Haliotis Discus Hannai Research Articles

Effects of dietary eicosapentaenoic acid on the growth performance, fatty acid profile, immunity and heat tolerance of juvenile abalone Haliotis discus hannai Ino

A 93-day growth trial was performed to evaluate the influences of graded dietary EPA levels (0.03% (control group), 0.24%, 0.63%, 1.07%, 1.72% and 2.25%) on the growth performance, immunity and heat tolerance of juvenile abalone Haliotis discus hannai with a mean initial weight of 4.15 ± 0.18 g. After the feeding trial, the findings found that the highest weight gain rate (WGR) belonged to the groups fed with 0.63% ∼ 1.72% of dietary EPA (P < 0.05). The lowest feed conversion ratio was distinguished in the groups with 0.63% ∼ 1.07% of dietary EPA (P < 0.05). Also, EPA supplementation in abalone feed increased the content of crude lipid in the soft body and the activity of lipase in the intestine (P < 0.05). The total antioxidative capacity increased when dietary EPA levels rose from 0.03% to 1.07%, and then decreased (P < 0.05). Furthermore, compared to the control group, the 0.24% and 0.24% ∼ 0.63% of dietary EPA significantly down-regulated the mRNA levels of IκB kinase and kelch-like ECH-associated protein 1, respectively (P < 0.05). However, nuclear factor-κB and interleukin 1 receptor-associated kinase 4 genes expression in the digestive gland were significantly up-regulated by the use of 1.72% and 2.25% of EPA in diet (P < 0.05). The mRNA levels of tumor necrosis factor α and interleukin 16 were significantly up-regulated by the 2.25% of dietary EPA (P < 0.05). The 1.72% of dietary EPA significantly increased the falling rate of abalone after the heat stress compared with the control (P < 0.05). In conclusion, the optimal dietary EPA requirement of juvenile abalone was determined as 1.36% based on quadratic regression analysis against WGR. Moderate dietary EPA content (0.63% ∼ 1.07%) improved the immunity and heat resistance of abalone. Excessive dietary EPA content (1.72% ∼ 2.25%) decreased the growth, meanwhile, increasing the oxidative stress, inflammation and susceptibility of abalone to heat stress.

Comprehensive Comparison of Effects of Antioxidant (Astaxanthin) Supplementation from Different Sources in Haliotis discus hannai Diet.

Dietary antioxidant supplementation, especially astaxanthin, has shown great results on reproductive aspects, egg quality, growth, survival, immunity, stress tolerance, and disease resistance in aquatic animals. However, the effects of dietary astaxanthin supplementation from different sources are still unknown. A comprehensive comparison of survival, growth, immune response, antioxidant activity, thermal resistance, disease resistance, and intestinal microbial structure was conducted in dietary antioxidant supplementation from the sources of Gracilaria lemaneiformis (GL), industrial synthetic astaxanthin (80 mg/kg astaxanthin actual weight, named as group 'SA80'), Phaffia rhodozyma (80 mg/kg astaxanthin actual weight, named as group 'PR80') and Haematococcus pluvialis (120 mg/kg astaxanthin actual weight, named as group 'HP120') at their optimal supplementation amounts. Furthermore, the SA80, PR80, and HP120 groups performed better in all aspects, including survival, growth, immune response, antioxidant activity, thermal resistance, and disease resistance, compared with the GL group. The PR80 and HP120 group also had a better growth performance than the SA80 group. In terms of heat stress and bacterial challenge, abalone in the PR80 group showed the strongest resistance. Overall, 80 mg/kg astaxanthin supplementation from Phaffia rhodozyma was recommended to obtain a more effective and comprehensive outcome. This study contributes to the discovery of the optimum dietary astaxanthin supplementation source for abalone, which is helpful to improve the production efficiency and economic benefits of abalone. Future research can further explore the action mechanism and the method of application of astaxanthin to better exploit its antioxidant role.

