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

Hypoxia was thought to inhibit immune responses, causing severe mortality to marine organisms. The Pacific abalone, Haliotis discus hannai , is the most widely cultured abalone species in China, but suffering from "summer mortality" in which hypoxia has been one of the main reasons. The effect of hypoxia exposure on immune responses in H. discus hannai was investigated, including cellular immune response using flow cytometry and transcriptome profiles. The influence of hypoxia treatment on the total hemocyte count (THC) of H. discus hannai was rather limited but the hemocyte survival rate of abalone increased during 48 h exposure. There was an initial rise in the production of phagocytes and reactive oxygen species (ROS) shortly (3 h) after hypoxic stimulation, but finally decreased after 48 h. This indicates that hypoxia inhibited redox activity of abalone. RNA-seq studies of gill tissues also revealed immune response mechanism in abalone after 24 h of hypoxia. Totally 954 differentially expressed genes (DEGs) were detected under different degrees of deoxygenation. Though oxidation-reduction turbulence was a result of both up- and down-regulated DEGs, cell death/apoptosis induction resulted from up-regulated DEGs, whilst DNA metabolic and immunity suppression resulted from down-regulated DEGs. In summary, our data provides evidence that deoxygenation greatly affects abalone immunity, probably making it more vulnerable. The present study also lays the foundation for further research in hypoxia-associated conditions in abalone aquaculture. The effect of hypoxia exposure on immune responses in Pacific abalone, H. discus hannai was investigated, including cellular immune response using flow cytometry (total hemocyte count, hemocyte mortality, phagocytosis and reactive oxygen species) and transcriptome profiles (differentially expressed genes, GO terms, KEGG pathways). Results of two parts indicated that environmental hypoxia greatly affects abalone immunity, probably making it more vulnerable. We hypothesize that the negative effects of hypoxia on the abalone immune system follow three major directions: turbulence of oxidation-reduction, induction of cell death/apoptosis, and suppression of DNA metabolic activity. Unlabelled Image [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The small abalone ( Haliotis diversicolor ) is an important aquaculture species in southern China. Traditional breeding programs have been implemented for this species. But due to long reproduction cycle of the small abalone, the traditional method takes too long. There is therefore an urgent need to accelerate molecular breeding in H. diversicolor. Here we report on the construction of a high-density genetic map and quantitative trait loci detection in the small abalone using an F1 cross population with 131 progeny based on restriction-site-associated DNA sequencing. The sex-averaged map spanned 2190.1 cM with a mean distance between single nucleotide polymorphisms (SNPs) of 0.59 cM. A total of 3717 SNPs were mapped on 16 linkage groups. There were 1728 SNPs on the female map and 2673 SNPs on the male map. The total length of the female and male map was 2197.8 and 1764.7 cM, respectively. Six growth-related traits (body weight, muscle weight, shell weight, shell length, shell width and shell height) were recorded to detect QTL. A total of 15 suggestive QTL were identified and most of them were found on LG11. A consensus QTL for six growth-related traits was detected on LG11. It suggests that these traits may be controlled by a common region. Our results would provide valuable tools which can be used for Marker-Assisted Selection (MAS) in breeding programs of H. diversicolor . Statement of relevance This paper published a high-density linkage map and QTL analysis for growth-related traits. The study will be valuable tools for in Marker-Assisted Selection breeding program in Haliotis diversicolor . [ABSTRACT FROM AUTHOR]

