Sea Anemone Research Articles

Early social isolation disrupts adult personality expression in group-living mites.

Animal personalities are characterized by intra-individual consistency and consistent inter-individual variability in behaviour across time and contexts. Personalities abound in animals, ranging from sea anemones to insects, arachnids, birds, fish and primates, yet the pathways mediating personality formation and expression remain elusive. Social conditions during the early postnatal period are known determinants of mean behavioural trait expressions later in life, but their relevance in shaping personality trajectories is unknown. Here, we investigated the consequences of early social isolation on adult personality expression in plant-inhabiting predatory mites Phytoseiulus persimilis. These mites are adapted to live in groups. We hypothesized that transient experience of social isolation early in life, that is, deprivation of any social contact during a sensitive window in the post-hatching phase, has enduring adverse effects on adult personality expression. Newly hatched mites were transiently reared in isolation or in groups and tested as adults for repeatability of various within-group behaviours, such as movement patterns and mutual interactions including sociability, defined as the propensity to associate and interact benignly with conspecifics, and activity patterns when alone. Groups composed of individuals with the same or different early-life experiences were repeatedly videotaped and individual behaviours were automatically analysed using AnimalTA. Social experiences early in life had persistent effects on mean behavioural traits as well as adult personality expression, as measured by intraclass correlation coefficients (indicating repeatability). On average, isolation-reared females moved at higher speeds, meandered less, kept greater distances from others and had fewer immediate neighbours than group-reared females. Group-reared females were highly repeatable in inter-individual distance, moving speed, meandering and area explored, whereas isolation-reared females were repeatable only in the number of immediate neighbours. Activity, quantified as the proportion of time spent moving within groups, was only repeatable in group-reared females, whereas activity, quantified as the proportion of time spent moving when alone, was only repeatable in females reared in isolation. Strikingly, also the early-life experiences of male mates influenced personality expression of mated females, with isolation-reared males boosting the repeatability of behavioural traits of group-reared females. Overall, our study provides evidence that a transient phase of social isolation during a critical period early in life has lasting effects that extend into adulthood, impairing adult personality expression. These effects should cascade upward, changing the phenotypic composition and diversity within populations.

Chromosome-level genome assembly of a deep-sea Venus flytrap sea anemone sheds light upon adaptations to an extremely oligotrophic environment.

The Venus flytrap sea anemone Actinoscyphia liui inhabits the nutrient-limited deep ocean in the tropical western Pacific. Compared with most other sea anemones, it has undergone a distinct modification of body shape similar to that of the botanic flytrap. However, the molecular mechanism by which such a peculiar sea anemone adapts to a deep-sea oligotrophic environment is unknown. Here, we report the chromosomal-level genome of A. liui constructed from PacBio and Hi-C data. The assembled genome is 522 Mb in size and exhibits a continuous scaffold N50 of 58.4 Mb. Different from most other sea anemones, which typically possess 14-18 chromosomes per haplotype, A. liui has only 11. The reduced number of chromosomes is associated with chromosome fusion, which likely represents an adaptive strategy to economize energy in oligotrophic deep-sea environments. Comparative analysis with other deep-sea sea anemones revealed adaptive evolution in genes related to cellular autophagy (TMBIM6, SESN1, SCOCB and RPTOR) and mitochondrial energy metabolism (MDH1B and KAD2), which may aid in A. liui coping with severe food scarcity. Meanwhile, the genome has undergone at least two rounds of expansion in gene families associated with fast synaptic transmission, facilitating rapid responses to water currents and prey. Positive selection was detected on putative phosphorylation sites of muscle contraction-related proteins, possibly further improving feeding efficiency. Overall, the present study provides insights into the molecular adaptation to deep-sea oligotrophic environments and sheds light upon potential effects of a novel morphology on the evolution of Cnidaria.

Nanos2 marks precursors of somatic lineages and is required for germline formation in the sea anemone Nematostella vectensis.

