Sea Anemone Research Articles

Recombinant Analogs of Sea Anemone Kunitz-Type Peptides Influence P2X7 Receptor Activity in Neuro-2a Cells

Purinergic P2X7 receptors (P2X7) have now been proven to play an important role and represent an important therapeutic target in many pathological conditions including neurodegeneration. Here, we investigated the impact of peptides on purinergic signaling in Neuro-2a cells through the P2X7 subtype in in vitro models. We have found that a number of recombinant peptides, analogs of sea anemone Kunitz-type peptides, are able to influence the action of high concentrations of ATP and thereby reduce the toxic effects of ATP. The influx of calcium, as well as the fluorescent dye YO-PRO-1, was significantly suppressed by the studied peptides. Immunofluorescence experiments confirmed that the peptides reduce the P2X7 expression level in neuronal Neuro-2a cells. Two selected active peptides, HCRG1 and HCGS1.10, were found to specifically interact with the extracellular domain of P2X7 and formed stable complexes with the receptor in surface plasmon resonance experiments. The molecular docking approach allowed us to establish the putative binding sites of the most active HCRG1 peptide on the extracellular domain of the P2X7 homotrimer and propose a mechanism for regulating its function. Thus, our work demonstrates the ability of the Kunitz-type peptides to prevent neuronal death by affecting signaling through the P2X7 receptor.

Modeling food dependent symbiosis in Exaiptasia pallida

Cnidaria, marine invertebrates that include reef-building stony corals, often rely on photosynthetic endosymbionts to obtain the energy they need for growth. Increased temperatures and/or nutrient pollution can disrupt mutualistic properties of the symbiosis, leading to host mortality. However, the precise mechanism by which this dysbiosis occurs is still unclear. Sea anemones, other cnidarians that may host algal endosymbionts, are used as a model organism for the coral holobiont to understand the costs and benefits of symbionts, but the exact nature of the costs of symbionts on the hosts is still unclear. Here we developed a Dynamic Energy Budget (DEB) model and fit the model to data from the anemone Exaiptasia pallida and its endosymbiotic algae, Breviolum minutum, in order to identify the most likely mechanism of symbiont costs. In order to match the laboratory dataset, our model needed an explicit symbiont demand term, in which the symbiont can “consume” host tissue to forcibly extract nitrogen. The model demonstrates the role of the symbiont as an amplifier of the host’s state: a growing anemone grows better with symbionts, while a malnourished anemone looses biomass faster with a symbiont than without. This model allows us to project Cnidaria holobiont growth as a function of environmental conditions and adds a new framework for which to capture the direct cost a symbiont has on Cnidaria hosts.

Molecular insights into the Darwin paradox of coral reefs from the sea anemone Aiptasia

Symbiotic cnidarians such as corals and anemones form highly productive and biodiverse coral reef ecosystems in nutrient-poor ocean environments, a phenomenon known as Darwin's paradox. Resolving this paradox requires elucidating the molecular bases of efficient nutrient distribution and recycling in the cnidarian-dinoflagellate symbiosis. Using the sea anemone Aiptasia, we show that during symbiosis, the increased availability of glucose and the presence of the algae jointly induce the coordinated up-regulation and relocalization of glucose and ammonium transporters. These molecular responses are critical to support symbiont functioning and organism-wide nitrogen assimilation through glutamine synthetase/glutamate synthase-mediated amino acid biosynthesis. Our results reveal crucial aspects of the molecular mechanisms underlying nitrogen conservation and recycling in these organisms that allow them to thrive in the nitrogen-poor ocean environments.

Chromatin Immunoprecipitation in the Cnidarian Model System Exaiptasia diaphana.

