Fish Physiology and Biochemistry

Fc receptors (FcRs), specific to the Fc portion of immunoglobulin (Ig), are required to regulate immune responses against pathogenic infections. However, FcγR is a member of FcRs family, whose structure and function remains to be elucidated in teleost fish. In this study, the FcγRII, from largemouth bass (Micropterus saloumoides), named membrane MsFcγRII (mMsFcγRII), was cloned and identified. The opening reading frame (ORF) of mMsFcγRII was 750 bp, encoding 249 amino acids with a predicted molecular mass of 27 kDa...

Early mild stress (EMS) is like preparedness and might help fish deal with stress appropriately. This study investigated how EMS and photoperiod changes can impact growth, haematology, blood biochemistry, immunological response, antioxidant system, liver enzymes, and stress response of oscar (Astronotus ocellatus; 7.29 ± 0.96 g) before and after acute confinement stress (AC stress). Ten experimental treatments included five different photoperiods 8L16D (08:16 light to dark), 12L12D (12:12 light to dark), 16L8D (16:08 light to dark), 20L4D (20:04 light to dark), and 24L0D (24:00 light to dark), and these five photoperiod schedules were conducted in an EMS condition...

Autophagy is a cellular process that involves the fusion of autophagosomes and lysosomes to degrade damaged proteins or organelles. Triglycerides are hydrolyzed by autophagy, releasing fatty acids for energy through mitochondrial fatty acid oxidation (FAO). Inhibited mitochondrial FAO induces autophagy, establishing a crosstalk between lipid catabolism and autophagy. Peroxisome proliferator-activated receptor α (PPARα), a transcription factor, stimulates lipid catabolism genes, including fatty acid transport and mitochondrial FAO, while also inducing autophagy through transcriptional regulation of transcription factor EB (TFEB)...

The present study investigated the effect of replacing fishmeal (FM) with insect meal of Hermetia illucens (HI) in the diet of Sparus aurata farmed inshore on growth, gut health, and microbiota composition. Two isolipidic (18% as fed) and isoproteic (42% as fed) diets were tested at the farm scale: a control diet without HI meal and an experimental diet with 11% HI meal replacing FM. At the end of the 25-week feeding trial, final body weight, specific growth rate, feed conversion rate, and hepatosomatic index were not affected by the diet...

Peroxisome proliferator-activated receptor β (pparβ) is a key gene-regulating lipid metabolism pathway, but its function in turbot remains unclear. In this study, the CDS of pparβ was cloned from kidney for the first time. The CDS sequence length was 1533 bp encoding 510 amino acids. Structural analysis showed that the pparβ protein contained a C4 zinc finger and HOLI domain, suggesting that the pparβ gene of turbot has high homology with the PPAR gene of other species. The high expression patterns of pparβ, acox, and cpt-1 at high temperatures, as shown through qPCR, indicated that high temperatures activated the transcriptional activity of pparβ and increased the activity of the acox and cpt-1 genes...

The effects of thermal shock on hematological, biochemical and antioxidant responses were evaluated in liver tissue of juvenile tambaqui (Colossoma macropomum) and tambatinga (♀ C. macropomum × ♂ Piaractus brachypomus). Forty juveniles of tambaqui and 40 juveniles of tambatinga, of the same age and with an initial weight of 23.3 ± 6.7 g, were randomly distributed in eight 28L circular tanks. A tank (n = 10 fish) of tambaqui and a tank (n = 10 fish) of tambatinga were then used to obtain basal data...

Gastrin is an important intragastrointestinal hormone, but reports on its regulation of feeding behavior in fish are still scarce. This study aimed to determine the feeding regulatory function of gastrin in sturgeon. In this study, a gastrin/cholecystokinin-like peptide was identified in the genomes of sturgeon and proved to be gastrin by evolutionary tree analysis. Tissue distribution of gastrin and its receptor, cholecystokinin receptor B (CCKRB), showed that both had high mRNA abundance in the hypothalamus and gastrointestinal tract...

Aquaculture has intensified tremendously with the increasing demand for protein sources as the global population grows. However, this industry is plagued with major challenges such as poor growth performance, the lack of a proper environment, and immune system impairment, thus creating stress for the aquaculture species and risking disease outbreaks. Currently, prophylactics such as antibiotics, vaccines, prebiotics, probiotics, and phytobiotics are utilized to minimize the negative impacts of high-density farming...

Catfish are a highly diverse group of fish that are found in various regions across the globe. The significance of catfish culture extends to various aspects, including food security, economic advancement, preservation of cultural legacy, and ecological stewardship. The catfish industry is presently encountering unprecedented challenges as a consequence of the variability in water temperature caused by climate change. Temperature is a significant abiotic component that regulates and restricts fish physiology throughout their life cycle...

This study was designed to determine the effects of papaya peel extract (PPE) supplementation on the growth and immunophysiological responses of rohu fingerlings at different stocking densities. In this study, three isonitrogenous (307.2-309.8 g kg-1 protein) and isocaloric diets (16.10-16.16 MJ digestible energy kg-1 ) were prepared using three different inclusion levels (0, 5, and 10 g kg-1 ) of PPE. Four hundred and five rohu fingerlings (mean weight: 4.24 g ± 0...