In animals, stem cell populations of varying potency facilitate regeneration and tissue homeostasis. Notably, germline stem cells in both vertebrates and invertebrates express highly conserved RNA binding proteins, such as nanos, vasa, and piwi. In highly regenerative animals, these genes are also expressed in somatic stem cells, which led to the proposal that they had an ancestral role in all stem cells. In cnidarians, multi- and pluripotent interstitial stem cells have only been identified in hydrozoans. Therefore, it is currently unclear if cnidarian stem cell systems share a common evolutionary origin. We, therefore, aimed to characterize conserved stem cell marker genes in the sea anemone Nematostella vectensis. Through transgenic reporter genes and single-cell transcriptomics, we identify cell populations expressing the germline-associated markers piwi1 and nanos2 in the soma and germline, and gene knockout shows that Nanos2 is indispensable for germline formation. This suggests that nanos and piwi genes have a conserved role in somatic and germline stem cells in cnidarians.

LRRK2 kinase activity is necessary for development and regeneration in Nematostella vectensis

BackgroundThe starlet sea anemone, Nematostella vectensis, is an emerging model organism with a high regenerative capacity, which was recently found to possess an orthologue to the human Leucine Rich Repeat Kinase 2 (LRRK2) gene. Mutations in this gene are the most common cause of inherited Parkinson’s Disease (PD), highlighting the importance of understanding its function. Despite two decades of research, however, the function of LRRK2 is not well established.MethodsTo investigate the function of LRRKs in Nematostella vectensis, we applied small molecule inhibitors targeting the kinase activity of LRRK2 to examine its function in development, homeostasis and regeneration in Nematostella vectensis.ResultsIn vivo analyses inhibiting the kinase function of this enzyme demonstrated a role of nvLRRK2 in development and regeneration of N. vectensis. These findings implicate a developmental role of LRRK2 in Nematostella, adding to the expanding knowledge of its physiological function.ConclusionsOur work introduces a new model organism with which to study LRRK biology. We report that LRRK kinase activity is necessary for the development and regeneration of Nematostella. Given the short generation time, genetic trackability and in vivo imaging capabilities, this work introduces Nematostella vectensis as a new model in which to study genes linked to neurodegenerative diseases such as Parkinson’s.

Connections on the Reef: Clownfish, Anemones, and Climate Change

From their adorable name to their leading role in the movie Finding Nemo, many people find clownfish, also called anemonefish, cute and lovable. Clownfish must live in animals called sea anemones to survive on a coral reef. For 19 years, we followed two-banded anemonefish off the coast of Israel in the Gulf of Eilat (Aqaba), Red Sea. Based on their size, we divided the fish into adults, teens, and babies. In 1997, 195 fish of all ages lived at the site. By 2015, 52 fish—mostly adults—remained, a 74% drop. From 1997 to 2015, the number of sea anemones also fell from 199 to only 27, and each one was more crowded with anemonefish. Climate change may affect sea anemone survival. Without their sea anemone homes, clownfish cannot exist, raising concerns about their future.

Multiple aortic valve papillary fibroelastomas causing recurrent cerebrovascular events

IntroductionPapillary fibroelastomas (PFE) are benign, rare primary cardiac tumors often discovered incidentally during cardiac imaging or as part of a workup for thromboembolic or obstructive events. We present a case of multiple PFE on the aortic valve's right coronary and non-coronary leaflets, presenting as recurrent cerebrovascular events managed by resection with valve preservation. Case SummaryA 53-year-old male presented with an acute right frontal cerebrovascular accident and a history of recurrent transient ischemic attacks. A transesophageal echocardiogram (TEE) revealed a 10 × 8 mm mass on the right coronary cusp of the aortic valve. Differential diagnosis included PFE versus thrombus. Following a neurology evaluation, the patient was anticoagulated and scheduled for urgent cardiac surgery. During surgery, an 8 × 7 mm mass was sharply excised from the right coronary leaflet's anterior surface. Further examination revealed additional masses: a 3 mm mass on the underside of the right coronary leaflet, a 2 mm mass on the non-coronary leaflet, and another 2 mm mass on its underside. All masses were excised, and pathology confirmed the diagnosis of PFE. The patient's post-operative course was unremarkable, and a pre-discharge transthoracic echocardiogram (TTE) demonstrated complete removal of the aortic valve masses with normal ventricular and aortic valve function. DiscussionPFE are rare benign cardiac tumors with a significant risk of thromboembolic or obstructive events, including stroke. Grossly, they are attached to the endocardium by a short fibrous pedicle with multiple papillary fronds resembling a sea anemone. More than 95 % originate from the left heart, most commonly affecting the aortic valve. Diagnosis is primarily through echocardiography, with TEE being more sensitive than TTE. Surgical excision is curative, offering an excellent long-term prognosis. ConclusionAll patients with suspected embolic cerebrovascular events should undergo echocardiographic evaluation to assess for potential cardiac etiologies. Surgical resection of PFE results in uniformly excellent clinical outcomes, with aortic valve preservation achievable in over 98 % of cases.

