Fish Physiology and Biochemistry最新文献

Owing to overfishing and habitat degradation, the population of wild seahorses has declined substantially. Aquaculture is recognized as the most efficient approach to reconcile market demands with the conservation of wild seahorse populations. However, the lack of research on basic biology, especially histological studies, has severely hindered the advancement of large-scale seahorse aquaculture. In this study, the organogenesis of the big-belly seahorse (Hippocampus abdominalis), the major farmed seahorse species in China, was analyzed from 1 to 75 days after birth (DAB), which corresponds to 19 to 1,425 day degrees (D°). Three main developmental stages were identified: 1) DAB 1-10 (19-190 D°, early planktonic stage): On the DAB 1 (19 D°), the mouth and anus opened, indicating that they had acquired basic food-selecting ability. On the DAB 10 (190 D°), the first intestinal loop appeared in the intestine to accommodate to intestinal growth and meet increasing nutritional demands. Meanwhile, the female ovary was observed for the first time. 2) DAB 10-30 (190-570 D°, late planktonic stage): This stage was primarily characterized by the maturation of the respiratory and urinary systems. Notably, the brood pouch was first observed on the DAB 15 (285 D°). 3) DAB 30-75 (570-1,425 D°, benthic stage): At DAB 30 (570 D°), the second intestinal loop appeared in the intestine by which time the intestinal tract was basically fully developed. The depth of the ocular fovea increased, which coincided with the transition of seahorses from the planktonic stage to the benthic stage. Throughout the research period (DAB1-75, 19-1,425 D°), the male gonads were not found. This study fills the gaps in the biological and physiological knowledge of this species, as well as provides a theoretical foundation for further insights into the growth and developmental mechanisms of the big-belly seahorse.

Microplastics (MPs), which are tiny particles measuring less than 5 mm, have emerged as a notable environmental issue due to their widespread presence in aquatic environments and their potential to harm aquatic organisms. In this study, the diet of tilapia (Oreochromis niloticus) exposed them to two types of MP materials: PE and PVC fragments. The fish were exposed for three weeks (21 days), and various behavioural changes and mortality were noticed. Moreover, microplastics can impact the growth, reproduction, and survival of tilapia, as evidenced by reduced growth rates and observed behavioural changes in exposed fish. Such modifications might have important effects on the general condition and population dynamics of aquatic environments. In both the gill and gastrointestinal tract (GIT), the MP fragments were accumulated. The GIT of tilapia fish revealed 4.8 ±2.7 items/individual from the collected PVC pieces; gills included 6.6±2.07 items/individual. Similarly, PE fragment accumulation in the GI tract of fish showed 5.6±2.6 items/individual, and the gills showed 5.8±0.84 items/individual. A dietary intake of microplastics led to increasing inflammatory alterations in the liver and intestines. This study assessed the levels of oxidative enzymes in exposed groups of fish (control, PVC, and PE fragments). The MP-exposed tilapia fish exhibited remarkable changes in the enzyme level and the nutritional values, which were compared to control groups. All things considered, microplastics seriously compromise the health and ecological processes of freshwater fish, including tilapia. More study is required to completely understand these effects as well as develop feasible strategies for reducing the microplastics' hazard in freshwater habitats.

A 42-day feeding trial was conducted to determine the effects of different lipid and phospholipid (PL) levels on growth performance, fatty acid composition, fat deposition, antioxidant capacity, and liver health of largemouth bass (Micropterus salmoides) larvae. Six diets were designed: 6% lipids and 0% PLs (L6/PL0), 3% lipids and 3% PLs (L6/PL50), 0% lipids and 6% PLs (L6/PL100), 12% lipids and 0% PLs (L12/PL0), 6% lipids and 6% PLs (L12/PL50), and 0% lipids and 12% PLs (L12/PL100). These correspond to gradient designs for PLs replacing 0%, 50%, and 100% lipids at the 6% and 12% lipids levels. Results showed that dietary PL supplementation significantly enhanced body weight gain (BWG) and specific growth rate (SGR), with the highest BWG in L12/PL100. PL supplementation reduced both the hepatosomatic index (HSI) and viscerosomatic index (VSI), with the L6/PL100 having the lowest levels. The PL supplementation efficiently reduced liver fat deposition and neutral lipid/polar lipid ratio. The n-3 polyunsaturated fatty acid content in the polar lipid fraction was significantly higher than that in the neutral lipid fraction. Dietary PL supplement significantly increased hepatopancreatic catalase and glutathione activities and decreased malondialdehyde content in the hepatopancreas. PL supplementation significantly reduced liver triglyceride and total cholesterol levels, with the lowest levels observed in the L6/PL100 and L12/PL100 groups. These findings demonstrate that graded PL replacement (up to 100%) at the 6% lipid level optimized growth, reduced fat deposition, increased antioxidant capacity, and avoided the metabolic burden induced by high fat (12% lipids), enhancing LB larval health.

