Metabolic and transcriptional responses demonstrating enhanced thermal tolerance in domesticated abalone.

Global warming threatens aquatic systems and organisms. Many studies have focused on the vulnerability and stress responses of aquaculture organisms to future thermal conditions. However, it may be of more practical significance to reveal their acclimation potential and mechanisms. In this study, the physiological, metabolic, and transcriptional responses to long-term temperature acclimation of northern and southern populations of Pacific abalone Haliotis discus hannai, a commercially important gastropod sensitive to environmental changes, were compared. This study conducted two common-garden experiments, including a thermostatic experiment in the lab and an aquaculture experiment on the farm. The abalone population cultured in warmer southern waters was tolerant of ongoing high temperatures, whereas the abalone population originally cultured in cooler northern waters exhibited vulnerability to high temperatures but could enhance its thermal tolerance through the process of natural selection in warmer southern waters. This difference was linked to divergence in the metabolic and transcriptional processes of the two populations. The tolerant population exhibited a greater capacity for carbohydrate and amino acid metabolism regulation and energy redistribution to cope with heat stress. This capacity may have been selected for, and accumulated, over many generations because the tolerant population originated from the intolerant population over two decades ago. This work provides insight into the vulnerability and acclimation potential of abalone to heat stress and discloses the molecular and metabolic traits underlying this phenomenon. Future research on the ability of abalone and other commercial shellfish species to acclimate to global warming should take this potential into account.

An Improved Finite-Time and Fixed-Time Stable Synchronization of Coupled Discontinuous Neural Networks.

This article focuses on the finite-time and fixed-time synchronization of a class of coupled discontinuous neural networks, which can be viewed as a combination of the Hindmarsh-Rose model and the Kuramoto model. To this end, under the framework of Filippov solution, a new finite-time and fixed-time stable theorem is established for nonlinear systems whose right-hand sides may be discontinuous. Moreover, the high-precise settling time is given. Furthermore, by designing a discontinuous control law and using the theory of differential inclusions, some new sufficient conditions are derived to guarantee the synchronization of the addressed coupled networks achieved within a finite-time or fixed-time. These interesting results can be seemed as the supplement and expansion of the previous references. Finally, the derived theoretical results are supported by examples with numerical simulations.

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.

Genomic insights into the adaptation and evolution of the nautilus, an ancient but evolving "living fossil".

The nautilus, commonly known as a "living fossil," is endangered and may be at risk of extinction. The lack of genomic information hinders a thorough understanding of its biology and evolution, which can shed light on the conservation of this endangered species. Here, we report the first high-quality chromosome-level genome assembly of Nautilus pompilius. The assembled genome size comprised 785.15 Mb. Comparative genomic analyses indicated that transposable elements (TEs) and large-scale genome reorganizations may have driven lineage-specific evolution in the cephalopods. Remarkably, evolving conserved genes and recent TE insertion activities were identified in N. pompilius, and we speculate that these findings reflect the strong adaptability and long-term survival of the nautilus. We also identified gene families that are potentially responsible for specific adaptation and evolution events. Our study provides unprecedented insights into the specialized biology and evolution of N. pompilius, and the results serve as an important resource for future conservation genomics of the nautilus and closely related species.

Transcriptome analysis reveals the molecular mechanisms of heterosis on thermal resistance in hybrid abalone.

BACKGROUND: Heterosis has been exploited for decades in different animals and crops due to it resulting in dramatic increases in yield and adaptability. Hybridization is a classical breeding method that can effectively improve the genetic characteristics of organisms through heterosis. Abalone has become an increasingly economically important aquaculture resource with high commercial value. However, due to changing climate, abalone is now facing serious threats of high temperature in summer. Interspecific hybrid abalone (Haliotis gigantea ♀ × H. discus hannai ♂, SD) has been cultured at large scale in southern China and has been shown high survival rates under heat stress in summer. Therefore, SD has become a good model material for heterosis research, but the molecular basis of heterosis remains elusive. RESULTS: Heterosis in thermal tolerance of SD was verified through Arrhenius break temperatures (ABT) of cardiac performance in this study. Then RNA-Sequencing was conducted to obtain gene expression patterns and alternative splicing events at control temperature (20 °C) and heat stress temperature (30 °C). A total of 356 (317 genes), 476 (435genes), and 876 (726 genes) significantly diverged alternative splicing events were identified in H. discus hannai (DD), H. gigantea (SS), and SD in response to heat stress, respectively. In the heat stress groups, 93.37% (20,512 of 21,969) of the expressed genes showed non-additive expression patterns, and over-dominance expression patterns of genes account for the highest proportion (40.15%). KEGG pathway enrichment analysis showed that the overlapping genes among common DEGs and NAGs were significantly enriched in protein processing in the endoplasmic reticulum, mitophagy, and NF-κB signaling pathway. In addition, we found that among these overlap genes, 39 genes had undergone alternative splicing events in SD. These pathways and genes may play an important role in the thermal resistance of hybrid abalone. CONCLUSION: More alternative splicing events and non-additive expressed genes were detected in hybrid under heat stress and this may contribute to its thermal heterosis. These results might provide clues as to how hybrid abalone has a better physiological regulation ability than its parents under heat stress, to increase our understanding of heterosis in abalone.

