Transcriptomics Reveal the Effects of Breeding Temperature on Growth and Metabolism in the Early Developmental Stage of Platax teira.

The growth, development, and survival of fish, especially in the early stages of development, is influenced by a complex of environmental factors, among which temperature is one of the most important. Although the physiological effects of environmental stress in fish have been extensively studied, the molecular mechanisms are poorly understood. However, recent advances in transcriptomic techniques have facilitated the study of the molecular mechanisms of environmental stress responses in aquatic species. Here, we aimed to elucidate the effects of breeding temperatures (21, 24, 27, and 30 °C) on the growth and nutrient metabolism in the early developmental stage of Platax teira, using transcriptomic techniques. Transcriptomic analysis identified 5492, 6937, and 4246 differentially expressed genes (DEGs) in the 21 vs. 24 °C, 27 vs. 24 °C, and 30 vs. 24 °C comparisons, respectively, most of which were involved in cell processes, single organism, metabolism, catalytic activity, and cell part, based on gene ontology (GO) functional annotations. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the DEGs were mainly enriched in pathways related to metabolism of matter and energy, protein digestion and absorption, and glucose and lipid metabolism. Additionally, the expression of genes related to energy, lipid, and glucose metabolism in the fish liver was upregulated under a low-temperature condition (21 °C), although increasing the temperature within the acceptable threshold improved nutrient metabolism and growth in the fish. Meanwhile, nutrient metabolism and growth were suppressed by an extremely high temperature (30 °C) owing to oxidative stress. Overall, it was shown that nutrient metabolism pathways were involved in thermal stress responses in P. teira, and the optimal breeding temperature range was 24-27 °C. Through transcriptomics, the regulatory mechanism of larval development in P. teira under different growth temperatures was elucidated, with the goal of establishing a theoretical basis for industrial breeding.

Characteristics of microplastic pollution in golden pompano (Trachinotus ovatus) aquaculture areas and the relationship between colonized-microbiota on microplastics and intestinal microflora.

Microplastic (MPs) pollution is a global marine environmental problem. The effects of MPs on the gut microbiota of aquatic organisms have received considerable attention. For example, microbes colonizing MPs in pond cultures alter the structure and function of the intestinal microbes of shrimp and fish. It was hypothesized that bacteria on MPs in natural mariculture areas also interact with the intestinal flora of golden pompano (Trachinotus ovatus) because biofilms can form on the surface of MPs during long-term floating in seawater. To our knowledge, this study is the first to investigate MPs pollution in T. ovatus aquaculture. DNA sequencing and bioinformatics analysis confirmed the effect of microbial colonization of MPs on the intestinal flora of T. ovatus. The MPs detected in the gut wet weight (w.w.) of golden pompano (546 ± 52 items/g) were mainly pellets and fragments of blue or green, whereas the sediment MPs dry weight (d.w.) (4765 ± 116 items/kg) were mainly black fibers. The MPs richness in the sediment gradually increased from the open-sea aquaculture area to the estuarine aquaculture area and was positively correlated with the MPs richness in the intestinal tract of golden pompano. MPs 20-200 µm were the most common in the gut and sediment. The intake of MPs increased the abundance of Proteobacteria and decreased that of Firmicutes in the intestinal flora. The functional compositions of MP-colonizing microbes and gut microbiota were similar, suggesting that the two communities influence each other. Network analysis further confirmed this and revealed that Vibrio plays a key role in the intestinal flora and surface microorganisms of MPs. Overall, the intake of MPs by aquatic animals not only affects the intestinal flora and intestinal microbial function, but also poses potential risks to aquaculture.

The combined effects of microplastics and the heavy metal cadmium on the marine periphytic ciliate Euplotes vannus.

Microplastics could be grazed by marine organisms and possibly transferred to higher trophic levels along the microbial loop. Due to their size and capacity to concentrate heavy metals that trigger joint toxic effects, microplastics (MPs) have already become a severe threat to marine organisms. The detrimental effects of MPs on large marine organisms have been studied, but the combined toxicity of MPs and cadmium (Cd) on protozoan ciliates remains unclear. In the present study, we selected different diameters and concentrations of polystyrene microspheres (PS-MPs) and Cd2+ as model MPs and heavy metals to evaluate their single and combined effects on the periphytic marine ciliate Euplotes vannus in relation to carbon biomass and oxidative stress. The MPs were indeed ingested by Euplotes vannus and significantly reduced the abundance and carbon biomass of ciliate populations. Combined exposure to MPs and Cd2+ not only increased the bioaccumulation of Cd2+ in ciliates but also exacerbated the decrease in ciliate biomass by increasing oxidative stress and membrane damage. In comparison, the effects of nano-sized plastics (0.22 µm) were more harmful than those of micro-sized plastics (1.07 µm, 2.14 µm and 5.00 µm). A smaller size represents a higher potential for penetrating biological members and a stronger adsorption capacity for cadmium. These results provide new insight into the combined toxicity of microplastics and heavy metals on ciliated protozoa and lay a foundation for higher trophic levels and ecosystems.

Effects of acute ammonia exposure and recovery on the antioxidant response and expression of genes in the Nrf2-Keap1 signaling pathway in the juvenile golden pompano (Trachinotus ovatus).

