Rhopilema Nomadica Research Articles

From ctenophores to scyphozoans: parasitic spillover of a burrowing sea anemone

Most host-parasite associations are explained by phylogenetically conservative capabilities for host utilization, and therefore parasite switches between distantly related hosts are rare. Here we report the first evidence of a parasitic spillover of the burrowing sea anemone Edwardsiella carnea from the invasive ctenophore Mnemiopsis leidyi to two scyphozoan hosts: the native Mediterranean barrel jellyfish Rhizostoma pulmo and the invasive Indo-Pacific nomad jellyfish Rhopilema nomadica, collected from the Eastern Mediterranean Sea. Edwardsiella carnea planulae found in these jellyfish were identified using molecular analyses of the mitochondrial 16S and nuclear 18S rRNA genes. Overall, 93 planulae were found on tentacles, oral arms, and inside of the gastrovascular canals of the scyphomedusae, whereas no infection was observed in co-occurring ctenophores. DNA metabarcoding approach indicated seasonal presence of Edwardsiella sp. in the Eastern Mediterranean mesozooplankton, coinciding with jellyfish blooms in the region. Our findings suggest a non-specific parasitic relationship between Edwardsiella carnea and various gelatinous hosts based on shared functionality rather than evolutionary history, potentially driven by shifts in host availability due to jellyfish blooms. This spillover raises questions about the ecological impacts of parasitism on native and invasive scyphozoan hosts and the potential role of Edwardsiella in controlling their populations.

Directional swimming patterns in jellyfish aggregations

Having a profound influence on marine and coastal environments worldwide, jellyfish hold significant scientific, economic, and public interest.1,2,3,4,5 The predictability of outbreaks and dispersion of jellyfish is limited by a fundamental gap in our understanding of their movement. Although there is evidence that jellyfish may actively affect their position,6,7,8,9,10 the role of active swimming in controlling jellyfish movement, and the characteristics of jellyfish swimming behavior, are not well understood. Consequently, jellyfish are often regarded as passively drifting or randomly moving organisms, both conceptually2,11 and in process studies.12,13,14 Here we show that the movement of jellyfish is modulated by distinctly directional swimming patterns that are oriented away from the coast and against the direction of surface gravity waves. Taking a Lagrangian viewpoint from drone videos that allows the tracking of multiple adjacent jellyfish, and focusing on the scyphozoan jellyfish Rhopilema nomadica as a model organism, we show that the behavior of individual jellyfish translates into a synchronized directional swimming of the aggregation as a whole. Numerical simulations show that this counter-wave swimming behavior results in biased correlated random-walk movement patterns that reduce the risk of stranding, thus providing jellyfish with an adaptive advantage critical to their survival. Our results emphasize the importance of active swimming in regulating jellyfish movement and open the way for a more accurate representation in model studies, thus improving the predictability of jellyfish outbreaks and their dispersion and contributing to our ability to mitigate their possible impact on coastal infrastructure and populations.

Long-Term Population Genetic Features of the Rhopilema nomadica Jellyfish from the Israeli Mediterranean Coasts

The rhizostomatid scyphozoan Rhopilema nomadica is one of the most notorious marine invasive species established in the eastern Mediterranean Sea. Using seven microsatellite loci, here, we examined the population genetic structures on 587 individual tissue samples collected from 21 sites along the Mediterranean coast of Israel over a period of 16 years. The results indicate unique microsatellite landscapes for all samples, which belong to a single unstructured population. The >20 alleles found in most loci, low fixation index (F) values (average 0.106), and high heterozygosity (average 0.667) suggest random or assortative mating. Additionally, the low overall differentiation (Fst) values (0.043) and pairwise Fst values between the samples collected in different years indicated gene flow and random mating over the years, potentially due to the long-lasting podocytes, scyphistomae, and adults causing a population overlap between the sampled months/years. Likewise, analyses were conducted between seasons, sites, and early/intermediate/late periods of collecting years. These results support the previous analyses performed on the mitochondrial gene cytochrome oxidase subunit I (COI) sequences, altogether indicating a highly polymorphic single unstructured R. nomadica population in the Levant, possibly backed by independent introductions. The results hint to the existence of highly functional connectivity with a genetically highly diverse source population.