Comparative Transcriptome and DNA Methylation Analysis of Phenotypic Plasticity in the Pacific Abalone (Haliotis discus hannai).

Phenotypic plasticity is an adaptive mechanism used by organisms to cope with environmental fluctuations. Pacific abalone (Haliotis discus hannai) are large-scale farmed in the temperate area of northern China and in the warmer waters of southern China. RNA-seq and comparative transcriptomic analysis here were performed to determine if the northern and southern populations have evolved divergent plasticity and if functional differences are associated with protein synthesis and growth-related biological progress. The DNA methylation (5mC) landscape of H. discus hannai from the two populations using whole genomic bisulfite sequencing (WGBS), exhibited different epigenetic patterns. The southern population had significant genomic hypo-methylation that may have resulted from long-term acclimation to heat stress. Combining 790 differentially expressed genes (DEGs) and 7635 differentially methylated genes (DMGs), we found that methylation within the gene body might be important in predicting abalone gene expression. Genes related to growth, development, transduction, and apoptosis may be regulated by methylation and could explain the phenotypic divergence of H. discus hannai. Our findings not only emphasize the significant roles of adaptive plasticity in the acclimation of H. discus hannai to high temperatures but also provide a new understanding of the epigenetic mechanism underlying the phenotypic plasticity in adaptation to climate change for marine organisms.

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

Due to anthropogenic activities that have increased global climate change and nutrient discharges, severe hypoxic events have frequently occurred in coastal waters in recent years. Relying on coastal waters, the aquaculture area has suffered ecological and economic losses caused by hypoxia, especially in summer. In this study, to investigate the stress resistance of the Pacific abalone Haliotis discus hannai (DD) and the hybrid H. discus hannai ♀ × H. fulgens ♂ (DF), a combination of physiological, biochemical, and metabolomic methods were used to compare the metabolic responses of these two abalones to acute hypoxia (~0.5 mg O2/L, 12 h) and reoxygenation (~6.6 mg O2/L, 10-20 h). Hemolymph characteristics and aerobic/anaerobic respiratory capacity changed significantly under hypoxia or reoxygenation conditions, and they were regulated in different trends in two abalones. The contents of hepatopancreas glycogen in two abalones reached the trough after 10 h recovery, implying that short-term hypoxia leads to a long-lasting (several hours) imprint on the energy storage of abalone. In response to dissolved oxygen fluctuation, metabolic profiles of two abalones changed in distinct ways both in the hypoxia group or the reoxygenation group. The conversion of carbohydrate metabolism and amino acid metabolism indicated that hypoxia prompts abalone to change the way of energy metabolism, which may also reflect the difference in the energy utilization of DD and DF abalones. In addition, 3 metabolites (L-glutamate, 2-hydroxy-butanoic acid, and 2-methyl-3-hydroxybutyric acid) as potential biomarkers for hypoxia and reoxygenation response in abalone were determined by operating characteristic analysis (ROC). Overall, this study provides information towards understanding the damage caused by frequent hypoxic events and implies the metabolic shifts that occur under hypoxia and reoxygenation conditions in DD and DF abalones.

Superior Sodium Storage of Carbon-Coated NaV6O15 Nanotube Cathode: Pseudocapacitance Versus Intercalation.

To realize the effect of Na+ pseudocapacitance on the sodium storage of cathode materials, clewlike carbon-coated sodium vanadium bronze (NaV6O15) nanotubes (Na-VBNT@C) were synthesized via a facile combined sol-gel/hydrothermal method. The resultant Na-VBNT@C delivers high reversible capacities of 209 and 105 mA h g-1 at the rates of 0.1 and 10 C, respectively. Notably, at the higher rate of 5 C (1250 mA g-1), it can retain 94% of the initial capacity after 3000 cycles. It was found that the outstanding rate performance and the long-term cycling life of Na-VBNT@C are primarily due to the Na+ pseudocapacitance. Our study reveals that the design of Na+ pseudocapacitance is beneficial for harvesting the superior performance of NaV6O15 cathode material in sodium-ion batteries.

The Preparation and Electrochemical Performance of Olivine Cathode Materials Based on LiMn1/3Fe1/3Co1/3PO4/C.

