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Abstract:Along with the development and innovations in genetic engineering and biotechnology, aquaculture breeding has expanded from traditional selective breeding and hybrid breeding to marker- assisted selective breeding, cell engineering breeding, genome-wide genotyping-based selective breeding, molecular design breeding, sex control breeding, gene transfer, gene editing, and other molecular marker-assisted breeding technologies. Although the aquaculture seed industry has advanced, several problems and challenges remain such as the low coverage rate of improved varieties and insufficient research depth. This review provides a detailed analysis of the main advances made in the field of aquaculture technology and summarizes the commercially valuable germplasm resources of echinoderms (sea cucumbers and sea urchins) and their applications. We also propose to the sea cucumber and sea urchin breeding industry to provide a reference for the development of germplasm resources for echinoderms of commercial value and promote the green development of the aquaculture industry.

Abstract:Echinodermata are important aquatic animals of commercial value in China. Enriched in proteins, amino acids, unsaturated fatty acids, and other physiologically active substances, they are considered healthy food with increasing consumer demand. Therefore, there is an urgent need to develop and industrialize echinoderm breeding. However, the high mortality rate, slow growth rate, and low nutritional quality during echinoderm breeding are the main bottlenecks limiting the development of the echinoderm industry. It is well known that marine animals require certain essential fatty acids, particularly n-3 and n-6 polyunsaturated fatty acids, for their normal growth, development, and immunity. Essential fatty acids can directly affect the development and survival of juvenile of echinoderms grown in aquaculture. To meet the nutritional needs of juveniles and adults, the supply of high-quality bait is essential to overcome these bottlenecks. Microalgae are rich in proteins, carbohydrates, vitamins, carotenoids, polyunsaturated fatty acids, and other nutrients, and have attracted increased attention in the development of new aquatic feed resources. Fresh bait for young animals is significantly better than artificial bait in promoting growth and improving survival rates. It is also widely used in breeding echinoderms. In this paper, the research progress on the application of microalgae and bioactive chemicals in typical commercial echinoderm (sea cucumber and sea urchin) farming and breeding were reviewed with respect to their effects on the growth, development, and impact on the larval growth. We have summarized the microalgae species commonly used in economic echinoderm breeding and the effects of microalgae on the fatty acid composition and immune status of sea cucumbers and sea urchins were analyzed. Furthermore, the challenges limiting the application of microalgae bait in echinoderm breeding and farming are discussed, and alternative solutions are offered for sea cucumber and sea urchin culture in China.

Abstract:Echinoderms hold the highest evolutionary status among the invertebrates and some species in the class Holothuroidea (sea cucumber) and Echinoidea (sea urchin) have very high economic and nutritional values. However, because of the impact of human activities, the number and biodiversity of several echinoderm species have severely declined, and germplasm degradation has been especially prominent in recent years, mainly manifesting as slow growth, frequent diseases, and low survival rates. Therefore, the preservation of germplasm resources is critical. Cryopreservation is an important method for the long-term preservation of germplasm resources. It has the advantages of breaking through geographical isolation, realizing distant hybridization, protecting germplasm resources, solving the problem of germplasm degradation, and protecting endangered species. This article reviews the progress in research on the cryopreservation of sperm of three major echinoderms (sea urchins, sea cucumbers, and starfish), and describes the various steps in sperm cryopreservation processes, such as sperm collection, extender and cryopreservation preparation, balance, cooling, thawing, and quality evaluation, to provide a ready reference for the future research and the industrial application of cryopreservation to echinoderm germplasm resources.