The Anti-Diabetic Effect of Rhopilema nomadica Jellyfish Natural Extracts in Streptozoticin-Induced Type-2 Diabetes Mellitus in Rats

The Anti-Diabetic Effect of Rhopilema nomadica Jellyfish Natural Extracts in Streptozoticin-Induced Type-2 Diabetes Mellitus in Rats

Jellyfish sting web survey: clinical characteristics and management of Rhopilema nomadica envenomation in the Mediterranean Sea

Jellyfish sting web survey: clinical characteristics and management of Rhopilema nomadica envenomation in the Mediterranean Sea

Selecting 16S rRNA Primers for Microbiome Analysis in a Host-Microbe System: The Case of the Jellyfish Rhopilema nomadica.

Amplicon sequencing of the 16S rRNA gene is extensively used to characterize bacterial communities, including those living in association with eukaryotic hosts. Deciding which region of the 16S rRNA gene to analyze and selecting the appropriate PCR primers remains a major decision when initiating any new microbiome study. Based on a detailed literature survey of studies focusing on cnidarian microbiomes, we compared three commonly used primers targeting different hypervariable regions of the 16S rRNA gene, V1V2, V3V4, and V4V5, using the jellyfish Rhopilema nomadica as a model. Although all primers exhibit a similar pattern in bacterial community composition, the performance of the V3V4 primer set was superior to V1V2 and V4V5. The V1V2 primers misclassified bacteria from the Bacilli class and exhibited low classification resolution for Rickettsiales, which represent the second most abundant 16S rRNA gene sequence in all the primers. The V4V5 primer set detected almost the same community composition as the V3V4, but the ability of these primers to also amplify the eukaryotic 18S rRNA gene may hinder bacterial community observations. However, after overcoming the challenges possessed by each one of those primers, we found that all three of them show very similar bacterial community dynamics and compositions. Nevertheless, based on our results, we propose that the V3V4 primer set is potentially the most suitable for studying jellyfish-associated bacterial communities. Our results suggest that, at least for jellyfish samples, it may be feasible to directly compare microbial community estimates from different studies, each using different primers but otherwise similar experimental protocols. More generally, we recommend specifically testing different primers for each new organism or system as a prelude to large-scale 16S rRNA gene amplicon analyses, especially of previously unstudied host-microbe associations.

Selecting 16S rRNA primers for microbiome analysis in a host-microbe system: the case of the jellyfish Rhopilema nomadica

Selecting 16S rRNA primers for microbiome analysis in a host-microbe system: the case of the jellyfish Rhopilema nomadica

Selecting 16S rRNA primers for microbiome analysis in a host-microbe system: the case of the jellyfish Rhopilema nomadica

Selecting 16S rRNA primers for microbiome analysis in a host-microbe system: the case of the jellyfish Rhopilema nomadica

Rising seawater temperatures affect the fitness of Rhopilema nomadica polyps and podocysts and the expansion of this medusa into the western Mediterranean

Since first reported in the eastern Mediterranean in the 1970s, the swarm-forming scyphomedusa, Rhopilema nomadica, has been continuously expanding westward. We examined the effect of temperature on the benthic stages of this jellyfish (polyps, podocysts, and strobilae) to assess whether it can survive and reproduce in the western Mediterranean temperature regime (12.2-26.2°C). In the first experiment, polyps and podocysts were maintained at 4 constant temperatures (12, 18, 24, and 30°C) for 55 d. In the second experiment, temperatures were gradually reduced over 14 d, kept constant for 18 d, and then gradually brought back to 25°C. High temperatures proved beneficial to polyp survival and asexual reproduction, yet in some cases, polyps were able to survive temperatures as low as 12°C. Strobilation occurred at temperatures between 22 and 30°C. Podocyst production, excystment, and strobilation all take place following a temperature increase, and excystment of podocysts occurs mainly during the first 2 wk following podocyst production. We propose that the role of podocysts in R. nomadica is mainly to increase the current season’s polyp population, contributing to swarm formation rather than as a means to maintain polyp populations during harsh environmental conditions. Since polyps are able to survive winter temperatures in the western basin (12°C) and reproduce by podocysts and strobilation during summer temperatures (24°C), thermal constraints will probably not restrict the expansion of R. nomadica into the western Mediterranean. Expected future climate change conditions will increase the performance and range expansion of this species.

