Physicochemical and Rheological Properties of Degraded Konjac Gum by Abalone (Haliotis discus hannai) Viscera Enzyme.

In the present study, a new degraded konjac glucomannan (DKGM) was prepared using a crude enzyme from abalone (Haliotis discus hannai) viscera, and its physicochemical properties were investigated. After enzymatic hydrolysis, the viscosity of KGM obviously decreased from 15,500 mPa·s to 398 mPa·s. The rheological properties analysis of KGM and DKGMs revealed that they were pseudoplastic fluids, and pseudoplasticity, viscoelasticity, melting temperature, and gelling temperature significantly decreased after enzymatic hydrolysis, especially for KGM-180 and KGM-240. In addition, the molecular weight of KGM decreased from 1.80 × 106 Da, to 0.45 × 106 Da and the polydispersity index increased from 1.17 to 1.83 after 240 min of degradation time. Compared with natural KGM, the smaller particle size distribution of DKGM further suggests enzyme hydrolysis reduces the aggregation of molecular chains with low molecular weight. FT-IR and FESEM analyses showed that the fragmented KMG chain did not affect the structural characteristics of molecular monomers; however, the dense three-dimensional network microstructure formed by intermolecular interaction changed to fragment microstructure after enzyme hydrolysis. These results revealed that the viscosity and rheological properties of KGM could be controlled and effectively changed using crude enzymes from abalone viscera. This work provides theoretical guidance for the promising application of DKGM in the food industry.

Dietary Clostridium autoethanogenum protein has dose-dependent influence on the gut microbiota, immunity, inflammation and disease resistance of abalone Haliotis discus hannai.

Clostridium autoethanogenum protein (CAP) is an eco-friendly protein source and has great application potential in aquafeeds. The present study aimed to investigate the effects of dietary CAP inclusion on the anti-oxidation, immunity, inflammation, disease resistance and gut microbiota of abalone Haliotis discus hannai after a 110-day feeding trial. Three isonitrogenous and isolipidic diets were formulated by adding 0 % (control), 4.10 % (CAP4.10) and 16.25 % (CAP16.25) of CAP, respectively. A total of 540 abalones with an initial mean body weight of 22.05 ± 0.19 g were randomly distributed in three groups with three replicates per group and 60 abalones per replicate. Results showed that the activities of superoxide dismutase and glutathione peroxidase in the cell-free hemolymph (CFH) were significantly decreased and the content of malondialdehyde in CFH was significantly increased in the CAP16.25 group. The diet with 4.1 % of CAP significantly increased the activities of lysozyme and acid phosphatase in CFH. The expressions of pro-inflammatory genes such as tumor necrosis factor-α (tnf-α), nuclear factor-κb (nf-κb) and toll-like receptor 4 (tlr4) in digestive gland were downregulated, and the expressions of anti-inflammatory genes such as ß-defensin and mytimacin 6 in digestive gland were upregulated in the CAP4.10 group. Dietary CAP inclusion significantly decreased the cumulative mortality of abalone after the challenge test with Vibrio parahaemolyticus for 7 days. Dietary CAP inclusion changed the composition of gut microbiota of abalone. Besides, the balance of the ecological interaction network of bacterial genera in the intestine of abalone was enhanced by dietary CAP. The association analysis showed that two bacterial genera Ruegeria and Bacteroides were closely correlated with the inflammatory genes. In conclusion, the 4.10 % of dietary CAP enhanced the immunity and disease resistance as well as inhibited the inflammation of abalone. The 16.25 % of dietary CAP decreased the anti-oxidative capacity of abalone. The structure of the gut microbiota of abalone changed with dietary CAP levels.

Carryover effects of embryonic hypoxia exposure on adult fitness of the Pacific abalone.

