Abalone Haliotis Discus Hannai Research Articles

Palliative effect of abalone insulin-related peptide 2 on emersion stress-induced hyperglycemia in the Pacific abalone (Haliotis discus hannai)

The Pacific abalone (Haliotis discus hannai), an economically important marine mollusk in East Asia, is often exposed to extreme environments, such as high water temperatures during summer and air exposure during handling or transportation. These stressful conditions lead to hyperglycemia and the generation of reactive oxygen species (ROS), resulting in oxidative stress and subsequent cell damage in the organism. To understand the role of insulin-related peptides in the regulation of elevated hemolymph glucose, hyperglycemia was confirmed in abalone under high water temperature and air (emersion) exposure (p < 0.05). To prove the existence of a glucose regulatory system in abalone, changes in hemolymph glucose were measured after bovine insulin injection, and hemolymph glucose was lowered by bovine insulin injection in hyperglycemia caused by both stressors (p < 0.05), supporting the existence of a glucose regulatory system functionally similar to that of vertebrates. Among the three abalone insulin-related peptides (AIPs), which were previously reported to be upregulated along with hemolymph glucose levels upon feeding, the relative mRNA expression of AIP2 in the cerebral ganglion showed a close correlation with high water temperature and emersion stress, which peaked 12 h after treatment (p < 0.05). Based on these results, we focused on the function of AIP2 in glucose homeostasis and characterized the localization of AIP2 mRNA-expressing cells in the cerebral ganglion using in situ hybridization. Positive signals from RNA probes were detected in neural cortex cells in the cerebral ganglion. Furthermore, suppressing AIP2 mRNA expression using RNA interference with double-stranded RNA (dsRNA) revealed that dsRNA-AIP2 injected abalone maintained high hemolymph glucose levels after 24 h of recovery following 1 h of emersion stress (p < 0.01). In contrast, abalones that received dsRNA-GFP and molluscan saline showed relatively rapid clearance of hemolymph glucose. This study demonstrates that AIP2 gene expression affects the recovery rate from emersion stress-induced hyperglycemia by regulating hemolymph glucose.

Dietary hydroxyproline supplementation improves the muscle texture and extends the shelf life of abalone Haliotis discus hannai

In the present study, an 84-day growth trial was conducted in abalone Haliotis discus hannai to evaluate the influences of dietary hydroxyproline (Hyp) levels (0.05, 0.53 and 1.24%) on the growth, collagen metabolism, muscle texture and its changes during storage at 4 °C. The results showed that the weight gain rate of abalones in the groups with 0.53% and 1.24% of dietary Hyp were significantly higher than that in the group with 0.05% dietary Hyp. The 0.53% and 1.24% of dietary Hyp significantly increased lysyl hydroxylase and prolyl 4-hydroxylase activity and pyridinium crosslink content, and up-regulated collagen biosynthesis-related gene expression in abalone muscle. Meanwhile, dietary Hyp supplementation significantly inhibited the mRNA expression of mmp-1 and significantly up-regulated the mRNA expression of timp. During the same storage time, the springiness, hardness and water-holding capacity of muscle in the dietary Hyp supplementation treatments were significantly higher. The muscle hardness in the dietary Hyp supplementation groups on day 6 was higher than that in the control group on day 3. Meanwhile, dietary Hyp significantly decreased the content of carbonyl and malonaldehyde, as well as the activity of cathepsin B and cathepsin L in the muscle of abalone during the storage. In conclusion, dietary Hyp supplementation increased collagen content, improved texture and extended the shelf life of 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.

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.