Abstract:Apostichopus japonicus is a species of economic importance cultured in northern China. In the past 10 years, the scale of the A. japonicus culture has expanded due to increased market demand for products. However, several challenges, such as germplasm degradation and the lack of stress-resistant varieties, have emerged in A. japonicus culture. Breeding new varieties is one way to overcome these challenges. New strains (F1 and F4) of A. japonicus with high temperature resistance were obtained by domestication and screening under environmental stress conditions. The genetic changes caused by breeding under environmental stress conditions not only originated from changes in the DNA sequence, but also from changes due to epigenetic modifications by bisulfite sequencing. To explore the genetic diversity of the selected populations (F1 and F4) and the control population (F) which was not subjected to temperature stress of A. japonicus, the genetic diversity of control population, selected population F1, and selected population F4 were analyzed using methylation-sensitive amplification polymorphisms (MSAP). The results showed that 698 loci were polymorphic among the 806 loci obtained by 10 pairs of primers, and the percentage of polymorphism was 86.60%. Based on the genetic analysis of non-methylated loci, the Shannon polymorphism index of the F4 was 0.3981 and Nei gene diversity was 0.2264. Based on the analysis of methylation sensitive sites, the Shannon polymorphism index of the F4 was 0.5873, and Nei gene diversity was 0.2598, both of which were higher than in the parent population. Moreover, the epigenetic diversity was higher than the sequence genetic diversity caused by variation in non-methylated loci, indicating that the frequency of epigenetic variation was higher than that of sequence genetic variation. Analysis of the MSAP methylation patterns revealed some changes in the methylation levels and patterns in the selected F1 and F4 after breeding, which indicated that the genome methylation status of the A. japonicus population was changed by breeding under temperature stress. The number of type Ⅱ bands in the F4 was 161, which was significantly higher than that of control population of A. japonicus and may have acquired epigenetic characteristics during breeding. Collectively, our results revealed the genetic changes and progress of the breeding population from the perspective of a genetic material basis and provide a reference for the study of epigenetics in the breeding of new stress resistant varieties.

Abstract:The sea cucumber Apostichopus japonicus requires its own defense mechanism to resist and adapt to high temperature stress. Epigenetic modification plays an important role in this regulation process. To investigate the changes of DNA methylation level and methylation pattern in A. japonicus (2-year-old) under different temperature stress, whole genomic bisulfite sequencing (WGBS) and enzyme-linked immunosorbent assay (ELISA) were used to detect whole genome methylation levels of the muscle, respiratory tree, digestive tract, and body wall. Three temperature gradients of 20℃, 26℃, and 32℃ were set up in this experiment. The results of WGBS showed that the total genome wide methylation levels of 20℃, 26℃, and 32℃ groups were (1.70±0.01)%, (1.79±0.11)%, and (1.59±0.04)%, respectively. The methylation level of the digestive tract genome of A. japonicus in the 26℃ group increased, while the methylation level of the 32℃ group decreased under high temperature stress. Among the total methylation sites, CG type was the main site of methylation modification (more than 96%), and CHH and CHG sites showed relatively low levels of modification. Among the methylation sites at 30% methylation level, CHG and CHH methylation sites showed the highest methylation, and were significantly higher than that of the CG type. The results of ELISA showed that the methylation levels of respiratory tree and digestive tract tissue ranged from 2.68% to 3.29% at three different temperatures, which were higher than those in muscle and body wall tissue. After temperature change, the total methylation level of respiratory tree and digestive tract tissue of sea cucumber changed significantly, while the total methylation level of muscle and body wall remained unchanged, indicating that DNA methylation may be involved in the regulation mechanism of high temperature stress in A. japonicus. The study on DNA methylation level of A. japonicus in response to temperature change can be used to analyze the effect of temperature rise on different tissues of sea cucumber from the perspective of epigenetics. This research can provide reliable basis for enriching the research content on methylation in A. japonicus and the occurrence of methylation in invertebrates.

Abstract:In order to clarify the differences in metabolism between female and male relatives of tropical sea cucumbers (Holothuria scabra), the sex-specific metabolites in their coelomic fluid were explored by a liquid chromatography-tandem mass spectrometry metabolite analysis, and the sex-specific metabolites and pathways were analyzed. The results showed that compared with male sea cucumbers, a total of 1352 up-regulated metabolites and 943 down-regulated metabolites were screened in the coelomic fluid of female sea cucumbers. According to a database comparison and annotation, a total of 66 metabolites with significant differences (P≤0.05, VIP≥1) were selected. Among them, β-carotene has the potential to be a gender difference metabolic marker. Spermidine and fatty acids that are less demanded by other organs were found at higher concentrations in females and males, respectively. We speculated that these compounds may be used by other physiological functions. In addition, it was also found that male coelomic fluid tended to accumulate xenobiotics. Metabolic pathway analysis by KEGG showed that the gonadal development-related pathways, glutathione metabolism, arginine and proline metabolism, steroid biosynthesis, and tyrosine metabolism of male sea cucumbers all occurred in the coelomic fluid. The gonadal development of female and male sea cucumbers was affected by sex hormones, which may be regulated by dopamine and have gender differences.

