Fish Physiology and Biochemistry最新文献

{"title":"Potential beneficial effects of dietary replacement of fish meal with Black soldier fly (Hermetia illucens) larvae meal on growth, general physiology, and microanatomy of Nile tilapia (Oreochromis niloticus).","authors":"Waqar Younas, Amina Zuberi, Faisal Ahmad Lodhi, Muhib Zaman, Muhammad Noorullah, Muhammad Ali","doi":"10.1007/s10695-025-01545-4","DOIUrl":"10.1007/s10695-025-01545-4","url":null,"abstract":"<p><p>The ongoing growth of aquaculture and reduced fish meal supply leads fish nutritionists to seek alternative protein sources for sustainable aquaculture development. Black soldier fly larvae meal (BSFLM) is gaining importance due to its high protein content with a well-balanced amino acid profile. A 90-day triplicate feeding trial was executed to evaluate the impact of partial and complete replacement of fish meal (FM) with BSFLM in the diet of Oreochromis niloticus. Fingerlings (average body weight:1.23 g) were divided into five groups and reared on 32% CP experimental diets with replacement of FM with BSFLM at 0%, 25%, 50%, 75%, and 100%, respectively. Results indicated the significant effect of FM replacement with BSFLM on growth performance, nutrient digestibility, FCR, activity of digestive enzymes, biochemical indices, intestinal and liver morphology, and expression of growth hormone, myoblast determination protein 1, and Myostatin genes. The 50% followed by 75% replacement of FM demonstrated the most significant positive effect on these parameters, while 100% replacement showed the most notable negative impact. In addition, some parameters like proximate composition, the status of antioxidant enzymes, and expression of stress-related genes heat shock proteins (HSP-70 and HSP-90) did not show any statistical difference among groups except a D100 (100% FM replacement) group, which showed higher activity of CAT, SOD, and mRNA levels of HSPs. Based on current findings, replacing 50% of FM with BSFLM in the diet of O. niloticus is recommended to reduce production costs.</p>","PeriodicalId":12274,"journal":{"name":"Fish Physiology and Biochemistry","volume":"51 4","pages":"143"},"PeriodicalIF":2.5,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144834675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In vivo assay for the evaluation of the effect of anesthesia on locomotor activity in the weakly electric fish Apteronotus leptorhynchus.","authors":"Mariam Ahmed, Günther K H Zupanc","doi":"10.1007/s10695-025-01546-3","DOIUrl":"10.1007/s10695-025-01546-3","url":null,"abstract":"<p><p>Despite a nearly 200-year long history of anesthesiology, there is a persistent need for new anesthetics with improved safety and specificity, both in animals and humans. The identification and characterization of candidate molecules for the development of such novel drugs depends crucially on suitable in vivo assays. Ideally, these assays test for gradual behavioral outcomes and for the possibility of differential effects on different behaviors and/or neural functions induced by an anesthetic agent. To accommodate these features, we have developed an in vivo assay, based on analysis of amplitude modulations of the electric organ discharge of the weakly electric fish Apteronotus leptorhynchus. It provides a quantitative measurement of the gradual changes in locomotor activity induced by anesthetics. An extension of this assay offers the opportunity for simultaneous evaluation of the effects of anesthetics on two neural functions of the brainstem oscillator that controls the fish's electric behavior. As a distinctive, unique feature, this multimodal Neuro-Behavioral Assay collects all data utilized for analysis from a single non-invasive recording of the electric organ discharge of the fish.</p>","PeriodicalId":12274,"journal":{"name":"Fish Physiology and Biochemistry","volume":"51 4","pages":"141"},"PeriodicalIF":2.5,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12339612/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144816083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"IFN-γ2 enhances proliferation and differentiation of muscle cells: a novel target of natural grass feeding mode improving muscle quality in grass carp (Ctenopharyngodon idella).","authors":"Huijie Chen, Yin Wang, Jieya Liu, Qiushi Yang, Jiamin Lu, Tingting Xu, Rong Tang, Dapeng Li","doi":"10.1007/s10695-025-01553-4","DOIUrl":"10.1007/s10695-025-01553-4","url":null,"abstract":"<p><p>Grass carp (Ctenopharyngodon idella), as the highest-yielding