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Scyphozoan medusae are critical components of marine ecosystems; however, our knowledge on their population dynamics and life history needed to understand their role on ecosystem functioning is relatively scarce. We used data from fish-stock assessment cruises (1993–2013), artisanal fisheries and stranding events (2006–2007), to assess spatio-temporal variation in biomass, growth and reproduction, of a large and abundant scyphomedusae (Lychnorhiza lucerna) in a productive estuarine ecosystem (Río de la Plata Estuary, RLPE) (35°S-57°W) from the Southwestern Atlantic Ocean. Medusae consisted of sexually mature individuals only, occurring consistently during austral summer. Medusae biomass displayed a patchy distribution, concentrating mainly in two geographically different hot-spots associated to a frontal feature (turbidity front) of the RLPE. Individual size, relative fecundity, and degree of gonad development varied significantly between hot-spots. Biomass varied greatly among years. Bell diameter, wet weight, and percentage of fully developed oocytes increased during the first half of the summer but decreased during the second half of it. Our results suggest high predictability of the period of occurrence and the distribution of L. lucerna in the RLPE. Physical mechanisms of medusa aggregation, potential effects of medusae on zooplankton dynamics, fisheries production, and conservation of sea turtles, as well as their potential for the development of a local jellyfish fishery, are here discussed. This work provides novel information on patterns of distribution, growth and development of L. lucerna medusae, which can help to enhance our understanding of the role of large medusae on ecosystem functioning of marine ecosystems worldwide. [ABSTRACT FROM AUTHOR]

This study presents an inventory of planktonic cnidarian species collected in Algerian coastal waters (1°10’00” W - 6°52’37” E and 35°37’42” N - 37°01’16” N) from May 2012 to February 2017. The aim was to analyse the qualitative distribution and identify the main components of this gelatinous fauna in different coastal ecosystems in western, central and eastern regions. A total of 60 taxa of planktonic cnidarians were identified, including 57 hydrozoans and three scyphozoans. The class Hydrozoa were represented by 34 hydromedusae, primarily belonging to orders Anthoathecata (15 taxa) and Siphonophorae (23 taxa). Several reported hydrozoan species were recorded for the first time in the southwestern Mediterranean Sea. These new regional records include the hydromedusae Kantiella enigmatica, Leuckartiara octona, Proboscidactyla ornata, Cunina globosa, Lovenella cirrata, Cirrholovenia tetranema, Phialella quadrata, Homoeonema platygonon and the siphonophore Forskalia contorta. Seasonal fluctuations were observed in biodiversity, with the highest species richness in spring and summer. The most common species are the calycophorous siphonophores Abylopsis tetragona, Muggiaea atlantica, Lensia subtilis Muggiaea kochii and the holoplanktonic medusae Aglaura hemistoma, Rhopalonema velatum, Solmundella bitentaculata, Liriope tetraphylla and Pelagia noctiluca. The species’ occurrence frequency exhibited seasonal and spatial variability. These distribution patterns were primarily determined by meroplanktonic hydrozoans (Anthoathecata and Leptothecata). [ABSTRACT FROM AUTHOR]

Cyanea nozakii, a common jellyfish distributed in offshore China, has a complex trophic relationship with other zooplankton groups. However, few studies have reported the predation rates and prey selection patterns of C. nozakii medusae on different prey items. Research is also lacking on the intraguild predation of Aurelia coerulea (another common bloom jellyfish in offshore China) by C. nozakii. To address the knowledge gaps, the clearance rates of C. nozakii for different prey items, including copepods (small<1 000 µm and large>1 000 µm), fish larvae, and gelatinous prey (hydromedusae, A. coerulea ephyrae, and chaetognaths), were measured. The influence of predator size on the clearance rate was also determined. Additionally, we examined the intraguild predation of C. nozakii on A. coerulea medusae. The clearance rates of C. nozakii varied widely with prey organisms, being independent of prey concentrations. Gelatinous organisms, except for chaetognaths, were captured with considerably high efficiency, followed by fish larvae and copepods, indicating the preferential prey selection of gelatinous organisms by C. nozakii. The clearance rate increased linearly with the cross-sectional area of C. nozakii. Body size in medusae may, to some extents, underpin their capacity to capture more prey by increasing the encounter rate and capture success through ontogeny. C. nozakii preyed voraciously on A. coerulea in high feeding efficiency, but the clearance rate decreased with increasing A. coerulea (as prey) size. This phenomenon of intraguild predation suggests a speculative hypothesis of potential population regulation of A. coerulea by C. nozakii. The information regarding the feeding ecology of C. nozakii reported in this study is important for understanding plankton dynamics in marine ecosystems with extensive occurrences of this jellyfish. [ABSTRACT FROM AUTHOR]