Understanding the effects of environmental temperature on marine fish larvae is crucial for optimizing feeding regimes and promoting optimal development and growth from a zootechnical perspective in aquaculture practices. The present study investigated the impact of different rearing temperatures on development, growth, and oxygen consumption rates of Totoaba macdonaldi larvae. An open-flow seawater recirculating system was used in which larvae (150 specimens/L) were exposed in triplicate to four rearing temperatures (20, 24, 26, and 28 °C) for 24 days under standard larval rearing conditions. Larvae were sampled at 7, 12, 16, 20, and 24 days post hatching (DPH) to assess growth performance, survival, histological condition, and respirometry. At the end of the trial, the highest total length (TL) and body weight (BW) values were observed at 26 °C, with larvae displaying negative allometric growth in terms of TL and BW, similar to those reared at 24 and 28 °C. In contrast, larvae reared at 20 °C showed lower growth and an isometric growth pattern. No significant differences in Fulton's condition factor (K) were detected among treatments. Survival rates were the highest at 28 °C, while increased cannibalism at 26 °C was associated with elevated specific growth rates and thermal growth coefficients. Histological analysis revealed better structural organization in the gills and liver of larvae reared at 26 °C, whereas other treatments showed signs of inflammation. Respirometry results indicated that larvae reared at 20 °C had significantly higher metabolic rates. However, these differences diminished by DPH 20 and 24, likely reflecting developmental changes and phenotypic plasticity during the larval-to-juvenile transition. Based on physiological and metabolic indicators, a rearing temperature of 26 °C is recommended for T. macdonaldi larviculture.

Fish are particularly vulnerable to microplastics (MPs), especially polypropylene microplastics (PP-MPs), which are widely used and environmentally persistent. Despite their prevalence, little is known about their impact on fish immune systems. Thus, this study's goal was to look at the antioxidants, immunotoxicological, and histopathological impact of PP-MPs on African catfish Clarias gariepinus and the ameliorating role of Spirulina and recovery. A total of 108 fish, weighing 125 ± 3 g and 27 ± 2 cm, were acclimated and divided into six experimental groups (in triplicate): control, PP-MPs-treated groups (0.14 and 0.28 mg/L), PP-MPs + Spirulina (200 mg/L), and Spirulina alone. Fish were exposed to treatments for 15 days, followed by a 45-day recovery period. Antioxidant enzymes (SOD, CAT, GST, MAD), immune biomarkers, and histopathological changes in the spleen and head kidney were assessed. PP-MPs exposure led to a significant (p < .05) decline in antioxidant enzymes and immune biomarkers compared to controls, with increased melanomacrophage centers and tissue damage. Spirulina supplementation significantly improved immune and antioxidant responses, although some parameters, like MAD and histopathological alterations, showed incomplete recovery even after 45 days. PP-MPs have immunotoxic and oxidative effects on Clarias gariepinus, with partial recovery possible through Spirulina supplementation. However, full restoration of immune tissue morphology requires longer recovery periods. The observed immune alterations were closely associated with histopathological damage in key immune organs.

Exemestane is an aromatase inhibitor that is used for the treatment of breast cancer. The aim of this study was to evaluate the effects of exemestane on liver development of zebrafish embryos. In this study, zebrafish embryos at 72 h post-fertilization (hpf) were exposed to varying concentrations (1, 2, and 3 mg/L) of exemestane for 72 h (until 144 hpf). The results demonstrated that exemestane exposure significantly reduced liver area and expanded the yolk sac in a dose-dependent manner, accompanied by progressive lipid accumulation. At the highest concentration (3 mg/L), exemestane markedly downregulated the expression of key liver development markers, including fatty acid-binding protein (fabp10a) and ceruloplasmin (cp). The study further revealed that exemestane exposure at 2 mg/L and 3 mg/L significantly increased reactive oxygen species (ROS) levels while decreasing the activities of antioxidant enzymes, specifically catalase (CAT) and superoxide dismutase (SOD). Interestingly, higher concentrations of exemestane resulted in reduced levels of the lipid peroxidation product malondialdehyde (MDA) and decreased mitochondrial numbers. Additionally, exemestane treatment altered the expression of genes related to sugar and lipid metabolism and upregulated pro-apoptotic genes, including bax, p53, and caspase 3, in zebrafish embryos. A crucial finding was that p53 knockdown in zebrafish embryos effectively mitigated the hepatotoxic effects induced by exemestane. These collective results indicate that exemestane induces hepatotoxicity in zebrafish primarily through activation of the p53 signaling pathway. This study provides valuable insights into the potential hepatotoxic effects of exemestane, offering important references for its clinical safety evaluation.

