AQUATIC PHYSIOLOGY AND BIOTECHNOLOGY
Year:2020 | Volume:7 | Issue:4|Papers Count:8

Considering that green tiger prawn is important for fisheries and economic in the Persian Gulf region, understanding of the immune system and defense mechanism will lead to improved disease management in this species. In this study, hemocytes of the immune system and hepatopancreas in green tiger shrimp were compared in cold and warm seasons. For this purpose in total, 50 specimens of green tiger shrimp with a mean length of 19± 1cm and a mean weight of 25± 0. 5g were prepared. Then 1mL of hemolymph combined with 1mL of anticoagulant and number and type of hemocytes were studied. Also for histological study, hepatopancreas was sampled from all shrimps and histological sections were prepared in usual methods. The results of this study indicated that in the cold season, the amount of all hemocytes increased. In both seasons, small granular hemocytes, without predominant change, were the highest in number and hyaline hemocytes were the lowest. In addition, a structural study of the hepatopancreas in both seasons showed that this organ was tubular, with the highest number of filamentary cells and the lowest amount of myoepithelial cells. There was a significant difference between absorptivestorage, bag and filamentary cells in both cold and warm seasons. Results of this study are consistent with the reports on other species and may be considered in vaccination cases due to stimulate and excite the immune system, especially during the cold season.

Algae are photosynthetic organisms that have developed protective compounds, such as mycosporine-like amino acids (MAAs), to counteract the optical damage. The purpose of this study was to extract ultraviolet absorbing compounds using different solvent and temperature. Thus, the cyanobacterium Leptolyngbya fragilis and red algae Hypnea musciformis were used to extract ultraviolet absorbing compounds. Different solvents including 100% and 20% methanol, 70% ethanol, distilled water and 100% ethyl acetate were used for MAA extraction at 2 different temperatures of 4° C and 45° C. The cyanobacterium Leptolyngbya fragilis showed the highest amount of UVabsorbing compounds in the 100% ethyl acetate extract at 4° C at a wavelength of 384nm (λ max = 1. 78154), while red algae Hypnea musciformis in the 20% methanol extract at 45° C at a wavelength of 336nm (λ max = 0. 933). Moreover, in the 70% ethanol extract, absorption in the ultraviolet range was almost zero. In general, it can be said that not only the solvent and temperature used to extract ultraviolet adsorbents effect the extraction efficiency, but these indices are not the same in different species.

It has been shown a dietary choline is essential for several crustacean species. However, the choline requirement of narrow-clawed crayfish has not been reported. Therefore, a 12-week feeding trial was conducted to determine the dietary choline requirement of narrow-clawed crayfish. Juvenile crayfish with an average body weight of 13. 8± 0. 9g were intensively stocked in an indoor recirculating aquaculture system consisting of 12 tanks. Four experimental diets were formulated to contain graded levels of dietary choline (0, 0. 2, 0. 4 and 0. 8% choline chloride). Results showed a crayfish fed diet with 0. 0 and 0. 2 % choline produced the highest and the lowest growth indices and enzymes activity including protease and amylase, respectively (P<0. 05). With an increase of choline content of experimental diets (0. 4 and 0. 8 %), no significant improvement was observed regarding growth indices, protease, and amylase activity (P>0. 05). However, no significant differences were observed in survival rate and lipase activity of various experimental groups (P>0. 05). In conclusion, the results indicated that dietary inclusion of 0. 2% choline would improve growth performance and digestive enzymes activity of juvenile narrow-clawed crayfish reared under intensive condition.

In this study, the effect of feeding with different sources of zinc supplements on reproductive indices of male rainbow trout was investigated. Feeding treatments for 16 weeks of research period included: (1) male broodstock fed with diet containing 40mg/kg of inorganic zinc, (2) male broodstock fed with diet containing 40mg/kg of zinc nanoparticles, (3) male broodstock fed with diet containing 40mg/kg of organic zinc and (4) male broodstock fed with zinc-free diet (control). Breeding and fertilization were performed for different treatments using the control of female oocytes. The highest percentage of fertilization eyed eggs and hatched eggs were observed in rainbow trout broodstock fed with diet containing 40mg/kg of inorganic zinc. Sperm concentration, volume, and motility duration, as well as hematocrit percentage, were higher in all treatments supplemented with zinc compared to control. Offspring survival up to 1g of weight was significantly higher in fish fed with diet containing inorganic zinc than other treatments (P<0. 05). The results of this study showed that zinc supplements would play an important role in improving the capability and functional performance of male rainbow trout.