In recent decades, the global environmental balance has been disrupted due to new environmental conditions and increasing anthropogenic pressure. In this context, the increase in frequency and magnitude of jellyfish proliferation in the Mediterranean Sea can be examined as an indicator closely associated with potential impacts of global changes. Despite their importance in ecosystem function and services, current knowledge of jellyfish diversity and phenology is largely lacking in the southern Mediterranean Sea, particularly along the Moroccan Mediterranean coast. Rhizostoma pulmo is a large scyphozoan jellyfish endemic to the Mediterranean. It is the second dominant scyphozoan species in the jellyfish community of Al Hoceima Bay. In this article, we explore the seasonal dynamics of the jellyfish R. pulmo between the estuaries of Oued Ghis and Nekkour at Souani Beach. Due to the disparity between the visual abundance of jellyfish and their rare beaching along the shores of Al Hoceima Bay, we implemented a specific method for collecting R. pulmo. This approach involves the use of a coastal trawl, a fishing net 200 meters long with a mesh size of 5 cm, deployed 80 meters from the shore and pulled from both sides by fishermen. Sampling missions conducted throughout the year 2022 revealed that R. pulmo reaches its maximum abundance in summer. The results indicate a maximum abundance of 0.28 ind/m2 in July 2022, with a maximum umbrella diameter reaching 26 cm in August 2022. Under the jellyfish umbrellas, fry of two fish species and one crustacean species were observed, adding an ecological dimension to this study.

Jellyfish are commonly considered a nuisance for their negative effects on human activities (e.g., fisheries, power plants and tourism) and human health. However, jellyfish provide several benefits to humans and are commonly eaten in eastern countries. Additionally, recent studies have suggested that jellyfish may become a source of high-value molecules. In this study, we tested the effects of the methanolic extracts and enriched fractions, obtained by solid-phase extraction fractionation, from the scyphomedusae Pelagia noctiluca, Rhizostoma pulmo, Cotylorhiza tuberculata and the cubomedusa Caryddea marsupialis on different human cancer cell lines in order to evaluate a potential antiproliferative activity. Our results indicated that fraction C from Caryddea marsupialis-(CM) and C. tuberculata oral arms (CTOA) were the most active to reduce cell viability in a dose-dependent manner. LC/MS based dereplication analyses highlighted that both bioactive fractions contained mainly fatty acids and derivatives, with CM additionally containing small peptides (0.7–0.8 kDa), which might contribute to its higher biological activity. The mechanism of action behind the most active fraction was investigated using PCR arrays. Results showed that the fraction C of CM can reduce the expression of genes involved in apoptosis inhibition in melanoma-treated cells, which makes jellyfish a potential new source of antiproliferative drugs to be exploited in the future. [ABSTRACT FROM AUTHOR]

Jellyfishes, which are one of the most important consumers in marine ecosystems, may have detri-mental effects on fish stocks that have economic value. Therefore, identifying and monitoring jelly-fish presence is important. We observed four individuals of symbiotic rhizostome scyphozoan Cot-ylorhiza tuberculata in the vicinity of the Princes’ Islands Archipelago, in the Northeast Sea of Marmara, Turkey in September 2020. Although this species is a common member of gelatinous plankton in the Mediterranean Sea, the present study is the first record from the Sea of Marmara.

The Australian spotted jellyfish Phyllorhiza punctata is native to the southwestern Pacific and was introduced to the western tropical Atlantic by the mid-20th century. Phyllorhiza punctata first appeared in the Mediterranean off the Israeli coast in 1965. Since then, it has been reported at various coastal waters along the Mediterranean either as few specimens or recently as swarms, especially in the western basin. The first record of P. punctata in the Mediterranean was in 1991 on El-Arish coast from Egypt. After this record, this species was reported on November 28, 2018 in Port Said, on the southeastern Mediterranean coast of Egypt, in this study. Therefore, this record confirms the re-occurrence of this species in Egypt coasts and reveal the spreading pattern of P. punctata in the Mediterranean. [ABSTRACT FROM AUTHOR]

