Strongylocentrotus Intermedius Research Articles

Effect of Phlorethol from the Brown Alga Costaria costata (Turn.) Saund. (Order Laminariales) on Gametes and Embryogenesis of the Sea Urchin Strongylocentrotus intermedius (A. Agassiz, 1864)

The effect of a fraction of phlorethol (CcPh), one of the polyphenolic compounds isolated from the brown alga Costaria costata (Turn.) Saund (Laminariales), on gametes and embryogenesis of the sea urchin Strongylocentrotus intermedius (A. Agassiz, 1864) was studied. Using a model of developing sea urchin embryos, it was shown that phlorethol at concentrations ≤700 µg/mL did not exert cytotoxic effect on early developmental stages (from zygote to 16-celled stage blastomere). The embryotoxic effect of phlorethol, causing death of 50% of embryos, was expressed in a concentration (I) range of 50 I ≤ 100 µg/mL only after 24 h of incubation, in the blastula stage. When exposed to concentrations of ≥100 µg/mL, embryos that survived to the blastula stage did not develop further and died after 36 h of incubation. Under the effect of phlorethol, the fertilizing capacity of sea urchin spermatozoa and oocytes reduced. The concentration of phlorethol inhibiting fertilization by 50% (IC50) when acting on sperm was 1.28±0.38 µg/mL and when acting on oocytes was 3.83±0.82 µg/mL. Thus, phlorethol reduces the fertilizing capacity of sea urchin gametes at concentrations much lower than embryotoxic concentrations and can potentially find practical application as part of new contraceptive drugs for mammals and humans.

Effects of a dietary probiotic on growth, gonadal development and quality, antioxidant capacity, intestinal health, and non-specific immunity of a sea urchin (Strongylocentrotus intermedius)

Effects of a dietary probiotic on growth, gonadal development and quality, antioxidant capacity, intestinal health, and non-specific immunity of a sea urchin (Strongylocentrotus intermedius)

Short-term exposure to okadaic acid induces behavioral and physiological responses in sea urchin (Strongylocentrotus intermedius)

Massive harmful algal blooms (HABs) have increased the risk of marine organisms encountering the dinoflagellate toxin, okadaic acid (OA). Strongylocentrotus intermedius, a globally significant benthic aquaculture species, has a large appetite for benthic algae. During red tide events, there is a high risk of red tide toxin accumulation. This study systematically evaluated the potential impact of short-term OA exposure on the behavior and physiological functions of juvenile S. intermedius. From typical (5 μg/L) to extreme OA concentrations (20 μg/L) during HAB outbreaks, OA exposure gradually inhibited a series of tube foot-related behaviors (sheltering, foraging, righting, and tube-foot tenacity). At OA concentrations during HAB outbreaks (5 μg/L), the tube foot function of S. intermedius was progressively inhibited. Further physiological indicator analyses revealed that the activity of antioxidants increased over a short period to prevent damage from reactive oxygen species induced by OA. However, OA ultimately suppressed the immune response of S. intermedius, leading to apoptosis. Although HAB-associated concentrations of OA (5 μg/L) did not induce a continuous increase in the integrated biological response index of S. intermedius, this study speculated that HABs pose a future risk to echinoderm species. Notably, principal component analysis results showed that OA exposure eventually induced significant changes in the production of O2−, malondialdehyde, and total glutathione, as well as in glutathione S-transferase activity and caspase-7, -8, and -9 levels. This study provides preliminary evidence of OA's toxic effects on sea urchins and essential data for urgent risk assessments of algal toxin pollution in aquaculture during HABs.

