This study was designed to optimize the culture conditions of juvenile Epinephelus fuscoguttatus (Forsskål, 1775) under laboratory conditions. To this effect, the rate of oxygen consumption was monitored as an index of stress under different temperature, salinity, pH, photoperiod, and urea concentrations. The result obtained after 12 h of exposure suggests the preference of the juvenile E. fuscoguttatus to a temperature range of 15-25 °C and salinity of 30 ppt. Based on this study, temperature was found to be the most lethal as 100% mortality was observed after 6 h in fish exposure to temperatures above the optimal (≥ 30 °C). However, the oxygen consumption rate was similar under the different pH, photoperiod, and urea concentration tested. It was concluded that water temperature was most critical in terms of respiration physiology of the juvenile E. fuscoguttatus given the range and levels of environmental factors tested in this study.
Oxyeleotris marmorata is an ambush predator. It is known for slow growth rate and high market demand. Farming of O. marmorata still remains a challenge. In order to establish a proper feeding practice to stimulate growth, knowledge of its metabolic processes and cost should be examined. Therefore, this study was designed to investigate the diel osmorespiration rhythms of O. marmorata in response to feeding challenge by using an osmorespirometry assay. The results have shown that oxygen consumption rate of the fed fish was approximately 3 times higher than that of the unfed fish in early evening to support specific dynamic action. Digestion and ingestion processes were likely to be completed within 18-20 h in parallel with the ammonia excretion noticeable in early morning. Under resting metabolism, metabolic oxygen consumption was influenced by diel phase, but no effect was noted in ammonia excretion. As a nocturnal species, O. marmorata exhibited standard aerobic metabolic mode under dark phase followed by light phase, with high oxygen consumption rate found in either fed or unfed fish. It can be confirmed that both the diel phase and feeding have a significant interactive impact on oxygen consumption rate, whereas ammonia metabolism is impacted by feeding state. High metabolic rate of O. marmorata supports the nocturnal foraging activity in this fish. This finding suggested that feeding of O. marmorata should be performed during nighttime and water renewal should be conducted during daytime.
This study reports the antioxidant property and molecular mechanism of a tryptophan-tagged peptide derived from a teleost fish Channa striatus of serine threonine-protein kinase (STPK). The peptide was tagged with tryptophan to enhance the antioxidant property of STPK and named as IW13. The antioxidant activity of IW13 peptide was investigated using in vitro methods such as DPPH, ABTS, superoxide anion radical scavenging and hydrogen peroxide scavenging assay. Furthermore, to investigate the toxicity and dose response of IW13 peptide on antioxidant defence in vitro, L6 myotubes were induced with generic oxidative stress due to exposure of hydrogen peroxide (H2O2). IW13 peptide exposure was found to be non-cytotoxic to L6 cells in the tested concentration (10, 20, 30, 40 and 50 μM). Also, the pre-treatment of IW13 peptide decreased the lipid peroxidation level and increased glutathione enzyme activity. IW13 peptide treatment upregulated the antioxidant enzyme genes: GPx (glutathione peroxidase), GST (glutathione S transferase) and GCS (glutamine cysteine synthase), in vitro in L6 myotubes and in vivo in zebrafish larvae against the H2O2-induced oxidative stress. The results demonstrated that IW13 renders protection against the H2O2-induced oxidative stress through a cellular antioxidant defence mechanism by upregulating the gene expression, thus enhancing the antioxidant activity in the cellular or organismal level. The findings exhibited that the tryptophan-tagged IW13 peptide from STPK of C. striatus could be a promising candidate for the treatment of oxidative stress-associated diseases.