Blooms of the Rhizostomeae Nemopilema nomurai and the Semaeostomeae Cyanea nozakii have become more prominent in the coastal waters of China since the end of the 20th century. However, the trophic ecology of these jellyfish species remain incompletely understood. In this study, the trophic characterizations of N. nomurai and C. nozakii populations were assessed using stable isotope analysis (SIA), with a focus on the important bloom area offshore of the Yangtze Estuary. Our results indicated obvious trophic differences between two scyphomedusae. The higher trophic position of the C. nozakii population in the coastal planktonic food web was reflected by its relatively large δ15N value compared to that of N. nomurai. The MixSIAR model indicated that small copepods (<1000 μm) and seston were important food sources for N. nomurai , and showed a stable dietary, irrespective of N. nomurai size. Conversely, C. nozakii exhibited a more diverse diet composition, and gelatinous organisms also were an important part of the diet of C. nozakii. Moreover, a pronounced ontogenetic shift in the diet of C. nozakii was observed, consisting of an increase in the proportion of zooplanktonic prey (excluding seston) in the C. nozakii diet with diameter. This study provides isotopic evidence of the substantial difference in trophic ecology between N. nomurai and C. nozakii , which resulted from the variations in SI values and diet compositions. Inconsistent size-based variation patterns were observed in trophic ontogenetic shifts within the N. nomurai and C. nozakii groups, highlighting a need for further investigation. These results will give insights into the characteristics of trophic ecology and functional roles of Rhizostomeae and Semaeostomeae, and indicate the need for a more careful consideration of the representations of Rhizostomeae and Semaeostomeae in coastal ecosystems, so as not to underestimate the knowledge of taxon-specific ecological effects on energy flow. • Significant differences in trophic ecology of N. nomurai and C. nozakii. • Large δ15N values reflect the higher trophic position of C. nozakii population. • Divergent size-based variation patterns in trophic ecology. [ABSTRACT FROM AUTHOR]

Abstract Ephyrae are the young scyphozoan jellyfishes that usually passes unnoticed, whereas their adult counterparts play major ecological roles and can negatively affect economic activities when they occur in high densities. We describe, for the first time, wild ephyrae of Lychnorhiza lucerna (Scyphozoa, Rhizostomeae) from the Patos Lagoon Estuary, Southern Brazil. A total of 10 ephyrae were found in salinities between 12 and 33 and temperatures between 16 and 27°C. The presence of digitata, eight oral arms and serrated tips on marginal lobes allowed species determination. Wild ephyrae were morphologically identical to laboratory-cultivated individuals. The youngest individual was about one to two days old, and the most developed one, between 12 and 14 days old. Recruitment of L. lucerna probably initiated during warmer months (December until February) because nine out of ten individuals were found in high temperature (> 20° C) and salinity (> 30) waters. On the other hand, a mid-winter occurrence of a single ephyra (T=16° C, S= 12) demonstrates that the species may support a considerable range of variation in the physical environment. We reinforce the importance of long-term studies to provide information about the species coupling with seasonal cycles and the dynamics of estuarine and coastal areas.

Cnidarians have large surface areas available for colonization by microbial organisms, which serve a multitude of functions in the environment. However, relatively few studies have been conducted on scyphozoan-associated microbial communities. Blooms of scyphozoan species are common worldwide and can have numerous deleterious consequences on the marine ecosystem. Four scyphozoan species, Aurelia coerulea, Cyanea nozakii, Nemopilema nomurai, and Rhopilema esculentum, form large blooms in Chinese seas. In this study, we analyzed the bacterial communities associated with these four jellyfish based on 16S rRNA gene sequencing. We found that the bacterial communities associated with each scyphozoan species were significantly different from each other and from those of the surrounding seawater. There were no significant differences between the bacterial communities associated with different body parts of the four scyphozoan jellyfish. Core bacteria in various compartments of the four scyphozoan taxa comprised 57 OTUs (Operational Taxonomic Units), dominated by genera Mycoplasma, Vibrio, Ralstonia, Tenacibaculum, Shingomonas and Phyllobacterium. FAPROTAX function prediction revealed that jellyfish could influence microbially mediated biogeochemical cycles, compound degradation and transmit pathogens in regions where they proliferate. Finally, Six genera of potentially pathogenic bacteria associated with the scyphozoans were detected: Vibrio, Mycoplasma, Ralstonia, Tenacibaculum, Nautella, and Acinetobacter. Our study suggests that blooms of these four common scyphozoans may cause jellyfish species-specific impacts on element cycling in marine ecosystems, and serve as vectors of pathogenic bacteria to threaten other marine organisms and human health.

Cnidarians have large surface areas available for colonization by microbial organisms, which serve a multitude of functions in the environment. However, relatively few studies have been conducted on scyphozoan-associated microbial communities. Blooms of scyphozoan species are common worldwide and can have numerous deleterious consequences on the marine ecosystem. Four scyphozoan species, Aurelia coerulea , Cyanea nozakii , Nemopilema nomurai , and Rhopilema esculentum , form large blooms in Chinese seas. In this study, we analyzed the bacterial communities associated with these four jellyfish based on 16S rRNA gene sequencing. We found that the bacterial communities associated with each scyphozoan species were significantly different from each other and from those of the surrounding seawater. There were no significant differences between the bacterial communities associated with different body parts of the four scyphozoan jellyfish. Core bacteria in various compartments of the four scyphozoan taxa comprised 57 OTUs (Operational Taxonomic Units), dominated by genera Mycoplasma , Vibrio , Ralstonia , Tenacibaculum , Shingomonas and Phyllobacterium. FAPROTAX function prediction revealed that jellyfish could influence microbially mediated biogeochemical cycles, compound degradation and transmit pathogens in regions where they proliferate. Finally, Six genera of potentially pathogenic bacteria associated with the scyphozoans were detected: Vibrio , Mycoplasma , Ralstonia , Tenacibaculum , Nautella , and Acinetobacter. Our study suggests that blooms of these four common scyphozoans may cause jellyfish species-specific impacts on element cycling in marine ecosystems, and serve as vectors of pathogenic bacteria to threaten other marine organisms and human health. [ABSTRACT FROM AUTHOR]

