Shifeng Wang

Growth, Body Composition, and Ammonia Tolerance of Juvenile White Shrimp Litopenaeus vannamei Fed Diets Containing Different Carbohydrate Levels at Low Salinity

ABSTRACT n Effects of dietary carbohydrate (CBH) levels on growth, body composition, and ammonia tolerance of juvenile white shrimp Litopenaeus vannamei at a low salinity of three were evaluated. Six isonitrogenous and isolipid diets containing different CBH levels were formulated and fed to juvenile L. vannamei for 42 days in triplicate for each treatment. Weight gain and survival rate of shrimp fed 20% CBH were the greatest and differed from those fed 5% CBH and 30% CBH. Shrimp whole-body crude protein of the 20% CBH group was significantly greater than that of other treatments. Whole-body crude lipid levels increased with the increase of dietary CBH, and was significantly higher in the 20%, 25%, and 30% CBH groups than in the control. Hepatosomatic index, condition factor, whole-body moisture, and ash contents were not affected by dietary CBH levels. Hepatopancreas soluble protein peaked in shrimp fed 20% CBH, and was significantly greater than in other groups. Hepatopancreas and muscle glycogen showed a similar tendency, but peaked in shrimp fed 15% CBH. Malate dehydrogenase, pyruvate kinase, and glucose-6-phosphate dehydrogenase activities were not affected significantly by dietary CBH levels. An ammonia challenge of 96 h showed that the shrimp in the 20% CBH group had the greatest survival rate, although no significant differences were observed among treatments. This study indicates that 15%–20% dietary CBH is optimal for growth and can improve the ability of L. vannamei to handle stress at low salinities.

Molecular characterization and expression of AMP-activated protein kinase in response to low-salinity stress in the Pacific white shrimp Litopenaeus vannamei.

AMP-activated protein kinase (AMPK) serves as a major regulator of cellular energy metabolism by activating ATP production pathways and blocking ATP consumption. However, information on AMPK genes in aquatic animals is limited. In this study, three subunits of AMPK were cloned from the Pacific white shrimp Litopenaeus vannamei. The full-length cDNAs of the α, β and γ subunits were 1617, 1243 and 3467bp long, respectively, with open reading frames of 1566, 873 and 2988bp encoding for 521, 290 and 996 amino acids, respectively. Amino acid sequence alignments of the three subunits showed that the functional domains in the L. vannamei proteins retained the highest similarity with those of other animals, at 89%, 58%, and 75%, respectively. The expression levels of the three subunits were higher in the muscle and gills than in the eyestalk and hepatopancreas. The mRNA levels of AMPK-α and AMPK-β were up-regulated in the hepatopancreas and muscle after acute low-salinity stress at 3psu for 6h compared with control salinity at 20psu. After 8-week salinity stress at 3psu, AMPK-α and AMPK-β mRNA levels in the hepatopancreas were significantly higher than those of the control at 30psu. However, in the muscle only AMPK-γ mRNA was significantly up-regulated at low salinity relative to controls. Muscle and hepatopancreas showed increases in AMPK protein after 6h exposure to low salinity, but there were no differences seen after long term acclimation. The change patterns of protein were slightly differing from the mRNA patterns due to the distinguishing function of individual subunits of AMPK. These findings confirm that three AMPK subunits are present in L. vannamei and that all encode proteins with conserved functional domains. The three AMPK subunits are all regulated at the transcriptional and protein levels to manage excess energy expenditure during salinity stress.

Gut Microbiota and its Modulation for Healthy Farming of Pacific White Shrimp Litopenaeus vannamei

ABSTRACT The Pacific white shrimp Litopenaeus vannamei is the most important crustacean species in aquaculture, accounting for 70% of the total shrimp production in the world. In the past decade, development of the shrimp industry has been greatly impeded by disease prevalence, poor growth in low salinity inland water, dietary use of plant ingredients, and antibiotic overuse. The animal gut is a vital organ, and most of the gut functions, such as the functions of immunity, health regulation and nutrient absorption, are achieved by bacterial metabolism in the gut. Therefore, understanding the role of the gut microbiota of L. vannamei is important for improving the performance and production of L. vannamei in aquaculture. This paper summarizes the recent advancements in research on the composition of the gut microbiota of L. vannamei, the factors that influence the microbiota, and nutritional manipulation of the gut microbiota. In addition, based on the review, current problems are raised and future studies directed at solving these problems are proposed. Proteobacteria is the core bacterial group found the gut of L. vannamei, but other groups of bacteria can also be beneficial to shrimp health and growth. The abundance of opportunistic pathogenic bacteria in the gut can change with the developmental stage of the shrimp, diet composition, environmental factors, and in the presence of ambient toxicants such as sulfide. Various prebiotics, probiotics isolated from the gut of L. vannamei and other crustacean species, synbiotics and some organic acids have been used as dietary supplements to evaluate the health of L. vannamei farms. These additives have been compared for their roles in regulating shrimp growth and immunity and in shaping the community structure of the gut microbiota. Future studies should focus on understanding the underlying mechanisms between shrimp metabolism and the gut microbiota and on practical applications of dietary additives to solve problems faced by the shrimp industry.

Analysis of differentially expressed gene fragments in the head kidney of lipopolysaccharide-stimulated Malabar grouper (Epinephelus malabaricus)

Se estudiaron los efectos inmunologicos y el mecanismo molecular preliminar de lipopolisacaridos (LPS) en el mero malabarico ( Epinephelus malabaricus ). El mero se inyecto intraperitonealmente dos veces (con 7 dias de diferencia) con 4 mg/kg –1 peso corporal de LPS provenientes de Escherichia coli (grupo de prueba, probadores) o solucion de tampon fosfato pH 7,2 (grupo control, conductores). Veintiocho dias despues, la actividad media de antibacterianos, lisozima y polifenol oxidasa del suero mostraron valores de probador de 0,228, 0,032 y 21,8 U/ml x min, respectivamente, mientras que los valores de controlador fueron 0,200, 0,015 y 15,5 U/ml x min. Se elaboro una libreria subtractiva de cDNA del rinon cefalico estimulado con LPS de mero malabarico utilizando hibridacion substractiva por supresion. Se seleccionaron y secuenciaron 376 clones de fragmentos de genes expresados de probadores especificos, y se obtuvieron 326 EST calificados. Despues de una busqueda con los programas BLASTn y BLASTx, 312 ESTs mostraron gran similitud para 13 fragmentos de genes (14 ESTs no se asemejaron a ninguno de los genes en el GenBank). De los 13 fragmentos, dos (15,4%) estaban relacionados con inmunodefensa (factor 2 regulador de interferon-proteina de union 2-A y complejo T de proteinas 1-theta); cinco (38,5%) estuvieron relacionados con la transcripcion o la traduccion; uno (7,7%) estuvo involucrado en el metabolismo (proteina CT054); dos (15,4%) codificarian homologoproteina de diferenciacion, leucemia mieloide y la proteina 3 que contiene el dominio parche G; y tres (23,1%) eran genes de transporte de oxigeno que codifican la cadena α de hemoglobina, la cadena β de la hemoglobina y de la cadena pesada de ferritina. Los resultados mostraron que LPS podrian mejorar significativamente la inmunidad innata y regular la expresion de genes relacionados con la inmunidad, la produccion de energia