Knowledge needs in economic costs of invasive species facilitated by canalisation

Canals provide wide-ranging economic benefits, while also serving as corridors for the introduction and spread of aquatic alien species, potentially leading to negative ecological and economic impacts. However, to date, no comprehensive quantifications of the reported economic costs of these species have been done. Here, we used the InvaCost database on the monetary impact of invasive alien species to identify the costs of those facilitated by three major canal systems: the European Inland Canals, Suez Canal, and Panama Canal. While we identified a staggering number of species having spread via these systems, monetary costs have been reported only for a few. A total of $33.6 million in costs have been reported from species linked to European Inland Canals (the fishhook waterflea Cercopagis pengoi and the zebra mussel Dreissena polymorpha) and $8.6 million linked to the Suez Canal (the silver-cheeked toadfish Lagocephalus sceleratus, the lionfish Pterois miles, and the nomad jellyfish Rhopilema nomadica), but no recorded costs were found for species facilitated by the Panama Canal. We thus identified a pervasive lack of information on the monetary costs of invasions facilitated by canals and highlighted the uneven distribution of costs.

Jellyfish diversity, trends and patterns in Southwestern Mediterranean Sea: a citizen science and field monitoring alliance

Abstract Jellyfish (Cnidaria and Ctenophora) are an essential component of marine ecosystems and represent a potential effect, positive or negative, for several economic activities. Jellyfish blooms and non-indigenous species (NIS) introduction can shift ecological community structure and energy transfer. Despite their importance in ecosystem function and services, knowledge of jellyfish fauna diversity and phenology are largely lacking for the southern Mediterranean Sea. Here, we present an overview of the current state of jellyfish biodiversity in Tunisia. Based on a comprehensive literature survey, historical records and unpublished data, 66 jellyfish species, including 11 non-indigenous species, have been recorded in Tunisia between 1994 and 2020. Additionally, based on field surveys and a citizen science sighting program between 2004 and 2020, we present data on the spatial distribution of 13 conspicuous jellyfish taxa and the phenology of the eight most frequently detected species (Aurelia solida, Cotylorhiza tuberculata, Pelagia noctiluca, Phyllorhiza punctata, Rhizostoma pulmo, Rhopilema nomadica, Olindias muelleri and Velella velella) in Tunisian two ecoregions, the Western Mediterranean and the Tunisian Plateau. The 17 year survey showed a shift in R. pulmo, A. solida and P. noctiluca phenology. Additionally, citizen science revealed an increase in the spatial range of P. punctata (NIS) and the distinct phenologies of populations in the two ecoregions.

Optimization of a Calcium-Based Treatment Method for Jellyfish to Design Food for the Future.

Edible jellyfish are a traditional Southeast Asian food, usually prepared as a rehydrated product using a salt and alum mixture, whereas they are uncommon in Western Countries and considered as a novel food in Europe. Here, a recently developed, new approach for jellyfish processing and stabilization with calcium salt brining was upgraded by modifying the pre-treatment step of freshly caught jellyfish and successfully applied to several edible species. Treated jellyfish obtained by the application of the optimized version of this method respected both quality and safety parameters set by EU law, including no pathogenic microorganisms, absence or negligible levels of histamine and of total volatile basic nitrogen, no heavy metals; and the total bacterial, yeast, and mold counts were either negligible or undetectable. Jellyfish treated by the presented method exhibited unique protein content, amino acid and fatty acid profiles, antioxidant activity, and texture. The optimized method, initially set up on Rhiszostoma pulmo, was also successfully applied to other edible jellyfish species (such as Cotylorhiza tuberculata, Phyllorhiza punctata, and Rhopilema nomadica) present in the Mediterranean Sea. This study discloses an innovative process for the preparation of jellyfish-based food products for potential future distribution in Europe.

Tracking Jellyfish Swarm Origins Using a Combined Oceanographic-Genetic-Citizen Science Approach