[Display omitted] • The effects of ALAN on behavior and physiology of abalone were assessed. • The behavioral characteristics of abalone movement under the impact of ALAN were quantified. • Melatonin secretion was negatively correlated with the movement behavior parameters of abalone. • Amino acid metabolism is the primary energy source for abalone under the ALAN impact. The evolvement of urbanization has caused artificial light at night (ALAN) to be one of the major pollution sources in major cities, resulting in numerous environmental concerns. In view of the increasing intensity and range of ALAN, this study aims to evaluate the influence of ALAN on the physiology and behavior of the Pacific abalone Haliotis discus hannai , a typical nocturnal marine shellfish. Street lighting at night (SL6, lights on from 18:00 until 00:00; SL12, lights on from 18:00 until 06:00 the next morning) and car lighting (CL, lights were turned once every hour for 30 s and then turned off) were simulated indoors, with the natural light cycle group (lights on from 06:00 to 18:00) treated as the control group (CTR). The significantly higher cumulative distance covered along with the duration of abalone movement was observed in Group SL12 upon comparison with other groups (P < 0.05). Cosine rhythm analysis revealed that the peak phase of abalone's movement duration and cumulative distance moved in Group SL6 was shifted to ZT16:25 and ZT15:32, respectively, relative to Group CTR (ZT12:53 and ZT13:07). Correlation analysis affirmed that melatonin concentrations in all groups were significantly and negatively correlated with the abalone's movement duration and cumulative distance moved. Transcriptome sequencing analysis revealed 1599, 2142, 1507, 1676, 2355, and 1922 differentially expressed genes in the CTR vs. SL12, SL6 vs. CL, CTR vs. CL, SL12 vs. CL, CTR vs. SL6, and SL12 vs. SL6 comparisons, respectively. Based on the significantly enriched Kyoto Encyclopedia of Genes and Genomes pathways and weighted geneco-expression network analysis, quantitative real-time PCR was conducted for the validation of expression levels of 12 key genes in different groups. Amino acid catabolism and protein processing were the primary pathways used by abalone to acquire energy under the impact of ALAN. The targeted metabonomics analysis revealed that the concentrations of 20 of 23 amino acids were up-regulated in Group SL6. These results reveal the physiological adaptation and behavioral mechanisms of nocturnal marine shellfish under the impact of ALAN, and they also provide guidance for the conservation of nearshore benthic biodiversity and the optimization of urban night lighting schemes. [ABSTRACT FROM AUTHOR]

Anthropogenically increased occurrence of hypoxic conditions in the aquatic environment, combined with climate change-induced temperature increase, is causing increased concern for aquaculture species. In this study, the survival of the Pacific abalone Haliotis discus hannai (DD) and its hybrid offspring (H. discus hannai ♀ × H. fulgens ♂, DF) were observed under 96 h hypoxia at both optimum temperature (20 °C) and high temperature (28 °C). The respiration rates (MO 2) of DD and DF facing acute hypoxia at three temperatures (20 °C, 25 °C, and 28 °C) and progressive hypoxia at three different sizes (2 cm, 4 cm, and 6 cm) were compared. At 20 °C, there was no significant (p >.05) difference between median lethal concentrations (LC 50) of DD and DF while considering all time intervals; however, at 28 °C, 96 h DO LC 50 of DF (3.18 mg/L) was lower than that of DD (4.82 mg/L), indicating that DF displayed stronger hypoxia tolerance ability than DD at 28 °C. MO 2 of DD and DF increased with rising temperature and larger sizes under acute and progressive hypoxia tests, while DF showed higher MO 2 than DD, indicating its better plasticity of oxygen uptake. These results suggest that DD might be more vulnerable to a combination of thermal and hypoxia stress than DF, revealing that hybridization could be a useful way to improve stress-resistance for the abalone aquaculture industry. • In this study, the survival of the Pacific abalone (DD) and its hybrid offspring (DF) were observed under 96 h hypoxia at both optimum temperature (20 °C) and high temperature (28 °C). • DF displayed stronger hypoxia tolerance ability than DD at high temperature. • DF showed higher respiration rates (MO 2) than DD, indicating better plasticity of oxygen uptake. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) results from the absorption of anthropogenic CO 2 emissions by the ocean and threatens the survival of many marine calcareous organisms including molluscs. We studied OA effects on adult shells of the abalone species Haliotis diversicolor and Haliotis discus hannai that were exposed to three pCO 2 conditions (ambient, ∼880, and ∼1600 μatm) for 1 year. Shell periostracum corrosion under OA was observed for both species. OA reduced shell hardness and altered the nacre ultrastructure in H. diversicolor , making its shells more vulnerable to crushing force. OA exposure did not reduce the shell hardness of H. discus hannai and did not alter nacre ultrastructure. However, the reduced calcification also decreased its resistance to crushing force. Sr/Ca in the shell increased with rising calcification rate. Mg/Ca increased upon OA exposure could be due to a complimentary mechanism of preventing shell hardness further reduced. The Na/Ca distribution between the aragonite and calcite of abalone shells was also changed by OA. In general, both abalone species are at a greater risk in a more acidified ocean. Their shells may not provide sufficient protection from predators or to transportation stress in aquaculture. • OA vulnerate H. diversicolor shell by reducing hardness and changing ultrastructure. • OA also makes H. discus hannai shell more vulnerable by reducing calcification. • Shell Sr/Ca increased with rising calcification rate. • Shell Mg/Ca increased under OA conditions. • Shell Na/Ca distribution between the aragonite and calcite was changed by OA. [ABSTRACT FROM AUTHOR]