The present study aims to investigate nutritional programming through early starvation in the European seabass (Dicentrarchus labrax). European seabass larvae were fasted at three different developmental periods for three durations from 60 to 65 dph (F1), 81 to 87 dph (F2), and 123 to 133 dph (F3). Immediate effects were investigated by studying gene expression of npy (neuropeptide Y) and avt (Arginine vasotocin) in the head, while potential long-term effects (i.e., programming) were evaluated on intermediary metabolism later in life (in juveniles)...

A homogeneous assay was developed to evaluate ligands that target the membrane progesterone receptor alpha (mPRα) of goldfish. This was achieved by employing graphene quantum dots (GQDs), a type of semiconductor nanoparticle conjugated to the goldfish mPRα. When progesterone-BSA-fluorescein isothiocyanate (P4-BSA-FITC) was combined with the other agents, fluorescence was observed through Förster resonance energy transfer (FRET). However, this fluorescence was quenched by binding between the ligand and receptor...

The current climate change situation could bring critical effects for marine species, especially those already considered endangered. Although some species can adapt fast to the environmental changes, it is necessary to get into the worst scenario and develop tools to anticipatedly assess the physiological effects of such environmental change. With this purpose, our study aims to determine the effect of a range of seawater temperatures and pHs on sperm motility in the European eel (Anguilla anguilla). Low seawater pH (6...

To alleviate amino acid imbalances in fermented soybean meal as a replacement for fishmeal feeds, this study evaluated the effects of adding lysine (Lys), methionine (Met), and α-ketoglutaric acid (AKG) to fermented soybean meals for Chinese perch. Chinese perch (34 ± 3 g) were fed five diets for 66 days (fishmeal as the protein source of the basal diet [FM]; fermented soybean meal as a substitute for 30% fishmeal in the soybean meal diet [FSM]; addition of crystalline Lys and Met [AA]; addition of α-ketoglutaric acid [AKG]; and simultaneous addition of crystalline Lys, Met, and AKG [BA] to the soybean meal diet)...

Animals often experience changes in their environment that can be perceived as stressful. Previous evidence indicates that different individuals may have distinct stress responses. The role of serotonin (5-HT) in stress adaptation is well established, but its relationship with different defense strategies and the persistence of physiological and behavioral responses in different individuals during repeated acute stress remain unclear. In this study, using olive flounder (Paralichthys olivaceus) as a model, we analyzed the relationship between boldness and neurotransmitter 5-HT activity...

Temperature fluctuations are inevitable and have an important impact on the survival of fish during transportation. Therefore, the effect of temperature fluctuation (15 ± 1 °C, 15 ± 2 °C, 15 ± 3 °C) on the muscle quality, physiological, and immune function of hybrid pearl gentian grouper before waterless keeping alive, during keeping alive (0 h, 3 h, 6 h, 9 h, 12 h), and after revival for 12 h was investigated. The plasma glucose concentration of grouper gradually decreased to 0...

The effects of long-term dietary supplementation with sandalwood (Santalum album L.) essential oil (SEO) was investigated on hemato-biochemical biomarkers, immune status, antioxidant capacity, and resistance against Staphylococcus aureus in Nile tilapia (Oreochromis niloticus). Five groups (with four replicates) of O. niloticus (12.60 ± 0.20 g) were fed diets supplemented with SEO at doses of 0, 0.5, 1.0, 2.0, and 4.0 mL/kg diet for 60 days. Results indicated a substantial increase in blood protein levels and lower serum cholesterol, cortisol, glucose, urea, creatinine levels and, transaminase activities of fish fed a 2...

Clarias gariepinus is an important freshwater fish with high economic value and breeding potential in China. It is a fast-growing and adaptable catfish, but the main problems facing the current market are its low price and poor taste, although starvation is a good solution to these problems. In this study, the effects of starvation on the physiology, biochemistry, and muscle quality of C. gariepinus were investigated. The results showed that compared with the control group, the weight gain rate and specific growth rate of the starvation group were significantly different...

Color changes and pattern formations can represent strategies of the utmost importance for the survival of individuals or of species. Previous studies have associated capture with the formation of blotches (areas with light color) of coral trout, but the regulatory mechanisms link the two are lacking. Here, we report that capture induced blotches formation within 4-5 seconds. The blotches disappeared after anesthesia dispersed the pigment cells and reappeared after electrical stimulation. Subsequently, combining immunofluorescence, transmission electron microscopy and chemical sympathectomy, we found blotches formation results from activation of catecholaminergic neurons below the pigment layer...

Common carp female generally matures at age 4-5 years old and spawns between April and July under the temperate climate. Contrary to a range of 0-28 °C of temperate freshwaters, the water temperature of Lake Hévíz (Hungary, Central Europe), the largest natural bathable thermal lake in the world, varies between 26 and 35 °C seasonally. The specific environmental conditions (continuously warm water and its individual chemical composition, special nutrient base, lack of natural lakeside spawning substrate compared to usual spawning grounds, continuous high human disturbance, etc...