Abalone Aquaculture Research Articles

Different Transcriptomic Responses to Thermal Stress in Heat-Tolerant and Heat-Sensitive Pacific Abalones Indicated by Cardiac Performance.

The Pacific abalone Haliotis discus hannai is one of the most economically important mollusks in China. Even though it has been farmed in southern China for almost 20 years, summer mortality remains the most challengeable problem for Pacific abalone aquaculture recently. Here, we determined the different heat tolerance ability for five selective lines of H. discus hannai by measuring the cardiac performance and Arrhenius breakpoint temperature (ABT). The Red line (RL) and Yangxia line (YL) were determined as the most heat-sensitive and most heat-tolerant line, respectively. Heart rates for RL were significantly lower than those of the YL at the same temperature (p < 0.05). The differentially expressed genes (DEGs), which were enriched in several pathways including cardiac muscle contraction, glutathione metabolism and oxidative phosphorylation, were identified between RL and YL at control temperature (20°C) and heat stress temperature (28.5°C, the ABT of the RL) by RNA-seq method. In the RL, 3370 DEGs were identified between the control and the heat-stress temperature, while only 1351 DEGs were identified in YL between these two temperature tests. Most of these DEGs were enriched in the pathways such as protein processing in endoplasmic reticulum, nucleotide binding and oligomerization domain (NOD) like receptor signaling, and ubiquitin mediated proteolysis. Notably, the most heat-tolerant line YL used an effective heat-protection strategy based on moderate transcriptional changes and regulation on the expression of key genes.

Environmental stress tolerance and immune response for the small abalone hybrids

Recently, mass mortality affected the cultured small abalone, Haliotis diversicolor diversicolor, which was the dominant cultured abalone species in southern China. Prior studies revealed that survivorship varied significantly between different stocks and crosses. However, the immunological basis for differences in susceptibility has not been well understood to date. Herein, low temperature, air exposure tolerance tests, and pull-off force measurement were assessed in the three groups (Japan, Taiwan, and their Hybrid stock). The results showed that the critical thermal minimum (CTMin) at 50% was 15.6 °C for the Taiwan stock, 12.1 °C for the Japan stock, and 13.2 °C for the Hybrid stock. Upon air exposure challenge, 100% abalones from the Taiwan group died after 8 h at 24 °C, while the survival rate in the Japan and Hybrid groups were 37.8% and 29.4%, respectively. The detachment stress for the Japan group was 42.3 kPa, which was 2.78-fold and 1.43-fold higher compared to the Taiwan and Hybrid groups, respectively. Variation in susceptibility to disease may be based on the effectiveness of the innate immune responses. Therefore, total hemocyte count, phagocytosis, respiratory burst, superoxide dismutase activity, acid phosphatase activity, alkaline phosphatase activity, and myeloperoxidase activity were determined for the healthy abalones in each group. Positive mid-parent heterosis on immunological parameters was consistent with the prior knowledge on the positive mid-parent heterosis for survival rate, which indicated the improvement on immune reaction and disease resistance through hybridization methods. The current study will be useful in efficient design of breeding programs for the development of sustainable abalone aquaculture.

The Utility of Dietary Phosphorus Enrichment During Transition to Formulated Feeds of Juvenile Abalone Haliotis tuberculata

Sustaining the growth of abalone aquaculture globally requires farm operators to satisfy the specific diet requirements of the particular abalone species grown. Components of commercial aquaculture feeds usually contain animal protein in the form of fishmeal. Rather than adding generic animal protein foodstuffs, formulated diets may be more effective when supplemented with particular substances of metabolic use to the abalone. The inclusion of animal proteins may have physiological demands on the growth and survival of different species of abalone as formulated feeds change the colour of the shell bands and the components of the feed may not exist in the natural diet of abalone. Inclusion and enrichment of phosphorus in mixed macroalgal-meal diets for juvenile abalone Haliotis tuberculata was investigated. Macroalgae is the natural diet for juvenile and adult abalone and can be limiting in bioavailable phosphorus. Increasing the available dietary phosphorus content in the diet of juvenile H. tuberculata to 0.9% and 1.5% increased growth rates in shell length compared to Palmaria palmata diet (P

