Distinct metabolic shifts occur during the transition between normoxia and hypoxia in the hybrid and its maternal abalone

Purifying surface water contaminated with azo dyes using nanofiltration: Interactions between dyes and dissolved organic matter

In this research, the interactions of two azo dyes, Methyl Orange (MO) and Eriochrome Black T (EBT), with dissolved organic matter (DOM) in surface water were studied, emphasizing their removal using nano-filtration membranes (NF-270 and NF-90). High-Performance Size Exclusion Chromatography (HPSEC) findings indicated that the dyes' molecular weight in deionized (DI) water ranged from 500 to 15k Dalton (Da), adjusting peak intensities with Jingmi River (JM) water Beijing. Notably, when dyes were diluted in JM water, ultraviolet (UV533 & 466, and UV254), together with total organic carbon (TOC) parameters, revealed color removal rates of 99.49% (EBT), 94.2% (MO), 87.6% DOM removal, and 86% TOC removal for NF-90. The NF-90 membrane demonstrated a 75% flux decline for 50 mL permeate volume due to its finer pore structure and higher rejection effectiveness. In contrast, the NF-270 membrane showed a 60% decline in flux under the same conditions. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) analysis of dye-treated membranes in JM water revealed that the NF-270 showed a CC bond peak at 1660 cm-1 across various samples, while analyzing NF-90, the peaks at 1400 cm-1, 1040 cm-1, 750 cm-1, and 620 cm-1 disappeared for composite sample removal. The hydrophobicity of each membrane is measured by the contact angle (CA), which identified that initial CAs for NF-270 and NF-90 were 460 and 700, respectively, that were rapidly declined but stabilized after a few seconds of processing. Overall, this investigation shows that azo dyes interact with DOM in surface waters and enhance the removal efficiency of NF membranes.

Transcriptome Analysis of Different Aquaculture Substrates on the Immune Response of Babylonia areolata

To assess the impact of different substrates in a recirculating water system on the immune response and antioxidant capacity of Babylonia areolata, we conducted a comparative analysis of the transcriptomes and antioxidant performance of the digestive glands in three substrate environments (sand-S group, ceramic granules-C group, and PVC breeding nest-P group). Transcriptome results revealed that the S group and P group exhibited the highest number of differentially expressed genes (DEGs), with a total of 2218 DEGs, including 928 upregulated and 1290 downregulated DEGs. The C group and P group had 1055 DEGs in common, with 316 upregulated and 739 downregulated DEGs. The C group and S group had the fewest DEGs, with 521 in total, including 303 upregulated and 218 downregulated DEGs. GO enrichment analysis showed that in the S vs P group, terms such as catalytic activity, membrane part, and cellular process were enriched with 287, 262, and 180 DEGs, respectively. In the C vs P group, binding, cellular process, and cell part were enriched with 146, 135, and 127 DEGs, respectively. In the C vs S group, catalytic activity, membrane part, and metabolic process were enriched with 90, 83, and 59 DEGs, respectively. Kegg enrichment analysis revealed significant changes in immune-related pathways in the S vs P group, including lysosome, phagosome, and leukocyte transendothelial migration, with 30, 13, and 10 enriched DEGs, respectively. In the C vs P group, phagosome, drug metabolism-other enzymes, and N-Glycan biosynthesis showed significant changes in immune-related pathways, with 9, 6, and 4 enriched DEGs, respectively. In the C vs S group, lysosome, PPAR signaling pathway, and fatty acid degradation exhibited significant changes in immune-related pathways, with 8, 4, and 3 enriched DEGs, respectively. Regarding antioxidant capacity, the S group showed significantly higher total T-AOC than the other experimental groups, while CAT, SOD, POD, and AKP were lower than in the C and P groups. The ACP level in the Sand group was not significantly different from the P group but significantly lower than the C group. In conclusion, substrate environments significantly influence the immune-related genes and key antioxidant enzyme activities in B. areolata.

Transcriptomic analysis revealed the dynamic response mechanism to acute ammonia exposure in the ivory shell, Babylonia areolata

The ivory shell (Babylonia areolata) is an economically important shellfish in tropical and subtropical regions, but its intensive culture and biological characteristic of hiding in the sandy substrate make it highly susceptible to ammonia stress. In this study, we investigated the dynamic changes in histopathology, oxidative stress, and transcriptome of the ivory shell at different time points under high concentration (60 mg/L) ammonia exposure. With prolonged exposure to stress, vacuoles appeared in the hepatopancreas while cell volume and intercellular space increased. The activities of superoxide dismutase (SOD) and catalase (CAT) decreased significantly under high concentrations of ammonia-induced stress while malondialdehyde (MDA) levels increased significantly. Integrated analysis of differentially expressed genes (DEGs), weighted gene co-expression network analysis (WGCNA), and quantitative real-time polymerase chain reaction (qRT-PCR) revealed that lipid transport primarily contributed to maintaining cellular homeostasis during the early stage of stress (6 and 12 h). Subsequently, a significant upregulation of oxidation-reduction reactions occurred at the middle stage (24 h), leading to oxidative stress. Finally, during the later stage (48 h), metabolic decomposition provided energy for survival maintenance. Additionally, lysosome and apoptosis were identified as potential key pathways in response to acute ammonia toxicity. Overall, our findings suggest that ivory shells can respond to acute ammonia toxicity via immune and antioxidant defense mechanisms but sustained high concentrations may cause irreversible damage. This study provides valuable insights into the response mechanism of mollusks towards ammonia and serves as a data reference for breeding ammonia-tolerant varieties of ivory shells.