Histone post-translational modifications (PTMs) and other epigenetic modifications regulate the chromatin accessibility of genes to the transcriptional machinery, thus affecting an organism's capacity to respond to environmental stimuli. Chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-seq) has been widely utilized to identify and map protein-DNA interactions in the fields of epigenetics and gene regulation. However, the field of cnidarian epigenetics is hampered by a lack of applicable protocols, partly due to the unique features of model organisms such as the symbiotic sea anemone Exaiptasia diaphana, whose high water content and mucus amounts obstruct molecular methods. Here, a specialized ChIP procedure is presented, which facilitates the investigation of protein-DNA interactions in E. diaphana gene regulation. The cross-linking and chromatin extraction steps were optimized for efficient immunoprecipitation and then validated by performing ChIP using an antibody against the histone markH3K4me3. Subsequently, the specificity and effectiveness of the ChIP assay were confirmed by measuring the relative occupancy of H3K4me3 around several constitutively activated gene loci using quantitative PCR and by next-generation sequencing for genome-wide scale analysis. This optimized ChIP protocol for the symbiotic sea anemone E. diaphana facilitates the investigation of the protein-DNA interactions involved in organismal responses to environmental changes that affect symbiotic cnidarians, such as corals.

Acontia, a Specialised Defensive Structure, Has Low Venom Complexity in Calliactis polypus.

Phylum Cnidaria represents a unique group among venomous taxa, with its delivery system organised as individual organelles, known as nematocysts, heterogeneously distributed across morphological structures rather than packaged as a specialised organ. Acontia are packed with large nematocysts that are expelled from sea anemones during aggressive encounters with predatory species and are found in a limited number of species in the superfamily Metridioidea. Little is known about this specialised structure other than the commonly accepted hypothesis of its role in defence and a rudimentary understanding of its toxin content and activity. This study utilised previously published transcriptomic data and new proteomic analyses to expand this knowledge by identifying the venom profile of acontia in Calliactis polypus. Using mass spectrometry, we found limited toxin diversity in the proteome of acontia, with an abundance of a sodium channel toxin type I, and a novel toxin with two ShK-like domains. Additionally, genomic evidence suggests that the proposed novel toxin is ubiquitous across sea anemone lineages. Overall, the venom profile of acontia in Calliactis polypus and the novel toxin identified here provide the basis for future research to define the function of acontial toxins in sea anemones.

A New Hope? Mediterranean Algae Mats Are Thriving With Life

Our oceans are full of life and home to many different species. High species diversity often concentrates in specific areas called “biodiversity hotspots” (e.g., coral reefs). These hotspots develop with the help of a few key engineering species (e.g., corals). In the Mediterranean Sea, well-known biodiversity hotspots are seagrass meadows. Macroalgae beds represent another typical habitat but usually do not provide the same diversity as seagrass meadows. High biodiversity is essential for an ecosystem’s stability and our lives: healthy coastal ecosystems provide food and shelter for fish species and stabilize the seafloor. We investigated a relatively unknown type of red macroalgae and were surprised to find it thriving with marine organisms such as sea stars, anemones, and tube worms. With the latter being an example of an extraordinary group of marine animals, we would like to take this example and show you what we learned about this new hotspot for diversity.

Sea anemones (Actiniaria, Corallimorpharia and Zoantharia) from the Western Bering Sea (Northwest Pacific)

Sea anemones (Actiniaria, Corallimorpharia and Zoantharia) from the Western Bering Sea (Northwest Pacific)

SEA ANEMONE TUMOR OF THE AORTA PRESENTING WITH DYSPNEA IN A WOMAN

SEA ANEMONE TUMOR OF THE AORTA PRESENTING WITH DYSPNEA IN A WOMAN

Invader in disguise for decades: the plumose sea anemone Metridium senile in the Southwestern Atlantic Ocean

Invader in disguise for decades: the plumose sea anemone Metridium senile in the Southwestern Atlantic Ocean

An abundant sea anemone from the Carboniferous Mazon Creek Lagerstӓtte, USA

AbstractSea anemones (Actiniaria) are among the rarest of recognized fossil organisms, even rarer than jellyfish. Here we demonstrate that the most abundant fossil in the Pennsylvanian Mazon Creek Lagerstätte of Illinois, Essexella asherae, is an infaunal or semi‐infaunal anemone. Essexella is redescribed based on a taphonomic analysis of thousands of specimens, as well as associated medusae and trace fossils. Specimens of Essexella (also known as the ‘blobs’) were long believed to be medusae, but we reassign Essexella to the order Actiniaria and reinterpret the putative jellyfish Reticulomedusa as the pedal or oral disc of Essexella. We also implicate Essexella as a producer of Conostichus, a widespread plug‐shaped trace fossil that occurs in coeval strata in the same region. Radiate structures comparable to the bases of Conostichus and the ichnofossil Bergaueria, as well as the pedal discs of modern anemones, characterize Reticulomedusa. Bona fide medusae are present in the Mazon Creek biota, and include Anthracomedusa turnbulli and Octomedusa pieckorum, whereas the soft‐bodied fossil Lascoa mesostaurata is referred to Problematica.

