet–1, respectively) and a control diet (CD; without yeast) were designed. Daily weight gain and specific growth rate were higher in fish fed with CD and 0.5% D. hansenii. High activities of trypsin, chymotrypsin LAP, and α-amylase, as well as overexpression of il-10 in the spleen, were detected in fish feed 0.5% D. hansenii. The inclusion of D. hansenii had no positive effect on aquaculture for A. tropicus, lower doses should be tested to optimize the diet.