freshwater species in China, has become a focus of muscle quality research. Previous studies have shown that natural grass feeding (GF) mode can improve the muscle quality of grass carp compared with artificial feeding (AF) mode, but its mechanism has not been revealed. In this study, we identified that interferon-γ2 (IFN-γ2) can be induced in the muscle tissues under GF mode. Therefore, recombinant IFN-γ2 protein was obtained to study its effect on grass carp muscle cells (GCMCs). We found that IFN-γ2 can facilitate the proliferation of GCMCs, and promote the myotube enlargement of GCMCs. Meanwhile, mRNA level investigations indicated that IFN-γ2 can regulate the expression of genes related to cell physiological processes. By transcriptome analysis, we screened a series of genes related to cell proliferation, differentiation, and migration. Using STAT1 inhibitor fludarabine in vitro, we confirmed that IFN-γ2 regulates the physiological development of GCMCs through JAK/STAT1. Finally, by knocking down IFN-γ2 in grass carp individuals, we verified that IFN-γ2 has an effective regulatory effect in vivo. This study provides novel target for improving the muscle quality of grass carp and provides inspiration for the development of aquaculture feeding mode. HIGHLIGHTS: 1. Natural grass feeding mode induces IFN-γ2 expression in grass carp muscle. 2. IFN-γ2 promotes the proliferation of grass carp muscle cells via JAK/STAT1. 3. IFN-γ2 regulates the expression of genes related to muscle proliferation in vivo.</p>","PeriodicalId":12274,"journal":{"name":"Fish Physiology and Biochemistry","volume":"51 4","pages":"140"},"PeriodicalIF":2.5,"publicationDate":"2025-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144793892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of responses to rapid changes in salinity between Hippocampus kuda and Oryzias melastigma.","authors":"Jinyang Xie, Wenxin Zhang, Penghong Lin, Xia Pan, Yongjian Xu","doi":"10.1007/s10695-025-01548-1","DOIUrl":"10.1007/s10695-025-01548-1","url":null,"abstract":"<p><p>In order to explore the similarities and differences of responses between Hippocampus kuda and Oryzias melastigma, this study analyzed and compared them from the aspects of growth, behavior, physiology, and gene expression. The results showed that H. kuda had a greater impact on its feeding behavior compared to O. melastigma at the same rates. And the continuous responses of enzymes indicated there was a more persistent stress in H. kuda, with stress-related genes like sod1 showing a slower response. Additionally, genes related to sugar and lipid metabolism were significantly different in H. kuda compared to O. melastigma. H. kuda exhibited sensitivity to nearly all treatments, while O. melastigma only responded to treatments of direct input. Furthermore, the responses of immune-related genes in H. kuda were also slower than those in O. melastigma. In summary, the osmotic pressure regulation ability of O. melastigma was more efficient than that of H. kuda in dealing with the stress caused by rapid changes in salinity.</p>","PeriodicalId":12274,"journal":{"name":"Fish Physiology and Biochemistry","volume":"51 4","pages":"139"},"PeriodicalIF":2.5,"publicationDate":"2025-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12331816/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144793880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of dietary long-chain polyunsaturated fatty acids on osmoregulation and salinity adaptation in red tilapia (Oreochromis mossambicus♀ × O. niloticus♂) under salinity stress.","authors":"Jiaying Xie, Junjun Sun, Yuanyou Li, Shuqi Wang, Douglas R Tocher, Cuihong You, Zhenqiang An, Dizhi Xie, Cuiying Chen","doi":"10.1007/s10695-025-01554-3","DOIUrl":"10.1007/s10695-025-01554-3","url":null,"abstract":"<p><p>The roles of long-chain polyunsaturated fatty acids (LC-PUFA) in osmoregulation and salinity adaptation in teleost fish were investigated in red tilapia (Oreochromis mossambicus♀ × O. niloticus♂). Groups of juvenile fish were reared initially in freshwater (FW, 0 ppt) or seawater (SW, 32 ppt) and fed diets containing either LC-PUFA-rich fish oil (FO) or rapeseed oil (VO) that lacks LC-PUFA, but is rich in C18 PUFA. After 8 weeks of feeding, the four groups of fish were subjected to salinity stress by directly changing to brackish water (BW, 16 ppt). Fish were sampled after 0 h, 3 h, 6 h, 1 d, 4 d, 8 d, and 16 d, and plasma osmoregulation-related parameters and tissue fatty acid compositions were analyzed. In red tilapia