This study investigated the effects of MS-222 on biochemical indices, antioxidant status, nonspecific immune responses, histomorphology (gill and liver), gut microbiota, and flesh quality in largemouth bass (Micropterus salmoides). The anesthetic effects of MS-222 at concentrations of 20, 40, 60, 80, and 100 mg/L were first evaluated in fish (~ 468.34 g). Deep sedation was achieved at 40 mg/L, which was identified as suitable for live transportation. Fish were then exposed to 40 mg/L MS-222 for 24 h and transferred to clean water for recovery. Serum, gill, liver, intestine, and dorsal muscle samples were collected at 6, 12, and 24 h during exposure and at the same intervals post-recovery. Serum cortisol, glucose, LDH, and AST levels did not change significantly during sedation or recovery, although BUN levels increased significantly. Antioxidant enzyme activities were not significantly affected, whereas malondialdehyde (MDA) decreased during sedation. MS-222 caused atrophy and hypertrophy of gill filaments, reduced nucleoli, and increased vacuolation in hepatopancreas cells; these changes were not fully reversed after 24 h of recovery. Gut microbial composition was altered, with a reduction in beneficial genera such as Cetobacterium. Flavor-related compounds, including sweet and umami amino acids, betaine, and nucleotides, increased during sedation and recovery. MS-222 also decreased the proportion of monounsaturated fatty acids (MUFAs) and increased polyunsaturated fatty acids (PUFAs). Electronic nose analysis showed distinct changes in muscle flavor during sedation, which diminished during recovery. Overall, MS-222 at 40 mg/L significantly influenced the physiology, biochemistry, and flesh quality of largemouth bass, providing a reference for its application in live transportation.

ECE1 is involved in the development of the lamprey embryonic heart. Endothelin converting enzyme 1 (ECE1) is a key enzyme for the production of endothelin, which, as a potent vasoconstrictor, plays a central role in regulating the growth and differentiation of cardiomyocytes and smooth muscle cells. The enzyme is widely expressed in human tissues and is significantly upregulated in a variety of cancers, with a key impact on the development and invasiveness of cancer. In addition, ECE1 is also involved in the development of neural crest cell-derived organs such as the heart. In vertebrates, jawed animals (such as mammals) mainly express ECE1, ECE1L, and ECE2 genes, but the function of ECE genes in jawless animals (such as the lamprey) has not yet been clarified. In this study, the ECE1 gene was cloned from the Lethenteron reissneri, and bioinformatics analysis showed that it had a high degree of similarity with the ECE1 of jawed vertebrates. This discovery provides important clues for exploring the role of ECE1 in lamprey biology, especially its potential functions in signal transduction, nervous system, cardiovascular system, digestive system, and immune diseases.

Degeneration of dopaminergic neurons is associated with several neurological and psychiatric disorders, including Parkinson's disease, schizophrenia, and Huntington's disease. To find new therapies for these conditions, animal models based on exposure to toxins, such as paraquat (Pq) or 6-hydroxydopamine (6-OHDA), have been developed. Purinergic signaling has emerged as a key factor in motor illness. This study evaluated the influence of Pq and 6-OHDA on ATP metabolism and gene expression of nucleotide- and nucleoside-metabolizing enzymes in zebrafish brain. Adult zebrafish were injected i.p. with saline or Pq (10 or 20 mg/kg) at two-day intervals for a total of six doses. For 6-OHDA treatment, zebrafish received one i.p. injection of saline or 6-OHDA (25 or 50 mg/kg). Six days after the 6-OHDA treatment or 6 i.p injections of Pq, ATP metabolism and gene expression assays were evaluated in zebrafish brain. A decrease in extracellular adenosine (ADO) catabolism was observed in Pq-treated animals compared to the controls. In 6-OHDA-treated fish, there were no changes in ATP levels; however, ADP levels were altered and AMP levels decreased at both doses tested. Meanwhile, ADO levels increased compared to the control. Both treatments led to increased extracellular inosine (INO) levels. Changes in adenosine deaminase gene expression were observed following 6-OHDA exposure. Given the observed alterations in ATP and adenosine catabolism, purinergic signaling emerges as a regulatory mechanism that could be targeted in the development of therapeutic strategies aimed at mitigating neurotoxic damage and preserving neuronal function.

Functional feeds designed to enhance the host's immune response and improve disease resistance are among the most popular strategies to mitigate the impact of infectious diseases and abiotic stressors in aquaculture. While reviewing the current scientific literature on this issue, we have detected that there is a need to standardize the evaluation criteria for feed additives with immunostimulant properties in terms of the duration of the trial and selection of key end-points related to the expected effect of the dietary intervention. The evaluation of the disease protective role of a feed additive should not be based only on end-points from cellular and immune biomarkers, but it should also be complemented with end-points based on survival data of specimens exposed to an in vivo infective challenge. We also recommend giving special consideration to the basal diet used in these studies since the inclusion of certain ingredients may have confounding results with those expected from the additive or functional ingredient of interest. Regardless of the in vivo challenge model selected (balneation, cohabitation, intraperitoneal injection, or oral/anal intubation), abiotic factors such as temperature, water flow, light, and water quality strongly influence the development of disease and must be also taken into consideration when designing experimental challenge models. Thus, it is of paramount importance to standardize the studies testing the efficacy of functional diets designed to protect the host from infectious agents and to assist in harmonizing the interpretation of their results.