Streptococcosis is the most destructive disease in world aquaculture, and many efforts have been made to curb these bacteria. In this study, the ability of artificial polypeptide hepcidin (EC-hepcidin1) was evaluated to control infection caused by Streptococcus iniae in primary cell culture of rainbow trout (Oncorhynchus mykiss). Antibacterial effects of this polypeptide were examined by disk diffusion and minimum inhibitory concentration (MIC) and minimum bactericidal concentration of EChepcidin1 were measured against Streptococcus iniae. The primary cells were produced from fish fin, and the toxicity range of the peptide was determined for the cells. The primary cells of the rainbow trout were infected with Streptococcus iniae and antimicrobial activity of EC-hepcidin1, as well as viability of the cells, were evaluated. Results showed the MIC and MBC were 75 and 150 μ g/mL, respectively. The level of peptide toxicity on fish cells show that EC-hepcidin1 had low toxicity after 48h in the range of 25 to 400 μ g/mL, and the cells had a viability of 60% to 80%. The viability of the cells was 55% after induction of the bacteria (10: MOI), and the survival rate of cells was increased up to 90% after induction of bacteria (10: MOI) with 150 μ g/mL peptide. In conclusion, the EC-hepcidin1 has shown an antibacterial effect on Streptococcus iniae (in vitro) and the peptide has low toxicity to fish cells. It has increased the vitality of cells infected with Streptococcus iniae. Therefore, complementary clinical research on larval stage, as well as broodstock of rainbow trout, could be suggested in the future. In conclusion, the EC-hepcidin1 has been shown an antibacterial effect on Streptococcus and low toxicity to fish cells. It has increased the vitality of cells infected with Streptococcus. Therefore, complementary clinical research on larval stage and broodstock of fish could be suggested.

Based on IUCN criteria, sterlet sturgeon (Acipenser ruthenus) has been shown as vulnerable species. Its male sex is inadequate or absent in the most of propagation and rehabilitation centers of Iran. The aim of this study is the induction of gynogenesis to produce male sterlet sturgeon using heterologous sperm. DNA of heterologous sperm from Siberian sturgeon (Acipenser baerii) was damaged successfully by UV irradiation with 473 µ w/cm2 intensity and 90 seconds duration. The irradiated sperm mixed with sterlet sturgeon eggs to induce gynogenetic progenies of sterlet sturgeon. For this purpose, 15 minutes after activation, the fertilized eggs exposed to 34º C heat shock for 2 minutes. Gynogenetic progenies were verified by microsatellite markers (AFU68 and AFUG195) as only maternal heritability. Histological observations of preliminary gonads of gynogenetic progenies were carried out by biopsy method at 17 months-age. Results showed that gynogenetic progenies consisted of 76. 6% female and 23. 3% male. Regarding to female heterogametic sex determination system in sterlet sturgeon, this study showed that both female and male as pure could be induced by inactivated heterologous sperm and gynogenesis.

Probiotic strains of Lactobacillus can be used as food preservatives. The purpose of this study was to investigate the use of Lactobacillus delbrueckii subsp. bulgaricus (PTCC1737), L. reuteri (1655 PTCC), L. brevis CD0817 and the combination of Lactobacillus on microbial quality of rainbow trout fillet in refrigeration and freezing temperature. Treatments were immersing fillets in suspensions of L. reuteri, L. brevis, L. delbrueckii and the combination of Lactobacillus. The control treatments consisted of additive-free fillet and fillet processed with 2% solution of lactic acid. The control and test treatments were refrigerated (five days) and frozen (six months). Staphylococcus aureus and Escherichia coli were not observed in test and control treatments. L. delbrueckii subsp. bulgaricus was not observed in frozen storage. The number of Lactobacillus showed a decrease in combination treatments during freezing (1. 34logCFU/g). In L. brevis, total saturated and unsaturated fatty acids were 23. 91% and 77%, respectively. In L. reuteri, total saturated and unsaturated fatty acids were 27. 12% and 72. 88%, respectively (P<0. 05). Significant increase in ratio of unsaturated to saturated fatty acids in L. brevis compared to L. reuteri and no significant difference in L. brevis number during storage at freezing temperature caused that L. brevis is recommended for preserving farmed rainbow trout fillet under refrigeration and at freezing temperatures.

A number of management and nutritional strategies are used to induce reproductive maturation and early puberty in sturgeons. Hormonal implants can have a promoting effect on sexual maturation and ovulation in sturgeons, but the surgical procedure for implantation leaves an external injury on the skin leading to further side effects on fish body. In this study, 20 three-year-old great sturgeon (6. 9± 0. 2kg) were maintained in concrete tanks for 168 days and implanted by cutting a small incision on fish abdomen. Implantation capsules contained 0, 3, 6 and 12mg 17-β estradiol (E2) per kg of body weight of fish and administrated each 45 days. The wound index and weight change trend of the implanted fish was evaluated every three weeks after implantation. Results showed that there were no significant differences between implanted fish and control fish in terms of wound healing index and after 3 weeks relative improvement was achieved. Weight change in the first, second and third biometry was not significantly different (P>0. 05). However, there was a significant difference in the fourth biometry between E2 implanted fish and control in terms of weight and growth performance indices (weight gain, specific growth rate and condition factor) (P<0. 05), but there were no significant differences between fish that was implanted with different levels of E2 (P>0. 05). These findings suggest that E2 implantation alters physiological pathways by partitioning energy from muscle growth toward support of maturation-related processes. This study showed that E2 can influence fish weight, but the wound healing process was almost unchanged and independent.