Xiaoting Zheng

This study evaluated dietary Eleutherine americana water extract (EAW, 0 [NC], 1 [LD], 5 [MD], and 10 [HD] mL/kg) in 480 juvenile leopard coral grouper (Plectropomus leopardus; initial body weight, 11.72 ± 0.34 g) over 8 weeks, with four replicate tanks of 30 fish per treatment. EAW did not significantly improve growth performance, but survival was higher in MD and HD than in NC (p < 0.05). Histological observations indicated more intact mucosal folds, greater crypt depth, and higher goblet-cell counts. Metabolomic analysis showed lower carnitine levels and higher phospholipid and prostaglandin metabolites, with annotated differences in bile acid biosynthesis, amino acid metabolism, and carbon metabolism pathways. Intestinal microbiota profiles showed lower relative abundances of Pseudomonadota and Basidiomycota in EAW groups, lower Actinomycetota in LD and MD, and higher Bacteroidota and Bacillota in MD. At the genus level, Bradyrhizobium, Microbacterium, and Sphingobium abundances were lower, and Afipia abundance was higher, in EAW groups. Functional profiles varied in carbohydrate, amino acid, and lipid metabolism categories. Microbiota–metabolite correlation networks identified Pseudomonadota, Actinomycetota, hexosylceramides, and carnitines as highly connected features. Network pharmacology identified pdgfra, pdgfrb, and sirt1 as candidate targets of the major EAW components eleutherol, eleutherin, and isoeleutherin. The survival and intestinal findings support further evaluation of EAW as a feed additive for intestinal health in leopard coral grouper.

Bacterial and viral diseases continue to remain major problem in aquaculture, and the growing limitations on the use of antibiotics have intensified a growing focus on host-directed nutrition-based disease management strategies. While vitamin D₃ (VD₃) has been recognized for its role in calcium-phosphorus metabolism, it is now increasingly recognized to exert an immunonutrient role in fish, which includes modulation of antimicrobial peptide production, inflammatory regulation, epithelial barrier integrity, oxidative homeostasis, microbiota-associated immune interactions, and antiviral signaling. This review critically synthesizes current knowledge on VD₃ metabolism and vitamin D receptor (VDR)-mediated signaling in relation to disease resilience in cultured aquatic species, with particular emphasis on antibacterial, antiviral, and functional-feed applications. Across experimental studies, VD₃ supplementation has frequently been associated with enhanced phagocytic activity, lysozyme and complement function, antimicrobial peptide induction, cytokine modulation, and improved mucosal stability. Emerging evidence further implicates VD₃ in type I interferon and JAK-STAT-associated antiviral pathways. However, these responses remain highly variable across species, supplementation doses, developmental stages, and environmental conditions, reflecting substantial biological and methodological heterogeneity. Importantly, the current evidence base is still frequently composed of transcriptomic and short-term laboratory studies with comparatively few studies demonstrating functional validity in form of pathogen-load reduction, histopathological protection, improvement of survival, or production level. The translation value for VD₃ is still not fully understood, although it holds promise for use in integrated functional feed systems. Overall, effective application will depend on species-specific dose optimization, long-term safety assessment, and stronger field-scale validation across diverse aquaculture systems. KEY POINTS: • Vitamin D₃ modulate antimicrobial peptides and innate and antibacterial immunity in fish. • VD₃ activates interferon pathways and strengthens antiviral defenses. • Optimal VD₃ dosing improves resilience; field validation is needed in aquaculture.

The American bullfrog (Aquarana catesbeiana), recognized for its aquaculture potential, presents a significant opportunity for sustainable and economically viable production. As the world's leading producer, China plays a pivotal role in the bullfrog industry yet lacks a comprehensive synthesis of its production advancements and challenges. This study addresses this gap by analyzing research and production data from 2020 to 2024, sourced from databases such as Web of Science, Google Scholar, and Scopus. A review of 193 articles across nine thematic areas—including biology, nutrition, aquaculture systems, and disease management—underscores the growing use of bullfrogs as model organisms while addressing ecological impacts and disease concerns. In 2023, China's bullfrog industry achieved a production volume exceeding 1 million tons, valued at 100 billion CNY (15.26 billion USD). However, challenges such as inconsistent production standards and wastewater‐induced environmental pollution remain unresolved. Through an evaluation of various farming models, this study identifies the concept of industrial parks utilizing greenhouses with recirculating aquaculture systems (RAS) as a highly promising strategy for improving food safety and promoting environmental sustainability. The findings emphasize the need for targeted improvements in farming practices and regulatory frameworks to ensure sustainable growth. As a strategic initiative, we propose establishing industrial parks dedicated to bullfrog farming, aligning economic development with environmental goals, and positioning the industry for long‐term global competitiveness.