Integrative transcriptome analysis and discovery of genes involving in immune response of hypoxia/thermal challenges in the small abalone Haliotis diversicolor

In recent years, the abalone aquaculture industry has been threatened by the deteriorating environmental conditions, such as hypoxia and thermal stress in the hot summers. It is necessary to investigate the molecular mechanism in response to these environmental challenges, and subsequently understand the immune defense system. In this study, the transcriptome profiles by RNA-seq of hemocytes from the small abalone Haliotis diversicolor after exposure to hypoxia, thermal stress, and hypoxia plus thermal stress were established. A total of 103,703,074 clean reads were obtained and 99,774 unigenes were assembled. Of the 99,774 unigenes, 47,154 and 20,455 had homologous sequences in the Nr and Swiss-Prot protein databases, while 16,944 and 10,840 unigenes could be classified by COG or KEGG databases, respectively. RNAseq analysis revealed that the differentially expressed genes (DEGs) after challenges of hypoxia, thermal stress, or hypoxia plus thermal stress were 24,189, 29,165 and 23,665, among which more than 3000 genes involved in at least 230 pathways, including several classical immune-related pathways. The genes and pathways that were involved in immune response to hypoxia/thermal challenges were identified by transcriptome analysis and further validated by quantitative real-time PCR and RNAi technology. The findings in this study can provide information on H. diversicolor innate immunity to improve the abalone aquaculture industry, and the analysis of the potential immune-related genes in innate immunity signaling pathways and the obtained transcriptome data can provide an invaluable genetic resource for the study of the genome and functional genes.

How Family Trees And DNA Fingerprinting Are Helping European Abalone Aquaculture

How Family Trees And DNA Fingerprinting Are Helping European Abalone Aquaculture

Hybridization improved bacteria resistance in abalone: Evidence from physiological and molecular responses

Hybridization is an effective way of improving germplasm in abalone, as it often generates benign traits in the hybrids. The hybrids of Haliotis discus hannai and H. gigantea have shown heterosis in terms of disease resistance than one or both parental species. In the present study, to elucidate the physiological and molecular mechanism of this heterosis, we analyzed the dynamic changes of several immune indexes including survival rate, total circulating haemocyte count (THC), phagocytic activity, reactive oxygen species level (ROS) and phenoloxidase activity (PO) in two parental species, H. discus hannai (DD) and H. gigantea (GG), and their reciprocal hybrids H. discus hannai ♀ × H. gigantea ♂ (DG), H. gigantea ♀ × H. discus hannai ♂ (GD) challenged with a mixture of Vibrio harveyi, V. alginolyticus and V. parahaemolyticus (which have been demonstrated to be pathogenic to abalone). Besides, we cloned and analyzed three important immune genes: heat shock protein 70 (hsp70), ferritin and cold shock domain protein (csdp) in H. discus hannai and H. gigantea, then further investigated their mRNA level changes in the four abalone genotypes after bacterial challenge. Results showed that these physiological and molecular parameters were significantly induced by bacterial exposure, and their changing patterns were obviously different between the four genotypes: (1) Survival rates of the two hybrids were higher than both parental species after bacterial exposure; (2) DG had higher THC than the other three genotypes; (3) Phagocytosis responded slower in the hybrids than in the parental species; (4) DD's ROS level was lower than the other three genotypes at 48 h post infection; (5) Phenoloxidase activity was lower in DD during the infection compared to the other genotypes; (6) mRNA levels of hsp70 and csdp, were always lower in at least one parental species (DD) than in the hybrids after the bacterial exposure. Results from this study indicate that the hybrids are more active or efficient in immune system function, hence they could effectively defense against a bacterial invasion, leading to higher survival rates after challenge. This study provides physiological and molecular evidences for interpreting the disease resistant heterosis in this abalone hybrid system, which could help us in a better understanding and utilization of heterosis in abalone aquaculture.