Hypoxia in aquatic invertebrates: Occurrence and phenotypic and molecular responses

Global deoxygenation in aquatic systems is an increasing environmental problem, and substantial oxygen loss has been reported. Aquatic animals have been continuously exposed to hypoxic environments, so-called "dead zones," in which severe die-offs among organisms are driven by low-oxygen events. Multiple studies of hypoxia exposure have focused on in vivo endpoints, metabolism, oxidative stress, and immune responses in aquatic invertebrates such as molluscs, crustaceans, echinoderms, and cnidarians. They have shown that acute and chronic exposure to hypoxia induces significant decreases in locomotion, respiration, feeding, growth, and reproduction rates. Also, several studies have examined the molecular responses of aquatic invertebrates, such as anaerobic metabolism, reactive oxygen species induction, increased antioxidant enzymes, immune response mechanisms, regulation of hypoxia-inducible factor 1-alpha (HIF-1α) genes, and differently expressed hemoglobin/hemocyanin. The genetic basis of those molecular responses involves HIF-1α pathway genes, which are highly expressed in hypoxic conditions. However, the identification of HIF-1α-related genes and understanding of their applications in some aquatic invertebrates remain inadequate. Also, some species of crustaceans, rotifers, sponges, and ctenophores that lack HIF-1α are thought to have alternative defense mechanisms to cope with hypoxia, but those factors are still unclear. This review covers the formation of hypoxia in aquatic environments and the various adverse effects of hypoxia on aquatic invertebrates. The limitations of current hypoxia research and genetic information about the HIF-1α pathway are also discussed. Finally, this paper explains the underlying processes of the hypoxia response and presents an integrated program for research about the molecular mechanisms of hypoxic stresses in aquatic invertebrates.

Living in a hypoxic world: A review of the impacts of hypoxia on aquaculture

Hypoxia is a harmful result of anthropogenic climate change. With the expansion of global low-oxygen zones (LOZs), many organisms have faced unprecedented challenges affecting their survival and reproduction. Extensive research has indicated that oxygen limitation has drastic effects on aquatic animals, including on their development, morphology, behavior, reproduction, and physiological metabolism. In this review, the global distribution and formation of LOZs were analyzed, and the impacts of hypoxia on aquatic animals and the molecular responses of aquatic animals to hypoxia were then summarized. The commonalities and specificities of the response to hypoxia in aquatic animals in different LOZs were discussed lastly. In general, this review will deepen the knowledge of the impacts of hypoxia on aquaculture and provide more information and research directions for the development of fishery resource protection strategies.

Divergent Carry-Over Effects of Hypoxia during the Early Development of Abalone

After being exposed to environmental stimuli during early developmental stages, some organisms may gain or weaken physiological regulating abilities, which would have long-lasting effects on their performance. Environmental hypoxia events can have significant effects on marine organisms, but for breeding programs and other practical applications, it is important to further explore the long-term physiological effects of early hypoxia exposure in economically significant species. In this study, the Pacific abalone Haliotis discus hannai was exposed to moderate hypoxia (∼4 mg/L) from zygote to trochophora, and the assessments of hypoxia tolerance were conducted on the grow-out stage. The results revealed that juvenile abalones exposed to hypoxia at the early development stages were more hypoxia-tolerant but with slower weight growth, a phenomenon called the trade-off between growth and survival. These phenotypic effects driven by the hypoxia exposure were explained by strong selection of genes involved in signal transduction, autophagy, apoptosis, and hormone regulation. Moreover, long non-coding RNA regulation plays an important role modulating carry-over effects by controlling DNA replication and repair, signal transduction, myocardial activity, and hormone regulation. This study revealed that the ability to create favorable phenotypic differentiation through genetic selection and/or epigenetic regulation is important for the survival and development of aquatic animals in the face of rapidly changing environmental conditions.