Biological invasions of jellyfish may critically affect ecosystems and ecosystem services, yet their complex life cycle makes tracking their origins and dispersal vectors a challenging task. Here we combine citizen science observations, oceanographic modeling, and population genetics to track swarms of the invasive nomad jellyfish,Rhopilema nomadica, across the Eastern Mediterranean Sea. Jellyfish observations were recorded by citizens from two Israeli beaches in two consecutive years. A Lagrangian model coupled with a high-resolution 3D hydrodynamic model (SINMOD) was then used to simulate drift of ephyrae from probable polyp bed locations. Finally, mitochondrial DNA (mtDNA) sequence was constructed to examine swarm connectivity. Temporal (both seasonal and interannual) variation in observed swarms generally exceeded spatial differences between the two surveyed beaches. Early detection of swarms by citizens in offshore waters and the higher offshore particle distribution shown by the drift model, point to considerable offshore transport of the swarms. However, a higher probability was found for a nearshore location of the polyp beds, as nearshore origins were more closely correlated to hits on target beaches.R. nomadicareleased as ephyrae in early spring were likely to reach target beaches 200-300 km down current within two to three months as swarms of young adults in the early summer bathing season.R. nomadicapopulations exhibited little temporal or spatial genetic differentiation, a typical feature of a species that has recently undergone rapid population expansion. The offshore transport, the lack of genetic structure, and the interannual differences in both hydrodynamics and citizen scientist observations, all indicate decentralized swarm origins. This type of interdisciplinary approach can thus provide viable tools to track bloom formations. Understanding the complexity of jellyfish swarm dynamics supports future management strategies such as forecasting, preparedness and public education.

Rhopilema nomadica (nomad jellyfish)

This datasheet on Rhopilema nomadica covers Identity, Overview, Distribution, Dispersal, Diagnosis, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Uses, Prevention/Control, Further Information.

Nomad Jellyfish Rhopilema nomadica Venom Induces Apoptotic Cell Death and Cell Cycle Arrest in Human Hepatocellular Carcinoma HepG2 Cells.

Jellyfish venom is a rich source of bioactive proteins and peptides with various biological activities including antioxidant, antimicrobial and antitumor effects. However, the anti-proliferative activity of the crude extract of Rhopilema nomadica jellyfish venom has not been examined yet. The present study aimed at the investigation of the in vitro effect of R. nomadica venom on liver cancer cells (HepG2), breast cancer cells (MDA-MB231), human normal fibroblast (HFB4), and human normal lung cells (WI-38) proliferation by using MTT assay. The apoptotic cell death in HepG2 cells was investigated using Annexin V-FITC/PI double staining-based flow cytometry analysis, western blot analysis, and DNA fragmentation assays. R. nomadica venom displayed significant dose-dependent cytotoxicity on HepG2 cells after 48 h of treatment with IC50 value of 50 μg/mL and higher toxicity (3:5-fold change) against MDA-MB231, HFB4, and WI-38 cells. R. nomadica venom showed a prominent increase of apoptosis as revealed by cell cycle arrest at G2/M phase, upregulation of p53, BAX, and caspase-3 proteins, and the down-regulation of anti-apoptotic Bcl-2 protein and DNA fragmentation. These findings suggest that R. nomadica venom induces apoptosis in hepatocellular carcinoma cells. To the best of the authors’ knowledge, this is the first scientific evidence demonstrating the induction of apoptosis and cell cycle arrest of R. nomadica jellyfish venom.

Respiration Rates, Metabolic Demands and Feeding of Ephyrae and Young Medusae of the Rhizostome Rhopilema nomadica

Jellyfish (cnidarians and ctenophores) affect the marine food web through high feeding rates and feeding efficiency, but in contrast to their great importance in the ecosystem, our knowledge of their dietary requirements is limited. Here we present the results of respiratory and feeding trials of the rhizostome Rhopilema nomadica, the dominant scyphozoan in the waters of the Eastern Mediterranean, which often establishes massive swarms, mainly in the summer months. Through multiple measurements of oxygen demand in R. nomadica at bell diameters of 3–49 mm, we were able to assess its minimum energetic requirements. These, and the results of the feeding trials on individuals of the same bell diameter range, show that R. nomadica is a very efficient predator. When presented with prey concentrations of 100 prey items per liter, a single hourly feeding session provided between 1.15 and 3 times the estimated daily basal carbon requirement. Our findings suggest that R. nomadica is well adapted to its environment, the hyperoligotrophic waters of the eastern Mediterranean, able to efficiently exploit patches of plankton, possibly at rates even higher than what we observed under laboratory conditions.

