Acute low-dose phosphate disrupts glycerophospholipid metabolism and induces stress in juvenile turbot (Scophthalmus maximus)

Phosphate, as the main nutrient factor of lake eutrophication brought by pollutants discharged from agriculture and industry, is always considered to be a low-toxicity substance to aquatic animals. But the toxicity mechanism is unclear, and published information is limited. In this study, a 96 h acute stress experiment was conducted on juvenile turbot (Scophthalmus maximus) with 0, 10, and 60 mg/L phosphate solutions. Metabonomic analysis revealed that low-dose phosphate (10 mg/L) disrupted glycerophospholipid, purine, and glycolipid metabolism, as well as the tricarboxylic acid (TCA) cycle in juveniles, even at 96 h of stress, which may lead to cell structure damage and signal recognition disorder between cells. Upregulated key genes in the main glycerophospholipid metabolic pathways, which matched the results of the metabolomic study, were detected. Furthermore, low-dose phosphate (10 mg/L) induced oxidative stress and immunotoxicity in fish, resulting in the raising of relevant genes expression such as cat and sod in liver and kidney. In addition, all phosphate-treated groups had induced lesions on gill tissue, as evidenced by pathological observations. In this study on toxic effects on and mechanism of phosphate in aquatic animals using metabolomics, gene expression, and histopathology, we confirm that acute low-dose phosphate could disrupt glycerophospholipid metabolism and induce stress in juvenile turbot. This can provide advice on the amount of phosphate accumulation for marine fish farming and on protecting species diversity and marine ecosystem from the point of view of phosphate toxicity to marine animals.

Polystyrene microplastic ingestion induces the damage in digestive gland of Amphioctopus fangsiao at the physiological, inflammatory, metabolome and transcriptomic levels

Microplastics are ubiquitous in the aquatic and terrestrial ecosystem, increasingly becoming a serious concern for aquatic organism health. However, information regarding the effects of microplastics on cephalopods is remain limited to date. Amphioctopus fangsiao, an important economic species in cephalopods, can serve as a potential indicator of environmental pollution due to its short life expectancy and high metabolic rates. Here, to explore the toxic effects during the microplastic stress response, we analyzed the growth performance, histopathological damage, oxidative stress biomarkers, metabolomic and transcriptomic response in digestive gland of A. fangsiao under different concentrations (0, 100 and 1000 μg/L) of commercial polystyrene microplastics (MPS) exposure (5 μm, sphere) for 21 days. The results showed that MPS exerted a huge influence on the growth performance of A. fangsiao. The oxidative stress and inflammation in digestive gland of A. fangsiao were also detected after exposure to MPS. In addition, most of the altered metabolites observed in the metabolic analysis were related to inflammation, oxidative stress and glucolipid metabolism. Transcriptome analysis detected the differentially expressed genes (DEGs) and the significantly enriched KEGG pathways associated with glycolipid metabolism, inflammation and DNA damage. Collectively, our results indicate that excessive environmental microplastic exposure will cause toxicity damage and then initiate the detoxification mechanism in A. fangsiao digestive gland to maintain homeostasis. This study revealed that microplastic can cause adverse consequences on cephalopods, providing novel insights into the toxicological effect of microplastic exposure.

Biological responses of shoal flounder (Syacium gunteri) to toxic environmental pollutants from the southern Gulf of Mexico

The Gulf of Mexico (GoM) is exposed to a diversity of contaminants, such as hydrocarbons and heavy metal(oid)s, either from natural sources or as a result of uncontrolled coastal urbanisation and industrialisation. To determine the effect of these contaminants on the marine biota along the Mexican GoM, the biological responses of the shoal flounder Syacium gunteri, naturally exposed, were studied. The study area included all the Mexican GoM, which was divided into three areas: West-southwest (WSW), South-southwest (SSW) and South-southeast (SSE). The biological responses included the global DNA methylation levels, the expression of biomarker genes related to contaminants (cytochrome P450 1A, glutathione S-transferase, glutathione reductase, glutathione peroxidase, catalase, and vitellogenin), histopathological lesions and PAH metabolites in bile (hydroxynaphthalene, hydroxyphenanthrene, hydroxypyrene and Benzo[a]pyrene). The correlation between the biological responses and the concentration of contaminants (hydrocarbons and metal(oid)s), present in both sediments and organisms, were studied. The shoal flounders in WSW and SSW areas presented higher DNA hypomethylation, less antioxidative response and biotransformation gene expression and a higher concentration of PAH metabolites in bile than SSE area; those responses were associated with total hydrocarbons and metals such as chromium (Cr). SSE biological responses were mainly associated with the presence of metals, such as cadmium (Cd) and copper (Cu), in the tissue of shoal flounders. The results obtained on the physiological response of the shoal flounder can be used as part of a permanent active environmental surveillance program to watch the ecosystem health of the Mexican GoM.