Characterization of myoinhibitory peptide signaling system and its implication in larval metamorphosis and spawning behavior in Pacific abalone

Myoinhibitory peptides (MIPs) affect various physiological functions, including juvenile hormone signaling, muscle contraction, larval development, and reproduction in invertebrates. Although MIPs are ligands for MIP and/or sex peptide receptors (MIP/SPRs) in diverse arthropods and model organisms belonging to Lophotrochozoa, the MIP signaling system has not yet been fully investigated in mollusks. In this study, we identified the MIP signaling system in the Pacific abalone Haliotis discus hannai (Hdh). Similar to the invertebrate MIPs, a total of eight paracopies of MIPs (named Hdh-MIP1 to Hdh-MIP8), harboring a WX5-7Wamide motif, except for Hdh-MIP2, were found in the Hdh-MIP precursor. Furthermore, we characterized a functional Hdh-MIPR, which responded to the Hdh-MIPs, except for Hdh-MIP2, possibly linked with the PKC/Ca2+ and PKA/cAMP signaling pathways. Hdh-MIPs delayed larval metamorphosis but increased the spawning behavior. These results suggest that the Hdh-MIP signaling system provides insights into the unique function of MIP in invertebrates.

Comparison of Growth, Gut Microbiota Composition, and Taste Sensory Profile of Abalone (Haliotis discus hannai) Fed Diets Formulated With Heat-Treated Or Fermented Seaweed (Sargassum horneri) Meal

Comparison of Growth, Gut Microbiota Composition, and Taste Sensory Profile of Abalone (Haliotis discus hannai) Fed Diets Formulated With Heat-Treated Or Fermented Seaweed (Sargassum horneri) Meal

Effects of reproductive condition on haemocyte parameters in the Pacific abalone Haliotis discus hannai during the spawning period

ABSTRACT The assessment of morphology and immunology of specimens at different maturity stages is essential for the determination of spawning strategy and reducing the risk of mortality. In this paper, female and male Pacific abalones (Haliotis discus hannai) at different statuses (pre-spawning, spawning and post-spawning) were collected to estimate the effects of spawning on the immune response. The haemocyte parameters, including total haemocyte counts (THC), haemocyte mortality, and reactive oxygen species production (ROS) were analysed using flow cytometry. THC decreased after spawning, which was lowest 3 days post-spawning. Haemocyte mortality was higher during spawning, and was highest 3 days post-spawning. Abalone also reduced their metabolic activity after spawning, reflected by an increase in ROS in both females and males. Moreover, our results show that female abalone reach the spawning period with a higher degree of activities of haemocytes and immune responses than male. The results confirmed that variability in abalone haemocytes during the spawning period might related to individual metabolic conditions.

Changes in water temperature: The effect of triploid performance in Pacific abalone (Haliotis discus hannai)

The triploid Pacific abalone (Haliotis discus hannai) has significant economic value and promising application prospects. However, the optimal cultural conditions that maximize the advantages of triploidy in the abalone have yet to be determined. This study examined the properties of triploid Pacific abalone after 3 months of culture under three constant temperatures (18 °C, 22 °C, and 26 °C) to fill up this information gap. The results showed that the survival rate of triploids in the 26 °C group was significantly higher than that of diploids (P < 0.05), while the survival rate of triploids in the other two groups was similar to that of diploids (P > 0.05). Except for the shell width of the 22 °C group and the shell length of the 26 °C group, triploid Pacific abalone exhibited significantly superior growth traits compared to diploids at all temperatures (P < 0.05). The most notable improvement was observed in the foot muscle weight trait, where there were triploid advantage rates of 81.44% (18 °C), 76.21% (22 °C), and 54.96% (26 °C). The specific growth rate and the ratio of shell length and body weight indicated that triploids grew the fastest in the 22 °C group. Furthermore, the thermal resistance of diploids and triploids was evaluated through the Arrhenius break temperature (ABT) of cardiac performance. The results demonstrated that the ABT of triploids was significantly higher than that of diploids (P < 0.05, ABT2N = 30.81 ± 0.43 °C, ABT3N = 31.38 ± 0.72 °C). Both diploid and triploid foot adhesion forces were measured, and the results showed that triploid foot adhesion force was stronger than that of diploids (P < 0.05). Additionally, there was a significant positive correlation between foot adhesion force and meat yield traits (foot muscle weight, fullness index (FI) and foot muscle-soft tissue index (FMSI)) (P < 0.05). In summary, this study confirmed the triploid advantage in meat yield of Pacific abalone and identified a temperature range that maximizes their growth rate. Moreover, triploids exhibited improved thermal resistance and adhesion capacity compared to diploids, with an increase in meat yield. The results of this study could serve as a reference for identifying a culture model suitable for triploid Pacific abalone and thus could promote the development of the triploid aquaculture industry.

