International Journal of Aquatic Biology

Dietary supplementation of Lactobacillus sp. and garlic extract on growth performance, digestive enzyme, and disease resistance of the whiteleg shrimp, Litopenaeus vannamei

Tu Thi Cam Phan — 2026-04-10

In the present study, the effects of a probiotic (Lactobacillus sp.), a prebiotic (1% garlic extract), and their combination were evaluated in whiteleg shrimp (Litopenaeus vannamei) using a feeding supplement. The shrimp in each tank were fed the following experimental diets for 56 days: the control diet (commercial feed) and experimental diets supplemented with Lactobacillus sp. (diet 1), garlic extract (diet 2), and Lactobacillus sp. + garlic extract (diet 3). The results showed that shrimp fed diets 1, 2, and 3 had higher growth indices, including weight gain, specific growth rate, and daily weight gain. The supplemented diet 3 recorded the lowest FCR and the highest shrimp survival rate after 56 days of feeding. In addition, the activities of amylase, protease, and aminopeptidase were significantly increased in shrimp fed the experimental diet relative to the control diet from day 28 until the end of the experiment. The overall bacterial count of Vibrio was significantly lower in diets 1, 2, and 3 than in the control diet at day 56. Moreover, shrimp fed diet 3 had the lowest cumulative mortality after 96 h post-challenge with Vibrio parahaemolyticus. Overall, the findings demonstrated that the addition of synbiotics containing 10⁸ CFU/kg Lactobacillus sp. and 1% garlic extract could promote growth, survival, and disease resistance in whiteleg shrimp reared under tank conditions.

A survey of freshwater Tardigrada of the Mississippi River and U.S. driftless area

Jacob Loeffelholz — 2026-04-18

The Mississippi River is the largest river in the United States of America (U.S.). While the Mississippi River provides a habitat for many animal species, much of the river has not been explored for microscopic organisms, like zooplankton, microfauna, and tardigrades. In the current study, we collected sixty freshwater samples from the Mississippi River and other freshwater systems in the U.S. Driftless Area. A total of eighty-five tardigrades were collected and four different species of tardigrades were identified using morphological analyses. The results presented here are the first peer-reviewed records of tardigrade species documented from the Mississippi River and other freshwater systems in the U.S. Driftless Area. The tardigrade species Grevenius granulifer, Pseudobiotus kathmanae, and Thulinius augusti were collected from the Mississippi River. The tardigrade species Dactylobiotus cf. dispar and Thulinius augusti present new biogeography records for the state of Iowa. These records update our knowledge of tardigrade biogeography and ecology in North America.

Enhancing the growth, hydrocolloid, and mineral content of Gracilaria verrucosa by selecting seedstock beyond local sources and various cultivation methods

Lestari L. Widowati — 2026-04-18

The quality of seedlings is essential for optimal growth rate and seaweed quality. The availability of local seedlings often poses constraints on quality and sustainability. This research aims to determine the optimal cultivation method for Gracilaria verrucosa using seeds from multiple locations. Seedlings of G. verrucosa were sourced from Semarang (S), Brebes (B), and Demak (D). Observations were conducted by cultivating the three seedlings using the off-bottom (O), broadcast (B), and longline (L) methods. A completely randomised design with a combination of seedling origin and cultivation method (3x3), namely SO, SB, SL, BO, BB, BL, and DO, DB, DL, was conducted in Brebes Regency, Central Java. The highest growth rate of G. verrucosa was observed in SL (3.21±0.07 % day^-1), while the lowest was observed in BB and DB. The broadcast cultivation method was shown to increase agar content across all seed sources, but this increase did not always correlate with gel strength. SB seedlings showed the best combination with high agar content (34.33±0.58%) and strong gel strength (294.7±6.05 g.cm?²), while SO produced the highest gel strength (324.7±5.21 g.cm?²) despite having lower agar content (26.65±0.80%). Integrating selective seed sources and optimised cultivation methods is crucial for enhancing growth, ensuring hydrocolloid quality, and achieving sustainable production of G. verrucosa.

