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.Versión del edito

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

This article belongs to the Special Issue Current Advances and Challenges in Fisheries and Aquaculture Science: Feature Papers for the New Journey of Fishes[EN] 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 implicationsSIThis work was partially funded by “Study of the digestive physiology in larvae and juveniles of tropical gar (Atractosteus tropicus) based on histological, biochemical and molecular techniques” project (Ref. CB-2016-01-282765) from the National Council for Science and Technology (CONACyT) of Mexico. I.F. acknowledges the funding from the MICIU and the European Social Fund, “The European Social Fund invests in your future” through the Ramón y Cajal (Ref. RYC2018-025337-I) contract from the Plan Estatal de Investigación Científica y Técnica e Innovación 2017–2020Authors also thanks the support from the RED LARVAplus “Estrategias de desarrollo y mejora de la producción de larvas de peces en Iberoamérica” (117RT0521) funded by the Programa Iberoamericano de Ciencia y Tecnología para el Desarrollo (CYTED

Incorporation of Fructooligosaccharides in Diets Influence Growth Performance, Digestive Enzyme Activity, and Expression of Intestinal Barrier Function Genes in Tropical Gar (<i>Atractosteus tropicus</i>) Larvae

This study was conducted to investigate the effects of dietary fructooligosaccharides (FOS) on the growth, survival rate, digestive enzyms activity, and the expression of intestinal barrier function genes in tropical gar (Atractosteus tropicus) larvae. A total of 960 larvae (0.030 ± 0.006 g) were fed three diets supplemented with increasing FOS concentrations (2.5, 5, and 7.5 g kg−1) and a control diet for 15 days. Results revealed that a 7.5 g kg−1 FOS supplementation improved weight gain, specific growth rate, and survival rate (p −1 FOS supplementation increased alkaline protease and amylase activities and induced an upregulation of the claudin-17 gene expression (p −1 FOS induced the upregulation of mucin 2 (muc-2), and the tight junction genes zo-2 and claudin-3 (p −1 FOS promoted the downregulation of the claudin-15 gene expression (p il-8 expression. We can conclude that 7.5 g kg−1 FOS supplementation improves growth performance, survival rate, and digestive capacity, and could contribute to the reinforcement of the intestinal barrier function of Tropical gar larvae

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 1016 CFU 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