Multi-omics analysis of sea urchin (Strongylocentrotus intermedius) adaptation to salt stress reveals epigenetic regulatory mechanisms

Increased precipitation and surface runoff due to global warming has reduced surface seawater and nearshore water salinity, affecting marine organism survival. Nevertheless, the epigenetic mechanisms underlying the adaptation of sea urchins (Strongylocentrotus intermedius) to low-salinity stress remains unknown. This study utilized response surface methodology to formulate growth models for S. intermedius at different salinity levels and shell diameters. Whole genome bisulphite sequencing, RNA-sequencing, and metabolome analysis were performed on low-salinity stressed sea urchins, and a total of 3006 differential methylated regions, 945 differential methylated genes, 886 differentially expressed genes, and 271 differential metabolites were identified. Multi-omics analysis revealed significant alterations in the gene expression and DNA methylation of key genes (e.g., SPHK2, Arpc1a, and SLC23A1) in S. intermedius under low-salinity stress conditions. These changes subsequently influenced the metabolism of substances, including sphingosine-1-phosphate, ethanolamine phosphate, vitamin C, taurine, and choline. These alterations impacted functions related to immunity, osmoregulation, and energy metabolism in the organism. This study was to comprehensively elucidate the epigenetic mechanisms of S. intermedius under low-salinity stress from the perspective of DNA-RNA-metabolites, providing new insights into salinity adaptation of marine invertebrates.

Feeding ecology of the urchin symbiont Dactylopleustes yoshimurai (Amphipoda) revealed by DNA metabarcoding

The nature of symbiotic relationships between organisms can be difficult to assess and may range from commensalism, to mutualism, and parasitism. Trophic linkage and feeding ecology are essential to disentangle symbiont-host relationships/interactions. Amphipods of the genus Dactylopleustes are known as urchin symbionts. Though their ecology remains largely unknown, Dactylopleustes was recently reported to aggregate on diseased hosts, suggesting that Dactylopleustes feeds on diseased urchins’ tissues and uses urchins as both a habitat and prey. We investigated by DNA metabarcoding analyses, the feeding ecology of Dactylopleustes yoshimurai in relation to growth and disease status of the host (Strongylocentrotus intermedius). Contrary to our hypothesis, sequence reads from the gut contents were dominated by planktonic copepods regardless of body size or host disease status. These results suggest that they mainly feed on copepod fecal pellets deposited on sediments, and do not have a strong trophic linkage with their host. Large individuals on diseased urchins feed more on urchins than those on healthy urchins. However, their main prey still remains copepods, implying that host disease has a limited effect on the feeding behavior. In conclusion, our study indicates that this species is mainly commensal, but also may parasitize its host depending on the situation.

Feeding Behavior, Gut Microbiota, and Transcriptome Analysis Reveal Individual Growth Differences in the Sea Urchin Strongylocentrotus intermedius.

Growth differentiation among farmed sea urchins (Strongylocentrotus intermedius) poses a significant challenge to aquaculture, with there being a limited understanding of the underlying molecular mechanisms. In this study, sea urchins with varying growth rates, reared under identical conditions, were analyzed for feeding behavior, gut microbiota, and transcriptomes. Large-sized sea urchins demonstrated significantly higher feeding ability and longer duration than smaller ones. The dominant phyla across all size groups were Campylobacterota, Proteobacteria, and Firmicutes, with Campylobacterota showing the highest abundance in small-sized sea urchins (82.6%). However, the families Lachnospiraceae and Pseudomonadaceae were significantly less prevalent in small-sized sea urchins. Transcriptome analysis identified 214, 544, and 732 differentially expressed genes (DEGs) in the large vs. medium, large vs. small, and medium vs. small comparisons, respectively. Gene Ontology and KEGG pathway analyses associated DEGs with key processes such as steroid biosynthesis, protein processing within the endoplasmic reticulum, and nucleotide sugar metabolism. Variations in phagosomes and signaling pathways indicated that size differences are linked to disparities in energy expenditure and stress responses. These findings provide a foundation for future investigations into the regulatory mechanisms underlying growth differences in S. intermedius and provide clues for the screening of molecular markers useful to improve sea urchin production.