Chemical profile and in vitro biological activities of volatile oil extracted from Arthrospira platensis

Layla Safar Jebur Khaledi — 2026-04-18

This study aimed to examine the chemical characteristics and biological actions of the volatile oil extracted from the cyanobacterium Arthrospira platensis. The results of gas chromatography-mass spectrometry (GC-MS) showed that the samples have a chemically diverse profile dominated by aliphatic hydrocarbons, terpenoid derivatives, aldehydes, ketones, and fatty acids, including 2-ionone, phytol, and unsaturated fatty acids. The antioxidant activity of the volatile oil was assessed using the DPPH free radical scavenging assay and was found to be concentration-dependent, although the overall activity was rather moderate compared with polar extracts. The antibacterial activity of the volatile oil was evaluated using the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods against Gram-positive and Gram-negative bacteria of interest. The findings showed a high level of concentration-dependent antibacterial activity, with inhibitory and bactericidal activities higher against Escherichia coli and Bacillus cereus than against Salmonella enterica and Staphylococcus aureus. Assessment by the MTT cytotoxicity assay revealed concentration-dependent and selective cytotoxic activity of the volatile oil against the human hepatocellular carcinoma (HepG2) and breast adenocarcinoma (MCF-7) cell lines, while preserving high cell viability in normal human dermal fibroblast cells. The half-maximal inhibitory concentration values showed good cytotoxicity against cancer cells and low toxicity to normal cells. The results revealed that the volatile oil of A. platensis is a potential source of bioactive compounds with moderate antioxidant activity, strong antibacterial effect, and selective anticancer potential, and indicate that the oil can be used as a natural source of biologically active metabolites in the pharmaceutical and biomedical industries.

A preliminary investigation on the effects of the echinoderm Archaster typicus extract on caudal fin regeneration and heart rate of zebrafish, Danio rerio

Angelo A. Responte — 2026-04-18

This study investigated the effect of the different concentrations of the crude hexanoic extract of the echinoderm, Archaster typicus, on the inherent ability of the zebrafish, Danio rerio, to regenerate its caudal fin after amputation, as well as on its heart function. The 100-ppm extract concentration showed the longest regenerated fin of 0.147 mm at 24h, 0.234 mm at 48h, and 0.598 mm at 72h. The fastest regeneration rate was at 100 ppm from 24 to 72. At 72h, the average length of fin regeneration in the negative control, 0.0 ppm (water only), and the concentrations 25 and 50 ppm were highly equivalent at 0.41 mm. The regenerated fin was longest in 100 ppm (0.6 mm) and shortest in 200 ppm (0.35 mm). After exposure to the positive control, benzaldehyde, for 72 h, the length of the regenerated fin was 0.66 mm at 25 ppm and 0.88 mm at 200 ppm. Increasing the benzaldehyde extract concentration also increased the regeneration length, with a maximum of 0.88 mm at 200 ppm. ANOVA showed significant differences in the length of the new fin among replicates, concentrations, and exposure durations. The effect of the echinoderm extract was a decrease in heart rate with increasing extract concentration and exposure duration (bradycardia).

Phytoremediation of some freshwater aquatic ornamental plants to treat wastewater from Indonesian shortfin eel, Anguilla bicolor

Hany Handajani — 2026-04-18

Abstract: This study evaluated the ability of freshwater ornamental aquatic plants to treat wastewater from Anguilla bicolor culture and the effects on growth performance. Over 60 days, plants including Cryptocoryne beckettii, Bacopa serpyllifolia, Echinodorus amazonicus, Echinodorus palaefolius, and a control group were tested. The average weight of A. bicolor was 7.01±0.18 g, with a stocking density of 4 g L?¹. The A. bicolor were maintained in 48 L aquariums with a recirculating system, using aquatic plants as phytoremediators, in a semi-outdoor laboratory to ensure adequate light. The feed protein content was 45.30%, and feeding occurred three times daily. The results showed that the aquatic plants efficiently removed nutrients from the water. Echinodorus palaefolius was the most effective, removing 23.33% of total ammonia nitrogen (TAN), 33.25% nitrite, 47.40% nitrate, and 43.92% phosphate. This species also promoted the highest specific growth rate (1.14±0.10%), biomass (22.67±1.65 g), and physiological response in A. bicolor, with the lowest feed conversion ratio (1.97±0.17). In conclusion, Echinodorus palaefolius effectively improved water quality and growth performance in A. bicolor, demonstrating its potential as a phytoremediator for sustainable aquaculture.

