نشریه علوم و فنون شیلات
سال یازدهم شماره 4 (پیاپی 40، پاییز 1401)

The aim of this study is to investigate the changes in fatty acid composition in Nannochloropsis oculata microalgae under physicochemical stresses (light intensity and salinity). In this regard, the growth rate, the amount of chlorophyll and carotenoid, the approximate analysis and the profile of fatty acid changes of marine microalgae N. oculata under two mutual stresses of salinity (15, 25 and 40 g/l) and light intensity (Lux 1500 and Lux 10000) which at the end of the phase Logarithms were applied are examined. The results showed that according to the application of stresses after the completion of growth, there was no significant difference in the growth rate in different treatments (P>0.05). Also, despite the fact that the highest amount of lipid was obtained under the salinity treatment of 40 g/l and the light intensity of Lux 1500, the highest amount of saturated fatty acids (SFA) was obtained under the treatment of salinity of 15 g/l and the light intensity of 10000 Lux, the highest amount of monounsaturated fatty acids (MUFA) under 25 g/l treatment and 10000 Lux light intensity and the highest amount of polyunsaturated fatty acids (PUFA) under 15 g/l treatment and 10000 Lux light intensity were obtained after 4 days of stress. Considering the effectiveness of fatty acid compounds in N. oculata microalgae, by controlling the cultivation conditions, the maximum amount of desired fatty acids can be achieved in accordance with the desired goals.

The present study was conducted with the aim of protein isolate production from the muscle of grass carp (Ctenopharyngodon idella) and investigation of the effect of extraction pH on different properties of isolated protein. Proteins were produced by pH-shift method in two treatments including dissolution in alkaline pH (11.5), and acidic pH (3), and then evaluated in terms of nutritional value, functional properties, and structural changes. According to the results, the yield of protein production was significantly higher in alkaline conditions than in acidic conditions. The evaluation of emulsifying and foaming capacity and water absorption capacity showed that the protein obtained from alkaline pH was better than acidic treatment. Also, the extracted proteins contained all essential amino acids within the recommended limit for daily consumption of adults. The evaluation of color indices showed that the protein obtained from acidic pH had a brighter and whiter color than alkaline pH. The images obtained from the scanning electron microscope and the FTIR spectra of samples showed that the pH-shift method did not lead to extensive destruction of the protein structure and both protein isolates had all the absorption peaks related to the main bonds of the proteins structure. In general, it can be concluded that the pH-shift method is an efficient method for extracting high quality protein from grass carp tissue, and different alkaline and acidic conditions lead to the production of proteins with different characteristics that can be used based on the application that is intended for the final product.

The aim of the current study was the evaluation of stepwise recovery of fucoidan extracted from seaweed Nizamuddinia zanardinii and the assessment of relationship between sulfate content and molecular weight with its antioxidant activity. After the removal of pigments and low molecular weight compounds, fucoidan extracted with water was precipitated using different concentrations of ethanol at three levels (30, 50 and 70%). Three fractions of Fuc30, Fuc50 and Fuc70 showed molecular weights of 731.62, 655.76 and 10.41 × 103 g/mol, respectively. The content of sulfate esters in the obtained fractions were measured between 6.49-25.03%. The color evaluation of produced fucoidans by a digital chroma meter indicated the highest lightness index for Fuc50 fraction. Antioxidant results were varying in DPPH radical (43.93-89.40%) and ABTS radical (25.05-96.10%) scavenging activities as well as Fe3+ reducing power (Abs of 0.142-0.259). Overall, the findings of the present study indicated that stepwise precipitation of fucoidan from N. zanardinii leads to production of fractions with different chemical and molecular weight characteristics and antioxidant activities. Besides, although all isolated fucoidan fractions are introduced as potent antioxidant compounds, polymers possessing lower molecular weight and greater sulfate content exert higher antioxidant activities.

