Cloning and expression analysis of hif-2? gene in cobia (Rachycentron canadum) under hypoxia stress

Hypoxia-inducible factor 2? (hif-2?) is a critical regulator of hypoxia response and plays a vital role in hypoxia stress in the organism. To understand the regulatory role of hif-2? in response to hypoxia stress in juvenile cobia (Rachycentron canadum), hif-2? was cloned using Rapid Amplification of cDNA Ends (RACE) technology. The full length of hif-2? is 4021 bp, with 2634 bp open reading frame (ORF), 5' non-coding region (5'UTR), 285 bp, 3' non-coding region (3'-UTR), 1102 bp, and encoding 877 amino acids. The encoded protein contains the HLH (Helix-loop-helix) domain (amino acids 20-75), the PAS (PER-ARNT-SIM) domain (amino acids 91-157 and 237-303), and the PAC (PAS Associated C-terminal) domain (amino acids 309-352). The results of phylogenetic tree analysis showed that hif-2? in cobia clustered with hif-2? in Echeneis naucrates and were closely related. Real-time fluorescence quantitative PCR (qRT-PCR) was used to analyze the expression of hif-2? in nine different tissues of cobia and the expression of hif-2? mRNA in the liver and gill under hypoxia stress. The results suggested that the hif-2? was expressed in all tissues of the cobia, with higher expression in the liver and gill. Under hypoxia stress, the expression of the hif-2? in the liver and gill was tissue-specific. In liver tissues, hif-2? expression was significantly higher than that of the control at 14 and 28 days. In gill tissues, hif-2? expression decreased at 7, 14, and 28 days and was lowest at 14 day. The results suggest that hif-2? plays a vital role in hypoxic stress in cobia and may provide basic information for studying the molecular genetic mechanism of hypoxia tolerance in cobia

Do lunar cycles affect molting of mud crabs Scylla olivacea reared in a closed recirculation system?

Mud crabs grow through molting, a process during which they become highly vulnerable to predation. This makes molting management crucial in crab aquaculture, including practices utilizing crab boxes. Environmental factors such as lunar cycles influence molting in natural habitats. However, research is limited to molting in controlled environments with closed recirculation systems that offer environmental stability, water resource efficiency, and precise feed management. This study investigated the effects of the lunar phase on the molting stages of mud crabs reared in a closed recirculation system. A total of 40 Scylla olivacea specimens were reared for three months to observe molting patterns across eight lunar phases: new moon (NM), waxing crescent (WXC), first quarter (FQ), waxing gibbous (WXG), full moon (FM), waning gibbous (WG), last quarter (LQ), and waning crescent (WNC). Overall, 77.5% of crabs were molted during the study period. No molting occurred during the WXC, WXG, WNC, and WG phases. Molting prevalence was higher during FM (22.5±2.5%) and NM (20±2.9%) phases compared to FQ (17.5±1.4%) and LQ (17.5±1.4%). Post-molting weight gain was 31.7±5.9 (NM), 32.2±4.4 (FQ), 31.2±5.9 (FM), and 27±3.2 (LQ), while carapace width (CW) increased by 9.0±1.6 (NM), 8.5±1.3 (FQ), 9.5±2.4 (FM), and 8.2±1.77 mm (LQ), respectively. The results showed molting frequency and growth did not differ significantly between lunar phases NM, FQ, FM and LQ. In closed recirculation aquaculture systems where natural fluctuations such as tidal changes were eliminated, molting remained associated with the lunar cycle, suggesting the persistence of instincts and circadian rhythms in mud crabs in controlled environments. This study provides valuable insights for mud crab farmers, particularly for optimizing productivity by understanding the influence of lunar phases on molting in closed recirculation systems

Quantitative evaluation of metabolism and body mass in yolk-sac larvae of Japanese whiting, Sillago japonica