Environmental modulation of Omega-3 fatty acid biosynthesis in microalgae: Comparative effects of light intensity, temperature, and UV exposure on Spirulina platensis, Chlorella vulgaris, and Nannochloropsis oceanica

Hamida Ayal Maktoof — 2026-04-18

Microalgae are increasingly recognized as sustainable biofactories for high-value lipids, particularly omega-3 polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are vital for human health and industrial applications. This study aimed to evaluate the influence of environmental factors, light intensity, temperature, and ultraviolet (UV) radiation, on omega-3 fatty acid biosynthesis in Spirulina platensis, Chlorella vulgaris, and Nannochloropsis oceanica. The experiment was conducted under controlled laboratory conditions, with light intensities ranging from 10-125 µmol m?² s?¹, temperatures from 15-45°C, and UV-B exposure durations of 0-3 hours. Fatty acid methyl esters were extracted and quantified using gas chromatography–mass spectrometry (GC-MS). The results revealed that moderate light (50-75 µmol m?² s?¹) and temperature (30-35°C) significantly enhanced EPA and DHA accumulation, while UV exposure led to a pronounced decline in both compounds. Nannochloropsis oceanica exhibited the highest productivity, with EPA and DHA peaks of 0.94 and 0.55%, respectively, under optimal conditions, followed by S. platensis and C. vulgaris. The results confirmed significant effects of all environmental factors on lipid biosynthesis. In conclusion, light and temperature play crucial regulatory roles in omega-3 production, whereas UV radiation inhibits fatty acid synthesis. The findings highlight N. oceanica as the most promising species for industrial-scale omega-3 production and provide valuable insights for optimizing microalgal cultivation systems.

Antimicrobial resistance profiles of presumptive Escherichia coli isolated from wild-caught tilapia (Oreochromis sp.) in Iloilo River, Iloilo, Philippines

Francis Harry Shone Leonora — 2026-04-18

Antimicrobial resistance (AMR) remains a growing global threat to human, animal, and environmental health. Aquatic environments have become important reservoirs and transmission pathways for antimicrobial-resistant bacteria due to increasing anthropogenic pressures. Escherichia coli, a common commensal bacterium in humans and animals, is widely used as an indicator organism for AMR surveillance and poses environmental and public health concerns when resistant strains are present. However, wild and apparently healthy fish remain underrepresented in AMR research. In this study, apparently healthy wild tilapia (Oreochromis sp.) were collected from the Iloilo River. Gut, kidney, liver, and spleen samples were plated to obtain bacterial isolates. Presumptively identified E. coli based on biochemical testing were subjected to antimicrobial susceptibility testing against 11 antibiotics representing seven classes. The highest resistance rates were observed for ampicillin, cefotaxime, and tetracycline. The average multiple antibiotic resistance (MAR) index was 0.09, with four isolates exhibiting multidrug resistance and six identified as potential extended-spectrum ?-lactamase (ESBL) producers. Although the MAR index indicates relatively low antimicrobial selective pressure, the detection of multidrug-resistant E. coli in wild, apparently healthy fish underscores their potential as sentinels of antimicrobial resistance in the river system. Further studies are warranted to characterize the genetic determinants and resistance mechanisms contributing to environmental AMR.

New findings from the first fish toxicity test conducted following the algal bloom of Polykrikos hartmannii (Dinophyceae) in the Bay of Izmir, Aegean Sea

Özlem Çakal Arslan — 2026-04-21

The excessive proliferation of harmful algae can lead to fish mortality in coastal ecosystems. This study presents the results of a toxicity test conducted in response to the excessive proliferation of the species Polykrikos hartmannii in the Inner Bay of Izmir. The experiment used Sparus aurata that were exposed for 120 hours to a 100% concentration (2.4 x 10³ ± 0.090 cells·mL^-¹) determined based on the cell density in nature, and to dilutions of this concentration at 50%, 25% and 12.5%. A control group was also included in the study. In addition to mortality, fish behaviour was observed. Based on the results, no mortality was recorded at any concentration, and behaviour remained normal. Although P. hartmannii has been reported as ichthyotoxic in the literature, the current findings suggest that the toxic effect of the species may be associated with environmental conditions and feeding strategy (mixotrophic feeding).

