Search Results (13)

We investigated the growth, preferences, and thermal resistance of the sea cucumber Isostichopus isabellae to understand its thermal biology. Sixty individuals were kept in tanks at two temperatures (23 °C and 26 °C) for 30 days to determine their favorable maintenance temperature. Their survival rates and specific growth rates were measured to establish their ideal conditioning temperature in the laboratory. The sea cucumbers’ thermal preference was evaluated over a gradient from 20 °C to 29 °C, and their behavior was monitored for 4 h. They preferred the temperature to which they were acclimated, aligning with the favorable temperature identified in this study. We did not find differences in the average weight loss between the two experimental temperatures. The highest survival rate (86%) was observed at 23 °C, which can be considered to be the most favorable maintenance temperature. The critical thermal maximum (CTMax) and minimum (CTMin) were determined by gradually heating or cooling the water until the sea cucumbers showed a loss of podia movement and body relaxation. CTMax was established at 36.5 ± 0.3 °C and CTMin at 8 ± 0.5 °C. Based on these results, Isostichopus isabellae could negatively respond to increased temperatures, so we recommend maintaining a favorable temperature of 23 ± 2.3 °C in captivity for its use in aquaculture. Full article

Phyllophorus proteus is a low-value sea cucumber from Indonesia and other tropical peripheral waters. In this study, a fucosylated glycosaminoglycan (FG) was extracted from P. proteus. It consists of GlcA, GalNAc, and Fuc, with a molecular weight of 67.1 kDa. The degraded FG (dFG) was prepared by β-elimination. Structural analysis revealed that the main chain of dFG was composed of GalNAc and GlcA, linked alternately by β1,3 and β1,4 glycosidic bonds. The sulfate group was located at the 4 and 6 positions of GalNAc. Fuc was attached to the 3 position of GlcA by an α1,3 glycosidic bond, and the side chain of Fuc exhibited various sulfate substitutions. FG significantly prolonged the coagulation time of APTT, PT, TT, and FIB, surpassing the effect of LMWH, thereby demonstrating its ability to exert anticoagulant effects in both the endogenous and exogenous coagulation pathways. Conversely, dFG had no significant effect on the clotting time of PT, suggesting its lack of impact on the intrinsic coagulation pathway. This study elucidates the structural properties and potent anticoagulant activities of fucosylated glycosaminoglycan from P. proteus. Full article

With the continuous rise of the sea cucumber aquaculture industry in China, the tropical sea cucumber aquaculture industry is also improving. However, research on the gut microorganisms of tropical sea cucumbers in captivity is scarce. In this study, high-throughput sequencing methods were used to analyze the gut microbial composition of Stichopus monotuberculatus and Holothuria scabra in the dry season and wet season of artificial environments. The results showed that 66 phyla were obtained in all samples, of which 59 phyla were obtained in the dry season, and 45 phyla were obtained in the wet season. The Tax4Fun analysis showed that certain gut bacterial communities affect the daily metabolism of two sea cucumber species and are involved in maintaining gut microecological balance in the gut of two sea cucumber species. In addition, compared with differences between species, PCoA and UPGMA clustering analysis showed the gut prokaryotes of the same sea cucumber species varied more in different seasons, indicating that the influence of environment was higher than the feeding choices of sea cucumbers under relatively closed conditions. These results revealed the gut bacterial community composition of S. monotuberculatus and H. scabra and the differences in gut bacterial structure between two sea cucumber species in different seasons were compared, which would provide the foundation for tropical sea cucumber aquaculture in the future. Full article

The growth of biofouling on aquaculture infrastructure is a universal challenge. Standard industry practices to remove biofouling in finfish aquaculture typically include in situ net cleaning via power washing. Since those cleaning practices can be potentially harmful to fish-gill health and expensive, development of other non-toxic biofouling controls is an industry priority. Deposit-feeding sea cucumbers are potentially well suited for biofouling control due to their feeding mechanism, but remain relatively untested in this capacity. We examined the use of California sea cucumbers (Apostichopus californicus) to control biofouling on cages containing adult Chinook salmon (Oncorhynchus tshawytscha) at a commercial farming operation. Four cage types were established: cages with salmon and sea cucumbers, cages with salmon only, cages with sea cucumbers only, and cages without either species. Results showed that the sea cucumbers actively fed on biofouling when salmon were absent (~16% cleaner on average) but preferred to consume uneaten feed/faeces at the bottom of the cages, neglecting the biofouling, when the salmon were present. It is hypothesized that biofouling control in cages with salmon may be possible with an increased density of sea cucumbers. This is the first study to examine the use of sea cucumbers as a direct net biofouling control agent with adult fish. Our results will be beneficial for industry to develop standard operating procedures for using California sea cucumbers as a biofouling control and could contribute to the development of a management framework for sea cucumber/salmon integrated multi-tropic aquaculture. Full article