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.

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.

Genome-wide identification and expression profiles of sex-related gene families in the Pacific abalone Haliotis discus hannai

In recent years, members of the Dmrt family, TGF-β superfamily and Sox family have been recognized as crucial genes for sex determination/differentiation across diverse animal species. Nevertheless, knowledge regarding the abundance and potential functions of these genes in abalone remains limited. In this study, a total of 5, 10, and 7 members of the Dmrt family, the TGF-β superfamily and the Sox family, respectively, were identified in the Pacific abalone Haliotis discus hannai. Sequence characteristics, phylogenetic relationships and spatiotemporal expression profiles of these genes were investigated. Notably, HdDmrt-04 (Dmrt1/1L-like) emerged as a potential mollusc-specific gene with a preponderance for expression in the testis. Interestingly, none of the TGF-β superfamily members exhibited specific or elevated expression in the gonads, highlighting the need for further investigation into their role in abalone sex differentiation. The Sox proteins in H. discus hannai were categorized into 7 subfamilies: B1, B2, C, D, E, F, and H. Among them, HdSox-07 (SoxH-like) was observed to play a crucial role in testis development, while HdSox-03 (SoxB1-like) and HdSox-04 (SoxC-like) probably cooperate in abalone ovary development. Taken together, the results of the present study suggested that HdDmrt-04 and HdSox-07 can be used as male-specific markers for gonad differentiation in H. discus hannai and imply conservation of their functions across invertebrates and vertebrates. Our findings provide new insights into the evolution and genetic structure of the Dmrt family, the TGF-β superfamily and the Sox family in abalone and pave the way for a deeper understanding of sex differentiation in gastropods.

Selective preferences and behavioral adaptation strategy of Pacific abalone in response to different water flow velocities

The water flow velocity is a crucial environmental physical factor that drastically impacts the survival and stock distribution of marine organisms. To facilitate the restoration of wild stocks of Pacific abalone (Haliotis discus hannai) and increase the success rate of release, abalones were monitored for 24 h without interruption in an experimental unit (developed in-house) to assess the flow velocity preferences of marine mollusks. Abalones tended to keep away from areas with higher flow velocities (> 5 cm/s) and they preferred to stay in areas with lower flow velocities (< 5 cm/s). Comparative study of the diurnal behavioral characteristics of abalones under seven different flow velocities (0, 5, 10, 15, 20, 25, and 30 cm/s) showed that the cumulative distance moved, movement duration, and feeding time decreased significantly as the flow velocity increased. At flow velocities over 20 cm/s, abalones barely moved or consumed food, and cosine rhythm analysis demonstrated that the diurnal rhythms of behavioral parameters disappeared and the peak movement phase occurred earlier than expected. In addition, increasing the flow velocity reduced the spacing between individuals and the polarity of movement was higher. Individuals changed their coordination levels in groups as an active adaptation to changes in the flow velocity. These findings provide new insights into the ecological habits of abalones. Based on the characteristic movement behaviors of abalones at different flow velocities, bottom-sowing should be conducted in areas with a flow velocity < 5 cm/s instead of areas with a flow velocity > 20 cm/s to improve the efficiency of bottom-sowing stock enhancement.

