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The current study evaluated the interactive impacts of water temperature and feeding rate on digestive enzymes, intestine histology, growth and stress-related genes, and cultivable intestinal microbiota of Asian seabass (Lates calcarifer). For this purpose, 180 fish (85.0±3.0 g) were reared at three different temperatures (20, 27, and 33 °C) and two feeding rates (apparent satiation and 2.5% of biomass) with three replications for 6 weeks. The results revealed no significant differences among different treatments regarding the activity of digestive enzymes (P˃0.05) of fish reared under different temperatures and feeding rates. The length, width, and thickness of intestinal villi were unaffected by different temperatures and feeding rates (P˃0.05). In addition, no variations were found in the total aerobic bacterial count of fish gut from different experimental groups (P˃0.05). At the molecular level, IGF-I and HSP70 coding genes were found to be highly expressed in experimental treatments (P<0.05). To conclude, present results showed that temperatures between 27 to 33 °C are more optimal for Asian seabass, and the different temperatures and feeding rates do not affect digestive enzymes, intestine histology, and gut microbiota after 6 weeks. Further molecular research is needed to unravel the complex impact and mechanisms of feeding rate and different rearing temperature on fish physiology.

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The cotton bollworm, Helicoverpa armigera (Hübner), is a serious pest on a wide range of economic crops in many parts of the world. In this study, digestive proteolytic and amylolytic activities of H. armigera larvae (3^rd to 5^th instars) were evaluated on five main host plants including chickpea (cv Hashem), cowpea (cv Mashhad), soybean (cv 033), navybean (cv Dehghan), and corn (cv SC 704) at 25 ± 1 °C, relative humidity of 65 ± 5% and a photoperiod of 16: 8 (L: D) hours. The results indicated that the highest enzyme activity was in 5^th instar. The highest general protease activity of 3^rd, 4^th and 5^thinstar larvae was found on corn. The larvae fed on corn had the lowest trypsin activity. This leads to hyperproduction of chymotrypsin and elastase-like enzymes to compensate the inhibition of trypsin. The larvae of H. armigera reared on cowpea had the highest level of amylase activity, and the lowest activity was in the larvae fed on corn. The results revealed that among host plants tested, corn was more resistant (unsuitable) to H. armigera. Study on digestive proteolytic and amylolytic activities of H. armigera can be used in identifying the antidigestive or antifeedent compounds, which will help us to design appropriate management programs.

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Effects of feeding Artemianauplii enriched with PHB (0, 0.1, 0.3 and 1 g/L concentration) on the growth performance, body composition, digestive enzyme activity and hindgut bacterial community in the Persian sturgeon hatchlings were investigated. PHB treatment significantly (p≤ 0.05) decreased growth performances of the hatchlings. The PHB also significantly increased the total saturated fatty acids (SFA) and n6, but decreased the total MUFAs, C18:3n3, n3 and n3/n6.  PHB also altered digestive enzyme by significantly decreasing  the total protease, amylase, and lipase. Based on molecular analysis, PHB changed the microbial community in the hindgut of the hatchlings where less dominant bands were observed. Our results show that PHB has negative effects on the Persian sturgeon hatchlings.  Further studies are needed to find out the optimal concentration of PHB to apply in early larval rearing of sturgeon.

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Single or combined effects of medicinal plants, garlic (Allium sativum) and ginger (Zingiber officinale) powders on hepatosomatic index, body composition, digestive enzymes and resistance rate in Sobaity sea bream (Sparidentex hasta) fry were investigated for 8 weeks. Biomar diet (54% protein and 18% lipid) supplemented with 0 (control), 1% garlic, 1% ginger and 1% garlic + 1% ginger in a totally randomized design trial in triplicate. A total of 240 fingerlings of 3.80 ± 0.31 (g) average weight were randomly distributed in 12 tanks. Results showed that there were significant differences in hepatosomatic index among treatments (p>0.05). Significant difference was observed in body composition (p>0.05), as protein and lipid contents in the whole body increased in fish fed with garlic/ginger and ginger groups. Lipase enzyme activity increased significantly in garlic/ginger and ginger groups compared to control group. The highest amylase enzymes activity was observed in ginger group (p<0.05). There was significant difference in survival index to acidity (pH=2), alkalinity (pH=12) and thermal (40°C) stress. In the test of pH and thermal stress, maximum of survival time was obtained in garlic/ginger and ginger groups, respectively (p<0.05).  In general, the fish fed with garlic/ginger powder had the highest body composition, digestive enzymes and resistance to environmental stress.

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The effect of methanolic extracts of Achillea millefolium and Teucrium polium on third instar larvae of Egyptian cotton leafworm, Spodoptera littoralis were investigated. Methanolic plant extracts were mixed with artificial diet and then nutritional indices, glutathione-S transferase, esterase, α-amylase and protease, activity were measured 72h later. Approximate digestibility was increased significantly in larvae fed on the food containing methanolic extract of T. polium but there was not any significant change in insects treated with A. millefolium. T. polium significantly decreased relative growth rate (RGR), relative consumption rate (RCR), efficiency of digested food (ECD) and efficiency of conversion of ingested food (ECI) whereas A. millefolium only decreased RGR and RCR. Feeding on artificial diet containing plant extract decreased α-amylase and protease activities in the midgut of the insect. Furthermore, the effect of methanolic extract of plants on detoxifying enzymes showed that they have no effect on glutathione S-transferase and esterase activities.