Based on 16S rRNA gene high-throughput sequencing technology, the microbial community structure in the gut of three tropical sea cucumber species, Holothuria atra, Stichopus chloronotus, and S. monotuberculatus, and their habitat sediments were analyzed. The OTUs in the gut contents of S. monotuberculatus, S. chloronotus, H. atra, and their sediments were 2489 ± 447, 1912 ± 235, 1628 ± 150, and 4162 ± 94, respectively. According to alpha diversity analysis (Ace, Chao1, Shannon, Simpson), the richness and diversity of microflora in the gut of all three sea cucumber species were significantly lower than that in sediments (p < 0.01). Anosim analysis showed that the intra-group differences were less than the inter-group differences (R > 0), and the microbial community composition of the sediment was distinctly different from those of three sea cucumber species (p < 0.05). UPGMA tree and Anosim analysis also revealed that the gut microbial communities of H. atra and S. chloronotus were more similar than that of S. monotuberculatus. Proteobacteria was the predominant phylum in all samples, and there was no significant difference in relative abundance among all groups. Actinobacteria was also a dominant phylum, and the relative abundance in S. chloronotus was significantly higher than that in other samples (p < 0.05). Potential probiotics and sequences related to Lactobacillus and Pseudomonas that may be developed for sea cucumber culture were also found in the study. It is speculated that the main reason for the difference in microbial communities between gut microbiota and environmental sediments may be the unique and quite different environment in the digestive tract of sea cucumbers. Whereas, the differences in gut microbiota among the three sea cucumber species were caused by selective feeding. These findings may provide basic data for tropical sea cucumber gut microflora studies and assist in the sea ranching and aquaculture development of the tropical sea cucumber species. Full article

Holothuria leucospilota and Stichopus chloronotus are among the most widespread tropical sea cucumber species usually harvested for food and medicine in Asian countries, for which natural stocks have collapsed worldwide. Both species can reproduce sexually and asexually, and a better understanding of their reproductive strategy can provide useful information for conservation purposes. To describe the genetic structure and diversity of sympatric populations from these species in space and time, individuals were sampled over different sites and seasons in Reunion Island (Southwestern Indian Ocean). They were genotyped using 24 and 9 specific microsatellite markers for H. leucospilota and S. chloronotus, respectively. Multi-locus genotypes (MLG) and lineages (MLL) were identified, and analyses of population structure were performed among sites and seasons. No repeated MLG nor MLL were found for H. leucospilota, demonstrating the absence of asexual reproduction. Populations of H. leucospilota were not genetically differentiated, acting as a metapopulation, with larval exchanges within the reef. Contrarily, repeated MLGs were found for S. chloronotus and all populations were genetically differentiated. Asexual reproduction seems to reach a high level for this species (mean clonal richness = 0.24). For both species, genetic structure was stable through seasons. Thus, these sympatric fissiparous sea cucumber species use two different strategies of reproduction, which may allow them to reduce interspecific competition. Full article

The interrelationship of the minerals calcium (Ca²⁺), magnesium (Mg²⁺) and silicon (Si) in the sediments and in the body walls of four tropical sea cucumber species was explored by modeling the concentrations of these minerals. The elemental concentrations of Ca²⁺, Mg²⁺ and Si were measured in the body walls and in the ambient sediments occupied by the sea cucumbers Holothuria scabra, H. leucospilota, H. atra and Bohadschia marmorata. The results indicate that the concentrations of Ca²⁺ and Mg²⁺ in the body walls of the four sea cucumber species are significantly different from each other, indicating a varying degree of biomineralization across sea cucumber taxa. In contrast, only B. marmorata showed a significant difference in the concentration of Si when compared to the rest of the species tested. Further analysis using linear mixed models revealed that the Ca²⁺, Mg²⁺ and Si concentrations in the body walls of the tested sea cucumber species are associated with the sediment concentrations of the same elements. The relatively high concentrations of Ca²⁺ and Mg²⁺ in the sediments indicate that these minerals are sufficiently high in sea cucumbers to support their biomineralization. The relationship between the Mg/Ca ratio in the body walls of the sea cucumbers and minerals in the sediments revealed that Si was the only mineral that was not correlated with the Mg/Ca ratio. Predicting the relationship of the elements Ca²⁺, Mg²⁺ and Si between the sediments and the body walls of sea cucumbers may be complex due to the various factors that influence the metabolism and biomineralization in sea cucumbers. Full article