Abstract:The estimation of heritability is a fundamental task in the selective breeding of aquatic animals. With the development of sequencing technology, the estimation of heritability based on single nucleotide polymorphism (SNP) markers has been widely used in breeding since it is more accurate than the traditional method. In this study, the genome-wide SNP heritabilities for papillae number in Apostichopus japonicus from different geographic locations were estimated, and the results showed that the estimated mean SNP heritabilities with different SNP densities at MAF (minor allele frequency)>0.05 ranged from 0.566±0.022 to 0.612±0.003, and the estimated mean SNP heritabilities with different SNP densities at MAF>0.1 ranged from 0.586±0.015 to 0.615±0.016 when sampled uniformly on 50K SNPs, indicating that 50K low-density SNP markers are sufficient to capture both large and small effects of the quantitative trait locus. Chromosome-wise SNP heritability estimates showed that the contribution of an individual chromosome was significantly correlated to its length, suggesting that the papillae number is a complex quantitative trait with effect sites scattered across the chromosomes and shared by multiple genes. The results of this study provide a theoretical basis for the design and development of A. japonicus low-density SNP chips and the evaluation of A. japonicus genetic parameters.

Abstract:To investigate the structure and function of the bacterial community in Apostichopus japonicus (sea cucumber) culture ponds in Changhai, North China, the bacterial community composition and diversity were seasonally analyzed by high-throughput sequencing and bioinformatics analysis. The results showed that the bacterial richness and diversity were the highest in the summer and the lowest in the autumn. In all seasons, the predominant phylum was Proteobacteria, followed by Bacteroidetes, but higher levels of other bacterial phyla were observed in the spring (Verrucomicrobia), summer (Actinobacteria), and winter (Firmicutes). There were no significant differences in the phyla of autumn with that of other seasons. Predictive functional profiling based on the Clusters of Orthologous Groups of proteins (COGs) database (functional codes denoted by [X]) showed significant differences (P<0.05) in 24 aquatic bacterial community proteins. In spring and winter, the proteins for energy production and conversion; nucleotide transport and metabolism; carbohydrate transport and metabolism; secondary metabolite biosynthesis, transport, and catabolism; cell wall/membrane/envelope biogenesis; cell motility; transcription; and replication, recombination, and repair were significantly upregulated. Proteins regulating carbohydrate transport and metabolism; translation, ribosomal structure, and biogenesis; and cell wall/membrane/envelope biogenesis were significantly downregulated in summer. In autumn, the proteins regulating cell cycle control, cell division, and chromosome partitioning; cytoskeleton; and secondary metabolite biosynthesis, transport, and catabolism were significantly downregulated, and the proteins for extracellular structures were upregulated. These results indicate that the richness and diversity of the bacterial community in the sea cucumber culture pond are the lowest in autumn and that seasonal changes in the community structure depend on the function. This study provides a theoretical basis for water microecology regulation and the prevention and control of A. japonicus diseases.

Abstract:Microbial communities are an important part of aquaculture pond ecosystems and play an important role in the processes of nutrient cycling and energy flow. It is, thus, of great importance to explore the seasonal succession characteristics of bacterial communities and factors influencing them for the precise management of sea cucumber ponds. In this study, the bacterial community composition in the sediment of Apostichopus japonicus culture ponds in different seasons were analyzed by high-throughput sequencing and bioinformatics analysis, and the factors influencing the bacterial community were identified. The results showed that the abundance and diversity of the bacteria community in the sediment of sea cucumber culture ponds in Yingkou were highest in summer, followed by spring, autumn, and winter seasons. Significant seasonal differences were observed in the specific bacterial communities of the sediment in different seasons. Among these, Bacteroides phylum was specifically associated with spring, Acidobacteria, Verrucomicrobia, and Planctomycetes were specific phyla observed in summer, Firmicutes was the specific phylum noted in autumn, and Actinobacteria was the specific phylum in winter. Although the proportion of the sediment bacterial community differed across seasons, the predominant phylum in the sediment was the Proteobacteria (relative abundance > 43.19%). The dominant environmental factors affecting the sediment bacterial community were temperature, total organic carbon, total nitrogen, and pH. These findings provide a theoretical reference for microecology regulation in sea cucumber culture ponds.