Effect of Crude Extract from the Sea Anemone Bunodeopsis globulifera on Voltage-Gated Ion Channels from Central and Peripheral Murine Nervous Systems.

Sea anemones are an important source of bioactive compounds with potential pharmacological applications. Their toxins are produced and stored in organelles called nematocysts and act on specific targets, including voltage-gated ion channels. To date, sea anemone toxins have demonstrated effects on voltage-gated sodium and potassium channels, facilitating investigations into the structure and function of these proteins. In this study, we evaluated the effect of Bunodeopsis globulifera sea anemone crude extract, and of a low molecular weight fraction, on voltage-gated sodium and calcium channels within the murine nervous system. Notably, the crude extract led to a significant reduction in total sodium current, while also triggering calcium-dependent glutamate release. Furthermore, the low molecular weight fraction, in particular, enhanced total calcium currents and current density. These findings underscore the existence of sea anemone toxins with diverse mechanisms of action beyond those previously documented.

Microhabitat acclimatization alters sea anemone-algal symbiosis and thermal tolerance across the intertidal zone.

Contemporary symbioses in extreme environments can give an insight into mechanisms that stabilize species interactions during environmental change. The intertidal sea anemone, Anthopleura elegantissima, engages in a nutritional symbiosis with microalgae similar to tropical coral, but withstands more intense environmental fluctuations during tidal inundations. In this study, we compare baseline symbiotic traits and their sensitivity to thermal stress within and among anemone aggregations across the intertidal using a laboratory-based tank experiment to better understand how fixed genotypic and plastic environmental effects contribute to the successful maintenance of this symbiosis in extreme habitats. High intertidal anemones had lower baseline symbiont-to-host cell ratios under control conditions, but their symbionts had higher baseline photosynthetic efficiency compared to low intertidal anemone symbionts. Symbiont communities were identical across all samples, suggesting that shifts in symbiont density and photosynthetic performance could be an acclimatory mechanism to maintain symbiosis in different environments. Despite lower baseline symbiont-to-host cell ratios, high intertidal anemones maintained greater symbiont-to-host cell ratios under heat stress compared with low intertidal anemones, suggesting greater thermal tolerance of high intertidal holobionts. However, the thermal tolerance of clonal anemones acclimatized to different zones was not explained by tidal height alone, indicating additional environmental variables contribute to physiological differences. Host genotype significantly influenced anemone weight, but only explained a minor proportion of variation among symbiotic traits and their response to thermal stress, further implicating environmental history as the primary driver of holobiont tolerance. These results indicate that this symbiosis is highly plastic and may be able to acclimatize to climate change over ecological timescales, defying the convention that symbiotic organisms are more susceptible to environmental stress.