Bullfrogs (Aquarana catesbeiana) are increasingly cultivated for their high nutritional value and adaptability to intensive aquaculture systems. However, ensuring optimal intestinal health and growth performance remains a challenge due to poor water quality and high stocking densities. This study evaluated the effects of varying dietary concentrations of citral, a natural compound from lemongrass essential oil, on the intestinal health, microbiota, antioxidant capacity, and growth performance of juvenile bullfrogs. A total of 200 juvenile bullfrogs (initial weight 6.85 ± 0.71 g) were randomly assigned into six groups, each receiving diets supplemented with citral at 0, 1, 2, 4, 8, and 16 mL/kg feed for 8 weeks. Citral supplementation significantly improved intestinal morphology, with goblet cell numbers, mucosal thickness, and villus-to-crypt ratios peaking at 2–4 mL/kg (P < 0.05). Optimal doses of 2–4 mL/kg also enhanced digestive enzyme activities, with α-amylase, lipase, and pepsin activities showing significant increases compared to the control group (P < 0.05). Antioxidant markers, including total antioxidant capacity (T-AOC) and glutathione (GSH), were highest at 2 mL/kg, while higher citral concentrations reduced superoxide dismutase (SOD) and catalase (CAT) activities, indicating potential oxidative stress at 8–16 mL/kg (P < 0.05). Citral also modulated the intestinal microbiota, increasing the relative abundance of beneficial bacteria such as Cetobacterium at 1–2 mL/kg (P < 0.05). However, microbial diversity decreased significantly at concentrations above 4 mL/kg. Growth performance analysis revealed that 4 mL/kg citral supplementation significantly improved weight gain rate (WGR), specific growth rate (SGR), carcass weight (CW), and feed efficiency (FE), while survival rates declined at 16 mL/kg (P < 0.05). A linear regression model determined the optimal dietary citral concentration to be 3.216–3.942 mL/kg. This study concludes that dietary citral at 2–4 mL/kg optimally enhances growth performance, intestinal health, and antioxidant capacity in juvenile bullfrogs, while higher concentrations may disrupt gut health and oxidative balance. These findings provide valuable insights into the use of natural compounds like citral for sustainable aquaculture practices.

Ecytonucleospora hepatopenaei (EHP), a microsporidian parasite first named and characterized from the Penaeus monodon (black or giant tiger shrimp), causes growth retardation and poses a significant threat to shrimp farming. We observed shrimp farms associated with disease conditions during our fish disease surveillance and health management program in West Bengal, India. Shrimp exhibited growth retardation and increased size variability, particularly in advanced stages, exhibiting soft shells, lethargy, reduced feeding and empty midguts. Floating white feces were observed on the surface of the pond water. Suspecting a microbial infection, the shrimp samples were collected and aseptically brought to the ICAR-CIFRI laboratory for molecular confirmation. A nested PCR was used to screen shrimp tissue, feces, feed and environmental samples for the possible presence of hepatopancreatic microsporidiosis caused by Ecytonucleospora hepatopenaei. The results confirmed that the shrimp samples were positive for EHP. Histopathological investigation revealed mature spores in the HP tubule lumen and epithelial cells along with necrotic tubule in the symptomatic group. Further, the transcription analysis revealed that ProPO, Hsp70 and α2-macroglobulin genes were significantly upregulated, while decreased expression of LGBP, PXN and Integrin ß was observed in shrimp infected with Hepatopancreatic microsporidiosis. Furthermore, compared with the healthy group, significant intestinal bacteria changes were observed in the EHP-infected group. The in vivo survival assay, using crustacean animal model Artemia franciscana, suggests that symptomatic shrimp gut samples harbour pathogenic Vibrio parahaemolyticus, V. harveyi and V. campbellii. These results significantly advance our understanding of the molecular and ecological aspects of EHP pathobiology.

Bullfrogs (Aquarana catesbeiana) are increasingly farmed for their high nutritional value and adaptability to intensive aquaculture systems. However, salinity stress due to environmental changes and habitat salinization poses a significant challenge for both wild and farmed bullfrogs. This study examines the physiological responses of juvenile bullfrogs to varying salinity levels (0, 2, 4, 6 ppt) to better understand their capacity for osmoregulation and adaptation to salinization. Juvenile bullfrogs underwent salinity treatments for one week, and various physiological parameters, including digestive enzyme activity, antioxidant enzyme activity, and serum biochemical indicators, were measured. The study revealed that moderate salinity (2–4 ppt) enhanced pepsin and amylase activity while maintaining high survival rates. However, higher salinity levels (6 ppt) impaired antioxidant defense mechanisms and liver tissue, increasing oxidative stress markers such as malondialdehyde (MDA). The results suggest that bullfrogs possess a degree of salt tolerance, which may predict their resilience to future landscape salinization driven by environmental changes. This research provides valuable insights into the osmoregulatory mechanisms of amphibians under salinity stress, addressing a critical gap in knowledge essential for both conservation and aquaculture management.

Introduction: The use of plant essential oils as anesthetics for fish has gained increasing attention, but ethanol, often used as a co-solvent, presents certain limitations. Recently, Magnolia denudata essential oil (MDO) has emerged as a promising alternative for fish anesthesia and sedation.Methods and results: To further improve MDO anesthesia efficacy, this study developed nanoemulsion (NE) and self-microemulsifying drug delivery system (SMEDDS) formulations of MDO. Transmission electron microscopy and stability tests confirmed that both NE and SMEDDS possess smaller particle sizes and are stable under various temperature conditions. Anesthetic trials on fish demonstrated that these formulations reduced the time needed to induce anesthesia compared with the non-formulations. Additionally, physiological assessments of the fish gills showed that neither NE nor SMEDDS caused irreversible damage to respiratory function.Discussion: Overall, NE and SMEDDS present a safe and effective delivery system for MDO, enhancing its anesthetic properties while minimizing potential harm to aquatic organisms compared to traditional methods.