The widespread and severe drop in dissolved oxygen concentration in the open ocean and coastal waters has attracted much attention, but assessments of the impacts of environmental hypoxia on aquatic organisms have focused primarily on responses to current exposure. Past stress exposure might also affect the performance of aquatic organisms through carryover effects, and whether these effects scale from positive to negative based on exposure degree is unknown. We investigated the carryover effects of varying embryonic hypoxia levels (mediate hypoxia: 3.0-3.1 mg O2/L; severe hypoxia: 2.0-2.1 mg O2/L) on the fitness traits of adult Pacific abalone (Haliotis discus hannai), including growth, hypoxia tolerance, oxygen consumption, ammonia excretion rate, and biochemical responses to acute hypoxia. Moderate embryonic hypoxia exposure significantly improved the hypoxia tolerance of adult Pacific abalone without sacrificing growth and survival. Adult abalone exposed to embryonic hypoxia exhibited physiological plasticity, including decreased oxygen consumption rates under environmental stress, increased basal methylation levels, and a more active response to acute hypoxia, which might support their higher hypoxia tolerance. Thus, moderate oxygen declines in early life have persistent effects on the fitness of abalone even two years later, further affecting population dynamics. The results suggested that incorporating the carryover effects of embryonic hypoxia exposure into genetic breeding programs would be an important step toward rapidly improving the hypoxia tolerance of aquatic animals. The study also inspires the protection of endangered wild animals and other vulnerable species under global climate change.

Structural and functional characterization of Hdh-HSBP1 and its involvement in heat stress and early development in Pacific abalone, Haliotis discus hannai.

Heat shock factor binding protein 1 (HSBP1) is known to regulate the activity of heat shock factor 1 (HSF1) and the early development of organisms. To understand the involvement of HSBP1 in the heat shock response and embryonic and larval development of Pacific abalone (Haliotis discus hannai), the Hdh-HSBP1 gene was sequenced from the digestive gland (DG) tissue. The full-length sequence of Hdh-HSBP1 encompassed 738 nucleotides, encoding an 8.42 kDa protein consisting of 75 deduced amino acids. The protein contains an HSBP1 domain and a coiled-coil domain, which are conserved features in the HSBP1 protein family. Protein-protein molecular docking revealed that the coiled-coil region of Hdh-HSBP1 binds to the coiled-coil region of Hdh-HSF1. Tissue expression analysis demonstrated that the highest Hdh-HSBP1 expression occurred in the DG, whereas seasonal expression analysis revealed that this gene was most highly expressed in summer. In heat-stressed abalone, the highest expression of Hdh-HSBP1 occurred at 30 °C. Moreover, time-series analysis revealed that the expression of this gene began to increase significantly at 6 h post-heat stress, with higher expression observed at 12 h and 24 h post-heat stress. Furthermore, Hdh-HSBP1 mRNA expression showed a link to ROS production. Additionally, the expression of Hdh-HSBP1 showed significantly higher expression in the early stages of embryonic development in Pacific abalone. These results suggest that Hdh-HSBP1 plays a crucial role in the stress physiology of Pacific abalone by interacting with Hdh-HSF1, as well as its embryonic development.

A metallothionein from disk abalone (Haliotis discus discus): Insights into its functional roles in immune response, metal tolerance, and oxidative stress.

Metallothioneins (MTs) are cysteine-rich metal-binding proteins whose expression is induced by exposure to essential and non-essential metals, making them potential biological markers for assessing metal pollution in various biomonitoring programs. However, the functional properties of these proteins are yet to be comprehensively characterized in most marine invertebrates. In this study, we identified and characterized an MT homolog from the disk abalone (Haliotis discus discus), referred to as disk abalone MT (AbMT). AbMT exhibited the same primary structural features as MTs from other mollusks containing two ß-domains (ß2ß1-form). AbMT protein demonstrated metal-binding and detoxification abilities against Zn, Cu, and Cd, as evidenced by Escherichia coli growth kinetics, metal tolerance analysis, and UV absorption spectrum. Transcriptional analysis revealed that AbMT was ubiquitously expressed in all analyzed tissues and upregulated in gill tissue following challenge with Vibrio parahaemolyticus, Listeria monocytogenes, and viral hemorrhagic septicemia virus (VHSV). Additionally, overexpression of AbMT suppressed LPS-induced NO production in RAW264.7 macrophages, protected cells against H2O2-induced oxidative stress, and promoted macrophage polarization toward the M1 phase. Conclusively, these findings suggest an important role for AbMT in environmental stress protection and immune regulation in disk abalone.