Arctic benthos in the Anthropocene: Distribution and drivers of epifauna in West Greenland

Albeit remote, Arctic benthic ecosystems are impacted by fisheries and climate change. Yet, anthropogenic impacts are poorly understood, as benthic ecosystems and their drivers have not been mapped over large areas. We disentangle spatial patterns and drivers of benthic epifauna (animals living on the seabed surface) in West Greenland, by integrating an extensive beam-trawl dataset (326 stations, 59–75°N, 30–1400 m water depth) with environmental data. We find high variability at different spatial scales: (1) Epifauna biomass decreases with increasing latitude, sea-ice cover and water depth, related to food limitation. (2) In Greenland, the Labrador Sea in the south shows higher epifauna taxon richness compared to Baffin Bay in the north. Τhe interjacent Davis Strait forms a permeable boundary for epifauna dispersal and a mixing zone for Arctic and Atlantic taxa, featuring regional biodiversity hotspots. (3) The Labrador Sea and Davis Strait provide suitable habitats for filter-feeding epifauna communities of high biomass e.g., sponges on the steep continental slope and sea cucumbers on shallow banks. In Baffin Bay, the deeper continental shelf, more gentle continental slope, lower current speed and lower phytoplankton biomass promote low-biomass epifauna communities, predominated by sea stars, anemones, or shrimp. (4) Bottom trawling reduces epifauna biomass and taxon richness throughout the study area, where sessile filter feeders are particularly vulnerable. Climate change with diminished sea ice cover in Baffin Bay may amplify food availability to epifauna, thereby increasing their biomass. While more species might expand northward due to the general permeability of Davis Strait, an extensive colonization of Baffin Bay by high-biomass filter-feeding epifauna remains unlikely, given the lack of suitable habitats. The pronounced vulnerability of diverse and biomass-rich epifauna communities to bottom trawling emphasizes the necessity for an informed and sustainable ecosystem-based management in the face of rapid climate change.

A non-toxic equinatoxin-II reveals the dynamics and distribution of sphingomyelin in the cytosolic leaflet of the plasma membrane

Sphingomyelin (SM) is a major sphingolipid in mammalian cells. SM is enriched in the extracellular leaflet of the plasma membrane (PM). Besides this localization, recent electron microscopic and biochemical studies suggest the presence of SM in the cytosolic leaflet of the PM. In the present study, we generated a non-toxic SM-binding variant (NT-EqtII) based on equinatoxin-II (EqtII) from the sea anemone Actinia equina, and examined the dynamics of SM in the cytosolic leaflet of living cell PMs. NT-EqtII with two point mutations (Leu26Ala and Pro81Ala) had essentially the same specificity and affinity to SM as wild-type EqtII. NT-EqtII expressed in the cytosol was recruited to the PM in various cell lines. Super-resolution microscopic observation revealed that NT-EqtII formed tiny domains that were significantly colocalized with cholesterol and N-terminal Lyn. Meanwhile, single molecule observation at high resolutions down to 1 ms revealed that all the examined lipid probes including NT-EqtII underwent apparent fast simple Brownian diffusion, exhibiting that SM and other lipids in the cytosolic leaflet rapidly moved in and out of domains. Thus, the novel SM-binding probe demonstrated the presence of the raft-like domain in the cytosolic leaflet of living cell PMs.

Molecular Insights into the Low Complexity Secreted Venom of Calliactis polypus.

Sea anemones are venomous animals that rely on their venom for prey capture, defense against predators, and intraspecific competition. Currently, comprehensive molecular and evolutionary analyses of the toxin repertoire for sea anemones are limited by a lack of proteomic data for most species. In this study, proteo-transcriptomic analysis was used to expand our knowledge of the proteinaceous components of sea anemone venom by determining the secreted venom proteome of Calliactis polypus. Electromechanical stimulation was used to obtain the secreted venom of C. polypus. We identified a low complexity proteome that was dominated by toxins with similarity to known neurotoxins, as well as six novel toxin candidates. The novel putative toxin candidates were found to be taxonomically restricted to species from the superfamily Metridioidea. Furthermore, the secreted venom of C. polypus had only three putative toxins in common with the venom of acontia from the same species and little similarity with the secreted venom of closely related species. Overall, this demonstrates that regionalized and lineage-specific variability in toxin abundance is common among sea anemone species. Moreover, the limited complexity of the toxin repertoire found in C. polypus supports the idea that peptide neurotoxins make up the dominant toxin arsenal found in the venom of sea anemones.