Exploring the Intestinal Microbiota and Metabolome Profiles Associated With Feed Efficiency in Pacific Abalone (Haliotis discus hannai)

Feed efficiency (FE) is critical to the economic and environmental benefits of aquaculture. Both the intestines and intestinal microbiota play a key role in energy acquisition and influence FE. In the current research, intestinal microbiota, metabolome, and key digestive enzyme activities were compared between abalones with high [Residual feed intake (RFI) = -0.029] and low FE (RFI = 0.022). The FE of group A were significantly higher than these of group B. There were significant differences in intestinal microbiota structures between high- and low-FE groups, while higher microbiota diversity was observed in the high-FE group. Differences in FE were also strongly correlated to variations in intestinal digestive enzyme activity that may be caused by Pseudoalteromonas and Cobetia. In addition, Saprospira, Rhodanobacteraceae, Llumatobacteraceae, and Gaiellales may potentially be utilized as biomarkers to distinguish high- from low-FE abalones. Significantly different microorganisms (uncultured beta proteobacterium, BD1_7_clade, and Lautropia) were found to be highly correlated to significantly different metabolites [DL-methionine sulfoxide Arg-Gln, L-pyroglutamic acid, dopamine, tyramine, phosphatidyl cholines (PC) (16:0/16:0), and indoleacetic acid] in the high- and low-FE groups, and intestinal trypsin activity also significantly differed between the two groups. We propose that interactions occur among intestinal microbiota, intestinal metabolites, and enzyme activity, which improve abalone FE by enhancing amino acid metabolism, immune response, and signal transduction pathways. The present study not only elucidates mechanisms of variations in abalone FE, but it also provides important basic knowledge for improving abalone FE by modulating intestinal microbiota.

iTRAQ-based quantitative proteomic analysis of Pelteobagrus vachelli liver in response to hypoxia

Dissolved oxygen is one of the determinants in the healthy farming of Pelteobagrus vachelli. This study, we conducted quantitative proteomics on the juvenile P. vachelli livers using iTRAQ. P. vachelli were treated by 3.75 ± 0.25 mg O₂/L (hypoxia group) and 7.25 ± 0.25 mg O₂/L (control group) for 90 days. The results revealed that under hypoxic conditions, P. vachelli grew slower than control group. Proteomic profiling enabled us to identify 2618 proteins, of which 176 were significantly differentially abundant proteins (DAPs). Verification of protein regulation based on qRT-PCR indicated that the proteomics data were reliable. The top 20 significantly DAPs (10 up-regulated, 10 down-regulated) were primarily involved in energy metabolism, apoptosis inhibition, and heavy metal detoxification. KEGG pathway enrichment analysis revealed significant enrichment of 'protein digestion and absorption', 'glycolysis/gluconeogenesis', and 'phagosome'. Combining the proteomics results of short-term hypoxia (treated with 0.70 ± 0.10 mg O₂ /L for 4 h), we screened 36 common DAPs. The analysis of the 36 common DAPs indicated that P. vachelli responded to the hypoxia by regulating energy supply, inhibiting apoptosis, and disturbing defensive system. Our results lay a theoretical foundation for the cultivation of hypoxia-tolerant species and eco-breeding of P. vachelli. SIGNIFICANCE OF THE STUDY: The hypoxia tolerance of Pelteobagrus vachelli is poor, which will seriously lead to its death in high-density culture. This study analysed the liver proteome of P. vachelli under long-term hypoxia stress (treated for 90 days at 3.75 ± 0.25 mg O₂/L), and then combined the proteome results of short-term hypoxia stress (treated for 4 h at 0.70 ± 0.10 mg O₂/L). The results showed P. vachelli responded to the hypoxia by regulating energy supply, inhibiting apoptosis and disturbing defensive system. The study contributes to the breeding of new hypoxia-tolerant species of P. vachelli and lays the theoretical foundation for eco-breeding.

The Effects of Live Transport on Metabolism and Stress Responses of Abalone (Haliotis iris)

The New Zealand abalone industry relies mostly on the export of processed products to distant Asian markets, notably China. Over the past five years, live export of high quality abalone from New Zealand has proven successful. However, transport of live animals is associated with multiple stressors that affect survival and meat quality at the end of the transport phase. Better understanding of transport-derived stress is needed to improve transport conditions and recovery at destination to ensure high product quality and safety throughout the supply chain. To this end, we applied an untargeted GC-MS-based metabolomics approach to examine the changes in metabolite profiles of abalone after a 2-day transport event and subsequent water re-immersion for 2 days. The results revealed alterations of many metabolites in the haemolymph and muscle of post-transported abalone. Decreased concentrations of many amino acids suggest high energy demands for metabolism and stress responses of transported abalone, while increases of other amino acids may indicate active osmoregulation and/or protein degradation due to oxidative stress and apoptosis. The accumulation of citric acid cycle intermediates and anaerobic end-products are suggestive of hypoxia stress and a shift from aerobic to anaerobic metabolism (resulting from aerial exposure). Interestingly, some features in the metabolite profile of reimmersed abalone resembled those of pre-transported individuals, suggesting progressive recovery after reimmersion in water. Evidence of recovery was observed in the reduction of some stress biomarkers (e.g., lactic acid, succinic acid) following reimmersion. This study revealed insights into the metabolic responses to transport stress in abalone and highlights the importance of reimmersion practices in the supply chain of live animal exports.