Molecular cloning and functional study of a Rel homologous gene in sea urchin Strongylocentrotus intermedius

NF-κB (Nuclear factor-kappa B) family proteins are versatile transcription factors that play crucial regulatory roles in cell development, growth, apoptosis, inflammation, and immune response. However, there is limited research on the function of these key genes in echinoderms. In this study, an NF-κB family gene (SiRel) was identified in sea urchin Strongylocentrotus intermedius. The gene has an open reading frame length of 1809 bp and encodes for 602 amino acids. Domain prediction results revealed that the N-terminal of SiRel protein encodes a conserved Rel homology domain (RHD), including the RHD-DNA binding domain and the RHD-dimerization domain. Multiple sequence comparison results showed that the protein sequences of these two domains were conserved. Phylogenetic analysis indicated that SiRel clustered with Strongylocentrotus purpuratus p65 protein and Rel protein of other echinoderms. Results from quantitative real-time PCR demonstrated detectable SiRel mRNA expression in all tested sea urchin tissues, with the highest expression level found in the gills. And SiRel mRNA expression levels were significantly induced after LPS (Lipopolysaccharide) and poly(I:C) (Polyinosinic:polycytidylic acid) stimulation. In addition, SiRel protein expression can be found in cytoplasm and nucleus of HEK293T cells. Co-immunoprecipitation results showed that SiRel could interact with sea urchin IκB (Inhibitor of NF-κB) protein. Western blotting and dual-luciferase reporter gene assay results indicated that overexpression of SiRel in HEK293T cells could impact the phosphorylation levels of JNK (c-Jun N-terminal kinase) and Erk1/2 (Extracellular signal-regulated kinases1/2) and activate interleukin-6 (IL-6), activating protein 1 (AP-1), interferon (IFN)α/β/γ, and signal transducer and activator of transcription 3 (STAT3) reporter genes in HEK293T cells. In conclusion, this study reveals that SiRel plays an important role in the innate immune response of sea urchins and enriches our understanding of comparative immunology theory.

Strongylocentrotus intermedius Extract Suppresses Adiposity by Inhibiting Adipogenesis and Promoting Adipocyte Browning via AMPK Activation in 3T3-L1 Cells.

The current study aimed to determine whether Strongylocentrotus intermedius (S. intermedius) extract (SIE) exerts anti-obesity potentials employing 3T3-L1 cells as in vitro model. Herein we reported that treatment of SIE for 6 days reduced lipid accretion and triglyceride content whereas it increased the release of free glycerol. The inhibited lipid accumulation and induced lipolysis were evidenced by the downregulation of lipogenesis proteins, such as fatty acid synthase and lipoprotein lipase, and the upregulation of hormone-sensitive lipase expression. Furthermore, the downregulation of adipogenic transcription factors, including peroxisome proliferator-activated receptor gamma, CCAAT/enhancer-binding protein α, and sterol regulatory element-binding protein 1, highlights that reduced lipid accumulation is supported by lowering adipocyte differentiation. Additionally, treatment activates brown adipocyte phenotype in 3T3-L1 cells by inducing expression of brown adipose tissue-specific proteins, such as uncoupling protein 1 and peroxisome proliferator-activated receptor-γ coactivator 1α. Moreover, SIE induced the phosphorylation of AMP-activated protein kinase (AMPK). The pharmacological approach using AMPK inhibitor revealed that the restraining effect of SIE on adipogenesis and promotion of adipocyte browning were blocked. In GC-MS analysis, SIE was mainly composed of cholest-5-en-3-ol (36.71%) along with saturated and unsaturated fatty acids which have favorable anti-obesity potentials. These results reveal that SIE has the possibility as a lipid-lowering agent for the intervention of obesity.