In this study, the eukaryotic composition of gut contents in three tropical sea cucumber species, Stichopus monotuberculatus, S. chloronotus and Holothuria atra were surveyed and compared by metabarcoding analysis based on 18S rRNA gene V4 region. The sequences were assigned to 21.80 ± 1.07, 22.60 ± 0.68 and 22.40 ± 0.25 different phyla from the gut contents of S. monotuberculatus, S. chloronotus and H. atra, respectively, and those in sediment samples were assigned to 21.00 ± 1.67 phyla. The results of α-diversity showed that surface sediments had a greater eukaryotic diversity than gut contents, yet the guts of sea cucumbers had an enrichment effect on some microorganisms, including Diatomea and Apicomplex. A comparison of the gut eukaryotic community among the three species suggested that the feeding preference was different: S. monotuberculatus fed mainly on Diatomea and Arthropoda, and the other two species had higher Apicomplexa concentrations, which may be due to differences in the morphology of the tentacles and habitat preferences. Moreover, obvious different eukaryotic community composition in the gut contents of the three sea cucumber species and the surrounding sediments also might result from the animals’ selective feeding for sediment patches. The current study filled in gaps about feeding mechanisms of tropical sea cucumbers and provided a basis for further exploring the mechanism about selective feeding and sea cucumber–sediment interaction in the future. Full article

Apoptosis, also known as programmed cell death, is a biological process that is critical for embryonic development, organic differentiation, and tissue homeostasis of organisms. As an essential mitochondrial flavoprotein, the apoptosis-inducing factor (AIF) can directly mediate the caspase-independent mitochondrial apoptotic pathway. In this study, we identified and characterized a novel AIF-2 (HlAIF-2) from the tropical sea cucumber Holothuria leucospilota. HlAIF-2 contains a conserved Pyr_redox_2 domain and a putative C-terminal nuclear localization sequence (NLS) but lacks an N-terminal mitochondrial localization sequence (MLS). In addition, both NADH- and FAD-binding domains for oxidoreductase function are conserved in HlAIF-2. HlAIF-2 mRNA was ubiquitously detected in all tissues and increased significantly during larval development. The transcript expression of HlAIF-2 was significantly upregulated after treatment with CdCl₂, but not the pathogen-associated molecular patterns (PAMPs) in primary coelomocytes. In HEK293T cells, HlAIF-2 protein was located in the cytoplasm and nucleus, and tended to transfer into the nucleus by CdCl₂ incubation. Moreover, there was an overexpression of HlAIF-2-induced apoptosis in HEK293T cells. As a whole, this study provides the first evidence for heavy metal-induced apoptosis mediated by AIF-2 in sea cucumbers, and it may contribute to increasing the basic knowledge of the caspase-independent apoptotic pathway in ancient echinoderm species. Full article

Cancer remains the primary cause of death worldwide. To develop less toxic anti-cancer drugs to relieve the suffering and improve the survival of cancer patients is the major focus in the anti-cancer field. To this end, marine creatures are being extensively studied for their anti-cancer effects, since extracts from at least 10% of the marine organisms have been shown to possess anti-tumor activities. As a classic Chinese traditional medicine, sea cucumbers and compounds extracted from the sea cucumbers, such as polysaccharides and saponins, have recently been shown to exhibit anti-cancer, anti-inflammatory, and anti-oxidant effects. Holothuria leucospilota (H. leucospilota) is a tropical edible sea cucumber species that has been successfully cultivated and farmed in large scales, providing a readily available source of raw materials to support the development of novel marine anti-cancer drugs. However, very few studies have so far been performed on the biological activities of H. leucospilota. In this study, we first investigated the anti-cancer effect of H. leucospilota protein on three cancer cell lines (i.e., HepG2, A549, Panc02) and three normal cell lines (NIH-3T3, HaCaT, 16HBE). Our data showed that H. leucospilota protein decreased the cell viabilities of HepG2, A549, HaCaT, 16HBE in a concentration-dependent manner, while Panc02 and NIH-3T3 in a time- and concentration-dependent manner. We also found that the inhibitory effect of H. leucospilota protein (≥10 μg/mL) on cell viability is near or even superior to EPI, a clinical chemotherapeutic agent. In addition, our data also demonstrated that H. leucospilota protein significantly affected the cell cycle and induced apoptosis in the three cancer cell lines investigated; in comparison, it showed no effects on the normal cell lines (i.e., NIH-3T3, HaCaT and 16HBE). Finally, our results also showed that H. leucospilota protein exhibited the excellent performance in inhibiting cell immigrations. In conclusion, H. leucospilota protein targeted the cancer cell cycles and induced cancer cell apoptosis; its superiority to inhibit cancer cell migration compared with EPI, shows the potential as a promising anti-cancer drug. Full article