Cloning, characterization, and spatio-temporal expression patterns of HdhSPARC and its responses to multiple stressors

SPARC is an extracellular Ca2+-binding, secreted glycoprotein that plays a dynamic role in the growth and development of organisms. This study aimed to describe the isolation, characterization, and expression analysis of HdhSPARC in Pacific abalone (Haliotis discus hannai) to infer its potential functional role. The isolated HdhSPARC was 1633 bp long, encoding a polypeptide of 284 amino acid residues. Structurally, the SPARC protein in abalone is comprised of three biological domains. However, the structure of this protein varied between vertebrates and invertebrates, as suggested by their distinct clustering patterns in phylogenetic analysis. In early development, HdhSPARC was variably expressed, and higher expression was found in veliger larvae. Moreover, HdhSPARC was highly expressed in juvenile abalone with rapid growth compared to their slower-growing counterparts. Among the testicular development stages, the growth stage exhibited higher HdhSPARC expression. HdhSPARC was also upregulated during muscle remodeling and shell biomineralization, as well as in response to different stressors such as heat shock, LPS, and H2O2 exposure. However, this gene was downregulated in Cd-exposed abalone. The present study first comprehensively characterized the HdhSPARC gene, and its spatio-temporal expressions were analyzed along with its responses to various stressors.

The growth performance, anti-oxidative capacity, immunity and resistance to heat stress of abalone Haliotis discus hannai can be improved by a mixture of herbs

An 84-day feeding trial was carried out to assess the effects of dietary Chinese herbs mixture (CHM) on the growth performance, anti-oxidative capacity, immunity and resistance to heat stress of abalone Haliotis discus hannai. The CHM included, Scutellariae Radix (Scutellaria baicalensis, Gardeniae Fructus (Gardenia jasminoides), Artemisiae Scopariae Herba (Artemisia capillaris), Uncariae Ramulus Cum Uncis (Uncaria rhynchophylla), Polygoni Cuspidati Rhizoma et Radix (Polygonum cuspidatum). Six diets containing 0.00% (control group), 0.02%, 0.04%, 0.06%, 0.08% and 0.10% of CHM were formulated and fed to abalone (initial weight: 3.59 ± 0.03 g). The group with 0.04% of dietary CHM exhibited the highest weight gain rate (WGR), while the survival was not significantly affected by dietary CHM. The optimal level of dietary CHM for abalone was determined to be 0.049% on the basis of the quadratic regression model for WGR. Dietary CHM significantly elevated the activities of lipase, trypsin, cellulase, Na+/K+-ATPase, acid phosphatase, alkaline phosphatase and lysozyme and total anti-oxidative capacity. Besides, dietary CHM significantly reduced the malondialdehyde content and alanine amino transferase activity. The mRNA levels of cationic amino acid transporter 1 (cat1) and nuclear factor erythroid 2-related factor 2 (nrf2) were significantly up-regulated in the group with 0.04% of dietary CHM. While the mRNA levels of kelch-like ECH-associated protein 1 (keap1), nuclear factor-κb (nf-κb) and tumor necrosis factor-α (tnf-α) were decreased in dietary CHM supplemented groups. The glucose and cortisol content in the CFH and the falling rate of abalone were significantly lower in the CHM supplemented groups than that in the control group. In conclusion, dietary supplementation of CHM improved the growth performance, anti-oxidative capacity, immunity and the resistance to heat stress of abalone. The recommended level of CHM supplemented in diets for abalone was 0.049%.

The Neuropeptide HGAP Regulates Growth, Reproduction, Metamorphosis, Tissue Damage Repair, and Response against Starvation in Pacific Abalone