Preliminary investigation on the effect of Vibrio splendidus stimulation on the intestinal flora of Strongylocentrotus intermedius

To better understand the effect of Vibrio splendidus infection on Strongylocentrotus intermedius, 16S rRNA sequencing was carried out to investigate the intestinal flora of S. intermedius stimulated by 0 CFU/mL (Con), 1.5 × 107 CFU/mL (Vib1) and 1.5 × 108 CFU/mL (Vib2) concentrations of V. splendidus. The results showed that there was significant difference in intestinal flora diversity between Con group and Vib1 group, but no significant difference between Con group and Vib2 group. However, there were significant differences in the composition of intestinal flora among all groups. Bacteroidota, Proteobacteria and Firmicutes were the dominant phylum in the Con group. The abundance of Bacteroidota and Firmicutes decreased and Proteobacteria increased in Vib1 and Vib2 groups. The relative abundance of the potential probiotic bacteria Muribaculaceae and Alloprevotella was significantly lower in the Vib1 and Vib2 groups. In addition, the opportunistic pathogen Desulfovibrio was found in Vib1 and Vib2 groups. It is evident that V. splendidus infection not only alters the composition of the microbial community in the intestinal tract of S. intermedius, but may also lead to the production of opportunistic pathogens, which could be potentially harmful to the health of S. intermedius. The results of this study provide a foundation for exploring the diseases caused by V. splendidus stimulation leading to an imbalance in the intestinal flora of S. intermedius, and contribute to our further understanding of the role of Vibrio on the health of S. intermedius.

Heterosis of the interspecific sea urchin hybrids between Strongylocentrotus intermedius and Heliocidaris crassispina

In order to study the heterosis of the interspecific hybrids between sea urchin Strongylocentrotus intermedius and Heliocidaris crassispina, comparative culturing experiments were conducted on individuals of the same age from four groups: S. intermedius (SI), H. crassispina (HC), S. intermedius ♀ × H. crassispina ♂ (SH), and H. crassispina ♀ × S. intermedius ♂ (HS). Growth rate at different stages of development, gonadal production and quality, high-temperature tolerance, and resistance to black-mouth disease were compared among these four species. The results were as follows: in the juvenile sea urchin stage, SH sea urchins exhibited 79.11% and 55.28% body weight heterosis at 16 and 20 °C, respectively, with particularly high single-parent heterosis observed at 16 °C compared to the male parent HC (247.79%). In the young sea urchin stage, SH sea urchins displayed mid-parent heterosis in body weight at all temperatures except 28 °C, reaching a maximum of 94.62% at 12 °C. HS Sea urchins showed mid-parent heterosis only at 12, 24, and 28 °C, with the highest observed at 28 °C (36.51%). The body weight specific growth rate of SH sea urchins was significantly higher than those of the other three species (P < 0.05), and they achieved the largest body weight (48.43 g) by the end of the experiment. The gonad wet weight of SH sea urchins was significantly higher than those of the other three species (P < 0.05). While there was no difference in gonad index between SH and SI sea urchins, it was significantly higher than those of HC and HS sea urchins. In terms of high-temperature tolerance, the upper thermal tolerances (UTT) of HC and HS sea urchins were significantly higher than those of SI and SH sea urchins (P < 0.05). Regarding resistance to black-mouth disease, there was no statistically significant difference in survival rates between SH sea urchins and SI sea urchins after infection with Vibrio echinoideorum at a concentration of 1 cfu/mL. However, the survival rate of HS sea urchins was significantly higher than that of SI. The study demonstrated that the SH hybrid sea urchins exhibit notable advantages in growth and gonad yield compared to its parental species, suggesting its potential as a valuable candidate for the cultivation of new sea urchin varieties in aquaculture. These findings hold significant promise for enhancing the efficiency and sustainability of sea urchin farming practices.

Comparison of Immune Indicators Related to Phagocytosis of Five Species of Sea Urchins under Artificial Infection with the Pathogenic Bacterium of Black Mouth Disease.