Total Iodine Quantification and In Vitro Bioavailability Study in Abalone (Haliotis discus hannai) Using Inductively Coupled Plasma Mass Spectrometry.

The aim of this study is to determine the total iodine content in Korean abalone (Haliotis discus hannai) and to investigate the bioavailability of iodine using an in vitro method. This research paper focuses on total iodine quantification in abalone (Haliotis discus hannai) and its components (viscera and muscle) using inductively coupled plasma mass spectrometry (ICP-MS). Additionally, an in vitro bioavailability study explored iodine absorption potential. Abalone pretreatment involved both the European standard method (ES) and microwave-assisted extraction method (MAE). The limits of detection (LOD) were 0.11 ng/g for both ES and MAE, with a limit of quantification (LOQ) of 5.4 ng/g for MAE. Accuracy, assessed using a reference material (fish muscle, ERM-BB422), showed values of 1.5 ± 0.010 mg/kg for ES and 1.6 ± 0.066 mg/kg for MAE, within an acceptable range of 1.4 ± 0.42 mg/kg. Precision, evaluated using the Horwitz ratio (HorRat) with a reference material, was determined to be 0.45 for ES and 0.27 for MAE. Therefore, total iodine contents were estimated as 74 ± 2.2 µg/g for abalone viscera and 17 ± 0.77 µg/g for abalone muscle with ES, and 76 ± 1.0 µg/g for abalone viscera and 17 ± 0.51 µg/g for abalone muscle with MAE. Recovery tests demonstrated an acceptable range of 90-110%. In the in vitro bioavailability assessment, digestion efficiency yielded ranges of 42-50.2% for viscera and 67-115% for muscle. Absorption efficiency variations were determined as 37-43% for viscera and 48-75% for muscle.

Limited genomic signatures of population collapse in the critically endangered black abalone (Haliotis cracherodii).

The black abalone, Haliotis cracherodii, is a large, long-lived marine mollusc that inhabits rocky intertidal habitats along the coast of California and Mexico. In 1985, populations were impacted by a bacterial disease known as withering syndrome (WS) that wiped out >90% of individuals, leading to the closure of all U.S. black abalone fisheries since 1993. Current conservation strategies include restoring diminished populations by translocating healthy individuals. However, population collapse on this scale may have dramatically lowered genetic diversity and strengthened geographic differentiation, making translocation-based recovery contentious. Additionally, the current prevalence of WS remains unknown. To address these uncertainties, we sequenced and analysed the genomes of 133 black abalone individuals from across their present range. We observed no spatial genetic structure among black abalone, with the exception of a single chromosomal inversion that increases in frequency with latitude. Outside the inversion, genetic differentiation between sites is minimal and does not scale with either geographic distance or environmental dissimilarity. Genetic diversity appears uniformly high across the range. Demographic inference does indicate a severe population bottleneck beginning just 15 generations in the past, but this decline is short lived, with present-day size far exceeding the pre-bottleneck status quo. Finally, we find the bacterial agent of WS is equally present across the sampled range, but only in 10% of individuals. The lack of population genetic structure, uniform diversity and prevalence of WS bacteria indicates that translocation could be a valid and low-risk means of population restoration for black abalone species' recovery.

Experimental Study on the Adhesion of Abalone to Surfaces with Different Morphologies.

To date, research on abalone adhesion has primarily analyzed the organism's adhesion to smooth surfaces, with few studies on adhesion to non-smooth surfaces. The present study examined the surface morphology of the abalone's abdominal foot, followed by measuring the adhesive force of the abalone on a smooth force measuring plate and five force measuring plates with different surface morphologies. Next, the adhesion mechanism of the abdominal foot was analyzed. The findings indicated that the abdominal foot of the abalone features numerous stripe-shaped folds on its surface. The adhesion of the abalone to a fine frosted glass plate, a coarse frosted glass plate, and a quadrangular conical glass plate was not significantly different from that on a smooth glass plate. However, the organism's adhesion to a small lattice pit glass plate and block pattern glass plate was significantly different. The abalone could effectively adhere to the surface of the block pattern glass plate using the elasticity of its abdominal foot during adhesion but experienced difficulty in completely adhering to the surface of the quadrangular conical glass plate. The abdominal foot used its elasticity to form an independent sucker system with each small lattice pit, significantly improving adhesion to the small lattice pit glass plate. The elasticity of the abalone's abdominal foot created difficulty in handling slight morphological size changes in roughness, resulting in no significant differences in its adhesion to the smooth glass plate.