The formation of the primary shell is a vital process in marine bivalves. Ocean acidification largely influences shell formation. It has been reported that enzymes involved in phenol oxidation, such as tyrosinase and phenoloxidases, participate in the formation of the periostracum. In the present study, we cloned a tyrosinase gene from Crassostrea angulata named Ca-tyrA1 , and its potential function in early larval shell biogenesis was investigated. The Ca-tyrA1 gene has a full-length cDNA of 2430 bp in size, with an open reading frame of 1896 bp in size, which encodes a 631-amino acid protein that includes a 24-amino acid putative signal peptide. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis revealed that Ca-tyrA1 transcription mainly occurs at the trochophore stage, and the Ca-tyrA1 mRNA levels in the 3000 ppm treatment group were significantly upregulated in the early D-veliger larvae. WMISH and electron scanning microscopy analyses showed that the expression of Ca-tyrA1 occurs at the gastrula stage, thereby sustaining the early D-veliger larvae, and the shape of its signal is saddle-like, similar to that observed under an electron scanning microscope. Furthermore, the RNA interference has shown that the treatment group has a higher deformity rate than that of the control, thereby indicating that Ca-tyrA1 participates in the biogenesis of the primary shell. In conclusion, and our results indicate that Ca-tyrA1 plays a vital role in the formation of the larval shell and participates in the response to larval shell damages in Crassostrea angulata that were induced by ocean acidification. [ABSTRACT FROM AUTHOR]

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 relevance The 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. [ABSTRACT FROM AUTHOR]

Increasing atmospheric CO 2 can decrease the seawater pH and carbonate ions, which may adversely affect the larval survival of calcareous animals. In this study, we simulated future atmospheric CO 2 concentrations (800, 1500, 2000 and 3000 μatm) and examined the effects of ocean acidification on the embryonic and larval stage of an infaunal clam Paphia undulate . Significant decrease of hatching of P. undulate was observed when the pCO 2 reached 3000 μatm, and larval deformation rate increased significantly when pCO 2 reached 2000 μatm, indicating a strong tolerance to ocean acidification compared with the embryonic development of other bivalves. The larvae cultured in 1500 μatm pCO 2 exhibited the fastest growth, highest survival and shortened planktonic period, which unordinary phenomenon reflected the beneficial effect of ocean acidification on P. undulate larval development. The better development of P. undulate larvae under a higher CO 2 condition maybe an adaptation in response to the acidified sediment in which they live. [ABSTRACT FROM AUTHOR]

Abstract: During a large-scale screen of the larval transcriptome library of the Portuguese oyster, Crassostrea angulata, the oyster gene RACK, which encodes a receptor of activated protein kinase C protein was isolated and characterized. The cDNA is 1148bp long and has a predicted open reading frame encoding 317 aa. The predicted protein shows high sequence identity to many RACK proteins of different organisms including molluscs, fish, amphibians and mammals, suggesting that it is conserved during evolution. The structural analysis of the Ca-RACK1 genomic sequence implies that the Ca-RACK1 gene has seven exons and six introns, extending approximately 6.5kb in length. It is expressed ubiquitously in many oyster tissues as detected by RT-PCR analysis. The Ca-RACK1 mRNA expression pattern was markedly increased at larval metamorphosis; and was further increased along with Ca-RACK1 protein synthesis during epinephrine-induced metamorphosis. These results indicate that the Ca-RACK1 plays an important role in tissue differentiation and/or in cell growth during larval metamorphosis in the oyster, C. angulata. [Copyright &y& Elsevier]

Abstract: We cloned and characterized a complete cDNA encoding a dopamine receptor (DAR) named Ca-DA1R from Fujian oyster, Crassostrea angulata. The 2843bp long cDNA sequence includes a 916-bp 5′-UTR, the 1197bp ORF which encodes a putative protein of 399 amino acids, and a 729bp 3′-UTR. The Ca-DA1R sequence possesses typical characteristics of a D1 receptor: two main features being a short third intracellular loop and a long inner COOH-terminal tail domain. Using a real-time PCR approach, expression profiles of Ca-DA1R were analyzed in adult tissues and during the four stages of ovarian development. Ca-DA1R was expressed ubiquitously, although transcript levels varied between tissues, with higher mRNA levels detected in the ovary, labial palps and mantle. During the four stages of ovarian development, Ca-DA1R mRNA expression level was higher in the proliferation stage than in the other three stages during the ovary cycle. In situ hybridization results reveal that the Ca-DA1R mRNA is mainly expressed in the epithelium of the gonoducts. These observations suggest that Ca-DA1R binding of DA probably plays an important role in early ovarian development and via regulating oocyte locomotion cooperates with the 5-HT receptor system during the ovarian cycle in C. angulata. [Copyright &y& Elsevier]