Long-term changes in population genetic features of a rapidly expanding marine invader: implication for invasion success

Large blooms of Rhopilema nomadica, a highly venomous rhizostamatid scyphozoan species introduced to the Mediterranean through the Suez Canal, have become ubiquitous in the summer and winter months along the Israeli coasts since the mid-1980s. This species has since spread across the eastern Mediterranean and was sighted as far west as Tunisia and Sardinia. For the past 12 years, we have studied changes in the mitochondrial COI haplotypes diversity of R. nomadica to investigate small scale fluctuactions of genetic diversity and to reveal possible genetic structuring of the fast spreading invader in the Eastern Mediterranean. The 1091 COI sequences analysed, revealed a highly diverse population displaying 89 haplotypes, 46 of which appeared as singletons, low frequency haplotypes. All the specimens analysed throughout the period belong to a single unstructured population. Though lacking data from the source population in the Red Sea, the high within-population diversity and the high diversity of COI haplotypes support the hypothesis of multiple introductions events, or an open corridor with a continuous influx of propagules. Tajima’s D and Fu’s Fst negative values and the increased numbers of COI singletons from early to late sampling periods, have verified that the Israeli population is characterized by a rapid expanding population. Further research is needed for the evaluation of COI diversity and patterns in R. nomadica populations across the eastern Mediterranean Sea and Red Sea, as well as any correlation of the high variability between COI locus and phenotypic diversity.

The effects of decomposing invasive jellyfish on biogeochemical fluxes and microbial dynamics in an ultra-oligotrophic sea

Abstract. Over the past several decades, jellyfish blooms have intensified spatially and temporally, affecting functions and services of ecosystems worldwide. At the demise of a bloom, an enormous amount of jellyfish biomass sinks to the seabed and decomposes. This process entails reciprocal microbial and biogeochemical changes, typically enriching the water column and seabed with large amounts of organic and inorganic nutrients. Jellyfish decomposition was hypothesized to be particularly important in nutrient-impoverished ecosystems, such as the Eastern Mediterranean Sea – one of the most oligotrophic marine regions in the world. Since the 1970s, this region has been experiencing the proliferation of a notorious invasive scyphozoan jellyfish, Rhopilema nomadica. In this study, we estimated the short-term decomposition effects of R. nomadica on nutrient dynamics at the sediment–water interface. Our results show that the degradation of R. nomadica has led to increased oxygen demand and acidification of overlying water as well as high rates of dissolved organic nitrogen and phosphate production. These conditions favored heterotrophic microbial activity and bacterial biomass accumulation, and triggered a shift towards heterotrophic biodegrading bacterial communities, whereas autotrophic picophytoplankton abundance was moderately affected or reduced. This shift may further decrease primary production in the water column of the Eastern Mediterranean Sea. Deoxygenation, acidification, nutrient enrichment, and microbial community shifts at the sediment–water interface may have a detrimental impact on macrobenthic communities. Based on these findings, we suggest that jelly-falls and their decay may facilitate an additional decline in ecosystem functions and services.

Diet composition and some observations on the feeding ecology of the rhizostome Rhopilema nomadica in Israeli coastal waters

AbstractSince the mid-1980s, swarms of the rhizostome Rhopilema nomadica have been an annual phenomenon in Israeli Mediterranean coastal waters during the summer months. Despite its annual prominence and the potential impact on food webs and ecosystem services, studies concerning its feeding ecology and its interactions with other biota in the marine food web have not been conducted. During summer 2015 gut contents of 41 R. nomadica were analysed as well as ambient plankton assemblages. More than 60% of the medusae diet was found to consist of microzooplankton <150 μm. Size correlations revealed that larger R. nomadica consumed faster swimming prey while smaller medusae relied more on the slower swimming taxa. The medusan diet reflected most of the ambient plankton taxa, but no statistically significant correlations between the relative abundance in diet and ambient plankton were found. As summer progressed, there was a gradual decrease in both mean medusa bell diameter (from 42.2–16 cm) and integrity of feeding structures. These findings suggest that R. nomadica, at least at the time of its appearance in Israeli coastal waters, may exert less predatory pressure on the plankton than we might otherwise expect.

Developing novel microsatellite markers by NGS technology for Rhopilema nomadica, an invasive jellyfish.

Twelve microsatellite loci, obtained by whole genome sequencing approach, were developed and validated for the rhizostomatid jellyfish Rhopilema nomadica, the most pernicious invasive species in the Mediterranean Sea. A sample of 40 specimens collected at six locations along the Mediterranean coast of Israel were genotyped and all loci presented suitable outcomes to population genetic studies, revealing 5-19 alleles/locus with clean and reproducible amplifications. Observed and expected heterozygosity ranged 0.0.353 to 0.971 and 0.335 to 0.870, respectively, and the fixation index (inbreeding coefficient) and the polymorphic information content (PIC) ranged between - 0.190 and 0.240 and 0.32 to 0.858, respectively. The new set of microsatellite loci will be used to study long-term changes in the population genetic parameters of this invasive species.