Continuous exposure to high levels of ammonia can cause oxidative damage to fish tissues and organs. To date, the mechanism by which juvenile golden pompano (Trachinotus ovatus) are poisoned by ammonia exposure has not been thoroughly elucidated. although the mechanisms of ammonia toxicity are not well described for the pompano, many other studies presented these effects to other fish species. So an overview would be given. First, an acute ammonia nitrogen toxicity experiment on juvenile golden pompano obtained a 96-h half-lethal concentration (96 h LC50) of 26.9 mg/L. In the ammonia exposure experiment, fish were sampled at 0 h, 6 h, 12 h, 24 h, 48 h, 72 h and 96 h after exposure to ammonia water (26.93 mg/L). The results showed that with the prolonged ammonia nitrogen exposure, plasma cortisol (COR), total cholesterol (TC), glutamic-pyruvic transaminase (ALT), glutamic oxalacetic transaminase (AST) and malonaldehyde (MDA) levels continued to rise, while glucose (GLU) levels first increased and later gradually decreased after 12 h. The activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) in the liver and the mRNA expression levels of antioxidant genes (SOD, CAT, and GPX) first increased and subsequently decreased with increasing exposure time. Through microscopic observation, it was found that the degree of liver damage increased with increasing stress time and was most serious at 96 h. In the post-poison recovery experiment, the fish exposed to ammonia were transferred to clean water, and samples were taken at 24 h, 48 h, 72 h and 96 h after recovery. The results showed that with the increasing recovery time, each index recovered to the initial level to varying degrees, but the recovery time of 96 h was not enough for the fish to return to the normal level. We also examined the regulation of the Nrf2-Keap1 signaling pathway by the molecular mechanism of the antioxidant defense system. The results of this analysis showed that there was a positive correlation between Nrf2 and liver antioxidant gene expression levels, while there was a negative correlation between Keap1 and liver antioxidant gene expression levels, which may be observed because Nrf2 plays a key role in inducing antioxidant genes, and Keap1 may hinder the response to Nrf2. These results may provide a deeper and more comprehensive understanding of the impact of ammonia exposure on fish and help to provide a foundation for managing the healthy reproduction of juvenile fish.

Gill oxidative damage caused by acute ammonia stress was reduced through the HIF-1α/NF-κb signaling pathway in golden pompano (Trachinotus ovatus).

This study aimed to investigate the intoxication mechanism of golden pompano (Trachinotus ovatus) exposed to high ammonia levels and the effects on the immune and antioxidant mechanisms of gills. Juvenile golden pompano was exposed to ammonia (total ammonia: 26.9 mg/L) to induce 96 h of ammonia stress, and a 96 h recovery experiment was performed after poisoning. Then, we evaluated hematological parameters, the histological structure and the expression of related genes. In this experiment, continuous exposure to high levels of ammonia led to a significant increase in plasma alkaline phosphatase (ALP), acid phosphatase (ACP) and lactate dehydrogenase (LDH) levels (P < 0.05), and the levels of triiodothyronine (T3) and tetraiodothyronine (T4) were significantly reduced (P < 0.05). Moreover, the expression of antioxidant genes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and inflammatory cytokines such as tumor necrosis factor α (TNF-α) and interleukin 1ß (IL-1ß) increased (P < 0.05). These results indicate that ammonia activates the active osmotic regulatory mechanism of fish gills and participates in defense and immune responses. However, with prolonged exposure to ammonia, the balance of the defense system is disrupted, leading to oxidative damage and inflammation of the gill tissue. This research not only helps elucidate the intoxication mechanism of golden pompano by ammonia at the molecular level but also provides a theoretical basis for further research on detoxification mechanisms.

Preparation of novel butyryl galactose ester-modified coix component microemulsions and evaluation on hepatoma-targeting in vitro and in vivo.

The butyryl galactose ester-modified coix component microemulsions (But-Gal-CMEs) was developed for enhanced liver tumor-specific targeting. The study was aimed to evaluate the hepatoma-targeting potential of But-Gal-CMEs in vitro and in vivo. But-Gal-CMEs with a uniform spherical shape exhibited a small particle size (56.68 ± 0.07 nm), a narrow polydispersity (PDI, 0.144 ± 0.005) and slightly negative surface charge (-0.102 ± 0.008 mV). In the cell uptake studies, But-Gal-CMEs showed a significant enhancement on the intracellular fluorescent intensity on HepG2 cells model, which was 1.93-fold higher relative to coix component microemulsions (CMEs). The IC50 of But-Gal-CMEs against HepG2 cells was 64.250 µg/mL, which was notably stronger than that of CMEs. In the cell apoptosis studies, compared with CMEs, But-Gal-CMEs (50 µg/mL) treatment resulted in a 1.34-fold rise in total apoptosis cells of HepG2. In the biodistribution studies in vivo, the intratumorous fluorescence of Cy5-loaded But-Gal-CMEs was 1.43-fold higher relative to that of Cy5-loaded CMEs, suggesting an obviously enhanced accumulation in the tumor sites. Taken as together, But-Gal could be incorporated into the coix component microemulsions as a novel ligand for realizing hepatoma-targeting drugs delivery.