To screen for immune indicators closely related to disease resistance, two species of sea urchin susceptible to black mouth disease (Strongylocentrotus intermedius, S. intermedius ♀ × Heliocidaris crassispina ♂) and three species of sea urchin resistant to black mouth disease (H. crassispina, H. crassispina ♀ × S. intermedius ♂ and Mesocentrotus nudus) were artificially infected with the black mouth pathogen Vibrio echinoideorum. The phagocytosis-related immune indices of the five sea urchin species were compared at different time points post-infection. The results demonstrated that the parameters such as apoptotic rate of phagocytes, mean contribution value (MCV) of single effective phagocyte on Acid Phosphatase (ACP), Reactive Oxygen Species (ROS), and Total Antioxidant Capacity (T-AOC) of the five sea urchin species first increased and then decreased after infection. The key time points were 3 h to 6 h and 48 h post-infection when the black mouth disease-resistant and susceptible sea urchins demonstrated differences. At 3 h or 6 h post-infection, the up-regulation folds in MCV of ACP, ROS and T-AOC of black mouth disease-resistant sea urchins were considerably higher than that of the susceptible sea urchins. At 6 h post-infection, the apoptosis rate and the phagocytic index (PI) of the black mouth disease-resistant sea urchins were significantly higher than those of the susceptible sea urchins (p < 0.05). At 48 h post-infection, the necrosis rate of phagocytes, MCV of ACP and MCV of ROS of the black mouth disease-resistant sea urchins were significantly lower than those of the susceptible sea urchins (p < 0.05). The apoptosis and necrosis rate of phagocytes, PI, and MCV on ACP, ROS may be used as indicators of disease resistance in sea urchins. Disease resistance standards in immune indices can be summarized as phagocytosis increases greatly in the early infection stage and decreases timely to a normal level after killing the pathogen in a short period.

HIF-1α interacting with miR-2013-3p regulates pathogen-induced energy production changes via targeting glutamate dehydrogenase in the sea urchin Strongylocentrotus intermedius

ABSTRACT To investigate the functions of hypoxia inducible factor-1α (HIF-1α) homologs, we cloned and characterized the full-length cDNA of a novel HIF-1α homolog (SinHIF-1α) from the sea urchin Strongylocentrotus intermedius. We then explored the functions of SinHIF-1α and its regulatory factor (miR-2013-3p) in the pathogen-induced metabolic response of S. intermedius. The results showed the following: 1) The full-length cDNA of SinHIF-1α was 4265 bp, with a high level of sequence conservation across the phylum Echinodermata. 2) MiR-2013-3p could bind to the 3’-UTR of SinHIF-1α and negatively regulate the expression of SinHIF-1α in S. intermedius. 3) Both SinHIF-1α silencing and miR-2013-3p overexpression suppressed the relative content of adenosine triphosphate (ATP) in coelomocytes as well as the relative expression (mRNA and protein) and total enzyme activity of glutamate dehydrogenase (GDH) in S. intermedius. 4) The miR-2013-3p/SinHIF-1α axis may regulate ATP production at 6–24 h and 48–72 h post-pathogen infection through accompanied by alterations in the relative expression and enzyme activity of GDH in S. intermedius. In summary, all observations from this study indicated that the pathogen utilizes the miR-2013-3p/SinHIF-1α axis to reduce ATP production and thereby attenuate the antimicrobial capability of the host via targeting GDH.

Establishment of Parentage Identification Method for Sea Urchin Strongylocentrotus intermedius Based on SSR-seq Technology.

To establish a parentage identification method for Strongylocentrotus intermedius, 15 microsatellite loci and simple sequence repeat sequencing (SSR-seq) technology were used to perform SSR sequencing and typing of the validation population with known pedigree information and the simulation population. Cervus v3.0 was used for gene frequency statistics, simulated analysis, and parentage identification analysis. The results showed that, in validation population, using 15 microsatellite loci, the highest success rate of parent pairs identification was 86%, the highest success rate of female parent identification was 93%, and the highest success rate of male parent identification was 90%. The simulated population was analyzed using 12-15 loci, and the identification rate was up to 90%. In cases where accurate parentage was not achieved, individuals could exhibit genetic similarities with 1-3 male or female parents. Individuals identified as lacking a genetic relationship can be selected as parents to prevent inbreeding. This study shows that parent pairs or single parents of most offspring can be identified successfully using these 15 selected loci. The results lay a foundation for the establishment of a parentage identification method for S. intermedius.