Understanding the early developmental physiology of marine fish larvae is crucial for elucidating their ecological adaptability and survival strategies. This study investigates the metabolic changes in Japanese whiting (Sillago japonica) yolk-sac larvae over the first four days post-hatching. Larvae were incubated under controlled laboratory conditions, and daily measurements of oxygen consumption rate (QO?), wet and dry body mass, and water content were conducted using in vitro pooled samples. The results reveal a gradual increase in absolute oxygen consumption and body mass, accompanied by a consistent wet-to-dry mass ratio, except for a transient increase on the third day. Although individual measurements were not feasible due to the minute size of the larvae, the internal consistency of pooled data supports the observed physiological trends. These findings offer novel insights into the physiological trajectories of Japanese whiting Yolk-sac larvae and provide a foundational dataset for future research on yolk-sac larval energetics and environmental sensitivity in coastal marine fishes

Evaluate the current status of fish species in the Tigris River between Al-Qurna and Al-Azayer cities in Southeastern Iraq

The Tigris River suffers from many problems in water quality due to human interference, climate change, and different discharges. This study aimed to investigate changes in fish assemblage composition and population structure in the Tigris River southeast of Iraq from August 2022 to July 2023. A total of 4343 individuals and 25 species were collected, including four marine species. The total count of native species was 12, exhibiting variation from eight species in June to eleven in August, November, December, February, April, and May. Alien species emerged during nine of the study months, ranging from five species in April to eleven species in June and July. Marine species were present in varying numbers, ranging from two species in December to four species in September, October, January, April, May, and June. Significant differences were found in the number of species among the study stations during different months. The fish species were categorized into three groups: common, seasonal, and occasional species, representing percentages of 72, 24, and 4%, respectively. Among them, Oreochromis aureus, Carassius gibelio, and Panaliza abu constituted 18.35, 16.97, and 10.82% of the total, contributing to 46.143% of the overall species count according to the dominance index (D3). Based on the results, factors such as dissolved oxygen, turbidity, and water salinity had the most positive effect on fish population and biodiversity, and nitrate, phosphate, and total dissolved solids had the most negative effect. In conclusion, the fish assemblage of the Tigris River was relatively similar to that of the downstream Euphrates River, but varied in terms of species number, with the appearance of marine species in this study

Induced breeding and seed production of seurukan fish (Osteochilus jeruk) using synthetic reproductive hormones

The commercial aquaculture of seurukan fish (Osteochilus jeruk) is common in Indonesia; however, seed availability from the wild is limited. Therefore, induced breeding technology in seurukan fish using synthetic reproductive hormones is crucial. This study evaluated the efficacy of five different types of synthetic reproductive hormones and their corresponding doses on the reproductive performance of seurukan fish in captivity. The methodology consisted of two experiments; first, four types of synthetic reproductive hormones were tested: ovaprim, ovaspec, human chorionic gonadotropin (HCG), and ovalumon. Second, several doses of ovaprim hormone were tested with doses of 0.25, 0.50, 0.75, and 1.0 ml kg-1 body weight. The results showed that ovaprim, ovaspec, and HCG successfully induced ovulation and spawning in seurukan fish. The hormones significantly affected the latency period, number of eggs released, fertilization, and survival rates (P<0.05), but did not significantly affect the hatching rate and survival of larvae (P>0.05). Ovaprim produced better egg quality compared to ovaspec and HCG. In the second experiment, the results showed a significant difference in the latency period and egg size (P<0.05) of fish treated with varying doses of ovaprim hormone. The hormone doses did not significantly affect the number of eggs, hatching rate, fertilization rate, survival rate, or larval survival (P > 0.05). The dose of 0.5 ml kg-1 BW of ovaprim produced the best results. Therefore, a dose of 0.5 ml kg-1 BW was recommended as an effective dose for induced spawning and seed production of seurukan fish

Population dynamics of horse mussels Modiolus modulaides (Röding, 1798) in Kendari Bay, Southeast Sulawesi, Indonesia