Introduction: Neuropeptides regulate vital physiological processes in multicellular organisms, including growth, reproduction, metamorphosis, and feeding. Recent transcriptome analyses have revealed neuropeptide genes with potential roles in vertebrate and invertebrate growth and reproduction. Among these genes, haliotid growth-associated peptide (HGAP) was identified as a novel gene in abalone. Methods: This study focused on HGAP in Pacific abalone (Haliotis discus hannai), where the complete cDNA sequence named Hdh-HGAP was identified and characterized. Samples from different experiments, such as metamorphosis, juvenile abalone growth, gonad development stages, muscle remodeling, and starvation, were collected for mRNA expression analysis. Results: The sequence spans 552 bp, encoding 96 amino acids with a molecular weight of 10.96 kDa. Expression analysis revealed that Hdh-HGAP exhibited higher levels in muscle tissue. Notably, during metamorphosis, Hdh-HGAP exhibited greater expression in the trochophore, veliger, and juvenile stages than in the cell division stages. Regarding growth patterns, Hdh-HGAP was highly expressed during rapid growth compared to stunted, minimal, and normal growth. In gonadal development, Hdh-HGAP mRNA reached its highest expression level during the ripening stage, indicating a potential role in gonadal cell proliferation and maturation. The in vivo effects of GnRH on gonad development and the expression of the Hdh-HGAP neuropeptide indicate its involvement in regulating reproduction in Pacific abalone. While tissue remodeling is primarily governed by immune genes, Hdh-HGAP was also upregulated during muscle tissue remodeling. Conversely, Hdh-HGAP was downregulated during prolonged starvation. Conclusion: This study marks the first comprehensive exploration of the Hdh-HGAP neuropeptide gene in Pacific abalone, shedding light on its involvement in growth, reproduction, metamorphosis, tissue remodeling, and response to starvation, although regulatory mechanisms are mostly unknown.

Persistent exposure to artificial light at night (ALAN) accelerates metamorphosis and colonization in larvae of marine shellfish

The ongoing course of urbanization has led to excessive use of artificial light at night (ALAN), which has rapidly become an important source of pollution in many cities. The Pacific abalone (Haliotis discus hannai) Larvae were kept under a 12/12 h light/dark photoperiod (DD) in order to determine the effects of ALAN on embryonic development. To simulate the street lighting conditions at night, the artificial light was switched on from 18:00 until midnight (AD) or until 06:00 the next day (ND). Moreover, Groups AD and ND had a considerably greater hatching success rate and metamorphosis rate than Group DD (P < 0.05), whereas Group DD had a significantly longer hatching period and course to complete the metamorphosis of the larvae (P < 0.05). Transcriptomic analyses showed that members of Groups AD and DD had considerably higher expression levels of genes involved in ribosome biogenesis, spliceosome function, and the mRNA surveillance pathway. Prostaglandin B2, L-palmitoylcarnitine, stearic acid, palmitic acid, leukotriene C4, and arachidonic acid were screened by non-targeted metabolomics as differential metabolic markers that played a vital role in the response of larvae to different ALAN conditions. Multi-omics correlation analysis suggested that five pathways related to fatty acid synthesis, catabolism, and metabolism, such as biosynthesis of unsaturated fatty acids and arachidonic acid metabolism, were enriched in each comparison. Further quantitative analysis showed that compared to Group DD, 33 out of 50 fatty acids were upregulated in Group AD, and the levels of almost all fatty acids were increased in Group ND, which in turn suggested that fatty acids played a vital role in the physiological response of larvae to illumination changes. The findings of this work were significant for the unbiased and full-scale assessment of the ecological effects of ALAN, as well as the structural stability of the marine benthic community.

Effects of flow velocity on the muscle nutrient content and flesh quality of the Pacific abalone (Haliotis discus hannai)

The aim of this study was to determine the effects of flow velocity (FV) on the growth and muscle texture of Pacific abalone (Haliotis discus hannai). Abalones were cultured at three sites for 90 days: LJ (119.912°E, 26.398°N), DS (119.903°E, 26.372°N), and JJ (119.875°E, 26.361°N). The FVs of the LJ, DS, and JJ sites were classified as high, medium, and low, respectively. The survival rate and specific growth rate were significantly greater for abalones cultured at sites DS and JJ than site LJ (p < 0.05), while the collagen content and the muscle parameters hardness, cohesiveness, chewiness, resilience, and shearing force were significantly higher at site LJ than sites DS and JJ (p < 0.05). Non-targeted metabolomics analyses of JJ vs. DS, JJ vs. LJ, and LJ vs. DS identified 124, 77, and 121 significantly different metabolites under the positive ion mode, and 68, 49, and 62 under the negative ion mode, respectively. Signaling pathways related to amino acid synthesis and metabolism were identified. Phenylalanine, glutamic acid, and histidine were confirmed as differential metabolic markers. Targeted metabolomics identified five “delicious amino acids” (glycine, aspartate, phenylalanine, tyrosine, and alanine), which had significantly higher contents in abalones cultured at site LJ than sites DS and JJ. Correlation analysis demonstrated that aspartate and phenylalanine were positively correlated to cohesiveness, chewiness, hardness, and shearing force, while negatively correlated to total protein content. These results provide theoretical references for cultivation of high-quality products and sustainable development of the abalone aquaculture industry.

