ALBERT

Description: The Macapule Lagoon (25º 21' and 25º 24' N; 108º 30' and 108º 45' W) is part of the San Ignacio-Navachiste-Macapule lagoon system, located in the southern region of the Gulf of California (Fig. 1). In 2000, it has been declared an "Area of Reserve and Refuge for Migratory Birds and Wildlife – Gulf of California Islands". This lagoon is very productive due to its location in the Gulf of California (Lluch-Cota et al. 2007). Water temperature, dissolved oxygen, pH, and salinity were measured in situ with an YSI (55-12FT) probe and a portable refractometer (RHS-10ATC). Nutrient (nitrate, ammonium, and phosphate) concentrations were determined in the laboratory during each sampling month using a photometer (YSI, 9500).

Description: In December 2013, June and December 2014, and July 2015, a total of 123 specimens of L. argentiventris were captured in the Macapule Lagoon with gillnets of 50 mm mesh size. The total length and weight of each specimen were recorded. The liver, stomach, and gutted weight were weighed to the nearest gram (g) and the data used to calculate the following morpho-physiological indices: 1) the Fulton's condition factor (CF) using the equation: CF = W~t~/L~t~3 * 100, where W~t~ = total weight and L~t~ = total length; 2) the hepatosomatic index (HSI) using the equation: HSI = W~h~/W~t~*100, where W~h~ = liver weight and W~t~ = total weight of the individual; and 3) the gastric repletion index (GRI) using the equation GRI = W~s~/W~t~ *100, where W~s~ = stomach weight and W~t~ = total weight. Parameters of the length-weight relationship of L. argentiventris were estimated using the equation: W = aL^b^, where W = weight of the fish (g), L = total length (cm), a = y-intercept or the initial growth coefficient, b = slope or the growth coefficient. Blood samples of 1±0.1 mL were extracted (only of fish larger than 10 cm total length) by caudal puncture with a disposable plastic syringe containing 0.5 mL of heparinized solution (Sigma-Aldrich). The blood samples were centrifuged at 9,500 g at 4ºC during 10 minutes to separate the blood cells from the plasma. Total protein concentrations were determined following Bradford's method (1976), which is based on the reaction of the amino groups with the dye Coomassie Blue G-250. Triglycerides, glucose, and cholesterol concentrations were determined with colorimetric commercial kits Randox, U.K (Apún-Molina et al., 2015);. Absorbance was determined with a microplate reader (Multiskan Go, Thermo Scientific UV, United States) and concentrations were calculated from a standard solution of substrates.

Description: Background: Fish reared under intensive conditions are repeatedly exposed to stress, which negatively impacts growth. Although most fish follow a conserved pattern of stress response, with increased concentrations of cortisol, each species presents specificities in the cell response and stress tolerance. Therefore, culturing new species requires a detailed knowledge of these specific responses. The red cusk-eel (Genypterus chilensis) is a new economically important marine species for the Chilean aquaculture industry. However, there is no information on the stress- and cortisol-induced mechanisms that decrease skeletal muscle growth in this teleost. Results: Using Illumina RNA-seq technology, skeletal muscle sequence reads for G. chilensis were generated under control and handling stress conditions. Reads were mapped onto a reference transcriptome, resulting in the in silico identification of 785 up-regulated and 167 down-regulated transcripts. Gene ontology enrichment analysis revealed a significant up-regulation of catabolic genes associated with skeletal muscle atrophy. These results were validated by RT-qPCR analysis for ten candidates genes involved in ubiquitin-mediated proteolysis, autophagy and skeletal muscle growth. Additionally, using a primary culture of fish skeletal muscle cells, the effect of cortisol was evaluated in relation to red cusk-eel skeletal muscle atrophy. Conclusions: The present data demonstrated that handling stress promotes skeletal muscle atrophy in the marine teleost G. chilensis through the expression of components of the ubiquitin-proteasome and autophagy-lysosome systems. Furthermore, cortisol was a powerful inductor of skeletal muscle atrophy in fish myotubes. This study is an important step towards understanding the atrophy system in non-model teleost species and provides novel insights on the cellular and molecular mechanisms that control skeletal muscle growth in early vertebrates.