switched from SW to BW, plasma osmolality initially decreased significantly (0 - 1 d) and then increased (4 - 16 d) in fish fed the VO diet, while there were no significant changes in fish fed the FO diet. Plasma osmolality increased significantly in tilapia fed both diets when subjected to high salinity stress (FW to BW). Both the plasma Na⁺ concentration and gill activity of Na⁺/K⁺-ATPase (NKA) showed similar significant changes after salinity stress in fish fed the VO diet, but not in fish fed the FO diet. Plasma levels of growth hormone, cortisol, and prolactin were significantly increased after salinity stress in fish fed the VO diet, while prolactin level showed the opposite trend in fish fed the FO diet. Reflecting the fatty acid composition of the diets, LC-PUFA contents of gills and intestines were significantly higher in fish fed the FO diet than in fish fed the VO diet. Moreover, the liver expression levels of fads2 and elovl5 genes, which are involved in LC-PUFA biosynthesis, were significantly higher in red tilapia fed the VO diet than in fish fed the FO diet, and also in fish reared in seawater than in fish reared in freshwater. The time course of responses suggested that the adaptability of red tilapia to salinity stress was impacted by dietary LC-PUFA levels and that the FO diet provided the LC-PUFA required for fish to adapt rapidly to salinity changes and maintain osmotic balance, while fish fed the VO diet lacking LC-PUFA required the endogenous synthesis of LC-PUFA to adapt to acute salinity stress and maintain osmotic balance. Dietary LC-PUFA may influence plasma hormone levels and the activity of NKA in red tilapia through increasing cell membrane fluidity in order to respond to salinity stress and maintain osmotic equilibrium.</p>","PeriodicalId":12274,"journal":{"name":"Fish Physiology and Biochemistry","volume":"51 4","pages":"138"},"PeriodicalIF":2.5,"publicationDate":"2025-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144788580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dietary inclusion of frass from black soldier fly (Hermetia illucens) larvae modulates gut microbiota without compromising the growth performance and health status of catfish (Ictalurus punctatus) juveniles.","authors":"Ana Beatriz de S Farias, Thiago M Santana, Vitor F Silva, Caitlin E Older, Crystal L Conde, Nicholas Romano, Delbert M Gatlin, Ligia U Gonçalves, Fernando Y Yamamoto","doi":"10.1007/s10695-025-01552-5","DOIUrl":"10.1007/s10695-025-01552-5","url":null,"abstract":"<p><p>The present study evaluated the potential of BSFL frass (BF), a by-product composed of larval excretions, undigested substrate, and exoskeletons, as a dietary ingredient for juvenile channel catfish (Ictalurus punctatus). The experiment included a control diet and three test diets with BSFL frass 1.25% (BF1.25%), 2.5% (BF2.5%), and 5.0% (BF5.0%). All diets were isonitrogenous (37% crude protein), isolipidic (6% crude lipid), and isoenergetic (15 MJ gross energy/kg). Six hundred channel catfish juveniles (~ 1.85 g) were equally distributed to 20 aquaria (30 fish/tank) in a recirculating aquaculture system and fed the experimental diets for 60 days. Dietary inclusion of BSFL frass did not significantly affect growth performance, viscerosomatic index, intraperitoneal fat, and hematological parameters. However, fish-fed BF5.0%diets showed a higher hepatosomatic index, suggesting effects on liver metabolism. No significant differences were observed in intestinal histomorphology. Fish-fed BF1.25% exhibited a higher relative abundance of Lactococcus spp. (~ 47%), along with increases in Streptococcaceae, Lactobacillales, and Weissella, accompanied by reduced Cetobacterium spp. and Plesiomonas spp. BSFL frass did not improve performance but significantly altered the catfish gut microbiota. This finding warrants further research to better understand the components of the BSFL frass that can serve as a substrate for commensal bacteria and which bacterial species are benefiting from this supplementation. Additionally, evaluating the feasibility of BSFL frass as an unconventional ingredient in aquafeeds could provide insights into its potential functional benefits and practical application in sustainable fish nutrition.