Abstract:A total of 56 strains of Lactobacillus were isolated using MRS medium from a sea cucumber (Apostichopus japonicus) culture pond in Dongying, Shandong Province. Their antibacterial activities were analyzed using the Oxford cup method, and Vibrio splendidus and Pseudoalteromonas nigrifaciens were used as indicator bacteria. A Lactobacillus strain, CSND-6, showed strong antibacterial activity. The morphology, antibacterial activities of intracellular and extracellular components, physiological and biochemical tests, 16S rDNA sequence analysis, growth characteristics, and effects of strain CSND-6 on sea cucumbers were studied. The results showed that strain CSND-6 had a significant inhibitory effect on the growth of V. splendens and P. nigrifaciens. The inhibition zones of the intracellular components were 17 mm and 21 mm, and that of extracellular components were 25 mm and 33 mm for V. splendens and P. nigrifaciens, respectively. The safety analysis showed that the strain was safe for sea cucumbers. The results of the physiological and biochemical tests and 16S rDNA sequence analysis showed that the strain CSND-6 belongs to family Lactobacillaceae; the similarity between CSND-6 and Lactobacillus paracasei JCM1171 was 99.83%. The strain CSND-6 grew rapidly between 30℃ to 44℃ and in a pH between 6 to 8. It entered the logarithmic growth phase after 24 h and reached the highest concentration (2.10×109 CFU/ml) after 28~32 h. Since strain CSND-6 was isolated from the environment of the sea cucumber culture ponds and exerted strong inhibitory effects on the main pathogenic bacteria of sea cucumbers, it holds potential as an agent to prevent and control infections and diseases in sea cucumber. This study provides the foundation for the development and utilization of probiotics in sea cucumber cultures.

Abstract:Salinity is a key ecological factor for the survival of the sea cucumber (Apostichopus japonicus), and analysis of the adaptation and tolerance mechanisms of new sea cucumber varieties can provide a scientific basis for their promotion. To study the adaptation of a new variety of sea cucumber, “Shenyou No. 1,” the growth, survival, respiratory metabolism, and immune enzyme activities in different salinities (ranging from 14 to 40) were measured. The results revealed that the survival rate was 100% within the salinity range of 23~40, whereas all seedlings died when the salinity was below 16. The specific growth rate (SGR) was positive within the salinity range of 23~40 and reached a peak within the salinity range of 29~37, with the highest SGR being 0.9932%/d at a salinity of 32. With a change in salinity, the oxygen consumption rate and ammonia excretion rate showed a “M” type change, with the trough values obtained at a salinity of 32 with values of 0.0130 mg/(g·h) and 0.00138 mg/(g·h), respectively. The O/N ratio showed no significant difference with the change in salinity. The ACP, AKP, LZM, and SOD activities changed significantly under the high and low salinity stresses. During the adaptation period, the peak of SOD enzyme appeared at 0 d, whereas the peak of ACP and AKP appeared at 10 d, and the peak of LZM appeared at 10~20 d. All the results indicated that the suitable salinity range for the new variety “Shenyou No. 1” was 23~40 and the optimum salinity range was 29~37. Changes in the salinity led to changes in the respiratory metabolism and immune enzyme activity of the seedlings. These results provide a scientific basis for the promotion of the new variety of sea cucumber “Shenyou No. 1.”

Abstract:To determine the optimal pH conditions and pH adaptation mechanisms of the juveniles new sea cucumber (Apostichopus japonicus) variety "Shenyou No.1", the differences in the growth, survival, respiratory metabolism, and immunoenzyme activity were analyzed under conditions of different pH (range: 6.5~10.0). The results showed that in the pH range of 6.5~9.5, the survival rate of the juveniles was 100% during the 30 days experimental period, whereas all juveniles died at pH 10.0. Within the pH range of 7.5~8.5, the juveniles showed a positive specific growth rate (SGR), and the highest SGR was 0.541%/d at pH 8.0, while the SGR was negative at the pH lower than 7.0 or higher than 9.0. The oxygen consumption rate (RO) and ammonia excretion rate (RN) were the lowest at pH 8.0, 19.07 μg/(g·h) and 1.34 μg/(g·h) for RO and RN, respectively. The oxygen-nitrogen ratios of the juveniles in different pH groups were approximately 11, and did not differ significantly with a pH change. The activities of acid phosphatase, alkaline phosphatase, lysozyme, and superoxide dismutase in the coelomic fluid of A. japonicus significantly increased at different pH values. While adapting to pH stress, the superoxide dismutase activity in each pH group generally peaked at 0 d, while the lysozyme activity peaked at 10 d. The survival pH of "Shenyou No.1" ranged between 6.5~9.5, and the optimal pH for growth ranged between 7.5~8.5. Our results show that the changes in the pH lead to changes in respiratory metabolism and immune enzyme activity in "Shenyou No.1.” These results provide the basis for the popularization of the new sea cucumber variety "Shenyou No.1".