Metabolomic insights into the effects of seasonal shifts on the dynamic variation of non-volatile compounds of abalone (Haliotis discus hannai).

Abalone (Haliotis spp.) is a shellfish known for its exceptional nutritional value and significant economic worth. This study investigated the dynamic characteristics of non-volatile compounds over a year, including metabolites, lipids, nucleotides, and free amino acids (FAAs), which determined the nutritional quality and flavor of abalone. 174 metabolites and 371 lipids were identified and characterized, while 20 FAAs and 11 nucleotides were quantitatively assessed. These non-volatile compounds of abalone were fluctuated with months variation, which was consistent with the fluctuations of environmental factors, especially seawater temperature. Compared with seasonal variation, gender had less influence on these non-volatiles. June and July proved to be the optimal harvesting periods for abalone, with the levels of overall metabolites, lipids, FAAs, and nucleotides in abalone exhibiting a higher value in June and July over a year. Intriguingly, taurine covered 60% of the total FAAs and abalone could be used as dietary taurine supplementation.

Ascorbic acid biosynthesis in Pacific abalone Haliotis discus hannai Ino and L-gulonolactone oxidase gene loss as an independent event.

Up to now, it has been believed that invertebrates are unable to synthesize ascorbic acid (AA) in vivo. However, in the present study, the full-length CDs (Coding sequence) of L-gulonolactone oxidase (GLO) from Pacific abalone (Haliotis discus hannai Ino) were obtained through molecular cloning. The Pacific abalone GLO contained a FAD-binding domain in the N-termination, and ALO domain and conserved HWAK motif in the C-termination. The GLO gene possesses 12 exons and 11 introns. The Pacific abalone GLO was expressed in various tissues, including the kidney, digestive gland, gill, intestine, muscle and mantle. The GLO activity assay revealed that GLO activity was only detected in the kidney of Pacific abalone. After a 100-day feeding trial, dietary AA levels did not significantly affect the survival, weight gain, daily increment in shell length, and feed conversion ratio of Pacific abalone. The expression of GLO in the kidney was downregulated by dietary AA. These results implied that the ability to synthesize AA in abalone had not been lost. From the evolutionary perspective, the loss of GLO occurred independently as an independent event by matching with the genomes of various species. The positive selection analysis revealed that the GLO gene underwent purifying selective pressure during its evolution. In conclusion, the present study provided direct evidence to prove that the GLO activity and the ability to synthesize AA exist in abalone. The AA synthesis ability in vertebrates might have originated from invertebrates dating back 930.31 million years.

Metagenome-assembled genome of withering syndrome causative agent, "Candidatus Xenohaliotis californiensis," from endangered white abalone (Haliotis sorenseni).

The genome of "Candidatus Xenohaliotis californiensis" was assembled from shotgun metagenomic sequencing of experimentally infected white abalone. Ninety-one percent genome completeness was achieved with low contamination. Sequencing this genome provides the opportunity to track pathogen evolution over time, conduct gene expression experiments, and study dynamics between this pathogen and its phage.

Preliminary analysis of pathways and their implications during salinity stress in abalone.