Molecular characterization of four genes encoding abalone insulin-related peptides and their roles in regulation of hemolymph glucose in the Pacific abalone Haliotis discus hannai

Members of the insulin superfamily play key roles in metabolism, growth, reproduction, and longevity via insulin/IGF signaling pathway. The presence of insulin and insulin-related peptides are found among animals. In Mollusca, molluscan insulin-related peptides (MIPs) are involved in their body and shell growth. Hence, this study aimed to understand if there was difference in these peptide levels of fast and slow growing Pacific abalones, Haliotis discus hannai. To this end, four abalone insulin-related peptides (AIPs) are mined from cerebral ganglia transcriptomes of fast-growing and slow-growing abalones: AIP1, −2, −3 and −6. Notably, these AIPs possess 8 cysteine residues in their predicted insulin A and B chains, potentially supporting four disulfide bridges. Further sequence analysis based on the phylogenetic tree and multiple alignment methods indicated that AIPs have sequence features that are conserved among MIPs in many gastropods. The tissue distributions of four AIPs showed ubiquitous and similar expression in the following tissues including the cerebral ganglion, hepatopancreas, gonad, and mantle of both genders. However, there is some difference in other tissue distribution. Since the food consumption is intimately associated with the hemolymph glucose and animal growth, relative AIP1, −2, −3 and − 6 expression levels in the cerebral ganglion were measured following seaweed supplementation. The animals fed with brown seaweed showed increased these AIPs by 1.6–4.7 folds from 3 h after feeding, which lasting to 12 h, coinciding with the peak of hemolymph glucose. Based on these results, we propose that a physiological glucose regulatory mechanism involving AIPs exists in the cerebral ganglion of the H. discus hannai neuroendocrine system.

Transcriptome Sequencing Reveals the Response to Acute Thermal Stress in the Pacific Abalone, Haliotis discus hannai

The Pacific abalone is an economically important cold-water shellfish. With its widespread culture, high temperature has become a key abiotic factor for the high mortality of Pacific abalone in summer, particularly in the south of China. To understand the molecular regulatory mechanisms of thermal stress response in Pacific abalone for further analyzing its heat adaptive capacity, we subjected Pacific abalone to acute heat stress at 28°C for 6, 24, and 48 hr, respectively. A total of 2,213, 2,337, and 1,420 differentially expressed genes (DEGs) were identified in Pacific abalone after 6, 24, and 48 hr of thermal stress, respectively, as compared with the control group without heat stimulation. These DEGs were significantly enriched in protein folding and chaperone-mediated protein folding process, antigen processing and presentation, and protein processing in endoplasmic reticulum pathways. The expression of numerous molecular chaperones was significantly upregulated after thermal stress. Maintaining cellular homeostasis through the upregulated expression of molecular chaperones associated with endoplasmic reticulum-associated degradation (ERAD) pathways might be central to the defense of Pacific abalone against thermal stress. In addition, the expression of Toll-like receptor 6 (TLR6) and myeloid differentiation factor 88 (MyD88) genes of the TLR signaling pathway was also induced. Therefore, the Pacific abalone might activate the immune defense system to resist the invasion of pathogenic bacteria by upregulating immune-related genes after thermal challenges. Our results not only contribute to a deeper understanding of heat stress regulation in the Pacific abalone but also provide basic data for molecular genetic breeding of heat-resistant abalone.

Short-Term Exposure to Combined Condition of Low Salinity and pH Affects ROS-Mediated Stress in Disk Abalone (Haliotis discus hannai)

Short-Term Exposure to Combined Condition of Low Salinity and pH Affects ROS-Mediated Stress in Disk Abalone (Haliotis discus hannai)

Aminopeptidase Play a Critical Role in the Accumulation of Free Amino Acids in Abalone (Haliotis discus hannai) During Cold Storage

Aminopeptidase Play a Critical Role in the Accumulation of Free Amino Acids in Abalone (Haliotis discus hannai) During Cold Storage

Evaluation of optimal dietary protein levels and meat quality of adult hybrid abalone (Haliotis discus hannai♀ × H. fulgens♂) under two representative water temperatures