Aquaculture of two commercially important molluscs (abalone and limpet): existing knowledge and future prospects

AbstractMolluscan aquaculture produces the most food fish by volume in the global mariculture market. The historical, cultural and ecological value of molluscs makes them a highly sought‐after delicacy in many regions of the world. Specifically, the aquaculture of abalone and that of limpets are two key industries with striking similarities and importance within the context of food production and food security. In this review, the current knowledge of these two commercially important seafood species is explored for a comprehensive understanding of its aquaculture status. The various culture methods and systems, animal nutrition and necessary improvements are discussed for abalone and limpets, respectively. For abalone, the knowledge base is extensive and some reviews have been written to compile essential information regarding different aspects of this healthy industry. For limpets, there is a small collection of aquaculture literature, and this is, to the authors’ knowledge, the first comprehensive review of the research. Our goal was to reveal, within the area of aquaculture research, the current status of both abalone and limpet industries while exposing their respective knowledge gaps for appropriate development of new technologies. With a firm understanding of these molluscs, the production of abalone and limpet will be sustainable for the long term.

Analysis of monthly variation of biological conditions, metabolic parameters and antioxidative capacities in sea-based farmed Pacific abalone during summer days

Pacific abalone, Haliotis discus hannai, has become the predominant farmed abalone species in Fujian, southern China, since 2006. As an introduced abalone species from northern China, mass mortality of the farmed Pacific abalones in Fujian often occurred during summer in recent years. However, this phenomenon of summer mortality still lacks thorough investigation. We conducted a field investigation to monitor biological conditions of the 2-year-old animals, including monthly survival rates; visual gonad index; monthly variation in metabolic parameters including protein, glycogen, and nonesterified fatty acid (NEFA) content; and enzyme activities of lactate dehydrogenase (LDH) and antioxidative capacities including superoxide dismutase (SOD) and total antioxidative capacity (T-AOC) from April to October 2014. A range of environmental parameters were assessed and correlated against biological indicators for abalone conditions, metabolic parameters, and antioxidative capacities. Results showed a total mortality rate of 58.58% over the sampled period. Visual gonad index assessment showed that the sampled animals had similar gonad development levels during each sampling date. Environmental parameters and abalone mortality monitored during the study showed significant positive correlation between seawater temperature and mortality of abalones. All energy resources tended to be depleted at the end of summer. Results also showed that both SOD and T-AOC increased in the first few months and then decreased in September and October. The variations of metabolic parameters and antioxidative capacities indicated an insufficient energy supply and peroxidative damage in the farmed animals during summer. This study provided the biological data of farmed Pacific abalone by field investigation in terms of summer mortality for the first time in southern China. These findings that might be applicable to the management and development of Pacific abalone aquaculture in sea-based farms of southern China were also discussed in the study.

완도지역 전복 양식어가 생산의 경영효율성 분석

This study is to estimate the production efficiency of abalone aquaculture and to find its determinants utilizing the survey data of operating expenses in 2015. The first part of the analysis applied both DEA and Super-DEA for the estimation of efficiency of each aquaculture household as DMU. We used wages, feeding costs and area as inputs and annual profits and sales as outputs of the model. The second part of the study applied both Tobit and OLS for the identification of determinants of the efficiency. We investigated cost-ratio, depreciation costs, careers, value of living seeds, cleaning costs of farming ground and a ratio of 1 and 2 year-old abalone at shipment as potential determinants. The estimation results show us that the average technical efficiency, pure technical efficiency, and scale efficiency score turn out to be 72%, 81% and 85% respectively. The Super-BCC and Super-CCR models reveal their average efficiency scores as 81% and 80%. All of the variables used to identify the determinants of the efficiency. The study results suggests that the production efficiency can be improved by cleaning farming ground and hence lowering the death rate of seeds.

Gonadal Development and Reproductive Cycle of Cultured Abalone,Haliotis discus hannai(Gastropoda: Haliotidae) in Korea: Implications for Seed Production

The objective of this study was to examine gonad development and reproductive cycle of the abalone Haliotis discus hannai at three main abalone aquaculture farms (Uljin, Wando, and Jeju Island) in Korea to obtain information on artificial seed production. The sex ratio (female:male) was approximately 1:1 without significant difference among the three regions or between females and males. Average gonad index was the highest during July in Uljin and Jeju Island and during August in Wando. There was no definitive seasonal change in condition index and meat weight index throughout the year in the three regions. The gonad of H. discus hannai displayed seasonal change histologically, thereby enabling us to distinguish the following stages: inactive (November–December), early active (January–March), late active (March–April), ripe (May–July), spent (August–October), and degenerative (October–November). The main spawning period of H. discus hannai was determined to be during September–October in Uljin and Wando, and August–September in Jeju Island.