</p>","PeriodicalId":12274,"journal":{"name":"Fish Physiology and Biochemistry","volume":"51 4","pages":"137"},"PeriodicalIF":2.5,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144783902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluating the role of condition indices in predicting maturity in Black Sea whiting.","authors":"Taner Yıldız, Nurdan Cömert, Özgür Çanak, Emre Yemişken, Uğur Uzer, Abdullah E Kahraman, F Saadet Karakulak","doi":"10.1007/s10695-025-01550-7","DOIUrl":"10.1007/s10695-025-01550-7","url":null,"abstract":"<p><p>Understanding the factors influencing fish maturation is crucial for predicting reproductive potential and ensuring sustainable management of aquatic resources. In this study, we evaluated the role of individual condition in explaining maturation probability in female Black Sea whiting (Merlangius merlangus), an overexploited demersal species. Using Fulton's K, the relative condition factor (K_r), and the liver condition index (LKr), we assessed their contribution to maturity probability alongside conventional predictors such as age and size. While condition indices positively influenced maturation likelihood, their overall contribution to explained variance was limited compared to age and length. However, among individuals of similar age and size, those in better condition had substantially higher odds of being mature, underscoring the value of condition metrics for refining maturity estimates. The pre-spawning fitness threshold (Kspawn50) was estimated at 0.82, within an observed K range of 0.4 to 3.4, representing the critical condition level associated with spawning readiness. These findings highlight that, although condition indices may be limited as standalone maturity benchmarks, they substantially enhance the precision of maturity predictions when integrated with age and length, emphasizing the value of multi-variable assessment approaches. Furthermore, by linking physiological condition to reproductive dynamics, our study provides insights into the resilience of demersal fish populations under fishing pressure, contributing to a broader understanding of ecosystem health in semi-enclosed seas like the Black Sea.</p>","PeriodicalId":12274,"journal":{"name":"Fish Physiology and Biochemistry","volume":"51 4","pages":"136"},"PeriodicalIF":2.5,"publicationDate":"2025-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144783903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Black soldier fly (Hermetia illucens) larvae exoskeleton as a potential source of chitin in diets for juvenile channel catfish (Ictalurus punctatus).","authors":"Thiago M Santana, Ana Beatriz de S Farias, Caitlin E Older, Nicholas Romano, Delbert M Gatlin, Matt J Griffin, Fernando Y Yamamoto, Ligia U Gonçalves","doi":"10.1007/s10695-025-01551-6","DOIUrl":"10.1007/s10695-025-01551-6","url":null,"abstract":"<p><p>This study investigated the effects of dietary supplementation of chitin from the exoskeleton (exuviae) of black soldier fly larvae (BSFL) and purified chitin (PC) from shrimp in diets for channel catfish juveniles. Five experimental diets were formulated to provide chitin at two inclusion levels (500 and 1000 mg kg^-1). A diet devoid of chitin was used as a control. The feeding trial was performed for 9 weeks with 1000 channel catfish juveniles (~ 1.8 g), randomly distributed into 25 experimental units (110 L; 40 fish aquarium^-1), in a recirculating aquaculture system. Data from production performance, whole-body proximate composition, whole-blood and plasma immunological responses, intestinal microbial community profiles, as well as susceptibility to Edwardsiella ictaluri challenge were evaluated. There was no impact on growth or health parameters of juvenile catfish; however, the BSFL500 diet resulted in a significantly lower viscerosomatic index. Fish-fed diets containing 1000 mg of chitin kg^-1, trended toward less rich intestinal bacterial communities compared to groups fed with other diets. Additionally, the BSFL groups had distinct bacterial community structures compared with the other treatments. After the feeding trial, the remaining fish were challenged with E. ictaluri immersion, and fish-fed BSFL1000 and PC500 demonstrated lower cumulative survival. These results fail to support the use of chitin as a feed supplement for improved fish growth or health parameters in juvenile catfish. However, shifts in the intestinal microbiota suggest a potential prebiotic role, warranting further research to better define the putative utility of chitin in catfish nutrition and health management.