Horse mussels are bivalves found in Kendari Bay and are frequently consumed by the people in the surrounding coastal communities. The population dynamic of this mussel species in Kendari Bay is not yet fully understood. This study aims to determine the size structure, growth, mortality, and exploitation rate of horse mussels in Kendari Bay. This research was carried out in Kendari Bay on the outskirts of Southeast Sulawesi, Indonesia, from January to December 2019. Horse mussel samples of all different sizes were randomly collected from different points of the area of the mussel habitat. The collected samples were counted in total, and their shell length was measured using a caliper with an accuracy of 0.05 mm. The size, growth, mortality, and exploitation rate data were analyzed using the Bhattacharya method, inverse von Bertalanffy, Pauly empirical, and length-converted catch curve accommodated in the FiSAT II. The results showed that the horse mussels comprised two dominant size groups, with one dominating most of the months. The asymptotic length (L?) of the mussels was 9.7 cm, with a growth coefficient (K) of 1.1 yr-1. Moreover, the growth performance index of the mussels was (Ø)'=2.01 yr-1, and the maximum age (Tmax) was 2.73 years. The generated inverse von Bertalanffy equation for the horse mussels was Lt = 9.7-(9.7-0.025)e-1.1t. The natural mortality (M), fishing mortality (F), and total mortality (Z) of the horse mussels were 2.73 yr-1, 1.17 yr-1, and 3.90 yr-1, respectively. The horse mussels in Kendari Bay were well within the underexploited category, with an exploitation rate of 0.30

Green synthesis of silver nanoparticles using Ascophyllum nodosum

Nanotechnology has emerged as a sustainable alternative for producing functional nanomaterials with unique properties. This study aims to develop and optimize a green synthesis protocol for producing silver nanoparticles using the brown algae Ascophyllum nodosum and to characterize their structural properties. Algal samples of A. nodosum were collected from their natural coastal habitat, thoroughly washed with distilled water to remove debris, air-dried under ambient conditions, mechanically ground into a fine powder, and subjected to aqueous extraction to obtain bioactive compounds essential for the synthesis of silver nanoparticles. Characterisation confirmed successful synthesis: UV-Vis spectroscopy showed a surface-plasmon-resonance peak at 420 nm; AFM and FESEM revealed spherical particles 10–30 nm; EDS indicated ? 85 % elemental silver with uniform distribution; FTIR identified O–H (3280 cm?¹), C = O (1635 cm?¹) and N–H (1540 cm?¹) groups capping the nanoparticle surface. GC-MS profiling of the algal extract detected more than fifty reducing/stabilising molecules, including fatty acids and phenolics. Antioxidant activity (DPPH assay) increases dose-dependently from 60.15% at 0.12 mg mL?¹ to 72.99% at 1 mg mL?¹, highlighting enhanced radical scavenging at higher nanoparticle concentrations. These findings demonstrate the efficiency of A. nodosum as a sustainable bio-factory for producing monodisperse, bio-capped silver nanoparticles with significant antioxidant capacity and broad prospects for medical, cosmetic, and industrial applications

Growth performance and nutrient utilization of glass catfish (Kryptopterus lais) larvae in response to varying dietary protein levels

This study evaluated the effects of varying dietary protein levels (35, 40, 45, and 50%) on growth, feed utilization, and body composition in Glass catfish, Kryptopterus lais, larvae over 30 days. Larvae with an initial average weight of 0.15±0.01 g were distributed into 12 aquaria at a density of 50 individuals per tank. Fish were fed four times daily to apparent satiation. The results indicated that weight gain (WG) increased with dietary protein levels up to 40%, beyond which WG declined. Similarly, the feed conversion ratio was lowest in fish fed the 40% protein diet. The protein efficiency ratio was significantly higher in K. lais larvae fed the 40% protein diet compared to those fed diets containing 45 and 50% protein. Body composition analysis revealed that larvae fed the 40% protein diet exhibited the highest protein content, while those fed the 35% protein diet had a significantly elevated lipid content. Broken-line regression analysis, based on the specific growth rate, estimated the optimal dietary protein requirement for maximal growth performance to be 42.89%. These findings provide a quantitative basis for formulating diets that effectively meet the protein requirements of K. lais larvae

Automated aquatic biodiversity monitoring using deep learning on the Tigris River: Species identification and ecosystem assessment