Due to widespread use of nanoparticles in various fields and the possibility of entering these nanoparticles into aquatic ecosystems, it is necessary to study the effects of these nanoparticles on surrounding environment. Artemia salina nauplii as a suitable biological model in ecotoxicology were exposed to different concentrations of 0.0001, 0.001, 0.005, 0.01 and 0.1 ppm mercury ions separately and simultaneously with a constant concentration of 0.1 ppm and 1 ppm titanium dioxide nanoparticles. The mortality rate of Artemia after 48 hours and the effects of these contaminants on fatty acid profile of Artemia were investigated. Artemia mortality in co-exposure treatment showed a dual effect. The mortality in the simultaneous exposure with constant concentration of 0.1ppm titanium dioxide increased compared with separate treatment of mercury. The mortality in simultaneous treatment with constant concentration of 1ppm titanium dioxide decreased compared with the separate treatment of mercury and the effect of mercury toxicity was reduced. Also, a decrease in saturated fatty acids was observed in the simultaneous exposure of mercury and titanium dioxide nanoparticles with a constant concentration of 1ppm compared with the separate treatment of mercury. The amount of monounsaturated and polyunsaturated fatty acids in the simultaneous exposure with constant concentration of 1ppm titanium dioxide was equal to control and increased compared with separate treatment of mercury. Present findings indicate the necessity of paying more attention to the potential interactions of pollutants in aquatic ecosystems and the effects of these interactions on the bioavailability and toxicity of pollutants regarding their concentration.

In this study, the effects of powder and leaf extract of Moringa oleifera on hemolymph factors of Litopenaeus vannamei in response to salinity stress were evaluated. After 8 weeks of feeding with powder (25, 50 and 100g / kg) and extract (0.25, 0.5 and 0.1 g/kg) leaves of Moringa and control treatment without Moringa, all treatments were exposed to short-term salinity stress (5 and 55 ppt). There was a statistically significant difference in total and differential count of homocytes in different dietary treatments in all three normal conditions and under salinity stress of 5 and 55 pp (p<0.05). Under normal conditions and high salinity, shrimps fed with Moringa leaf extract showed higher number of homocytes than other treatments. In stress-free conditions, the number of semi-granular cells in powder and extract treatments was higher than the control group. At 5 ppt, Moringa powder treatments had higher semi-granular and at 55 ppt salinity, the leaf powder group (100 g/kg) and the leaf extract (0.25 g/kg) showed the highest values, respectively. Overall, the results of this study showed the positive effects of using Moringa leaf powder and extract on innate immune system function and exposure to salinity stress in shrimp

We studied the abundance, biomass and diet of Platevindex aff. tigrinus in the Hara Biosphere Reserve in the Persian Gulf. The seasonal sampling (two seasons) was conducted in winter 2018 and summer 2019. Samples were collected from six sites in Qeshm Island and Bandar Khamir. To determine the effect of environmental parameters on distribution of the species, temperature, salinity, pH, sediment grain size, total nitrogen and organic carbon were measured at each site. The results showed that the abundance of P. tigrinus was significantly higher in the winter compare to summer season. However, there was no significant difference in the biomass of the species between seasons. The PCA results showed that salinity, temperature and sediment grain size contributed to the separation of between seasons. The pH and total nitrogen followed the similar pattern in different sites and seasons. Although, temperature, salinity, sediment grain size, and organic carbon showed difference between seasons. The results showed that salinity and temperature were two important parameters in the distribution of the species during both seasons. The species was mainly feeding on the microphytobenthos during winter and on the sediment organic matter during summer.

The accumulation of nanoparticles in the environment and aquatic ecosystems due to their wide application in industries, agriculture, medicine and pharmaceuticals has caused an increasing concern about the environment and increasing exposure to nanoparticles in ecosystems and humans. Iron oxide nanoparticles easily enter the bloodstream, accumulate in different tissues and cause damage to these tissues. Therefore, in this research, changes in the intestinal tissue of gray mullet fish (M. cephalus) and tissue accumulation in oral exposure to iron oxide nanoparticles were investigated. 110 pieces of young gray mullet after 2 weeks of adaptation were treated in four-time groups of 1, 7, 14 and 28 days, and one group was considered as a control. The mullet fish received iron oxide nanoparticles twice a day at the rate of 15 mg/kg attached to the food. The results showed that although the amount of tissue iron increased significantly only in the 28-day group, the consumption of iron oxide nanoparticles in almost all groups increases the tissue accumulation of iron in the intestine. The intestinal histological study showed changes such as the increase in the number and size of goblet cells, destruction of microvilli structure, bleeding and degrees of necrosis, and the intensity and extent of the changes in the intestinal tissue increased with increasing exposure time. These observations showed that the consumption of iron oxide nanoparticles has a negative effect on intestinal function and causes iron accumulation and the occurrence of time-dependent injuries.