Assessment of the thermal tolerance of abalone based on cardiac performance in Haliotis discus hannai, H. gigantea and their interspecific hybrid

Temperature stress is one of the major threats to the economic and ecological sustainability of marine fisheries and aquaculture. The abalone aquaculture in China has been in development for more than twenty years, while summer mortality for Pacific abalone (Haliotis discus hannai) is still the most serious issue for its aquaculture in southern China. Therefore, an effective and accurate measurement for evaluating the abalone's thermal tolerance is crucial for both scientific researchers and farmers. In this study, we evaluate the thermal tolerance of two abalone species: H. discus hannai (DD), H. gigantea (GG) and their offspring H. gigantea ♀×H. discus hannai ♂ (GD) using Arrhenius break temperatures (ABT) of cardiac performance. These three groups possessed different thermal limits, as indicated by ABT, GD (32.50±0.71°C)>GG (31.30±1.52°C)>DD (30.00±1.23°C). The results were similar to further assessments of lethal temperature, Kaplan–Meier cumulative survival curves and critical thermal maximum. These results indicate that cardiac performance is an effective method to assess heat tolerance and can represent the different physiological statuses of abalones. Moreover, the results also suggested that global warming may have a profound influence on abalone aquaculture in China in the near future. Statement of relevanceThe results of the present study may facilitate in better understanding the difference on the thermal tolerance ability of H. discus hannai, H. gigantea and their offspring H. gigantea ♀×H. discus hannai ♂ using Arrhenius break temperatures (ABT) of cardiac performance. The results were similar to further assessments of lethal temperature, Kaplan–Meier cumulative survival curves and critical thermal maximum. These findings indicate that cardiac performance is an effective method to assess heat tolerance and can represent the different physiological statuses of abalone. The ABT of cardiac performance could afford an efficient method to predict abalone thermal performance, which would be greatly beneficial in aquaculture and breeding projects.Moreover, it may have potentially broad application in the study of thermal tolerance of abalone and other commercially aquaculture species.

Socio-economic analysis on the role of local government in developing the abalone industry in Korea

Many Koreans regard abalone (Haliotus discus hannai) as a desirable luxury food because of its limited availability and high price. Abalone aquaculture was developed during the late 2000s, and production has greatly increased in Korea, reaching 9,147 tons in 2014. Policy experts said this trend means many fishers who cultivate abalone could increase their income. However, their incomes had not increased since fishers started cultivating abalone, because a conventional “addition” was applied to abalone transactions. The distribution structure for abalone products relies almost entirely on wholesalers instead of fisheries cooperatives, which are commonly used for other types of seafood products. Therefore, a new distribution structure was required in the Korean abalone industry. The objective of this study was to document how the establishment of an abalone cooperative by the local government has affected fishers’ income and production since 2009. This research was conducted in Wando District in South Jeolla Province, which accounts for over 90% of the domestic abalone production. Wholesalers, fishers, and a public officer were interviewed. A shift from a wholesalercontrolled distribution structure to a cooperative run by the local government helped to reduce the “addition” and increase fishers’ incomes overall.Res. Agric., Livest. Fish.3(2): 345-353, August 2016

Effects of light intensity on metabolism and antioxidant defense in Haliotis discus hannai Ino