A study was conducted to evaluate the gonad differentiation of juvenile yellow perch (YP, Perca flavencens) and determine the latest labile period related to hormone treatment. Juvenile fish were subjected to two dietary concentrations of methyltestosterone (MT; 20 and 50 mg/kg feed) for 60 days in three (3) age groups of 38-, 46-, and 67-days post-hatching (dph), where control group were fed with standard commercial feed. Following a 10-month on-growing period, sex phenotypes were determined by gross and histological gonad morphology. Results showed the juvenile YP responded to the exogenous hormone when it was applied at 38 dph for both 20 and 50 mg/kg feed resulting in 100% males. At 46 dph, only 50 mg/kg feed resulted in 100% males. Both MT-treated at 38 and 46 dph significantly differed (P
The study investigated the alleviated effects of Alpha-ketoglutaric acid (AKG) on the intestinal health of mirror carp (Cyprinus carpio Songpu) caused by soy antigenic protein. The diets were formulated from fishmeal (CON), 50% soybean meal (SBM), the mixture of glycinin and β-conglycinin (11 + 7S) and adding 1% AKG in the 11 + 7S (AKG). Carp (~ 4 g) in triplicate (30 fish per tank) was fed to apparent satiation thrice a day for six weeks. Compared with CON, SBM treatment resulted in significantly poor growth performance (P 0.05). Gene expression of tumor necrosis factor (TNF-α) and interleukin-1 β (IL-1β) in proximal intestines (PI) and distal intestines (DI) were increased (P
Aquatic bacterial pathogens can cause severe economic loss in aquaculture industry. An opportunistic pathogen, Aeromonas hydrophila is responsible for Motile Aeromonas Septicemia, leading to high mortality rates in fish. The present study was focused on the efficacy of Aloe barbadensis replacing fishmeal diets on hematological, serum biochemical, antioxidant, histopathological parameters, and disease resistance against A. hydrophila infection in Labeo rohita. Isonitrogenous fishmeal replaced diets (FMR) were prepared with varying levels of A. barbadensis at D1 (0%) (control), D2 (25%), D3 (50%), D4 (75%) and D5 (100%) then fed to L. rohita. After 60 days of post-feeding, the experimental fish were challenged with A. hydrophila. Blood and organs were collected and examined at 1- and 15-days post infection (dpi). The results demonstrated that on 1 dpi, white blood cells (WBC), total protein, cholesterol and low-density lipoprotein (LDL) levels were significantly increased in D3 diet fed groups. The D2 and D3 diet fed group showed decreasing trends of serum glutamic pyruvic transaminase (SGPT) and antioxidant enzymes activity on 15 dpi. The histopathological architecture results clearly illustrated that the D3 diet fed group had given a higher protective effect by reducing the pathological changes associated with A. hydrophila infection in liver, intestine and muscle. Higher percentage of survival rate was also observed in D3 diet fed group. Therefore, the present study suggested that the dietary administration of A. barbadensis up to 50% fishmeal replacement (D3 diet) can elicit earlier antioxidant activity, innate immune response and improve survival rate in L. rohita against A. hydrophila infection.
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. One of the promising prophylactic agents incorporated in fish feed is resveratrol, a commercial phytophenol derived via the methanol extraction method. Recent studies have revealed many beneficial effects of resveratrol in aquatic animals. Therefore, this review discusses and summarizes the roles of resveratrol in improving growth performance, flesh quality, immune system, antioxidant capacity, disease resistance, stress mitigation, and potential combination with other prophylactic agents for aquatic animals.
This study was designed to evaluate the tolerance of Clarias gariepinus juveniles to a gradual and abrupt increase in salinity over time. To this effect, C. gariepinus juveniles were exposed to three salinity incremental protocols namely 1 g L-1 day-1, 5 g L-1 day-1, and 10 g L-1 day-1. Changes in the hematological parameters and the gill histology of fish were analyzed to determine the impact of osmotic stress on the health status of the fish and its osmoregulatory ability. The result obtained showed that juveniles of C. gariepinus can tolerate salinity stress up to 14 g L-1. At 15 g L-1 and beyond, all samples died regardless of gradual (i.e., 1 g L-1 day-1 administered for 15 days) or abrupt salinity exposure (i.e., 5 g L-1 day-1 administered for three days and 10 g L-1 day-1 administered for two days). Interestingly, more than 90% of the fish survived a direct 10 g L-1 exposure for 24 h without prior acclimation. The hematological parameters accessed in the fish exposed to 10 g L-1 (either gradually or abruptly) showed a significant increase in the white blood cells and a decrease in the red blood cells, packed cell volume, hemoglobin concentration, and all derived blood parameters. The results of the serum biochemistry show a lower total protein and albumin in the salinity-treated fish compared to the control group. However, the serum glucose and the plasma electrolytes (i.e., K+, Na+, and Cl-) were higher in the former group than in the latter. Aside from the stress response expressed in the blood parameters, severe gill degenerations were seen in the histological micrograph obtained for the salinity-treated fish, while the control had a near-normal gill architecture. It was concluded that C. gariepinus could tolerate salinity exposure of 10 g L-1 day-1 (administered gradually or abruptly) and below without killing the fish within 24 h.
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. The impact of severe temperatures on various species of catfish is dependent upon the magnitude of the stressor and additional influencing factors. This paper presents an analysis of the effects of temperature fluctuations on various aspects of catfish species, including growth and survival, blood parameters, enzymatic and hormone response, oxygen consumption rates, sound generation and hearing skills, nutritional requirements, and other phenotypic attributes. While this review is certainly not exhaustive, it offers a broad synopsis of the ideal temperature ranges that are most favorable for several catfish species. In-depth research to investigate the interacting impacts of severe temperature occurrences in conjunction with other associated environmental stresses on a wider variety of catfish species is crucial in order to further our understanding of how catfish species will respond to the anticipated climate change in the future.