In this study, the optimal dietary protein levels for adult hybrid abalone (H. discus hannai♀ × H. fulgens♂) were evaluated at two representative temperatures, and the interactive influences of dietary protein and water temperature on abalone meat quality were examined. Six isoenergetic and isolipidic diets containing graded levels of protein (15%, 20%, 25%, 30%, 35%, and 40%) were fed to the hybrid abalone for 90 days. Based on the specific growth rate, the optimum dietary protein levels for adult hybrid abalone using a quadratic curve model were estimated to be 28.07% and 26.47% of the diet at 23 °C (optimum temperature) and 27 °C (high temperature), respectively. The amount of crude protein in the abalone body increased linearly with the dietary protein levels and water temperature. Antioxidation enzyme activities of abalone muscle, including GPx and GST were significantly affected by the interaction of dietary protein levels and water temperature. As for texture analysis, the abalone kept at 23 °C exhibited higher meat hardness than those fed the same diets at 27 °C. The n-3 PUFAs (particularly DHA and EPA) in abalone meat were significantly influenced by dietary protein levels, and the highest content was observed in the 30% dietary protein group. These levels were not affected by water temperature. In addition, higher dietary protein levels and water temperatures increased the total contents of free amino acids and flavor amino acids (Asp + Glu + Gly + Ala + Arg + Tau). The cooking loss of abalone meat was reduced with increased protein levels and was significantly lower in the 23 °C group, along with a higher meat postmortem pH value. The collagen fiber ratio and collagen content of abalone meat were higher in the 23 °C group. In summary, for multiple diet feeding strategies in practical production of abalone aquaculture, the balance between the seasonally specific feeds cost benefits and the abalone meat quality should be carefully evaluated.

Impacts of replacing dietary fish meal with poultry by-product meal on growth, digestive enzymes and gut microbiota, biomarkers of metabolic and immune response, and resistance to Vibrio challenge in abalone (Haliotis discus hannai)

A 110-day feeding trial was carried out to investigate the impacts of replacing dietary fish meal (FM) with poultry by-product meal (PBM) on growth performance, digestion, gut microbiota, immunity, and disease resistance of abalone Haliotis discus hannai (initial weight: 22.53 ± 0.21 g). The control diet (PBM0) without PBM contained 20% of FM. Based on PBM0, the other four isonitrogenous (about 30% of crude protein) and isolipidic (about 4% of crude lipid) diets were formulated replacing 25, 50, 75 and 100% of FM by PBM (designated as PBM25, PBM50, PBM75 and PBM100), respectively. Every diet was fed to triplicate cages (40 × 35 × 70 cm) with 60 abalones per cage. At the end of the feeding trial, abalones were starved for 3 days and anesthetized with 5% ethanol before sampling. Results indicated that biomass gain of the abalone fed PBM75 (916.71 g) and PBM100 (659.93 g) was significantly lower than that of the abalone fed PBM0 (1222.51 g). Feed conversion ratio of the abalone fed PBM50 (2.93), PBM75 (2.89) and PBM100 (4.04) were significantly higher than that of the abalone fed PBM0 (2.37). The muscle crude protein content of the abalone fed PBM100 (16.01% wet weight) was significantly lower than that of the abalone fed PBM0 (16.67% wet weight). Activities of trypsin and α-amylase in the digestive gland in the PBM100 group (309.21 and 0.064 U/mg prot., respectively) were significantly lower than the PBM0 group (463.57 and 0.078 U/mg prot., respectively). When the substitution levels rose over 50%, expressions of phosphatidylinositol 3 kinase, threonine kinase/protein B, mammalian target of rapamycin and eukaryotic translation initiation factor 4E in muscle were significantly reduced, while 4E binding protein was significantly increased. The most abundant phyla across the abalones' gut were Proteobacteria and Firmicutes. Catalase (from 2.90 to 1.69 U/mL), superoxide dismutase (from 98.93 to 74.39 U/mL), lysozyme (from 345.86 to 247.81 U/mL) and acid phosphatase (from 21.68 to 15.71 U/100 mL) activities in cell-free hemolymph were markedly decreased with substitution level increasing. When the replacement levels rose over 50%, myeloid differentiation primary response gene 88 and tumor necrosis factor α expressions in the digestive gland were markedly upregulated, while β-defensin and mytimacin 6 expressions were markedly downregulated. The cumulative mortality of abalone challenged with Vibrio parahaemolyticus (1.0 × 107 CFU/mL) for 7 days was remarkably increased in the PBM50 (83.49%), PBM75 (89.56%) and PBM100 (100%) groups compared with the PBM0 group (58.82%). In conclusion, 50% of dietary FM could be replaced by PBM without influencing abalone growth. When the replacement level was over 50%, the growth and immunity of abalone were decreased, and the mTOR pathway was negatively affected.