Parental exposure to ocean acidification impacts gamete production and physiology but not offspring performance in Nematostella vectensis.

Ocean acidification (OA) resulting from anthropogenic CO2 emissions is impairing the reproduction of marine organisms. While parental exposure to OA can protect offspring via carryover effects, this phenomenon is poorly understood in many marine invertebrate taxa. Here, we examined how parental exposure to acidified (pH 7.40) versus ambient (pH 7.72) seawater influenced reproduction and offspring performance across six gametogenic cycles (13 weeks) in the estuarine sea anemone Nematostella vectensis. Females exhibited reproductive plasticity under acidic conditions, releasing significantly fewer but larger eggs compared to ambient females after 4weeks of exposure, and larger eggs in two of the four following spawning cycles despite recovering fecundity, indicating long-term acclimatization and greater investment in eggs. Males showed no changes in fecundity under acidic conditions but produced a greater percentage of sperm with high mitochondrial membrane potential (MMP; a proxy for elevated motility), which corresponded with higher fertilization rates relative to ambient males. Finally, parental exposure to acidic conditions did not significantly influence offspring development rates, respiration rates, or heat tolerance. Overall, this study demonstrates that parental exposure to acidic conditions impacts gamete production and physiology but not offspring performance in N. vectensis, suggesting that increased investment in individual gametes may promote fitness.

Anemonefishes: A model system for evolutionary genomics

Anemonefishes are an iconic group of coral reef fish particularly known for their mutualistic relationship with sea anemones. This mutualism is especially intriguing as it likely prompted the rapid diversification of anemonefish. Understanding the genomic architecture underlying this process has indeed become one of the holy grails of evolutionary research in these fishes. Recently, anemonefishes have also been used as a model system to study the molecular basis of highly complex traits such as color patterning, social sex change, larval dispersal and life span. Extensive genomic resources including several high-quality reference genomes, a linkage map, and various genetic tools have indeed enabled the identification of genomic features controlling some of these fascinating attributes, but also provided insights into the molecular mechanisms underlying adaptive responses to changing environments. Here, we review the latest findings and new avenues of research that have led to this group of fish being regarded as a model for evolutionary genomics.

Sneathiella marina sp. nov., isolated from a sea anemone in the Western Pacific Ocean.

A novel marine bacterium designated strain PHK-P5T was isolated from a sea anemone (Actinostolidae sp. 1). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain PHK-P5T belonged to the genus Sneathiella. The bacterium was Gram-stain-negative, aerobic, oxidase- and catalase- positive, oval- to rod-shaped, and motile. Growth was observed at pH 6.0-9.0, salinities of 2.0-9.0 % and temperatures of 4-37 °C. The G+C content of the chromosomal DNA was 49.2 %. The respiratory quinone was determined to be Q-10. The principal fatty acids of strain PHK-P5T were C19 : 0cyclo ω8c (25.19 %), C16 : 0 (22.76 %), summed feature 8 (C18 : 1 ω7c/ω6c; 16.14 %), C14 : 0 (8.81 %), C17 : 0cyclo (8.10 %), summed feature 2 (C12 : 0 aldehyde and/or unknown 10.928; 7.19 %) and C18 : 1 ω7c 11-methyl (5.03 %). The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The average nucleotide identity and digital DNA-DNA hybridization values among the genomes of strain PHK-P5T and the reference strains were 68.7-70.9 % and 17.4-18.1 %, respectively. The combined genotypic and phenotypic data showed that strain PHK-P5T represents a novel species within the genus Sneathiella, for which the name Sneathiella marina sp. nov. is proposed, with the type strain PHK-P5T (=MCCC M21824T=KCTC 82924T).