Abstract:In this study, the effects of light intensities on the growth rate (GR) and digestive enzyme activity of purple sea urchin (Anthocidaris crassispina) larvae were studied by simulating and analyzing the natural light cycle through the flume experiment method, aiming to provide necessary biological parameters for the large-scale breeding of juvenile sea urchins. The sea urchin larvae were exposed to different light intensities (0 lx, 500 lx, 1000 lx, 2000 lx, and 3000 lx) for 18 days (12 h light:12 h dark, 08:00~20:00) and samples were taken on days 8, 11, and 16). The GR was examined to identify the size (larval length, body-rod length, and post-oral arm length). The activities of digestive enzymes (amylase, lipase, and protease) were examined to elucidate their response to light intensities. At the end of the experiment, the GR under different light intensities decreased as follows: 500 lx > 0 lx > 1000 lx > 2000 lx > 3000 lx. The larval length, body-rod length, and post-oral arm length of sea urchin larvae in the 500 lx treatment were the highest among all light intensity treatments (P<0.05), and the activities of lipase and amylase were the strongest. The maximum activity of protease was observed in the 2000 lx treatment (P<0.05). By day 11, all sea urchin larvae died in the 3000 lx treatment. The results showed that the sea urchin larvae could maintain the best GR, digestive enzyme activity, and survival rate under 500 lx light intensity, which was the best light intensity for the growth and development of the sea urchin larvae.

Abstract:It is well-known that serotonin (5-hydroxytriptamine, 5-HT) can act as a neurotransmitter as well as a neurohormone to regulate reproduction in marine invertebrates. Serotonin can prompt ovarian and embryonic development in crustaceans and trigger oocyte maturation and sequential spawning in bivalve mollusks. In this study, the effects of serotonin on the reproductive performance and quality of the offspring of sea cucumber (Apostichopus japonicus) treated with serotonin were examined. During hatchery broodstock conditioning, sea cucumbers were injected with serotonin at four different doses (20 μg/g, 50 μg/g, 100 μg/g, and 200 μg/g body weight) and four frequencies (every 5, 10, 15, and 20 days). Sea cucumbers injected with physiological saline were used as the control group, and untreated sea cucumbers were used as the blank group. At the end of the experiment, the spawning of sea cucumbers was triggered using a combination of desiccation, running water, and thermal shock. The results revealed that the spawning rate and fecundity of female sea cucumbers injected with serotonin were higher than those of the control and blank groups. The female sea cucumbers injected with serotonin at dose of 50 μg/g body weight every 10 days showed the highest spawning rate and fecundity of (33.3±1.9)% and (637.0±111.1)×104 cells per individual, respectively. The egg diameter, fertilization rate of eggs, hatching rate of larvae, body length of late auricularia larvae, and settlement rate of larvae in the 50 μg/g body weight every 10 days group and blank group were evaluated further. The egg diameter, fertilization rate, hatching rate, larval body length, and settlement rate of the 50 μg/g body weight every 10 days group were (165.0±3.5) μm, (93.0±1.5)%, (82.7±1.2)%, (856.0±24.8) μm, and (24.0±1.9)%, respectively. No significant differences were observed in these parameters between this group and blank group. These results indicate that serotonin, as a neurotransmitter, prompts ovarian development in sea cucumbers, and injecting serotonin during broodstock conditions can improve the reproductive performance of female sea cucumbers.