Transcriptome sequencing has offered immense opportunities to study non-model organisms. Abalone is an important marine mollusk that encounters harsh environmental conditions in its natural habitat and under aquaculture conditions; hence, research that increases molecular information to understand abalone physiology and stress response is noteworthy. Accordingly, the study used transcriptome sequencing of the gill tissues of abalone exposed to low salinity stress. The aim is to explore some enriched pathways during salinity stress and the crosstalk and functions of the genes involved in the candidate biological processes for future further analysis of their expression patterns. The data suggest that abalone genes such as YAP/TAZ, Myc, Nkd, and Axin (involved in the Hippo signaling pathway) and PI3K/Akt, SHC, and RTK (involved in the Ras signaling pathways) might mediate growth and development. Thus, deregulation of the Hippo and Ras pathways by salinity stress could be a possible mechanism by which unfavorable salinities influence growth in abalone. Furthermore, PEPCK, GYS, and PLC genes (mediating the Glucagon signaling pathway) might be necessary for glucose homeostasis, reproduction, and abalone meat sensory qualities; hence, a need to investigate how they might be influenced by environmental stress. Genes such as MYD88, IRAK1/4, JNK, AP-1, and TRAF6 (mediating the MAPK signaling pathway) could be useful in understanding abalone's innate immune response to environmental stresses. Finally, the aminoacyl-tRNA biosynthesis pathway hints at the mechanism by which new raw materials for protein biosynthesis are mobilized for physiological processes and how abalone might respond to this process during salinity stress. Low salinity clearly regulated genes in these pathways in a time-dependent manner, as hinted by the heat maps. In the future, qRT-PCR verification and in-depth study of the various genes and proteins discussed would provide enormous molecular information resources for the abalone biology.

Unraveling the relationship between aroma characteristics and lipid profile of abalone (Haliotis discus hannai) during seasonal fluctuation and thermal processing.

Abalone, a highly sought-after aquatic product, possesses significant nutritional value. In this study, the relationship between aroma characteristics and lipid profile of abalone (Haliotis discus hannai) during seasonal fluctuation and thermal processing were profiled via volatolomics and lipidomics. 46 aroma compounds and 371 lipids were identified by HS-SPME-GC-MS and UPLC-Q-Extractive Orbitrap-MS, respectively. Multivariate statistical analysis indicated that carbonyls (aldehydes and ketones) and alcohols were the characteristic aroma compounds of abalone. The fluctuations in the aroma compound and lipid composition of abalone were consistent with the seasonal variation, especially seawater temperature. In addition, based on the correlation analysis, it was found that carbonyls (aldehydes and ketones) and alcohols had a positive correlation with phospholipids (lysophosphatidylethanolamines and lysophosphatidylcholines), while a negative correlation was observed with fatty acyls. These findings suggested that the effect of seasonal variations on the aroma changes of abalone might achieved by modulating the lipids composition of abalone.

Melatonin injection and red light irradiation affect the antioxidant response and cell damage in disk abalone (Haliotis discus hannai) exposed to high water temperatures.

The effects of red light-emitting diode (LED) light irradiation (630 nm, 0.5 W/m2) and melatonin (10-8 and 10-7 M) on oxidative stress and physiological responses in abalones exposed to high temperatures (28°C) were investigated. Changes in messenger RNA (mRNA) expressions of melatonin receptor (MT-R), heat shock protein 70 (HSP70), and antioxidant enzymes, as well as alterations in H2O2 levels in the hemolymph, were examined. The results revealed that high-temperature-stressed abalones treated with melatonin injections or exposed to red LED light showed a significant increase in MT-R mRNA expression, while HSP70 mRNA expression decreased. Notably, HSP70 mRNA expression levels in the red LED light-irradiated group were similar to those in the group injected with 10-8 M melatonin after 24 h exposure. Abalones treated with melatonin at 20°C or irradiated with red LED light exhibited decreased H2O2 levels and reduced antioxidant enzyme mRNA expression compared with those of the control group. However, the high-temperature environment induced oxidative stress in abalones, leading to increased antioxidant enzyme mRNA expression compared with that under 20°C conditions. Moreover, abalones exposed to high-temperature stress exhibited hepatopancreatic DNA damage, which was attenuated by melatonin treatment or red LED light irradiation. Hence, red LED light reduces oxidative stress, boosts antioxidant enzymes, and alleviates DNA damage in high-temperature-stressed abalones, akin to 10-8 M melatonin treatment. Therefore, considering the practical challenges of continuous melatonin administration to abalones, utilizing red LED light emerges as a practical, effective alternative to protect abalones from oxidative stress compared to 10-8 M melatonin treatment.