Solid solution LiMn1/3Fe3Co1/33PO4/C ternary materials were prepared by sol-gel method with glycine or citric acid as chelating agents. SEM images indicate that the particles are well distributed with regular morphologies, and the particle sizes are around 300 nm for both samples. The cyclic voltammetry (CV) and charge-discharge curves show that the reversibility of Mn²+/Mn3+ couple is improved apparently. The redox potential corresponding to Fe²âº/Fe³âº couple has been increased which is beneficial to the energy density, and the redox potential related to Co²âº/Co³âº couple has been declined which could accelerate dynamics of intercalation/deintercalation and make the electrochemical reaction more smoothly. The obtained LiMn1/3Fe1/3Co1/33PO4/C materials with glycine as chelating agent deliver a capacity of 151.5, 142.6, 122.8, 97.9 mAh g⁻¹ at 0.05 °C, 0.1 C, 0.5 C and 1 C, respectively. And the obtained material with citric acid as chelating agent delivers a capacity of 150.8, 135.0, 111.5, 85.2 mAh g⁻¹, respectively, at the same rates.

Heteroclinic bifurcation for a general predator-prey model with Allee effect and state feedback impulsive control strategy.

In this paper, we analyze a general predator-prey model with state feedback impulsive harvesting strategies in which the prey species displays a strong Allee effect. We firstly show the existence of order-1 heteroclinic cycle and order-1 positive periodic solutions by using the geometric theory of differential equations for the unperturbed system. Based on the theory of rotated vector fields, the order-1 positive periodic solutions and heteroclinic bifurcation are studied for the perturbed system. Finally, some numerical simulations are provided to illustrate our main results. All the results indicate that the harvesting rate should be maintained at a reasonable range to keep the sustainable development of ecological systems.

An investigation of a novel MnO2 network-Ni/PVDF double shell/core membrane as an anode for lithium ion batteries.

A novel MnO2 network-Ni/PVDF double shell/core fiber membrane is synthesized for the first time as an anode material for lithium ion batteries. The freestanding MnO2 nanosheet network is grown directly onto a conductive network-Ni/PVDF shell/core fiber membrane 3D current collector, avoiding the application of binders and conductive additives and simplifying the fabrication processing. The MnO2 nanosheet network can be tightly anchored to the Ni/PVDF fiber 3D current collector, and some small pores between the fibers and between the MnO2 nanosheets lead to fast charge transfer and ion transport. The unique MnO2 network-Ni/PVDF double shell/core fiber membrane exhibits a high charge/discharge capacity, long-term cycling stability and good rate capability.

Vertically aligned CNT-supported thick Ge films as high-performance 3D anodes for lithium ion batteries.

The electrochemical performance of a thick Ge film (ca. 1020 nm) is dramatically improved by adopting vertically aligned carbon nanotube (VACNT) arrays as a 3D current collector. The VACNT-supported thick Ge film exhibits high reversible specific capacity (1352 mAh g(-1) ), and excellent capacity retention (97.2% after 100 cycles) and rate capability (843 mAh g(-1) at 10 C).

High performance carbon nanotube-Si core-shell wires with a rationally structured core for lithium ion battery anodes.

Core-shell Si nanowires are very promising anode materials. Here, we synthesize vertically aligned carbon nanotubes (CNTs) with relatively large diameters and large inter-wire spacing as core wires and demonstrate a CNT-Si core-shell wire composite as a lithium ion battery (LIB) anode. Owing to the rationally engineered core structure, the composite shows good capacity retention and rate performance. The excellent performance is superior to most core-shell nanowires previously reported.

An ear punch model for studying the effect of radiation on wound healing.

PURPOSE: Radiation and wound combined injury represents a major clinical challenge because of the synergistic interactions that lead to higher morbidity and mortality than either insult would produce singly. The purpose of this study was to develop a mouse ear punch model to study the physiological mechanisms underlying radiation effects on healing wounds. MATERIALS AND METHODS: Surgical wounds were induced by a 2 mm surgical punch in the ear pinnae of MRL/MpJ mice. Photographs of the wounds were taken and the sizes of the ear punch wounds were quantified by image analysis. Local radiation to the ear was delivered by orthovoltage X-ray irradiator using a specially constructed jig that shields the other parts of body. RESULTS: Using this model, we demonstrated that local radiation to the wound area significantly delayed the healing of ear punch wounds in a dose-dependent fashion. The addition of sublethal whole body irradiation (7 Gy) further delayed the healing of ear punch wounds. These results were replicated in C57BL/6 mice; however, wound healing in MRL/MpJ mice was accelerated. CONCLUSIONS: These data indicate that the mouse ear punch model is a valuable model to study radiation and wound combined injury.