Sea cucumbers are bottom dwelling invertebrates, which are mostly found on subtropical and tropical sea grass beds, sandy reef flats, or reef slopes. Although constantly exposed to fouling communities in these habitats, many species are surprisingly free of invertebrate epibionts and microfouling algae such as diatoms. In our study, we investigated the anti-fouling (AF) activities of different crude extracts of tropical Indo-Pacific sea cucumber species against the fouling diatom Cylindrotheca closterium. Nine sea cucumber species from three genera (i.e., Holothuria, Bohadschia, Actinopyga) were selected and extracted to assess their AF activities. To verify whether the sea cucumber characteristic triterpene glycosides were responsible for the observed potent AF activities, we tested purified fractions enriched in saponins isolated from Bohadschia argus, representing one of the most active anti-fouling extracts. Saponins were quantified by vanillin-sulfuric acid colorimetric assays and identified by LC-MS and LC-MS/MS analyses. We were able to demonstrate that AF activities in sea cucumber extracts were species-specific, and growth inhibition as well as attachment of the diatom to surfaces is dependent on the saponin concentration (i.e., Actinopyga contained the highest quantities), as well as on the molecular composition and structure of the present saponins (i.e., Bivittoside D derivative was the most bioactive compound). In conclusion, the here performed AF assay represents a promising and fast method for selecting the most promising bioactive organism as well as for identifying novel compounds with potent AF activities for the discovery of potentially novel pharmacologically active natural products. Full article

Nine new sulfated triterpene glycosides, magnumosides A₁ (1), A₂ (2), A₃ (3), A₄ (4), B₁ (5), B₂ (6), C₁ (7), C₂ (8) and C₄ (9) as well as a known colochiroside B₂ (10) have been isolated from the tropical Indo-West Pacific sea cucumber Neothynidium (=Massinium) magnum (Phyllophoridae, Dendrochirotida) collected in the Vietnamese shallow waters. The structures of new glycosides were elucidated by 2D NMR spectroscopy and mass-spectrometry. All the isolated new glycosides were characterized by the non-holostane type lanostane aglycones having 18(16)-lactone and 7(8)-double bond and differed from each other by the side chains and carbohydrate moieties structures. Magnumoside A₁ (1) has unprecedented 20(24)-epoxy-group in the aglycone side chain. Magnumosides of the group A (1–4) contained disaccharide monosulfated carbohydrate moieties, of the group B (5, 6)—tetrasaccharide monosulfated carbohydrate moieties and, finally, of the group C (7–9)—tetrasaccharide disulfated carbohydrate moieties. The cytotoxic activities of the compounds 1–9 against mouse spleen lymphocytes, the ascites form of mouse Ehrlich carcinoma cells, human colorectal carcinoma DLD-1 cells as well as their hemolytic effects have been studied. Interestingly, the erythrocytes were more sensitive to the glycosides action than spleenocytes and cancer cells tested. The compounds 3 and 7 significantly inhibited the colony formation and decreased the size of colonies of DLD-1 cancer cells at non-cytotoxic concentrations. Moreover, the synergism of effects of radioactive irradiation and compounds 3 and 7–9 at subtoxic doses on proliferation of DLD-1 cells was demonstrated. Full article

To avoid predation, holothuroids produce feeding-deterrent molecules in their body wall and viscera, the so-called saponins. Five tropical sea cucumber species of the family Holothuriidae were investigated in order to study their saponin content in two different organs, the body wall and the Cuvierian tubules. Mass spectrometry techniques (MALDI- and ESI-MS) were used to detect and analyze saponins. The smallest number of saponins was observed in Holothuria atra, which contained a total of four congeners, followed by Holothuria leucospilota, Pearsonothuria graeffei and Actinopyga echinites with six, eight and ten congeners, respectively. Bohadschia subrubra revealed the highest saponin diversity (19 congeners). Saponin mixtures also varied between the two body compartments within a given animal. A semi-quantitative approach completed these results and showed that a high diversity of saponins is not particularly correlated to a high saponin concentration. Although the complexity of the saponin mixtures described makes the elucidation of their respective biological roles difficult, the comparisons between species and between body compartments give some clues about how these molecules may act as predator repellents. Full article