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Abstract: Larval rearing of Asian seabass is dependent on live food, similar to several other carnivorous fish species. The present study aimed to find suitable predigested protein sources for use in Asian seabass larval diets in order to reduce dependency on live feed. Fish muscle, squid mantle and soybean meal were hydrolyzed by Alcalase (alkaline enzyme), pepsin (acidic enzyme), and the combination of both enzymes producing a total of 9 protein hydrolysate (PH) products. The soybean meal was found least favorable for the larvae and omitted from the in vivo investigation. Fish muscle and squid mantle hydrolysate products were selected based on in vitro digestibility to replace fishmeal protein at 25% and 50% in isonitrogenous (50% protein) and isolipidic (20% lipid) diets. A diet with 0% PH was used as a control diet, and two other diets, one with minced mackerel muscle supplying protein, and a commercial diet were included as reference diets. The experimental diets were fed to larvae four times daily for 30days from 17days post hatch. Survival rate and growth performance were measured and enzyme activity and gene expression of stomach, pancreatic and brush border enzymes were determined. Larvae accepted all PH diets and the control diet well but did not accept the two reference diets which caused 100% mortality in the third week of the trial. In general, 25% PH inclusion increased larval growth compared to the 0% control group and increased specific activity of pancreatic and brush border enzymes. At 50% inclusion level, negative effects on growth performance and survival rate were observed. High levels of small peptides in the PH might have influenced digestive enzyme capacity as reflected in induced chymotrypsin activity but reduced mRNA level and specific enzyme activity of the brush border enzyme, leucine aminopeptidase. In conclusion, incorporation of 25% PH from either fish muscle or squid mantle treated with the Alcalase-pepsin enzyme combination improved digestive capacity and growth performance of the larvae with acceptable survival rate. [Copyright &y& Elsevier]

Abstract: A sub-acute experiment that tested carbon and nitrogen metabolisms and the plant's antioxidant defence system was used to investigate the effects of nitrate enrichment and salinity reduction on the tropical seagrass Thalassia hemprichii that had previously been grown in low light conditions. Shading significantly reduced leaf growth rate, nitrate reductase activity and non-structural carbohydrate (NSC) content in both aboveground and belowground tissues, but enhanced superoxide dismutase and guaiacol peroxidase (POD) activities and free amino acids in aboveground tissue. After shade removal, salinity reduction with pre-shading decreased minimum fluorescence and maximum fluorescence under all nitrate conditions. Pre-shading aggravated the negative effect of nitrate enrichment and salinity reduction on leaf growth rate. Nitrate enrichment led to a greater reduction in NSC in aboveground tissues of pre-shading plants compared to the control. Furthermore, salinity reduction with pre-shading even induced effective NSC translocation from belowground to aboveground tissues. Nitrate enrichment and salinity reduction both increased POD activity in T. hemprichii grown previously in low light. Therefore, pre-shading increases the vulnerability of T. hemprichii to eutrophication and hyposalinity, which must be considered when predicting future responses and effective management of seagrass resources. [Copyright &y& Elsevier]

Abstract: We carried out a cultivation experiment using an artificial red mutant of Porphyra yezoensis isolated by heavy-ion beam mutagenesis to evaluate whether the red mutant has potential as a new cultivar. The blade length of the red mutant was shorter than that of a wild-type HG-511 at the first harvest. However, the results of the present study suggest that the red mutant tends to increase the contents of phycoerythrin, total free amino acid (FAA), alanine and taurine in comparison with the wild type. These tendencies toward the FAA contents were strongly supported by the laboratory culture experiment. From these superior characteristics of pigment and FAA contents, the red mutant IBY-R1 may become a new cultivar in nori cultivation, although it is possible that the mutant harvest will be lower than that of other cultivars. [Copyright &y& Elsevier]