Quality properties of fish ball with abalone and its relationship with sensory properties.

In this work, whiteness, water-holding capacity, gel strength, textural profile analysis were performed to examine the quality of fish balls with abalone (FBA). In addition, a correlation between quality and sensory properties was established. The addition of abalone significantly increased the water holding capacity, gel strength and textural properties of FBA, and decreased their whiteness, the best overall quality was achieved at 9 % w/w abalone addition. The E-nose and E-tongue results revealed that the addition of abalone changed the flavour of FBA. HS-SPME-GC-MS identified 65 volatile organic compounds (VOCs) and proved to be effective in reducing fishy flavour. E-nose can distinguish between the VOCs in FBA. Moreover, Umami and 1-octen-3-ol can serve as important indicators to observe changes in the quality of FBA, as they were positively connected with WHC, gumminess, chewiness, resilience, a*, hexanal, etc. The results provided a theoretical basis for the development of abalone and surimi products.

Molecular and structural analysis of Hdh-MIRP3 and its impact on reproductive regulation in female Pacific abalone, Haliotis discus hannai.

Molluscan insulin-related peptides (MIRP) play a crucial role in various biological processes, including reproduction and larval development in mollusk species. To investigate the involvement of MIRP in the ovarian development of Pacific abalone (Haliotis discus hannai), the Hdh-MIRP3 was cloned from cerebral ganglion (CG). Hdh-MIRP3 cDNA was 993 bp long, encoded a 13.22 kDa peptide, comprising 118 amino acids. Fluorescence in situ hybridization confirmed the localization of Hdh-MIRP3 in the CG and ovary. Molecular docking revealed that Hdh-MIRP3 binds to the N-terminal region of Hdh-IRP-R. Tissue expression analysis showed the highest Hdh-MIRP3 expression in the CG, followed by ovarian tissue. Hdh-MIRP3 expression was significantly upregulated in the CG and ovary during the ripe stage of seasonal ovarian development and in effective accumulative temperature conditioned abalone. Furthermore, siRNA silencing of Hdh-MIRP3 significantly downregulated the expression of four reproduction-related genes, including Hdh-GnRH, Hdh-GnRH-R, Hdh-IRP-R, and Hdh-VTG in both the CG and ovary, and Hdh-MIRP3 as well. These results indicate that Hdh-MIRP3 acts as a regulator of ovarian development in Pacific abalone. Additionally, expression analysis indicated that Hdh-MIRP3 plays a role in embryonic and larval development. Overall, the present findings elucidate the role of Hdh-MIRP3 in reproductive development in female Pacific abalone.

Toxic effects of combined exposure to homoyessotoxin and nitrite on the survival, antioxidative responses, and apoptosis of the abalone Haliotis discus hannai.

Homoyessotoxin (homo-YTX) and nitrite (NO2-N), released during harmful dinoflagellate cell lysis adversely affect abalones. However, their toxicity mechanisms in shellfish remain unclear. This study investigated the economic abalone species Haliotis discus hannai exposed to varying concentrations of homo-YTX (0, 2, 5, and 10 µg L-1) and NO2-N (0, 3, and 6 mg L-1) on the basis of their 12 h LC50 values (5.05 µg L-1 and 4.25 mg L-1, respectively) and the environmentally relevant dissolved concentrations during severe dinoflagellate blooms, including mixtures. The test abalones were exposed to homo-YTX and NO2-N for 12 h. The mortality rate (D), reactive oxygen species (ROS) levels, antioxidant defense capabilities, and expression levels of antioxidant-related, Hsp-related, and apoptosis-related genes in abalone gills were assessed. Results showed that the combined exposure to homo-YTX and NO2-N increased the D and ROS levels and upregulated B-cell lymphoma-2 (BCL2)-associated X (BAX) and caspase3 (CASP3) expression levels while reducing glutathione peroxidase (GPx) activity and GPx, CuZnSOD, and BCL2 expression levels. High concentrations of homo-YTX (10 µg L-1) and NO2-N (6 mg L-1) solutions and the combinations of these toxicants inhibited the activities of superoxide dismutase (SOD) and catalase (CAT) and downregulated the expression levels of MnSOD, CAT, Hsp70, and Hsp90. The ROS levels were negatively correlated with the activities of SOD, CAT, and GPx and the expression levels of MnSOD, CuZnSOD, CAT, GPx, Hsp70, Hsp90, and BCL2. These results suggest that homo-YTX, in conjunction with NO2-N, induces oxidative stress, disrupts antioxidant defense systems, and triggers caspase-dependent apoptosis in the gills of abalone. ROS-mediated antioxidative and heat-shock responses and apoptosis emerge as potential toxicity mechanisms affecting the survival of H. discus hannai due to homo-YTX and NO2-N exposure.