</p>","PeriodicalId":12274,"journal":{"name":"Fish Physiology and Biochemistry","volume":"51 4","pages":"135"},"PeriodicalIF":2.5,"publicationDate":"2025-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144783901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An integrated approach to evaluate the immunomodulatory effect of functional feed on rainbow trout (Oncorhynchus mykiss) during an A. salmonicida outbreak.","authors":"Teresina De Iorio, Maria Carmela Scatà, Francesca Apuzzo, Andrea Gustinelli, Arianna Martini, Marco Martinoli, Riccardo Napolitano, Domitilla Pulcini, Nicolò Tonachella, Fabrizio Capoccioni","doi":"10.1007/s10695-025-01537-4","DOIUrl":"10.1007/s10695-025-01537-4","url":null,"abstract":"<p><p>Different strategies have been proposed to boost the resistance of fish against Aeromonas salmonicida, one of the major pathogens of salmonids. This study conceived an integrated approach to evaluate the immunomodulatory effects of two commercial feeds (Protec and Optiline, Skretting) on rainbow trout during an Aeromonas salmonicida outbreak that caused high mortality in a fish farm. Welfare indicators, biometric, autoptic, and haematology indices, and innate immunity parameters (leukocyte viability, reactive oxygen species (ROS) production, and phagocytosis) were evaluated in fish fed with either Protec (containing β-glucans, vitamin C, E, and zinc) or a control diet (Optiline). Trout fed with Protec showed a higher proportion of blood lymphocytes (4.58 vs. 3.35; p < 0.05) and thrombocytes (2.21 vs. 1.54; p < 0.05), and a lower number of neutrophils (1.83 vs. 2.54; p < 0.05). Leukocytes isolated from individuals fed with Protec showed significantly higher viability (53.73 vs. 42.59; p < 0.01), lower apoptosis (29.61 vs. 36.49; p < 0.05), and lower death (10.99 vs. 20.38; p < 0.05), parallelled by lower ROS production. Furthermore, they displayed a higher proportion of phagocytic-ROS-producing live myeloid cells (20.91 vs. 14.34; p < 0.05). These data suggest that the immunostimulant-enriched diet strengthens rainbow trout's innate immune system, partially mitigating A. salmonicida infection.</p>","PeriodicalId":12274,"journal":{"name":"Fish Physiology and Biochemistry","volume":"51 4","pages":"133"},"PeriodicalIF":2.5,"publicationDate":"2025-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144768545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Protein sparing by dietary lipids in the diets of Pangasianodon hypophthalmus: an appraisal of growth, body composition, digestive enzymes, and metabolic responses.","authors":"Sadaf Khadim, Mahroze Fatima, Syed Zakir Hussain Shah, Hamda Azmat, Muhammad Afzal Rashid","doi":"10.1007/s10695-025-01542-7","DOIUrl":"10.1007/s10695-025-01542-7","url":null,"abstract":"<p><p>Lipid-induced protein sparing conserves protein for growth, reducing feed costs and nitrogenous waste in the environment. In a 90-day experiment, the protein-sparing effects of lipids on the growth, nutrient content, amino acid profile, hematobiochemical parameters, digestive enzymes, and antioxidant status of Pangasianodon hypophthalmus were evaluated. Four isoenergetic diets (3223.26 kcal/kg) with varying protein (P) and lipid (L) contents were formulated: D1 (P39/L10, control), D2 (P35/L12), D3 (P31/L15), and D4 (P27/L18). Acclimatized fingerlings (N = 240; initial weight, 12.75 ± 0.2 g) were randomly allocated to four dietary treatment groups (20 fish/aquarium) in triplicate and fed to satiation twice daily. Reducing dietary protein from 39 to 35% with increasing lipids from 10 to 12% maintained optimal growth, indicating a protein-sparing effect. However, further reductions (31-27% protein) in lipids (15-18%) impaired growth and increased biological indices. The body and muscle protein contents remained stable between 39 and 35% protein but declined with increasing reduction, whereas the lipid content increased. Essential amino acids (lysine, methionine, isoleucine), antioxidant status, hepatic enzymes, plasma metabolites (glucose, cholesterol, triglycerides), and protease were stable at 39 to 35% protein but decreased beyond that point, whereas the lipase and malondialdehyde contents showed opposite trends. Intestinal morphology (villus height and width, muscle thickness) was unaffected by 39 to 35% protein but was reduced with further protein reduction. These findings highlight the protein-sparing effect of lipids in P. hypophthalmus when lipids increase from 10 to 12% and when proteins decrease from 39 to 35%.</p>","PeriodicalId":12274,"journal":{"name":"Fish Physiology and Biochemistry","volume":"51 4","pages":"134"},"PeriodicalIF":2.5,"publicationDate":"2025-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144768575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}