Single-cell atavism reveals an ancient mechanism of cell type diversification in a sea anemone

Cnidocytes are the explosive stinging cells unique to cnidarians (corals, jellyfish, etc). Specialized for prey capture and defense, cnidocytes comprise a group of over 30 morphologically and functionally distinct cell types. These unusual cells are iconic examples of biological novelty but the developmental mechanisms driving diversity of the stinging apparatus are poorly characterized, making it challenging to understand the evolutionary history of stinging cells. Using CRISPR/Cas9-mediated genome editing in the sea anemone Nematostella vectensis, we show that a single transcription factor (NvSox2) acts as a binary switch between two alternative stinging cell fates. Knockout of NvSox2 causes a transformation of piercing cells into ensnaring cells, which are common in other species of sea anemone but appear to have been silenced in N. vectensis. These results reveal an unusual case of single-cell atavism and expand our understanding of the diversification of cell type identity.

First In Situ Observation of Sperm Release in Corynactis carnea (Anthozoa: Corallimorpharia) from Patagonia, Argentina

Jewel sea anemones constitute a relatively small group of solitary cnidarians, a sister group of scleractinian corals. In the southwest Atlantic Ocean off Argentina, two species of jewel sea anemones have been found: Corynactis carnea and Corallimorphus rigidus. Corynactis carnea is a common and abundant species in shallow water of northern Atlantic Patagonia, but reproductive data on this species is scarce; the species is known to reproduce asexually. During a SCUBA diving survey in an Atlantic rocky reefs (20 m depth) in Patagonia, we observed for the first time specimens of C. carnea releasing sperm, eight days after the full moon and during the summer season while spawning has been previously observed in at least three species of Corynactis, but all were recorded as occurring in winter.

Applications of Polyaniline–Alkaline Copper Carbonate Composites for Anti-Bio-Attachment of Concrete in Marine Environments

This study proposed the use of polyaniline–alkaline copper carbonate composites as anti-corrosion and anti-biofouling concrete additives and established a set of high-dispersion preparation methods for this composite additive. The effects of polyaniline–alkaline copper carbonate composites in concrete were investigated in marine environments via the preparation of concrete specimens, actual sea suspension experiments, concrete mechanical property tests, and biological attachment avoidance tests. The experimental results showed that (1) the yield of the chemical reactions leading to the preparation of the composite was above 96.46% with a good output. The composite was hydrophilic. The addition of ethylene carbonate as a surfactant and the mixing of the composite into the concrete in a suspension form enabled uniform dispersion of the composite. (2) In the sea waters of Zhoushan, China, bio-attachment was mainly dominated by barnacles and sea anemones. Polyaniline–alkaline copper carbonate composites had good anti-bio-attachment properties and could significantly reduce the amount of bio-attachment in concrete. (3) When the additive content was less than 0.20% of the concrete mass, it did not negatively affect the mechanical properties of the concrete specimens and exerted anti-corrosion and anti-biofouling effects. This reduced the strength loss of concrete and increased the service life of the concrete specimens in the ocean. To ensure the best application effect of the compound in concrete, the recommended content of the compound is 0.05–0.15% of the concrete mass.

The genome sequence of the starlet sea anemone, Nematostella vectensis (Stephenson, 1935)

We present a genome assembly from an individual Nematostella vectensis (the starlet sea anemone; Cnidaria; Anthozoa; Actiniaria; Edwardsiidae). The genome sequence is 269.4 megabases in span. Most of the assembly is scaffolded into 15 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 16.4 kilobases in length.

Cell volume maintenance capacity of the sea anemone Bunodosoma cangicum: the effect of copper.