Molecular mechanisms underlying the vulnerability of Pacific abalone (Haliotis discus hannai) to Vibrio harveyi infection at higher water temperature.

Climate change is one of the most important threats to farmed abalone worldwide. Although abalone is more susceptible to vibriosis at higher water temperatures, the molecular mode of action underlying this has not been fully elucidated. Therefore, this study aimed to address the high susceptibility of Halitotis discus hannai to V. harveyi infection using abalone hemocytes exposed to low and high temperatures. Abalone hemocytes were divided into four groups, 20C, 20V, 25C, and 25V, depending on co-culture with (V)/without (C) V. harveyi (MOI=12.8) and incubation temperature (20°C or 25°C). After 3h of incubation, hemocyte viability and phagocytic activity were measured, and RNA sequencing was performed using Illumina Novaseq. The expression of several virulence-related genes in V. harveyi was analyzed using real-time PCR. The viability of hemocytes was significantly decreased in the 25V group compared to cells in the other groups, whereas phagocytic activity at 25°C was significantly higher than at 20°C. Although a number of immune-associated genes were commonly upregulated in abalone hemocyte exposed to V. harveyi, regardless of temperature, pathways and genes regarding pro-inflammatory responses (interleukin-17 and tumor necrosis factor) and apoptosis were significantly overexpressed in the 25V group compared to the 25C group. Notably, in the apoptosis pathway, genes encoding executor caspases (casp3 and casp7) and pro-apoptotic factor, bax were significantly up-regulated only in the 25V group, while the apoptosis inhibitor, bcl2L1 was significantly up-regulated only in the 20V group compared to the control group at the respective temperatures. The co-culture of V. harveyi with abalone hemocytes at 25°C up-regulated several virulence-related genes involved in quorum sensing (luxS), antioxidant activity (katA, katB, and sodC), motility (flgI), and adherence/invasion (ompU) compared to those at 20°C. Therefore, our results showed that H. discus hannai hemocytes exposed to V. harveyi at 25°C were highly stressed by vigorously activated inflammatory responses and that the bacterial pathogen overexpressed several virulence-related genes at the high temperature tested. The transcriptomic profile of both abalone hemocytes and V. harveyi in the present study provide insight into differential host-pathogen interactions depending on the temperature conditions and the molecular backgrounds related to increased abalone vulnerability upon global warming.

Circadian feeding characteristics of different abalone species and construction of a gastrointestinal evacuation model