Interactive effects of chronic ocean acidification and warming on the growth, survival, and physiological responses of adults of the temperate sea urchin Strongylocentrotusintermedius

To investigate the interactive effects of chronic ocean acidification and warming (OAW) on the growth, survival, and physiological responses of sea urchins, adults of the temperate sea urchin Strongylocentrotus intermedius were incubated separately/jointly in acidic (ΔpHNBS = −0.5 units) and thermal (ΔT = +3.0 °C) seawater for 120 days under lab-controlled conditions based on the projected ocean pH and temperature for 2100 put forward by the Intergovernmental Panel on Climate Change (IPCC). Survival rate (SR), average food consumption rate (FCR), gut index (GuI), specific growth rate (SGR), digestive capability, energy production, and antioxidant capability were subsequently determined. The results showed that 1) the SR, FCR, GuI and SGR decreased sharply under OAW conditions. Significant interactive effects of OAW on SR and SGR were observed at 120 days post-incubation (dpi), and on FCR this occurred at 90 dpi. 2) OAW altered the activities of both digestive and antioxidant enzymes. There were significant interaction effects of OAW on the activities of amylase, trehalase, and superoxide dismutase. 3) The relative gene expression levels and activities of key enzymes involved in glycometabolism pathways (i.e., glycolysis and the tricarboxylic acid cycle) were significantly affected by OAW, resulting in an alteration of the total ATP content in the sea urchins. Interaction effects of OAW were observed in both relative gene expression and the activity of enzymes involved in glycolysis (hexokinase), the transformation of glycolysis end-products (lactate dehydrogenase), the tricarboxylic acid cycle (citrate synthetase), and ATP production (Na+/K+-ATPase). The data from this study will enrich our knowledge concerning the combined effects of global climate change on the survival, growth, and physiological responses of echinoderms.

TMT-based proteomics analysis of sea urchin (Strongylocentrotus intermedius) under high temperature stress

In the context of global warming and continuous high temperatures in the northern part of China in summer, the mortality rate of Strongylocentrotus intermedius through the summer reaches 70–80 %. The protein regulatory mechanism of S. intermedius in response to high temperature stress is still unclear. In order to investigate the protein expression of S. intermedius under high temperature stress, the study was conducted with the high-temperature resistant strain of S. intermedius and the control group of S. intermedius. Tandem Mass Tag (TMT) tagging technique was applied to resolve the protein expression profile of S. intermedius in response to high temperature stress. The results showed that, compared to 15 °C，136 DEPs were screened in high-temperature resistant strain groups of S. intermedius under high temperature stress and 87 DEPs were screened in the control group of S. intermedius. There were 33 common differential proteins in the two groups, such as APOLP, HSP 70, CDC37 and CALM. Further Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analyses revealed that the up-regulated proteins CALM and HSP70 are significantly enriched in the “Phosphatidylinositol signaling system” and “Protein processing in endoplasmic reticulum” in heat-tolerant S. intermedius strains under high temperature stress. The control group of S. intermedius DEPs were significantly enriched in protein processing in the endoplasmic reticulum. These results provide a theoretical basis for the molecular mechanism of sea urchin heat tolerance and fundamental data for sea urchin selection and breeding for high temperature tolerance.

An Investigation on the Effects of Dietary Vitamin E on Juvenile Sea Urchin (Strongylocentrotus intermedius): Growth, Intestinal Microbiota, Immune Response, and Related Gene Expression.