Sea anemones (Actinia equina) show consistent individual differences in boldness and thoroughness but lack a behavioural syndrome.

Behavioural syndromes are suites of behaviours that corelate between-individuals but the same behaviours may also show within-individual correlations owing to state dependency or trade-offs. Therefore, overall phenotypic behavioural correlations must be separated into their between- and within-individual components. We investigate how startle response duration (an index of boldness) and time taken to reject an inert item (an index of investigation thoroughness) covary in beadlet sea anemones, Actinia equina. Anemones took longer to reject a more complex item compared to a simpler one, validating this measure of investigation thoroughness. We then quantified between- and within-individual correlations using a Bayesian analysis and an alternative frequentist analysis, which returned the same results. Startle responses decreased with anemone size while thoroughness decreased across repeated observations, indicative of simple learning. For each behaviour, repeatability was significant but relatively low and there was no behavioural syndrome. Rather, the two behaviours showed a negative within-individual correlation in most individuals. Thus, boldness and thoroughness are unlikely to be under correlative selection, and they may instead be expressed independently, in line with the general pattern that cross-contextual behavioural syndromes are comparatively rare. It now appears that this pattern may extend broadly across animal diversity.

Induction of apoptosis by double-stranded RNA was present in the last common ancestor of cnidarian and bilaterian animals.

Apoptosis, a major form of programmed cell death, is an essential component of host defense against invading intracellular pathogens. Viruses encode inhibitors of apoptosis to evade host responses during infection, and to support their own replication and survival. Therefore, hosts and their viruses are entangled in a constant evolutionary arms race to control apoptosis. Until now, apoptosis in the context of the antiviral immune system has been almost exclusively studied in vertebrates. This limited phyletic sampling makes it impossible to determine whether a similar mechanism existed in the last common ancestor of animals. Here, we established assays to probe apoptosis in the sea anemone Nematostella vectensis, a model species of Cnidaria, a phylum that diverged approximately 600 million years ago from the rest of animals. We show that polyinosinic:polycytidylic acid (poly I:C), a synthetic long double-stranded RNA mimicking viral RNA and a primary ligand for the vertebrate RLR melanoma differentiation-associated protein 5 (MDA5), is sufficient to induce apoptosis in N. vectensis. Furthermore, at the transcriptomic level, apoptosis related genes are significantly enriched upon poly(I:C) exposure in N. vectensis as well as bilaterian invertebrates. Our phylogenetic analysis of caspase family genes in N. vectensis reveals conservation of all four caspase genes involved in apoptosis in mammals and revealed a cnidarian-specific caspase gene which was strongly upregulated. Altogether, our findings suggest that apoptosis in response to a viral challenge is a functionally conserved mechanism that can be traced back to the last common ancestor of Bilateria and Cnidaria.

Proteomes of native and non-native symbionts reveal responses underpinning host-symbiont specificity in the cnidarian-dinoflagellate symbiosis.

Cellular mechanisms responsible for the regulation of nutrient exchange, immune responses, and symbiont population growth in the cnidarian-dinoflagellate symbiosis are poorly resolved, particularly with respect to the dinoflagellate symbiont. Here, we characterized proteomic changes in the native symbiont Breviolum minutum during colonization of its host sea anemone Exaiptasia diaphana ("Aiptasia"). We also compared the proteome of this native symbiont in the established symbiotic state with that of a non-native symbiont, Durusdinium trenchii. The onset of symbiosis between Aiptasia and Breviolum minutum increased the accumulation of symbiont proteins associated with the acquisition of inorganic carbon and photosynthesis, nitrogen metabolism, micro- and macronutrient starvation, suppression of host immune responses, tolerance to low pH, and management of oxidative stress. Such responses are consistent with a functional, persistent symbiosis. In contrast, D. trenchii predominantly showed elevated levels of immunosuppressive proteins, consistent with the view that this symbiont is an opportunist that forms a less beneficial, less well-integrated symbiosis with this model anemone. By adding symbiont analysis to the already known responses of the host proteome, our results provide a more holistic view of cellular processes that determine host-symbiont specificity and how differences in symbiont partners (i.e. native versus non-native symbionts) may impact the fitness of the cnidarian-dinoflagellate symbiosis.