EF-Hand-Binding Secreted Protein Hdh-SMP5 Regulates Shell Biomineralization and Responses to Stress in Pacific Abalone, Haliotis discus hannai.

The development of a shell is a complex calcium metabolic process involving shell matrix proteins (SMPs). In this study, we describe the isolation, characterization, and expression of SMP5 and investigate its potential regulatory role in the shell biomineralization of Pacific abalone Haliotis discus hannai. The full-length Hdh-SMP5 cDNA contains 685 bp and encodes a polypeptide of 134 amino acids. Structurally, the Hdh-SMP5 protein belongs to the EF-hand-binding superfamily, which possesses three EF-hand Ca2+-binding regions and is rich in aspartic acid. The distinct clustering patterns in the phylogenetic tree indicate that the amino acid composition and structure of this protein may vary among different SMPs. During early development, significantly higher expression was observed in the trochophore and veliger stages. Hdh-SMP5 was also upregulated during shell biomineralization in Pacific abalone. Long periods of starvation cause Hdh-SMP5 expression to decrease. Furthermore, Hdh-SMP5 expression was observed to be significantly higher under thermal stress at temperatures of 15, 30, and 25 °C for durations of 6 h, 12 h, and 48 h, respectively. Our study is the first to characterize Hdh-SMP5 comprehensively and analyze its expression to elucidate its dynamic roles in ontogenetic development, shell biomineralization, and the response to starvation and thermal stress.

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.

Crustacean cardioactive peptide signaling system in the gastropod mollusk Pacific abalone

Crustacean cardioactive peptide (CCAP) signaling systems have been characterized in a diverse range of protostomes, representatively in arthropods. The cyclic CX5C-type CCAP regulates various biological activities through CCAP receptors (CCAPRs), which are orthologous to neuropeptide S receptors (NPSRs) in deuterostomes. However, the CCAPRs of the lophotrochozoa remain poorly characterized; therefore, the relationship between the CCAP, NPS, and CX4C-type oxytocin/vasopressin (OT/VP) signaling systems is unclear. In this study, we identified a CCAP precursor and two CCAPR isoforms in the Pacific abalone (Haliotis discus hannai; Hdh). The Hdh-CCAP precursor was found to harbor three CX5C-type and one CX4C-type CCAPs. The Hdh-CCAPRs displayed homology with protostome CCAPRs and deuterostome NPSRs, having characteristics of the rhodopsin-type G protein-coupled receptors. Phylogenetic analysis showed that lophotrochozoan CCAPRs, including Hdh-CCAPRs, form a monophyletic group distinct from arthropod CCAPRs. Reporter assays demonstrated that all examined Hdh-CCAPs and insect CCAP-induced intracellular Ca2+ mobilization and cAMP accumulation in Hdh-CCAPR-expressing HEK293 cells, whereas none of the CCAP peptides inhibited the forskolin-stimulated cAMP signaling pathway even at micromolar concentrations. In silico ligand-receptor docking models showed that the N-terminal FCN motifs of Hdh-CCAPs are deeply inserted inside the binding pocket of Hdh-CCAPR, forming extensive hydrophobic interactions. In mature Pacific abalone, the transcripts for Hdh-CCAP precursor and Hdh-CCAPR were highly expressed in the neural ganglia compared to the peripheral tissues. Collectively, this study characterized the first CCAP signaling system linked to both Ca2+/PKC and cAMP/PKA signal transduction pathways in gastropod mollusks and gives insights into the evolutional origins of deuterostomian NPS and OT/VP signaling systems.