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Gastrointestinal ontogenetic studies constitute one of the basic and important investigations related to the nutrition of aquatic animals. In this investigation, specimens of the western white shrimp (Litopenaeus vannamei) at different developmental stages (from nauplius 1 to postlarvae 120) were assayed for the activities of digestive enzymes. According to the results, at all developmental stages, trypsin, amylase, and lipase enzymes were found to be active. In addition, the peak activities of all enzymes were revealed to occur during the late zoea larval stages (Z3). On the other hand, minimum activities were observed to occur at metamorphosis. During the postlarval developmental stages, amylase and lipase activities increased steadily, whereas the trypsin activity was more or less constant up to the eighteenth week. In conclusion, ontogenetic change in digestive enzyme activity may reflect either a developmentally cued change in enzyme synthesis or a secondary effect of change in the function and relative size of the midgut during its differentiation.
 
 
 
 

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Saline rhizospheric areas are untouched environments for isolating actinomycetes with the potential of valuable salt tolerant enzyme production. In this study, we isolated and evaluated a total number of of 26 actinomycete strains from plant rhizosphere of the periphery of Dasht-e-Kavir desert. Isolated actinomycetes produced different enzymes. Among them 50, 46, 39, 27, 10 and 7 % of the isolates produced amylase, lipase, protease, gelatinase, lecithinase and urease, respectively. The most frequently produced enzymes among the isolates were amylase, lipase and protease. Combined hydrolytic activity was also detected in some actinomycete strains. Among the isolates, strains Q1, Q4 and Q11 with the most diverse enzymes production, were identified and their 16s rRNA analysis showed that they are mostly similar to the Streptomyces scopiformis, Streptomyces argenteolus and Streptomyces manipurensis, respectively. Finally, due to the enzymatic diversity obtained and the valubility of the halophilic bacterial enzymes in industry, it seems that actinomycetes isolated from this saline habitat are potentially suitable for biotechnological applications.