Cell volume regulation is an essential strategy for the maintenance of life under unfavorable osmotic conditions. Mechanisms aimed at minimizing the physiological challenges caused by environmental changes are crucial in anisosmotic environments. However, aquatic ecosystems experience multiple stressors, including variations in salinity and heavy metal pollution. The accumulation of heavy metals in aquatic ecosystems has a significant effect on the biota, leading to impaired function. The aim of this study was to investigate the capacity of volume regulation in isolated cells of the sea anemone Bunodosoma cangicum exposed to nominal copper (Cu) concentrations of 5 and 50µg L-1, associated or not with hypoosmotic (15‰) or hyperosmotic (45‰) shock for 15min. In the absence of the metal, our results showed volume maintenance in all osmotic conditions. Our results showed that cell volume was maintained under all osmotic conditions in the absence of Cu. Similarly, no significant differences were observed in cell volumes under isosmotic and hyperosmotic conditions in the presence of both Cu concentrations. A similar homeostatic response was observed under the hypoosmotic condition with 5µg L-1 Cu. Our results showed an increase in cell volume with exposure of the cells to the hypoosmotic condition and 50µg L-1 Cu. The response could be associated with the increased bioavailability of Cu, reduced ability to resist multixenobiotics and their efflux pathways, and the impairment of water efflux in specialized transmembrane proteins. Therefore, B. cangicum pedal disk cells can tolerate osmotic variations in aquatic ecosystems. However, the capacity to regulate cell volume under hypoosmotic conditions can be affected by the presence of a metal contaminant (50µg L-1 Cu), which could be due to the inhibition of water channels.

MRI Tracking of Marine Proliferating Cells In Vivo Using Anti-Oct4 Antibody-Conjugated Iron Nanoparticles for Precision in Regenerative Medicine

Marine invertebrates are multicellular organisms consisting of a wide range of marine environmental species. Unlike vertebrates, including humans, one of the challenges in identifying and tracking invertebrate stem cells is the lack of a specific marker. Labeling stem cells with magnetic particles provides a non-invasive, in vivo tracking method using MRI. This study suggests antibody-conjugated iron nanoparticles (NPs), which are detectable with MRI for in vivo tracking, to detect stem cell proliferation using the Oct4 receptor as a marker of stem cells. In the first phase, iron NPs were fabricated, and their successful synthesis was confirmed using FTIR spectroscopy. Next, the Alexa Fluor anti-Oct4 antibody was conjugated with as-synthesized NPs. Their affinity to the cell surface marker in fresh and saltwater conditions was confirmed using two types of cells, murine mesenchymal stromal/stem cell culture and sea anemone stem cells. For this purpose, 106 cells of each type were exposed to NP-conjugated antibodies and their affinity to antibodies was confirmed by an epi-fluorescent microscope. The presence of iron-NPs imaged with the light microscope was confirmed by iron staining using Prussian blue stain. Next, anti-Oct4 antibodies conjugated with iron NPs were injected into a brittle star, and proliferating cells were tracked by MRI. To sum up, anti-Oct4 antibodies conjugated with iron NPs not only have the potential for identifying proliferating stem cells in different cell culture conditions of sea anemone and mouse cell cultures but also has the potential to be used for in vivo MRI tracking of marine proliferating cells.

Divergence in metabolomic profile in clownfish and damselfish skin mucus

IntroductionThe clownfish - sea anemone mutualism was suggested to have triggered the adaptive radiation of clownfishes, but the origin of clownfish resistance to stinging tentacles of host anemones remains unclear. The presence of specific compounds in the mucus of clownfishes conferring them the unique ability to prevent nematocyst discharge from their hosts has been the most supported hypothesis. Yet the mystery regarding the types of compounds found in clownfish skin mucus remains unsolved.MethodsWe analyzed the chemical composition of clownfish and damselfish mucus using an untargeted metabolomics (HILIC-HRMS) and lipidomics (RPLC-HRMS) approach.Results and DiscussionThe polar and lipid metabolome signatures were highly specific and allowed to discriminate between the clownfish and damselfish clades. The most discriminative part of the signature was the sphingolipid profile, displaying a broader diversity of ceramides present in significantly higher levels in clownfish mucus. Importantly, the inter-specific variability of metabolic signature was significantly higher in clownfishes, although their diversification is evolutionarily more recent, thus implying the impact of symbiosis on metabolic variability and adaptation. Furthermore, specialists and generalists clownfish species displayed distinctive metabolite signature. Two strict clownfish specialists, which are phylogenetically distant but share the same host species, clustered together based on their molecular signature, suggesting a link with their mutualistic nature. Overall, comparative analyses of metabolic signatures highlight differences in chemical composition of clownfish mucus and provide insight into biochemical pathways potentially implicated in clownfish adaptation to inhabit sea anemones and consequently diversify.