The cellular basis of feeding-dependent body size plasticity in sea anemones.

Many animals share a lifelong capacity to adapt their growth rates and body sizes to changing environmental food supplies. However, the cellular and molecular basis underlying this plasticity remains only poorly understood. We therefore studied how the sea anemones Nematostella vectensis and Aiptasia (Exaiptasia pallida) respond to feeding and starvation. Combining quantifications of body size and cell numbers with mathematical modelling, we observed that growth and shrinkage rates in Nematostella are exponential, stereotypic and accompanied by dramatic changes in cell numbers. Notably, shrinkage rates, but not growth rates, are independent of body size. In the facultatively symbiotic Aiptasia, we show that growth and cell proliferation rates are dependent on the symbiotic state. On a cellular level, we found that >7% of all cells in Nematostella juveniles reversibly shift between S/G2/M and G1/G0 cell cycle phases when fed or starved, respectively. Furthermore, we demonstrate that polyp growth and cell proliferation are dependent on TOR signalling during feeding. Altogether, we provide a benchmark and resource for further investigating the nutritional regulation of body plasticity on multiple scales using the genetic toolkit available for Nematostella.

Social predation by a nudibranch mollusc.

Social predation is a common strategy used by predators to subdue and consume prey. Animals that use this strategy have many ways of finding each other, organizing behaviors and consuming prey. There is wide variation in the extent to which these behaviors are coordinated and the stability of individual roles. This study characterizes social predation by the nudibranch mollusc, Berghia stephanieae, which is a specialist predator that eats only the sea anemone, Exaiptasia diaphana. A combination of experimental and modeling approaches showed that B. stephanieae does predate upon E. diaphana in groups. The extent of social feeding was not altered by length of food deprivation, suggesting that animals are not shifting strategies based on internal state. It was unclear what cues the individual Berghia used to find each other; choice assays testing whether they followed slime trails, were attracted to injured anemones, or preferred conspecifics feeding did not reveal any cues. Individuals did not exhibit stable roles, such as leader or follower, rather the population exhibited fission-fusion dynamics with temporary roles during predation. Thus, the Berghia provides an example of a specialist predator of dangerous prey that loosely organizes social feeding, which persists across hunger states and uses temporary individual roles; however, the cues that it uses for aggregation are unknown.

Prospects of Sea Anemone Peptides for Pharmacology

It has been found that the genes of a number of protein components of sea anemone venoms underwent significant diversification in the course of evolution. The elucidation of the molecular mechanisms of sea anemone peptides interactions with targets let investigators in the last decade actively study the molecular organization and the functioning mechanisms of cytoplasmic membranes, the various types and subtypes of ion channels/receptors involved in the processes of perception, processing, intra- and intercellular signal transduction, both in a body physiological and pathological state. A short characteristic of the structure and functional activity of several classes of sea anemone peptide components, which have pronounced pharmacological potential, is presented in this mini-review.

Intelligent Soft Quasi‐Organism Equipped with Sensor‐Driven Integrated Tentacles

AbstractIntegration of soft electronic system components is critical to create a closed‐loop system that seamlessly integrates sensing, driving, processing, and autonomous control capabilities. However, the existence of these components, particularly sensors and actuators, in isolated or discrete forms complicates the endeavor to achieve seamless interface matching and in situ integration, no more than the autonomic system. Here, an intelligent soft quasi‐organism (SQO) equipped with sensor‐driven integrated tentacles is demonstrated, featuring real‐time state recognition and autonomous object recognition inspired by the sea anemones. By employing a heterogeneous mechanisms homotopic integration (HMHI) strategy, the tentacles of the SQO possess the unique ability to simultaneously perceive state changes and flexibly drive motions, utilizing the same material and structure. The sea anemone‐shaped SQO exhibits real‐time autonomous state identification capabilities through the integration of machine learning and customized circuits, attaining 100% recognition accuracy across sixteen states. With a neuromuscular system that facilitates active autonomous perception, the anemone‐shaped SQO can recognize and intelligently grasp static objects with an accuracy of 80.7%, surpassing that of a human hand (74.7%). The SQO provides a promising approach for realizing artificial neuromuscular systems, with great potential for applications in crucial areas such as intelligent soft robotics and in vivo therapy.