We examined the effects of light intensity on the metabolism, antioxidant enzymes, and expression of related genes in Haliotis discus hannai Ino, to determine the optimal lighting conditions for aquaculture of these animals. Succinate dehydrogenase activity was significantly lower after 48h in animals exposed to light intensities of 30 and 60μmol/m2/s, while lactate dehydrogenase activity and lactic acid content at 96h were significantly higher compared with animals in the dark or exposed to 5 or 15μmol/m2/s (both P<0.05). There was no significant difference in reactive oxygen species (ROS) contents between animals in the dark and those exposed to 5 or 15μmol/m2/s (P>0.05) throughout the experiment. However, ROS contents under light intensities of 30 and 60μmol/m2/s peaked at 12h, when expression levels of genes encoding catalase (CAT), thioredoxin peroxidase (TPX), sigma-glutathione-s-transferase (GSTS), and mu-glutathione-s-transferase (GSTm) also began to increase, and CAT and glutathione peroxidase (GPX) activities were significantly higher than in animals in the dark or exposed to 5 or 15μmol/m2/s (P<0.05). After a further 12h, the ROS content at 30μmol/m2/s began to decrease, and GPX activity and malondialdehyde (MDA) content also gradually decreased, followed by increases in ROS and MDA 48h later, to reach respective peaks at 96h. Gene expression levels of TPX, GSTS, GSTm, heat shock protein 70 (HSP70), and CAT began to decrease 72h later, suggesting that excessive accumulation of ROS may have caused oxidative damage to the tissues. At a light intensity of 60μmol/m2/s, expression levels of TPX, GSTS, GSTm, and HSP70 genes, total antioxidant capacity, and GPX activity peaked at 48h, and the ROS content was significantly higher than in any other group 48h later (P<0.05). However, gene expression levels of TPX, GSTS, GSTm, HSP70, HSP90, and CAT, and reduced glutathione content began to decrease, indicating that the antioxidant system had been unable to perform its normal physiological functions to withstand the long-term stress of adverse environmental factors. These results suggest that the light intensity should be controlled at 5–15μmol/m2/s during H. discus hannai aquaculture, to maintain the organism's normal physiological metabolism. Statement of relevanceThe disc abalone Haliotis discus hannai is an economically important shellfish in China, with demand growing for this high-protein and low-fat seafood. In 2014, 11,5397 tons of H.discushannai were harvested from aquacultural sources, but supply cannot currently meet consumer demand. In recent years, the natural habitat of H. discus hannai has declined as a result of overfishing, marine reclamation, water pollution, among others, leading to a sharp decrease in the numbers of H. discus hannai in the wild. Thus, the development of an aquacultural system for farming H. discus hannai, as well as for its protection in the wild, are a focus of current research.Light, including photoperiod, quality and intensity, is one of the key environmental factors influencing the growth, culture and survival of aquatic organisms. Over evolutionary time, organisms have evolved both physiological and behavioral mechanisms that enable them to adapt to diurnal fluctuations in light. In Chinese traditional abalone aquaculture, a sunshade net is usually used because of the photophobic nature of abalone. In particular, the aquaculturist usually provides a darkened setting for adult abalones to increase their food intake rate, facilitate their growth and promote gonadal development. For abalones in their natural environment, the light intensity in the water area is relatively stable, suggesting that there is a key regulative effect of light intensity on their growth and development.Gao et al. (2016a,b) found that a dark environment not only adversely affected the daily aquaculture production, but was also associated with a lower growth rate compared with animals reared under higher light intensities, because of lower food conversion efficiency and greater energy losses through excretion and feces. Physiological metabolism and antioxidant defense systems may therefore be key indicators for measuring the suitability of light intensity for aquaculture production. We therefore examined the effects of light intensity on the metabolism and antioxidant defense system, and on the expression of related genes, in H. discus hannai using a light-emitting diode (LED) to replace the conventional fluorescent light source. The results of this study will improve our understanding of the physiological tolerance and antioxidant defense characteristics of abalone under different light intensities, and enable the optimization of environmental light conditions in abalone aquaculture.

RNA interference in Haliotis rufescens myostatin evidences upregulation of insulin signaling pathway

Muscle growth rate is a critical issue for abalone aquaculture due to impacts on production costs. However, knowledge of the molecular mechanisms involved in molluscan myogenesis is limited. Therefore, the myostatin gene in the red abalone Haliotis rufescens (Hr-MSTN) was characterized and evaluated at the transcriptional level using RNA interference and gene silencing correlated with the insulin pathway as a proxy for somatic growth. Hr-MSTN cDNA was comprised of 2346 base pairs that encoded 489 amino acids and that contained structural characteristics typical of the transforming growth factor-β superfamily, including C-terminal signal peptide, propeptide domain, and transforming growth factor-β regions. Gene expression analysis revealed ubiquitous transcript expression in all tested red abalone tissues, but the muscle and mantle evidenced the highest transcriptional activity. RNA interference against MSTN mRNA significantly downregulated MSTN at 14days post-injection, correlating with an upregulation of the insulin-related genes Insulin receptor, Growth factor receptor bound 2, and Proto-oncogene serine/threonine-protein kinase. These results suggest that MSTN silencing can promote activation of the insulin transcription pathway and consequently trigger somatic growth in the red abalone. This study is the first to evaluate the role of MSTN in gastropods using RNA interference, thus providing new perspectives for genetic improvement programs in abalone aquaculture.