Abalone are of significant economic importance in the marine shellfish market in China. In order to examine feeding characteristics and formulate a model of gastrointestinal evacuation for Haliotis discus hannai, H. gigantea, and H. discus hannai ♀ × H. fulgens ♂, fecal output after intake of feed labelled with chromium sesquioxide (Cr2O3) was subjected to uninterrupted monitoring for 72 h. Feed consumption levels of H. discus hannai, H. gigantea, and H. discus hannai ♀ × H. fulgens ♂ were seen to harbor a circadian rhythm. Over 90% of the feed intake occurred between 20:00 and 04:00, and fecal output of H. discus hannai, H. gigantea, and H. discus hannai ♀ × H. fulgens ♂ was continuous over the experimental period. The cosine fitting peak phases of fecal output of H. discus hannai, H. gigantea, and H. discus hannai ♀ × H. fulgens ♂ appeared at 09:07, 08:46, and 08:24, respectively, all about 9 h after the appearance of each feeding peak. Based on the measured Cr2O3 content in feces, about 70% of the gastrointestinal evacuation of the labelled feed occurred 12–24 h after consumption. The time-dependent variation of the percentage evacuated of three abalone species agrees well with the logistic model (R2 > 0.99); H. discus hannai, H. gigantea, and H. discus hannai ♀ × H. fulgens ♂ evacuated 50% of the feed within about 19 h, and 95% was evacuated at 32.99, 30.09, and 29.96 h, respectively. In this work, a non-destructive method was used to accurately measure the time required for the gastrointestinal evacuation of abalone, provided that abalone could ingest feed without fasting. This work not only enriched the basic knowledge of abalone’ digestive physiology, but also provided a theoretical reference for developing reasonable feeding strategies.

Detection of markers for proliferation, stem cell, and EMT in the gills of Pacific abalone Haliotis discus hannai

Detection of markers for proliferation, stem cell, and EMT in the gills of Pacific abalone Haliotis discus hannai

An efficient approach for extraction of polysaccharide from abalone (Haliotis Discus Hannai Ino) viscera by natural deep eutectic solvent

In this study, a natural deep eutectic solvent (NADES) was proposed for the ultrasonic-assisted extraction of polysaccharides from abalone (Haliotis Discus Hannai Ino) viscera. Eleven NADESs were employed for abalone viscera polysaccharide (AVP) extraction. NADES, composed of choline chloride and ethylene glycol in a molar ratio 1: 3 had the highest extraction efficiency. The optimal extraction conditions were obtained using a four-factor, three-level Box-Behnken design and specific response surface methodology. The maximum predicted polysaccharide yield was 17.32 %. Fick's second law was fitted to the extraction process of AVP by ultrasonic-assisted NADES based on a high linear correlation (R2 ≥ 0.9). The extraction rate constants (k), diffusion coefficients (Du) and half-lives (t1/2) were calculated. Compared to the polysaccharides prepared by the conventional method, the polysaccharides extracted by NADES had a higher sugar content, lower molecular weight, more glucuronic acid, and stronger antioxidant capacity. Overall, the NADES extraction method established in this research can become a strategy for the preparation of high-purity and highly bioactive abalone viscera polysaccharides, which has implications for the exploitation and application of marine food byproduct resources.

Combined effects of toxic Karenia mikimotoi and hypoxia on the juvenile abalone Haliotis discus hannai

Eutrophication in aquaculture areas concurrently leads to a high incidence of dissolved oxygen deficiency and toxic algal blooms. The combined effects of hypoxia and typical toxic algae on cultured organisms should be given sufficient consideration. Abalone breeding in China has greatly suffered from hypoxia and toxic Karenia mikimotoi blooms for many years. In this study, the individual and combined effects of the toxic dinoflagellate, K. mikimotoi, and hypoxia on juvenile abalone were determined based on abalone survival and oxidative stress indicators in their gills, hepatopancreas and hemolymph. The results showed that at a density of 106 to 3×107 cells/L, K. mikimotoi alone had a negligible influence on the survival of juvenile abalone under sufficient dissolved oxygen (DO) conditions. The 24 h-half lethal concentration (LC50) of DO alone for juvenile abalone was 0.75 mg/L in seawater. When K. mikimotoi was added at a density of 3×106 cells/L, the 24 h-LC50 of DO for juvenile abalone significantly increased to 2.59 mg/L, indicating obvious synergistic effects. The individual effects of hypoxia or K. mikimotoi on the oxidative stress indicators were limited, and only the superoxide dismutase (SOD) activity in the abalone gills significantly decreased under K. mikimotoi stress. However, the combined stress of hypoxia and K. mikimotoi led to significant changes in the antioxidant indicators in all tested tissues. The SOD activity in gills and hepatopancreas decreased, while the SOD and catalase (CAT) activity and malondialdehyde (MDA) content in the hemolymph increased due to the combined stress of hypoxia and K. mikimotoi. These results illustrated that the synergistic effects of hypoxia and K. mikimotoi caused serious oxidative damage in abalone and that the hemolymph exhibited greater sensitivity than did the gills and hepatopancreas. Further investigation found that K. mikimotoi increased the oxygen consumption rate in abalone and that hypoxia enhanced the hemolytic toxicity of K. mikimotoi. These results revealed that hypoxia and typical toxic algae cause synergistic harm to cultured organisms, which is expected to provide a new understanding of the destructive mechanisms of typical toxic algal blooms in aquacultural areas.

