فصلنامه فیزیولوژی و بیوتکنولوژی آبزیان
سال سیزدهم شماره 1 (بهار 1404)

Polyethylene is one of the most abundant microparticles that can be found everywhere. This research aims to investigate the effects of high-density polyethylene (HDPE) microplastics on the growth indices and food conversion ratio of fry stellate sturgeon, Acipenser stellatus. Twelve tanks, in each tank 10 stellate sturgeon fry were stocked with an average weight of 18-20g. For 30 days, to evaluate the effects of adding microplastics to the diet (encapsulated), fry were divided into three treatments and a control group. The biometric characteristics of the fish were performed at the end of the course and growth indices including final weight and length, specific growth rate (SGR), percent body weight gain (BWI), condition factor (CF), average daily growth (ADG), feed conversion ratio (FCR) and survival rate (SR) were assayed. According to the results of present research, high-density polyethylene microplastics caused a decrease in appetite and desire for diet. In addition, some adverse effects were observed on growth parameters including the average final weight, the percentage of weight gain, daily growth, specific growth rate and food conversion ratio with a significant difference compared to the control (P<0.05). The presence of microplastics in diet caused false satiety in the fish, leading to not eating with an increase in the doses of microplastics in the diet. The presence of microplastics in diet with doses of 1, 10 and 100 mg/kg of diet reduced the growth of fish and reduced diet digestion and absorption of food and had adverse effects on juvenile fish such as weight loss and lack of proper growth.

The study of reproductive activity mechanisms in fishes, which makes it possible to regulate sexual periods, is important and is increasingly directed towards assisted reproduction technologies. In this study, 90 breeding female rohu fish (Labeo rohita) with an average weight of 3±0.41kg were used and the effect of two doses of pituitary gland extract were investigated on fish spawning performance, the level of sex steroids, the expression of genes related to steroidogenesis and ovary histology. This study showed that the highest spawning success was observed with a pituitary dose of 5mg/kg, the incubation period of the female decreased with increasing dose and the fertility of this treatment was significantly higher than other groups. Treatment with pituitary gland extract in both doses caused a significant increase in gonadosomatic index, percentage of fertilization, hatching and survival of larvae compared to the control and sham groups. At 12 hours after injection, pituitary treatments showed a significant increase in the levels of steroid hormones and the expression of related genes in the ovarian tissue compared to the control and sham treatments. Microscopic examinations of ovarian tissue follicles showed a steroidogenic change in the presence of asynchronous ovaries in this species, in which oocyte maturation was accelerated by injection of pituitary extract, especially a dose of 5mg/kg. As a result, the findings showed that rohu females treated with pituitary extract did ovulate and the extract of the pituitary has synergistic effects on hormonal factors and increases the fertility and survival of the larvae of rohu.

In the present study, the effects of adaptation to formulated diet using live food were evaluated on growth performance and amino acid profile of beluga (Huso huso) larvae. The beluga sturgeon larvae with an initial weight of 0.44±0.01g were randomly distributed into 12 fiberglass tanks. The adaptation process was carried out by live food organisms, including frozen chironomid larvae (CH), frozen Artemia biomass (A), and a combination of chironomid and Artemia (M) during 42 days. Also, fish in group D received the formulated diet throughout the trial. The live foods were decreased by 16.6% every six days and added to the formulated diet. At the end of trial, growth index, survival and amino acids profile of larvae were evaluated. The results of this study revealed that final weight and weight gain were significantly higher in D and CH groups than others (P<0.05). The highest survival rates were observed in the groups CH (98.33%) and M (95%) (P<0.05). Levels of leucine and methionine as two essential amino acids were significantly higher in CH, in comparison to other treatments (P<0.05). Furthermore, despite the insignificant differences, the highest threonine content among treatments fed by live foods and the lowest composition of total essential amino acids were shown in the CH group (P>0.05). Regarding the achieved results, it is recommended to use the chironomid larvae for the adaptation of beluga larvae to the formulated diet due to its positive effects on growth and amino acid content.