IGFBP7 is involved in abalone metamorphosis

Metamorphosis is the most critical life stage for abalone. There are morphogenetic transformations and habitat selection with metamorphosis. A large amount of larvae often die during this stage. Insulin/insulin-like growth factor signaling pathway (IIS) plays a role in the development. However, there is little knowledge of IIS function in metamorphosis. IGFBP7, a component of IIS, was found to be involved in metamorphosis of small abalone Haliotis diversicolor. The expression of saIGFBP7 mRNA rapidly increased before metamorphosis, which were mainly localized in the velum and foot. There was a significant decrease of metamorphosis rate after competent larvae were exposed to 5μg/mL dsRNA of saIGFBP7 (p=2.50×10−10, F=389.05). The expressions of three downstream genes of IIS (PI3K, ERKα and AKT) as well as saIGFBP7 were decreased in the dsRNA exposure experiment. There was no significant difference of metamorphosis rate (p=0.97, F=0.071) after competent larvae were induced in different concentrations of insulin. The expression of saIGFBP7, PI3K and ERKα also had no significant difference in insulin inducing assay. However, AKT expression level of 1μmol/L insulin induced group was significantly higher than that of other concentrations (p=3.41×10−7, F=26.68). These results suggested that IGFBP7 is involved in metamorphosis of abalone larvae. Our study provides insight on developing new methods for increasing the metamorphosis rate in abalone aquaculture. However, it does not work as a negative regulator of IIS activity, or plays its role in an IGF- and insulin-independent manner during metamorphosis of abalone larvae.

Effect of LED light quality on respiratory metabolism and activities of related enzymes of Haliotis discus hannai

Oxygen consumption and ammonia excretion rates of abalone (Haliotis discus hannai) of differing sizes (wet weight 63.74±8.49g, 17.49±3.20g, and 3.52±0.94g) were evaluated under five different light emitting diode (LED) conditions (red, orange, purple, green, and blue light) and in dark and natural light environments. The weight-specific oxygen consumption/ammonia excretion rates decreased significantly with increasing body weight, and these relationships could be expressed by the exponential equations R=aWb and E=aWb (P<0.05), respectively. The oxygen consumption/ammonia excretion rates of abalone in the red light, orange light, and dark environment treatments were lower than those in the green, blue, natural, and purple light treatments, and the highest rates (3.27mgg−1 h−1/187μgg −1 h −1) occurred in the purple light treatment (P<0.05). The O/N ratio exceeded 10 in all light quality groups, indicating that the energy requirements were met by carbohydrate and fat. In another experiment, the effects of different light qualities on the activities of hexokinase (HK), pyruvate kinase (PK), superoxide dismutase (SOD), and catalase (CAT) in juvenile abalone (wet weight 17.49±3.20g) were investigated at 0.5, 1, 3, 6, 12, 24, and 72h of light exposure. HK and PK activities in the green, purple, blue, and natural light groups were significantly higher than those in the red light, orange light, and dark environment (P<0.05). SOD activity increased immediately when the abalones were placed in green, purple, blue, and natural light, then decreased gradually and returned to its original level. CAT activity did not increase until 12h and was higher in the green, purple, blue, and natural light groups than in the red light, orange light, and dark environment (P<0.05). These results suggest that more carbohydrates were provided and utilized by the glycolytic cycle when the abalones were exposed to adverse light conditions. Therefore, the selection of appropriate light conditions (red and orange light) and the control of metabolic waste ammonia will have a significant impact on high-intensity aquaculture in recirculating cultivation systems. Statement of relevanceThe disk abalone Haliotis discus hannai is an economically important shellfish in China, with demand growing for this high-protein and low-fat seafood. In 2012, 90 694t of H. d. hannai were harvested from aquacultural sources, but supply cannot currently meet consumer demand. In recent years, the natural habitat of H. d. hannai has declined as a result of overfishing, marine reclamation, water pollution, among others, leading to a sharp decrease in the numbers of H. d. hannai in the wild. Thus, the development of an aquacultural system for farming H. d. hannai, as well as for its protection in the wild, are a focus of current research.Light, including photoperiod, quality and intensity, is one of the key environmental factors influencing the growth, culture and survival of aquatic organisms. Over evolutionary time, organisms have evolved both physiological and behavioral mechanisms that enable them to adapt to diurnal fluctuations in light. This is particularly relevant to coastal aquatic environments, where various phytoplanktonic species and dissolved organic matter in the water can absorb or scatter blue light, converting the light quality of transmitted light from blue-green to green-orange. Blue light (470nm) has the strongest penetrability in clean seawater, whereas red light and ultraviolet (UV) are quickly absorbed in clean seawater. In its natural environment, H. d. hannai is mostly distributed in shallow inshore waters at a depth of less than 10m. Such waters are also inhabited by dense populations of phytoplankton and contain high levels of dissolved organic matter, which both diminish the transmission capacity of light, particularly of blue light, and this can result in an extended range of red and orange light, rather than blue light, in the water.In Chinese traditional abalone aquaculture, a sunshade net is usually used because of the photophobic nature of abalone. In particular, the aquaculturist usually provides a darkened setting for adult abalones to increase their food intake rate, facilitate their growth and promote gonadal development. For abalones in their natural environment, the light quality in the water area is relatively stable, suggesting that there is a key regulative effect of light quality on their growth and development.The aim of the present study was to evaluate the effects of different LED light qualities on the respiratory metabolism and physiological response of abalones by measuring oxygen consumption rate, ammonia excretion rate, glycolytic enzyme activity, and antioxidant defense. Our results may be used to optimize the light conditions for optimal growth and survival of abalones and to provide basic theory for regulation and control of light conditions in closed recirculating aquaculture systems in general.