Dietary arachidonic acid affects the growth performance, fatty acid profile, immunity and resistance to heat stress in juvenile abalone Haliotis discus hannai Ino

A 93-day feeding trial was performed to evaluate the effects of dietary arachidonic acid (ARA) on the growth performance, antioxidative capacity, immunity and anti-stress capacity of juvenile abalone Haliotis discus hannai Ino with an initial mean body weight of 4.26 ± 0.11 g. Six practical diets with 0.04% (the control), 0.31%, 0.44%, 0.68%, 0.94% and 1.34% of ARA were designed. After the feeding trial, abalones were subjected to a heat stress test. The findings showed that the survival of abalone (91.7–96.7%) after the feeding trial was not significantly influenced by dietary ARA. The 0.31–0.44% of dietary ARA significantly increased the weight gain rate (WGR). The feed conversion ratio (FCR) was decreased by 0.31–0.68% of dietary ARA. The 0.44% of dietary ARA significantly enhanced the activity of trypsin, lipase and α-amylase in the intestine. Besides, dietary ARA supplementation significantly elevated the total antioxidative capacity and activity of superoxide dismutase, catalase and lysozyme in the cell-free hemolymph. Higher levels of dietary ARA (≥0.94%) significantly up-regulated the mRNA levels of nuclear factor κB, inhibitor of κBα and transcription factor AP-1 in the digestive gland. The 0.68% of dietary ARA significantly decreased the falling rate of abalone after heat stress. In conclusion, appropriate dietary ARA levels improved the growth performance and feed utilization of abalone. The optimal dietary ARA content for juvenile abalone was 0.52% based on the quadratic regression analysis of WGR. The 0.44–0.68% of dietary ARA improved the antioxidative capacity, immunity and anti-heat stress of abalone.

Development of near-infrared reflectance spectroscopy (NIRS) model and genome-wide association study for glycogen and protein content in Pacific abalone

Quality traits have recently become the key objective in aquaculture selection breeding recently. The Pacific abalone (Haliotis discus hannai) is the most widely farmed abalone species in China. In this study, we investigated the potential of the near-infrared reflectance spectroscopy (NIRS) model to predict the glycogen and protein content of Pacific abalone. Additionally, we performed a genome-wide association study (GWAS) analysis to identify related SNPs and candidate genes for these two quality traits. Our results showed that the prediction accuracy of the NIRS model was 0.9929 and 0.9808 for glycogen and protein content, respectively. Moreover, the external cross-validation showed an accuracy above 0.95, indicating the reliability and robustness of the models. A total of 274 individuals were predicted by the NIRS model and genotyped with 69,530 high quality SNPs. Fourteen and fifteen genes were identified for glycogen and protein content, respectively, including slit2, fgfr2, gria4, hnrnpm, and megf11. These genes may affect glycogen and protein traits through biological processes such as energy metabolism, transmembrane transport, immune regulation, and signal transduction. This study not only constructed a rapid and reliable NIRS prediction model, but also helped us better understand the genetics of glycogen and protein content of Pacific abalone, which will improve the quality of Pacific abalone.