A 90 d feeding experiment was conducted to investigate the effects of vitamin E (VE) on growth, intestinal microbiota, immune response, and related gene expression of juvenile sea urchin (Strongylocentrotus intermedius). Six dry feeds were made to contain graded levels of VE (78, 105, 152, 235, 302, and 390 mg/kg); these were named E78, E105, E152, E235, E302, and E390, respectively. Dry feed E50 and fresh kelp (HD) were used as the control diets. There were six replicates of cages in each dietary group, and each cage held 20 sea urchins with an initial body weight of approximately 1.50 g. Results exhibited that weight gain rate and gonadosomatic index (GSI) of the sea urchins were not significantly affected by dietary VE ranging from 78 to 390 mg/kg. Sea urchins in the dry feed groups showed poorer growth performance, but significantly higher GSI than those in the fresh kelp groups. The pepsin and lipase activities were not significantly promoted by low or moderate VE, but were inhibited by a high level of VE (302-390 mg/kg), while amylase and cellulase activities were significantly increased by low or moderate VE, with the highest values observed in the E105 and E235 groups, respectively. VE addition at a low dosage (105-152 mg/kg) showed inhibitory effects on immune and antioxidant enzyme activities and expression of inflammation-related genes, but showed no beneficial effects at moderate or high dosage (235-390 mg/kg), while a moderate or relatively higher level of VE (235-302 mg/kg) significantly increased the expression of several immune-related genes. The relative abundance of Proteobacteria, Actinobacteria, Ruegeria, and Maliponia in the intestine of the sea urchins increased with the increase in VE in the dry feeds. On the contrary, the relative abundance of the Firmicutes, Bacteroidetes, Escherichia-Shigella, Bacteroides, and Clostridium sensu stricto 1 gradually decreased as VE content increased. These results indicated that a moderate level of VE (172.5-262.4) can achieve ideal digestive enzyme activities and growth performance, but a relatively higher level of VE (235-302 mg/kg) was beneficial for maintaining the immune and antioxidant capacity of juvenile S. intermedius by regulating the expression of inflammation- and immune-related genes and abundance of some bacteria to a healthy state.

Effects of Supplementary Kelp Feeding on the Growth, Gonad Yield, and Nutritional and Organoleptic Quality of Subadult Sea Urchin (Strongylocentrotus intermedius) with Soya Lecithin Intake History.

A 23-week feeding experiment was conducted to investigate the effects of supplementary kelp feeding on the growth, gonad development, and nutritional and sensory properties of sea urchin (Strongylocentrotus intermedius) with soya lecithin (SL) intake history. The feeding experiment was divided into experimental phase I and phase II. During phase I, 48 subadult sea urchins (initial weight: 6.28 ± 0.07 g) were fed one of the feeds with different levels of SL (0%, 1.6%, 3.2%) or kelp (Saccharina japonica) for 12 weeks. Then, all sea urchins were fed kelp for the next 11 weeks during the phase II. Each diet was randomly allocated to six cages of sea urchins. The results of phase I showed that weight gain rate (WGR), gonadosomatic index (GSI), gonad sensory properties (color and texture), and essential amino acid (EAA) contents were not significantly affected by SL level in the feed groups. High level (3.2%) of SL suppressed gonad development of S. intermedius with retarded gametogenesis in the 3.2% SL group (stage Ⅱ) compared to those fed 0% and 1.6% SL groups (stage Ⅲ). Sea urchins fed dry feeds exhibited significantly lower WGR and values of color (redness and yellowness) and texture (hardness and gumminess) but higher contents of EAA in the gonads than those fed kelp. The n-3/n-6 polyunsaturated fatty acid (PUFA) and eicosapentaenoic acid (EPA) of gonads in the groups fed with dry feeds showed no significant differences, but were significantly lower than that of kelp group. At the end of phase II, the gonad yellowness and EPA content of gonads in all dry feed groups were significantly increased by supplementary kelp feeding, with a higher increase observed in S. intermedius with SL intake history, while arachidonic acid (ARA) content was significantly improved by supplementary kelp feeding in S. intermedius with SL intake history. Gonad texture was improved to some extent by supplementary kelp feeding. These results indicated that S. intermedius fed dry feeds showed significantly higher GSI and EAA but poorer organoleptic quality and lower n-3/n-6 PUFA and EPA than those fed kelp. Kelp supplementary feeding improved the fatty acid value and organoleptic quality of gonads, especially for the sea urchins with SL intake history.