Aquatic ecosystems play a crucial role in biodiversity and ecological stability but are increasingly threatened by climate change, pollution, habitat degradation, and invasive species. Traditional monitoring methods are labor-intensive, costly, and limited in spatial and temporal coverage. This study integrates deep learning techniques with biodiversity monitoring to enhance species identification, abundance estimation, and ecosystem assessment in freshwater environments. Focusing on the Tigris River, Iraq, we developed convolutional neural network (CNN) - based models to automate species detection and classification from underwater imagery. Our multi-tiered data collection approach, which includes direct field sampling, remote sensing, and citizen science, yielded a dataset of over 8,000 images across six camera locations. The Faster R-CNN model achieved a mean average precision (mAP) of 88% for fish identification, while U-Net segmentation models demonstrated 99% accuracy in organism detection, significantly outperforming traditional methods. The application of optimized deep learning models significantly enhanced the accuracy and efficiency of aquatic biodiversity monitoring. The Faster R-CNN model, after hyperparameter optimization and transfer learning, achieved an accuracy of 88% in species identification, outperforming baseline models that averaged around 75%. The optimization techniques, particularly data augmentation and early stopping, improved the model’s robustness to environmental variations, such as high turbidity and poor lighting conditions. Unlike traditional methods that rely on expert identification, the deep learning model provided automated, scalable, and real-time monitoring capabilities, reducing the need for labor-intensive field surveys. Additionally, the model demonstrated higher precision in detecting species that are typically misclassified in traditional statistical models, thereby offering a more reliable approach to biodiversity conservation and ecological assessments. These results underscore the potential of deep learning to provide scalable, automated, and highly accurate biodiversity assessments. Our findings demonstrate how artificial intelligence can revolutionize ecological conservation, offering a cost-effective and reliable solution for biodiversity monitoring. The study also emphasizes the importance of interdisciplinary approaches in addressing global biodiversity loss and advancing conservation strategies

Biodiversity of macro-benthic and physicochemical quality (IRWQIsc) and toxic (IRWQIst) indices in the rivers of the Maharloo wetland basin

The Maharloo Wetland in the Fars Province has a great ecosystem and socio-economic importance for the city of Shiraz. The two rivers, Chenarrahdar and Khoshk River, as well as some springs in this basin, are the main suppliers of water to the wetland. These two rivers originate upstream of Shiraz city and, after passing through Shiraz city and receiving various wastewaters and pollutants, reach the Maharloo Wetland in the southeast of Shiraz city. This study was conducted to investigate the biodiversity of benthic organisms and the physicochemical and toxicity status of the rivers in the Maharloo watershed. Water and benthic organisms were sampled from 12 stations from the two rivers and springs, and the biological indices of benthic organisms, water quality, and water toxicity were evaluated in four seasons. According to the results, in all four sampling seasons, the water quality index (IRWQIsc) and toxicity index (IRWQIst) were suitable at the upstream stations and before the rivers enter the city of Shiraz, due to the entry of various types of domestic, agricultural, industrial and surface sewage of the city, these two indices are severely reduced and reach a severely polluted and critical ecosystem eutrophication condition. For studies of the benthic fauna of the rivers of the Maharloo watershed, sampling was performed at the stations. Then the benthic biodiversity indices, including HFBI, BMWP, ASPT, and Shannon-Wiener, were examined and evaluated. Based on the results of the biological indices, the biological communities in the rivers are completely different before entering the city of Shiraz and after that, and in parts of both rivers in the downstream stations, anaerobic conditions are created, and the possibility of life for benthic fauna is lost. The dominant benthic communities at the sampling stations before entering Shiraz city were mainly from the families Caenidae, Tipulidae, Baetidae, Gammaridae, Hydropsychidae, and Dytiscidae, but at the downstream stations within Shiraz city and the entrance to Maharloo Wetland, the dominant benthic communities were mainly from the families Naididae, Culicidae, Staphylinidae, Erpobdellidae, and Tubificidae. According to the results, the need to develop a comprehensive quality management program for basin entering the two rivers of Shiraz, Chenarrahdar and Khoshk, is essential to improve the ecosystem of the rivers in the basin and the Maharloo Wetland