Gut content analysis of snake mackerel Gempylus serpens (Cuvier, 1892) in Iligan Bay, northern Mindanao, Philippines

Krisha Mae E. Agura — 2026-04-21

Gut content analysis of the snake mackerel, Gempylus serpens (Cuvier, 1829), a commercially important fish in Iligan Bay, Philippines, is critical for understanding its ecological role in marine ecosystems. From July 2022 to March 2023, 58 individuals (total length 64.3 to 100.7 cm) were collected from Barangay Tambacan, Iligan City, a coastal city along Iligan Bay in Northern Mindanao, Philippines. Fish were the dominant prey, indicated by mean weight, frequency of occurrence, and index of relative importance. Cannibalism was documented, as two specimens contained remains of G. serpens. The species is a generalist predator, and significant positive correlations were found between gut length and total length, and between body weight and stomach weight with contents. Prey items were mostly in advanced stages of digestion, suggesting rapid digestion. This study highlights the ecological significance of G. serpens in Iligan Bay. Understanding the feeding ecology of G. serpens enriches our knowledge of marine food webs and supports the development of sustainable fishing practices, ensuring the long-term health of marine ecosystems.

Microplastic contamination in the gastrointestinal tract of Caspian kutum (Rutilus kutum) from Miankaleh fishing grounds: Implications for ecosystem and human health

Abdolghafoor Arkhi — 2026-04-24

Microplastic (MP) pollution has emerged as a pervasive threat to aquatic ecosystems globally, with significant implications for fish health and human food safety. The Caspian Sea, as the world's largest enclosed water body, acts as a terminal sink for contaminants, yet comprehensive assessments of MP contamination in commercially important fish species from its southeastern basin remain limited. This study investigated the occurrence, abundance, physical characteristics, and polymer composition of microplastics in the gastrointestinal tracts of Caspian kutum (Rutilus kutum) collected from three major fishing grounds, Chargoli, Shayan, and Niazabad, along the Miankaleh coastline, Golestan Province, Iran, during August–September 2024. A total of 30 fish specimens were examined using 10% potassium hydroxide digestion, density separation with saturated NaCl solution, and microscopic identification, followed by polymer confirmation via micro-Fourier transform infrared (?-FTIR) spectroscopy. Microplastics were detected in 93.7% of individuals, with a mean abundance of 2.84±1.67 items per fish, ranging from 0 to 9 items per individual. Significant spatial variation was observed, with Niazabad exhibiting the highest contamination (3.42±1.89 items fish?¹), followed by Shayan (2.76±1.54 items fish?¹) and Chargoli (2.34±1.42 items fish?¹), reflecting proximity to riverine inputs from the Gorganrud River. Fibers constituted the dominant morphology (91.3%), followed by fragments (6.2%) and films (2.5%). The predominant size class was 100-500 ?m (42.3%), indicating high bioavailability and potential for trophic transfer. Color distribution revealed distinct site-specific signatures: Niazabad was characterized by green (33.3%) and red (22.2%) MPs, while Chargoli and Shayan were dominated by black, gray, and transparent particles. Seven polymer types were identified, with cellophane (28.3%), polyamide (22.1%), and polyester (18.4%) being most prevalent, reflecting contributions from packaging materials, fishing gear degradation, and textile fibers. The predominance of high-density polyamide and polyester polymers, which have a high affinity for persistent organic pollutants, raises concerns about vector effects and co-exposure to associated contaminants. No significant correlation was found between fish length and MP abundance (p = 0.187), while a weak positive relationship with wet weight (p = 0.034) suggested moderate accumulation with increased body mass. The high occurrence and abundance of small, bioavailable MPs in R. kutum from the Miankaleh fishing grounds indicate substantial contamination pressure in this critical habitat, with direct implications for food safety, given the species' commercial importance and high consumption rates in northern Iran.