Examination of the effects of blue light stress on monoamine oxidase-mediated immunomodulatory function in the Pacific abalone, Haliotis discus hannai

Marine environments harbor a growing number of stressors brought about by global climate change, local human activities and the urbanization of coastal areas. The Pacific abalone, Haliotis discus hannai, is a nocturnal animal that avoids strong light and prefers darkness. Previous research showed that the abalone mortality rate under short-wavelength blue light was remarkably greater than that under darkness, natural light and orange light. In this study, the temporal variations in the dopamine content of abalone hemolymph under various light conditions were compared, and the dopamine content after exposure to blue light for 6 h was remarkably higher than that in any other group. The full-length monoamine oxidase (MAO) gene sequence for the catecholamine metabolism-related MAO enzyme was obtained by cloning. This gene encoded 545 amino acids, in which the predicted sequence contained a domain that was characteristic for monoamino oxidase. The MAO expression levels were highest in the hepatopancreas and in situ hybridization further revealed that MAO was widely localized around the hepatic nerve cord. The in vitro recombinant MAO protein could catalyze the degradation of epinephrine and dopamine. After 3 h exposure to blue light, the expression levels of MAO, Mn-superoxide dismutase (Mn-SOD), and catalase (CAT) genes were remarkably greater than those in any other group, but the lysozyme (LYZ) and sigma-glutathione-s-transferase (GSTs) expression levels began to increase at 12 h and 6 h, respectively. After the MAO expression levels were knocked-down by RNAi technology, the dopamine concentration significantly increased, but the phagocytic activity, nitric oxide concentration, and the Mn-SOD, CAT, GSTs and LYZ expression levels were remarakbly lower than in the control group and the enhanced green fluorescent protein (GFP) group, suggesting that the normal dopamine metabolism process played a vital role in maintaining the immune response. The above results show that monoamine oxidase may act as an immunomodulator in abalone when responding to adverse light conditions. These results could also be useful when drawing up conservation measures for preserving nearshore benthic biodiversity, such as optimizing urban night lighting schemes.

Molecular Characterization and Function of Bone Morphogenetic Protein 7 (BMP7) in the Pacific Abalone, Haliotis discus hannai.

Bone morphogenetic proteins (BMPs) play important roles in a lot of biological processes, such as bone development, cell proliferation, cell differentiation, growth, etc. However, the functions of abalone BMP genes are still unknown. This study aimed to better understand the characterization and biological function of BMP7 of Haliotis discus hannai (hdh-BMP7) via cloning and sequencing analysis. The coding sequence (CDS) length of hdh-BMP7 is 1251 bp, which encodes 416 amino acids including a signal peptide (1-28 aa), a transforming growth factor-β (TGF-β) propeptide (38-272 aa), and a mature TGF-β peptide (314-416 aa). The analysis of expression showed that hdh-BMP7 mRNA was widely expressed in all the examined tissues of H. discus hannai. Four SNPs were related to growth traits. The results of RNA interference (RNAi) showed that the mRNA expression levels of hdh-BMPR I, hdh-BMPR II, hdh-smad1, and hdh-MHC declined after hdh-BMP7 was silenced. After RNAi experiment for 30 days, the shell length, shell width, and total weight were found to be reduced in H. discus hannai (p < 0.05). The results of real-time quantitative reverse transcription PCR revealed that the hdh-BMP7 mRNA was lower in abalone of the S-DD-group than in the L-DD-group. Based on these data, we hypothesized that BMP7 gene has a positive role in the growth of H. discus hannai.

Shelter limitations reduce forage frequency by affecting forage motivation in juvenile Pacific abalones (Haliotis discus hannai), but not in adults