Chitinolytic and Fungicidal Potential of the Marine Bacterial Strains Habituating Pacific Ocean Regions.

Screening for chitinolytic activity in the bacterial strains from different Pacific Ocean regions revealed that the highly active representatives belong to the genera Microbulbifer, Vibrio, Aquimarina, and Pseudoalteromonas. The widely distributed chitinolytic species was Microbulbifer isolated from the sea urchin Strongylocentrotus intermedius. Among seventeen isolates with confirmed chitinolytic activity, only the type strain P. flavipulchra KMM 3630T and the strains of putatively new species Pseudoalteromonas sp. B530 and Vibrio sp. Sgm 5, isolated from sea water (Vietnam mollusc farm) and the sea urchin S. intermedius (Peter the Great Gulf, the Sea of Japan), significantly suppressed the hyphal growth of Aspergillus niger that is perspective for the biocontrol agents' development. The results on chitinolytic activities and whole-genome sequencing of the strains under study, including agarolytic type strain Z. galactanivorans DjiT, found the new functionally active chitinase structures and biotechnological potential.

Integrated microRNA-mRNA analysis provides new insights into gonad coloration in the sea urchin Strongylocentrotus intermedius

Comparative microRNA (miRNA) and mRNA transcriptome analyses were performed on Strongylocentrotus intermedius of the same sex with significant gonadal color differences. The results indicated that 1) the color of female gonads was generally superior to that of males. 2) Comparative and integrated miRNA and mRNA transcriptome analyses identified differentially expressed genes (DEGs) and differentially expressed miRNAs (DEMs) in female and male individuals with significant gonadal color differences. Common and sex-specific DEGs and “DEM-DEG” pairs involved in carotenoid absorption, accumulation, and transformation were identified as candidates correlated with gonad coloration in S. intermedius. Collectively, the results from this study have enriched our knowledge of the process of sea urchin gonad coloration and should provide additional clues for increasing the gonad quality of commercial sea urchins from molecular and metabolic aspects.

High temperature influences DNA methylation and transcriptional profiles in sea urchins (Strongylocentrotus intermedius)

BackgroundDNA methylation plays an important role in life processes by affecting gene expression, but it is still unclear how DNA methylation is controlled and how it regulates gene transcription under high temperature stress conditions in Strongylocentrotus intermedius. The potential link between DNA methylation variation and gene expression changes in response to heat stress in S. intermedius was investigated by MethylRAD-seq and RNA-seq analysis. We screened DNA methylation driver genes in order to comprehensively elucidate the regulatory mechanism of its high temperature adaptation at the DNA/RNA level.ResultsThe results revealed that high temperature stress significantly affected not only the DNA methylation and transcriptome levels of S. intermedius (P < 0.05), but also growth. MethylRAD-seq analysis revealed 12,129 CG differential methylation sites and 966 CWG differential methylation sites, and identified a total of 189 differentially CG methylated genes and 148 differentially CWG methylated genes. Based on KEGG enrichment analysis, differentially expressed genes (DEGs) are mostly enriched in energy and cell division, immune, and neurological damage pathways. Further RNA-seq analysis identified a total of 1968 DEGs, of which 813 genes were upregulated and 1155 genes were downregulated. Based on the joint MethylRAD-seq and RNA-seq analysis, metabolic processes such as glycosaminoglycan degradation, oxidative phosphorylation, apoptosis, glutathione metabolism, thermogenesis, and lysosomes are regulated by DNA methylation.ConclusionsHigh temperature affected the DNA methylation and expression levels of genes such as MOAP-1, GGT1 and RDH8, which in turn affects the metabolism of HPSE, Cox, glutathione, and retinol, thereby suppressing the immune, energy metabolism, and antioxidant functions of the organism and finally manifesting as stunted growth. In summary, the observations in the present study improve our understanding of the molecular mechanism of the response to high temperature stress in sea urchin.