Involvement of Antizyme Characterized from the Small Abalone Haliotis diversicolor in Gonadal Development.

The small abalone Haliotis diversicolor is an economically important mollusk that is widely cultivated in Southern China. Gonad precocity may affect the aquaculture of small abalone. Polyamines, which are small cationic molecules essential for cellular proliferation, may affect gonadal development. Ornithine decarboxylase (ODC) and antizyme (AZ) are essential elements of a feedback circuit that regulates cellular polyamines. This paper presents the molecular cloning and characterization of AZ from small abalone. Sequence analysis showed that the cDNA sequence of H. diversicolor AZ (HdiODCAZ) consisted of two overlapping open reading frames (ORFs) and conformed to the +1 frameshift property of the frame. Thin Layer chromatography (TLC) analysis suggested that the expressed protein encoded by +1 ORF2 was the functional AZ that targets ODC to 26S proteasome degradation. The result demonstrated that the expression level of AZ was higher than that of ODC in the ovary of small abalone. In addition, the expression profiles of ODC and AZ at the different development stages of the ovary indicated that these two genes might be involved in the gonadal development of small abalone.

The effect of macroalgal, formulated and combination diets on growth, survival and feed utilisation in the red abalone Haliotis rufescens

Abstract Abalone aquaculture in Chile is dominated by production of the red abalone Haliotis rufescens using a diet comprised predominantly of fresh, wild-harvested macroalgae. Concerns over the long-term supply of macroalgae have led farmers to investigate the suitability of various formulated feeds, however there has been limited commercial adoption. Combination diets of macroalgal and formulated feed fed together provide a mechanism to explore and adapt to formulated feed use without entirely abandoning macroalgal feed. The current study evaluated the use of formulated, macroalgal and two combination diets (low and high macroalgal supplementation) on production indicators and canning yields of juvenile abalone H. rufescens in a culture system modified for formulated feed. The macroalgal diet and the high macroalgal-formulated pellet combination diet (76.1% macroalgae: 23.9% pelleted diet as dry weight) produced significantly higher growth indicators (SGR and LGR) than the low macroalgal-formulated pellet combination diet (31.6% macroalgae: 68.4% pelleted diet as dry weight) and the formulated pellet diet. The protein efficiency ratio of the experimental treatments was positively related to the proportional contribution of fresh macroalgae in the diet. Furthermore, calculation of the protein efficiency ratio of the formulated component in combination diets (PER f ) revealed a significant positive relationship between macroalgae contribution and PER f . This suggests that the increase in total PER is driven by the increased utilisation of protein in the formulated component of combination diets associated with increasing levels of fresh macroalgal supplementation. We suggest possible reasons why the presence of seaweed increased the availability of the formulated feed protein to the abalone. A simulated canning trial highlighted a significant positive linear relationship between meat canning yield and the proportional contribution of formulated feed. This study highlights the value of combination diets as a tool for abalone producers to harness the potential production advantages of macroalgae while still accessing the processing benefits associated with nutrient dense formulated feed. Statement of relevance We believe that this manuscript describes novel insights into the efficiency of protein utilisation in juvenile red abalone fed combination diets as well as the effect of diet, particularly formulated feed inclusion level, on canned meat yields. This provides empirical information to inform commercial abalone farmers of H. rufescens when exploring dietary options for optimal culture.