Behaviours serve as indicators of the status of, and proxies for the welfare of, cultured specimens. In the abalone farming sector, many factors are known to influence abalone activity, but little is known about how shelter limitations affect behaviour. In this study, we investigated the behavioural responses of juvenile and adult abalones to shelter limitations and the relationship between abalone size and activity level. Cohorts of 139 adult and 272 juvenile Pacific abalones (Haliotis discus hannai) of farm origin were observed under laboratory conditions during a 2-week period with a high level of shelter availability and a 2-week period with limited shelter. We recorded the locomotion under the shelters in the daytime, their positions in aggregations just before the forage time window, and the number of foraging nights. Our data analyses confirmed that in conditions of shelter limitation, juveniles showed increased forage frequency variation, and both active and inactive showed juveniles decreased activity levels. In contrast, adults showed decreased forage frequency variation, and while active adults showed decreased activity levels, inactive adults showed increased activity levels. We found that shelter limitations decreased the forage frequency of juveniles by affecting their forage motivation, not by restricting their access to forage.The results improve our understanding of the differences in Pacific abalone behaviours at the juvenile and adult stages and provide us with valuable information for the future design of abalone culture tanks and cages.

Haemolymph pH of two important mollusc species is susceptible to seawater buffering capacity instead of pH or pCO2

The acid-base status and balance of molluscs are considered to be susceptible to environmental changes, especially in the context of ocean acidification (OA). Here, we studied the effects of manipulated seawater carbonate chemistry on the acid-base status of scallop Chlamys farreri and abalone Haliotis discus hannai. The haemolymph pH of the tested individuals showed a fast response to acidified seawater incubation, and the pH level was restored to a normal value within 1 h of recovery in control seawater. However, no significant correlation (P > 0.05) was found between haemolymph pH and seawater pCO2 or pH, while the squared Pearson correlation coefficient (R2) ranged from close to zero to 0.41. In addition, although the pCO2 level of total alkalinity (TA)-lowered seawater was lower than half of that in the control, molluscs eliminated less CO2 (less than 80%) to TA lowered waters than to the control waters. These findings seem to disagree with the crucial role of seawater pCO2 in influencing the acid-base balance of molluscs. CO2 elimination occurs in the microenvironment, and CO2 first diffuses to limited amounts of seawater that tightly surround the gills, causing dissolved inorganic carbon (DIC) accumulation in the ventilation sites, which leads to a sharp increase in the pCO2 of the surrounding seawater. Moreover, in this microenvironment, the pCO2 level increases much faster and more greatly if the environmental seawater is acidified or contains a lower level of TA. Therefore, mollusc acid-base status is influenced by rapidly varying pCO2 levels at the ventilation site, which is largely independent of that of the rest of the incubating seawater. In summary, CO2 elimination by molluscs relies heavily on the carbonate chemistry of environmental seawater, and seawater buffering capacity should be taken into consideration instead of considering only pCO2 or pH in studying the acid-base balance of marine molluscs.

Acoustic Characterization for The Feeding Activities of Haliotis discus Hannai

In order to analyze the sound production mechanism and the acoustic characteristics of Haliotis discus hannai during feeding, this paper proposes a multi-source information fusion approach combining passive acoustics with videos. In the experiments, abalones with a shell length of 60 ± 2.7 mm were divided into two groups: Group A was fed with fresh macro algae Gracilaria lemaneiformis as food once each day; Group B was placed on a small amount of sand as impurities at the bottom of the tank. As control groups, Group C did not have abalone or food and Group D did not have abalones but food was added. The eating acoustic signals of abalone were mainly concentrated in the frequency range between 9.49 kHz and 44.36 kHz, wherein the peak frequency is 37.86 ± 2.55 kHz, with the maximum energy −66.43 ± 5.17 dBm/Hz. Each pulse sequence is with a duration of 119.12 ± 70.51 ms and consists of several sub-pulses. Nearly 70% of the pulse sequences consist of 1~2 sub-pulses and the duration of the pulse containing one sub-pulse is 42.62 ± 19.72 ms. The eating rate was kept at 0.61 ± 0.04 times/min at the beginning and was decreased significantly to 0.48 ± 0.08 times/min after 60 min. Note that the characteristic analysis of abalone acoustic signals during feeding are first reported in this manuscript to the best of our knowledge, and this paper also demonstrates that the sound of abalone is produced by scraping and grinding food with radula. Because the eating rate decreases with the reduction in the abalone’s level of hunger, the results may be used as an acoustic indicator of feeding strategy for the abalone aquaculture industry.