Abstract:To evaluate the breeding effect of sea cucumber (Apostichopus japonicus) salt tolerant strains, the growth, feeding and digestive physiological changes of the fourth generation (G4) and the fifth generation (G5) sea cucumber strains under low and high salinity environments were studied. The results showed that the growth of G4 and G5 were similar in low salt environment during a 30-day experiment. The final body weight in low salt environment decreased with the decrease in experimental salinity, and the final body weight in high salinity environment decreased with the increase in experimental salinity. The specific growth rate (SGR) and feeding rate (FR) of salinity 22 and salinity 35 were not significantly different from those of the control group at salinity 31 (P>0.05). In the salinity range of 18~31, the protease activity of G4 and G5 decreased with the decrease in salinity, and the lowest value was 1.55 U/mgprot observed in the G5. In the salinity range of 31~39, the protease activity of each experimental group decreased with the increase in salinity, but there was no significant difference between salinity 35, 37, and control group (P>0.05). There was no significant difference in amylase activity between G4 and G5 with the change in salinity; in the range of salinity 18~31, the protease activity of the G4 and G5 was not significantly different. The lipase activity of sea cucumber decreased with the decrease in salinity, and the lipase activity of salinity 18 and salinity 22 was significantly lower than that of salinity 31 (P<0.05). The results showed that there were significant differences between selected sea cucumbers and common sea cucumbers in adapting to growth, feeding, and activating digestive enzyme activities under different salinity treatments. The stability of breeding traits was strong in G4 and G5, and the directional breeding played an active role in genetic improvement of stress resistance in sea cucumbers.

Abstract:To explore the potential of fermented feed in sea cucumber cultivation, the effects of fermented feed on the energy budget, growth, non-specific immune enzymes, and digestive enzyme activities of sea cucumber (Apostichopus japonicus) seedlings were measured, and changes in water quality (including ammonia nitrogen, nitrite, and pH) in the culture ponds during a 7-day substrate change period were measured. The results showed that during the 50 day experimental period, the survival rate of the fermented feed group was (91.51±0.74)%, which was significantly higher than that of the unfermented feed group [(82.35±2.22)%] (P<0.05), and there was no significant difference between the two groups for specific growth rate. The growth energy ratio and metabolic energy ratio of the fermented feed group was (13.25±1.01)% and (32.32±2.00)%, respectively, whereas the values in the unfermented feed group were (11.38±1.05)% and (44.12±0.54)%, respectively; therefore, the fermented feed enhanced the growth energy of the seedlings. For the nonspecific immune-enzyme and digestive activities fed the different types of feed, the alkaline phosphatase, lysozyme, and pancreatic enzyme activity of the fermented feed group was (0.74±0.04) king U/100 ml, (95.52±14.80) U/ml, and (335.89±13.01) U/mg prot, respectively, which was significantly higher than that of the unfermented feed group (P<0.05). The concentration of ammonia nitrogen and nitrite on the 7th day of the substrate change period in the fermented feed group reached (263.27±32.57) µg/L and (315.15±61.41) µg/L, respectively. The values in the unfermented feed group were (462.86±14.69) µg/L and (572.87±25.75) µg/L, respectively, which were significantly higher than that of the fermented feed group (P<0.05). All the results showed that the fermented feed improved the physiological metabolism level of the sea cucumber seedlings and maintained the water quality of the culture system; therefore, fermented feed has a broad application prospect for sea cucumber seedling culture.

Abstract:In the present study, the concentrations of protein, fat, and crude polysaccharide were determined in the body wall of three body color variants of the sea cucumber Apostichopus japonicus (Selenka), along with the composition of fatty acids and amino acid microelements. The results showed that the protein content in green sea cucumbers was significantly lower than in purple and white sea cucumbers (P<0.05), the fat content showed no significant differences (P>0.05), and the crude polysaccharide contents in green and purple sea cucumbers were higher than in white sea cucumbers (P< 0.05). A total of 17 amino acids were determined in the sea cucumbers, with the purple and white sea cucumbers containing higher amino acid contents (about 48%), while the contents in the green sea cucumber was about 44%. The contents of amino acids such as lysine, phenylalanine, threonine, and valine in purple and white sea cucumbers were significantly higher than in green sea cucumbers. The linoleic acid (LA), arachidonate (ARA), timnodonic acid (EPA), and docosahexaenoic acid (DHA) had higher proportions than other polyunsaturated fatty acids in the three sea cucumbers. As an important polyunsaturated fatty acid, LA in both the purple and white sea cucumbers was significantly higher than in green sea cucumbers (by 4.6 times, P<0.05). The ARA contents in purple and white sea cucumbers were also significantly higher than in green sea cucumbers, while the EPA and DHA contents were significantly lower (P<0.05). Additionally, we found that iron was the highest among the inorganic elements in all sea cucumbers, but was significantly lower in purple sea cucumbers than in green and white sea cucumbers. The manganese content in green sea cucumbers was significantly higher than in purple and white sea cucumbers, and chromium was significantly higher in white sea cucumbers than in green and purple sea cucumbers. Therefore, the nutritional composition of the three body color variants of sea cucumbers were quite different, and all of them have values for further development and utilization.