Characterisation of the role of an alkaline protease from Vibrio midae SY9 in enhancing the growth rate of cultured abalone fed a probiotic-supplemented feed

Abstract South Africa has a rapidly developing abalone aquaculture industry based largely on the cultivation of Haliotis midae . The prophylactic use of probiotic microorganisms has been shown to enhance the health, growth and nutritional status of a variety of cultured aquaculture species. Furthermore, research has shown that H. midae fed a high protein artificial diet supplemented with the proteolytic marine bacterium Vibrio midae SY9 have enhanced digestive protease activity levels, protein digestion and absorption, and growth. The predominant V. midae SY9 extracellular alkaline protease, VmproA, has been previously shown to be present in the crop/stomach and intestinal regions of H. midae fed a diet supplemented with V. midae SY9. Therefore, VmproA may be responsible for the probiotic properties of the bacterium in farmed abalone. In this study, the role of VmproA on abalone growth was investigated using the mutant strain V. midae SY9Mut2, which is unable to produce VmproA. Over the course of a 180 day laboratory-based growth trial the growth rate of small (28 mm) abalone improved by 6.5 and 14.5% following dietary supplementation with V. midae SY9 and V. midae SY9Mut2, respectively, in comparison to abalone fed a basal diet. In situ protease activity within the H. midae digestive tract was significantly increased in animals fed the V. midae SY9 supplemented diet compared to abalone fed either the basal feed or the V. midae SY9Mut2 supplemented diet. Thus, VmproA does not appear to be the factor responsible for increased growth of probiotic-supplemented abalone. Statement of relevance The manuscript addresses the mechanism of how probiotics function in a farmed abalone species. This is important since probiotic supplementation of feed is proving successful in increasing the growth of these molluscs, and yet very little is known regarding the underlying relationship between the host animal and the probiont.

Experimental hybridization and genetic identification of Pacific abalone Haliotis discus hannai and green abalone H. fulgens

Abstract The temperate-water Pacific abalone, Haliotis discus hannai , has replaced the local subtropical species Haliotis diversicolor , as the main cultured abalone species in southern China in recent years. Although the ability to tolerate high temperature has increased for Pacific abalone, summer mortality still has a serious effect on cultivation success, as the temperature in southern China is significantly higher than the temperature in natural habitats. Hybridization has been demonstrated as an effective way to improve adaptability to particular environmental conditions. In this study, we introduced green abalone, Haliotis fulgens , from North America into China and successfully conducted hybridization trials with Pacific abalone. Fertilization rate for H. discus hannai ♀ × H. fulgens ♂ was at an acceptable level for commercial production. The hybrids exhibited hybrid vigor for growth and survival, as well as a higher temperature tolerance, showing great potential for application in the abalone aquaculture industry in southern China. Moreover, two-step PCR methods using three primers were developed, which can be used for quick genetic identification of green abalone, Pacific abalone and their reciprocal hybrids. Statement of relevance Summer mortality still has a serious effect on cultivation success of abalone farming in China. In this study, green abalone, H. fulgens were introduced and successfully conducted hybridization trials with Pacific abalone. The hybrids exhibited exciting hybrid vigor and adaptation to the higher temperature tolerance, which showed great potentials on application to the abalone aquaculture industry in southern China.