Mrigal (Cirrhinus cirrhosus) is one of the three most important species of Indian carp in tropical fish breeding system in the world. In order to diversify the tropical fish aquaculture system, Indian carp species were imported to Iran in 2008. In order to compare the indicators, 40 brooder females with mean weight and total length of 3212.69±5.31 grams and 635.38±3.32 cm were investigated. The propagation temperature was recorded 28-28.5°C. The synthetic ovulation induction hormones OvaPAS (made in Iran) and Ovaprim and pituitary extract were used to stimulate spawning. Physiological serum was injected to the control group. The injection was done intra-muscularly and in one step. Reproduction indices were investigated in different groups. The results showed that the percentage of spawning success in mentioned groups was recorded as 100, 90 and 80%, respectively, and in the control group, the spawners did not respond to the injection. Latency period was calculated to be 6.5-8 hours long, which the shortest time was in the OvaPAS hormone group. Mrigal fish had non-adherent eggs. The number of eggs per gram and per mL, and the size of extracted eggs, fertilized eggs and the hatched eggs did not show significant difference between the groups. The average fertilization percentage was 91.2±5.33, egg hatching percentage was 80.66±1.7, and larval survival percentage was 70.81±2.83. The hatching time of larvae was 16 hours and 20 minutes after fertilization. The size of newly hatched larvae was 4.55±0.06 mm. Reproduction data showed that OvaPAS hormone can be a good substitute for imported hormones such as ovaprim and pituitary extract. The results obtained in determining the breeding biotechnique of mrigal, can be used in the development of breeding and farming of this species and introducing it to the country's aquaculture system.

Ultraviolet rays of the sun have a very negative and dangerous effect on human skin and cause skin cancer. Conventional sunscreens cause problems in some people due to the presence of chemical compounds, which has increased the demand for sunscreens containing natural ingredients. In this direction and in order to obtain safe natural sunscreen compounds, two polymers, chitosan and melanin, were used as ultraviolet (UV) filters in sunscreen creams. First, chitosan was extracted from shrimp waste and melanin from squid ink and synthesized in the form of chitosan-melanin complex. In the following, the ultraviolet ray absorbing activity of the resulting complex was investigated by spectroscopic method and using a spectrophotometric device. Measuring the amount of SPF (in wavelength of 290 to 320 nm) showed that this composition has SPF 22.6. From the results of this research, it can be concluded that the chitosan-melanin complex can be considered as a suitable alternative for chemical compounds in sunscreens and other cosmetic-sanitary products due to its biological function and non-toxicity.

Despite the high potential that aquatic plants can have in the field of biotechnology, few studies have been focused on this area. This study has investigated the antibacterial and antioxidant effects of the ethanolic extract obtained from the seeds of the wetland plant lotus (Nelumbo nucifera). The antioxidant activity of this extract was evaluated using tests including iron reduction potential, phenol content and DPPH radical scavenging activity. Antibacterial activity was evaluated using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests. The results indicated high antioxidant effects of the extract (EC50: 226.8µg/mL) and increased iron reduction potential and phenol content (192.93mg of gallic acid per g of extract). Antibacterial activity against Escherichia coli and Staphylococcus aureus was observed (at the concentrations of 50µg/mL) in which the increase in the concentration of the extract led to the increase of its antibacterial effects significantly (P<0.05). However, despite the halo formation for the antibiotic disc, no halo was observed for the disc containing the concentrations of 200, 400 and 800µg/mL extract. In this study, also the flavonoid content of the extract was analyzed and its level obtained 50.3mg of quercetin per g of extract. These findings showed that the ethanolic extract of lotus seeds not only has antioxidant properties, but the use of appropriate concentrations can reduce the growth of bacteria, and open a window for future studies on the extract of this plant for use in traditional medicine and pharmaceutical industries.