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Aims: The present study investigated the effects of different levels using of mealworm (Tenebrio molitor L., TM) on the growth and feed performance, body composition and digestive enzymes of rainbow trout, Oncorhynchus mykiss.
Materials & Methods: Fish (8.58± 0.27 g) in a completely randomized design in 4 treatments and each with 3 replications. Rainbow trout with different levels of 0, 15, 30 and 60% diet (TM0, TM15, TM30 and TM60) (including 50% moisture) of live worm for 30 days. Data were analyzed by one-way (SPSS 17). When p values were significant (P<0.05), means were compared using Duncan's multiple-range test.
Findings: At the end of the experimental, there were significant difference between treatments in growth performance and feed utilization. The results revealed that fish growth parameters and efficiency of nutrient utilization tended to increase with increasing dietary TM levels from 0 to 60%. Feed Conversion Ratio (FCR) was significantly reduced in fish fed the diet with the highest worm level (TM60). The treatments fed TM showed highest protein and lower lipid content compared to fish fed control diet.
The analysis of gastrointestinal enzymes showed that amylase, protease and lipase had a statistically significant difference between the control and other treatments. Protease and amylase activities were found to be significantly higher for fish fed the TM60 diet compared with fish fed TM0 diet.
Conclusion: The results showed that using 60% (TM60) of worm instead of the base diet can improve growth, carcass composition and digestive enzymes.

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The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) is one of the most destructive insect pests, feeding exclusively on wild and cultivated cruciferous species. The attacked plants produce considerable amount of glucosinolates in response to insects’ feeding. Herein, we studied digestive activities of P. xylostella on four different genotypes of family Brassicaceae including two canola cultivars (SLM₀₄₆ and RGS₀₀₃) and two cabbage cultivars (Green-Cornet and Glob-Master). The highest proteolytic and amylolytic activities of P. xylostella were observed on Green-Cornet and the lowest occurred on RGS₀₀₃ and Glob-Master, respectively. The highest activity of α-glucosidase and β-glucosidases were observed on Green-Cornet and SLM₀₄₆ and the lowest was observed on Glob-Master and RGS₀₀₃. The zymogram analysis revealed different isozymes of protease, trypsin-like and α-amylase in the midgut extract of P. xylostella. Activity of the above mentioned isozymes was inhibited in larvae feeding on RGS₀₀₃ and Glob Master as resistant host cultivars. Also, larvae feeding on the resistant genotypes showed more glucosidase activities, indicating possibility of high glycosinolate existence in the resistant genotypes. By these results we can state that host plant property can affect insect digestive physiology through inhibiting digestive enzyme activities. These findings provide insights into the direct effects of host plants on insect physiology which are conducive to change in insect fitness.

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Potato tuberworm, Phthorimaea operculella Zeller (Lepidoptera; Gelechiidae) is a worldwide pest of solanaceous crops. Larvae feed inside galleries in foliage, stems and tubers making chemical control unsuccessful, so other control methods should be applied. In recent years many plants have received genes that encode toxic proteins as a strategy to resist insect pests. In this study, optimal pH and temperature of digestive α-amylase and protease activities of potato tuberworm and the effect of triticale (X Triticosecale wittmack cv. Sanabad), rye (Secale cereale L. cv. Danko) and black nightshade (Solanum nigrum L.) seed proteinaceous extracts against enzymes activities were evaluated using starch 1% and azocasein 2% as a substrate, respectively. The optimum pH of α-amylase and protease activities was found to be highly alkaline. Enzymes inhibition assays showed that amylase activity was significantly affected by extracts from triticale and rye by pH (P= 0.05; maximum effect at pH 9) and influencing of protease activity by extracts mentioned above did not vary by pHs 8-11 and 9-11, respectively. Extracts from black nightshade seed had no effect on enzymes activity. Inhibition manner of various concentrations; 1.5, 0.75, 0.375, 0.187 and 0.093 (mg protein ml^-1) of extracts were dose-dependent. Maximum inhibitory effect occurred at the highest concentration and the minimum was at the lowest concentration. In polyacrylamide gel assay, both enzymes, without inhibitors showed two isozymes, which at highest concentration of extracts, both bands disappeared or their intensity decreased. So, these proteins can be introduced to be encoded in producing resistant potato crops against potato tuberworm.

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The impact of three different fabaceous host plants including cowpea (Vigna unguiculata), chickpea (Cicer arietinum), and mung bean (Vigna radiata) seeds was investigated using biochemical approaches on possible changes of gut proteolytic activity of the cowpea weevil, Callosobruchus maculatus at 30±1˚C and 70±5% RH and a photoperiod of 8:16 (L:D). Results revealed that pH of 4-5 and 9 was optimal for the activity of larval gut proteases using azocasein and hemoglobin as general substrates. Different serine (BApNA, SAAPFpNA, PMSF, TLCK, and TPCK) and cysteine (Z-Arg-Arg- pNA, Z-Phe-Arg-pNA and DTT) specific substrates inhibitors and activator were used as a further proof of the proteolytic profile in the gut of C. maculates. Although combinations of serine and cysteine proteases were observed, the cysteine proteases had the highest rate on the studied hosts. The protease activity, especially cystein protease, was the highest on cowpea, which was supported by hemoglobin (0.156±0.045 U mg^-1), Z-Phe-Arg-pNA (2.85 U mg^-1) substrates and DTT (90.00±0.10%) as an activator. Due to the importance and frequency of cysteine proteinases and their effects on biological and physiological process, it would be better to design pest management programs based on cysteine plant proteinase inhibitors as transgenic plants.