Determination of 57 pesticide residues in fishery products by GC tandem mass spectrometry combined with QuEChERS (quick, easy, cheap, effective, rugged, and safe) extraction.

An analytical method using GC-MS/MS combined with quick, easy, cheap, effective, rugged, and safe extraction was developed to determine 57 pesticides in fishery products. The limits of detection and quantification (LOD and LOQ, respectively) of the analytical method ranged between 0.91 and 2.12 ng/g wet mass and 3 and 7 ng/g wet mass, respectively. Moreover, the linearity of the calibration curves was acceptable (R2 > 0.99). The relative pesticide recoveries ranged between 53.87 and 127.2%, and reproducibility ranged between 0.25 and 10.87%. The pesticide residues in brown seaweed, eel, flatfish, shrimp, and abalone samples were analyzed using the developed analytical method, and the results indicate that most samples were not contaminated by the 57 target pesticides, except low levels (< 10 ng/g) of 1,1-dichloro-2,2-bis(4-chlorophenyl)ethene, alachlor, ametryn, isoprothiolane, and prometryn in several samples.

Spirochaete genome identified in red abalone sample represents a novel genus Candidatus Haliotispira gen. nov. within the order Spirochaetales.

A fully assembled spirochaete genome was identified as a contaminating scaffold in our red abalone (Haliotis rufescens) genome assembly. In this paper, we describe the analysis of this bacterial genome. The assembled spirochaete genome is 3.25 Mb in size with 48.5 mol% G+C content. The proteomes of 38 species were compared with the spirochaete genome and it was discovered to form an independent branch within the family Spirochaetaceae on the phylogenetic tree. The comparison of 16S rRNA sequences and average nucleotide identity scores between the spirochaete genome with known species of different families in Spirochaetia indicate that it is an unknown species. Further, the percentage of conserved proteins compared to neighbouring taxa confirm that it does not belong to a known genus within Spirochaetaceae. We propose the name Candidatus Haliotispira prima gen. nov., sp. nov. based on its taxonomic placement and origin. We also tested for the presence of this species in different species of abalone and found that it is also present in white abalone (Haliotis sorenseni). In addition, we highlight the need for better classification of taxa within the class Spirochaetia.

Exposure to bisphenol A and fiber-type microplastics induce oxidative stress and cell damage in disk abalone Haliotis discus hannai: Bioaccumulation and toxicity.

Along with environmental pollution caused by rapid economic development and industrialization, plastic waste is emerging as a global concern in relation to marine ecosystems and human health. Among the microplastics, fiber-type microfibers (MF) and bisphenol A (BPA), which are widely used as plasticizers, do not decompose well in the ocean, and tend to accumulate in organisms, generating an increased oxidative stress response. This study investigated the abalones' antioxidant and cell death responses following exposure to the environmental pollutants MF and BPA. Levels of malondialdehyde (MDA) and DNA damage increased over time, demonstrating the degree of lipid peroxidation and DNA damage in abalones exposed to individual and combined environmental conditions of MF and BPA. Compared to the single MF and BPA exposure groups, the combined exposure group showed a higher expression of antioxidant enzymes. A similar pattern was seen in the expression of the apoptosis enzyme caspase-3. Both MF and BPA caused oxidative stress and antioxidant enzymes were expressed to alleviate it, but it is believed that cell damage occurred because the stress level exceeded the allowed range.