Doublecortin-like kinase is required for cnidocyte development in Nematostella vectensis

The complex morphology of neurons requires precise control of their microtubule cytoskeleton. This is achieved by microtubule-associated proteins (MAPs) that regulate the assembly and stability of microtubules, and transport of molecules and vesicles along them. While many of these MAPs function in all cells, some are specifically or predominantly involved in regulating microtubules in neurons. Here we use the sea anemone Nematostella vectensis as a model organism to provide new insights into the early evolution of neural microtubule regulation. As a cnidarian, Nematostella belongs to an outgroup to all bilaterians and thus occupies an informative phylogenetic position for reconstructing the evolution of nervous system development. We identified an ortholog of the microtubule-binding protein doublecortin-like kinase (NvDclk1) as a gene that is predominantly expressed in neurons and cnidocytes (stinging cells), two classes of cells belonging to the neural lineage in cnidarians. A transgenic NvDclk1 reporter line revealed an elaborate network of neurite-like processes emerging from cnidocytes in the tentacles and the body column. A transgene expressing NvDclk1 under the control of the NvDclk1 promoter suggests that NvDclk1 localizes to microtubules and therefore likely functions as a microtubule-binding protein. Further, we generated a mutant for NvDclk1 using CRISPR/Cas9 and show that the mutants fail to generate mature cnidocytes. Our results support the hypothesis that the elaboration of programs for microtubule regulation occurred early in the evolution of nervous systems.

Microbiome depletion and recovery in the sea anemone, Exaiptasia diaphana, following antibiotic exposure.

Microbial species that comprise host-associated microbiomes play an essential role in maintaining and mediating the health of plants and animals. While defining the role of individual or even complex communities is important toward quantifying the effect of the microbiome on host health, it is often challenging to develop causal studies that link microbial populations to changes in host fitness. Here, we investigated the impacts of reduced microbial load following antibiotic exposure on the fitness of the anemone, Exaiptasia diaphana and subsequent recovery of the host's microbiome. Anemones were exposed to two different types of antibiotic solutions for 3 weeks and subsequently held in sterilized seawater for a 3-week recovery period. Our results revealed that both antibiotic treatments reduced the overall microbial load during and up to 1 week post-treatment. The observed reduction in microbial load was coupled with reduced anemone biomass, halted asexual reproduction rates, and for one of the antibiotic treatments, the partial removal of the anemone's algal symbiont. Finally, our amplicon sequencing results of the 16S rRNA gene revealed that anemone bacterial composition only shifted in treated individuals during the recovery phase of the experiment, where we also observed a significant reduction in the overall diversity of the microbial community. Our work implies that the E. diaphana's microbiome contributes to host fitness and that the recovery of the host's microbiome following disturbance with antibiotics leads to a reduced, but stable microbial state.IMPORTANCEExaiptasia diaphana is an emerging model used to define the cellular and molecular mechanisms of coral-algal symbioses. E. diaphana also houses a diverse microbiome, consisting of hundreds of microbial partners with undefined function. Here, we applied antibiotics to quantify the impact of microbiome removal on host fitness as well as define trajectories in microbiome recovery following disturbance. We showed that reduction of the microbiome leads to negative impacts on host fitness, and that the microbiome does not recover to its original composition while held under aseptic conditions. Rather the microbiome becomes less diverse, but more consistent across individuals. Our work is important because it suggests that anemone microbiomes play a role in maintaining host fitness, that they are susceptible to disturbance events, and that it is possible to generate gnotobiotic individuals that can be leveraged in microbiome manipulation studies to investigate the role of individual species on host health.