Jellyfish are commonly considered a nuisance for their negative effects on human activities (e.g., fisheries, power plants and tourism) and human health. However, jellyfish provide several benefits to humans and are commonly eaten in eastern countries. Additionally, recent studies have suggested that jellyfish may become a source of high-value molecules. In this study, we tested the effects of the methanolic extracts and enriched fractions, obtained by solid-phase extraction fractionation, from the scyphomedusae Pelagia noctiluca, Rhizostoma pulmo, Cotylorhiza tuberculata and the cubomedusa Caryddea marsupialis on different human cancer cell lines in order to evaluate a potential antiproliferative activity. Our results indicated that fraction C from Caryddea marsupialis-(CM) and C. tuberculata oral arms (CTOA) were the most active to reduce cell viability in a dose-dependent manner. LC/MS based dereplication analyses highlighted that both bioactive fractions contained mainly fatty acids and derivatives, with CM additionally containing small peptides (0.7–0.8 kDa), which might contribute to its higher biological activity. The mechanism of action behind the most active fraction was investigated using PCR arrays. Results showed that the fraction C of CM can reduce the expression of genes involved in apoptosis inhibition in melanoma-treated cells, which makes jellyfish a potential new source of antiproliferative drugs to be exploited in the future.

The presence of non-indigenous species outside their home range attracts growing attention by the scientific community, as well as policy makers and common citizens. However, dispersal pathways of most non-indigenous species remain poorly understood. The association between non-indigenous and indigenous species may facilitate dispersal in non-native habitats. Identifying such associations is therefore paramount, but few studies have addressed this issue to date. The present work reports the association between the non-indigenous spider crab Pyromaia tuberculata, morphologically and molecularly identified, with the autochthonous scyphomedusa Catostylus tagi in European waters. This is the first time this widespread invasive brachyuran crab is described associated with jellyfish. In the laboratory, P. tuberculata was observed feeding on the gonadal tissues of its cnidarian host, although this behaviour needs to be confirmed in the wild. The association between P. tuberculata and C. tagi raises awareness on how the dispersal potential of this non-indigenous species may be significantly enhanced. As recommended by the Marine Strategy Framework Directive, it is important to include P. tuberculata in the European monitoring programmes of non-indigenous species. Future studies should continue to investigate the prevalence of this specific association, as well as other associations between jellyfish and non-indigenous fauna, as an early warning initiative. Researchers may benefit from ongoing citizen science projects to gather data on this overlooked pathway for dispersal of non-indigenous species. [ABSTRACT FROM AUTHOR]

The order Coronatae (Scyphozoa) includes six families, of which Nausithoidae Haeckel, 1880 is the most diverse with 26 species. Along the Brazilian coast, three species of the genus Nausithoe Kölliker, 1853 have been recorded: Nausithoe atlantica Broch, 1914, Nausithoe punctata Kölliker, 1853, and Nausithoe aurea Silveira & Morandini, 1997. Living polyps (n = 9) of an unidentified nausithoid were collected in September 2002 off Arraial do Cabo (Rio de Janeiro, southeastern Brazil) at a depth of 227 m, and have been kept in culture since then. We compared these specimens with three species cultured in our laboratory: Nausithoe aurea (from Ilhabela, São Paulo, Brazil), Nausithoe maculata Jarms, 1990 (from Cuba and Puerto Rico), and Nausithoe werneri Jarms, 1990 (from the Atlantic Ocean off Morocco and from the Mediterranean Sea). The criteria used for comparison were: main aspects of the morphology, life cycle, and DNA sequences (18S, 28S, and COI). The results indicate that the unidentified polyps belong to N. werneri. Furthermore, N. aurea is considered a junior synonym of N. maculata. [ABSTRACT FROM AUTHOR]

A single specimen of a pelagiid jellyfish collected next to Ashdod port, Israel, is referred to the genus Chrysaora Péron and Lesueur, 1810 based on molecular examinations. Despite the inability to check morphological features of diagnostic value, molecular analyses based on the mitochondrial barcoding gene cytochrome oxidase sub unit I (COI), 16S and 28S ribosomal DNA reveal marked dissimilarities from both the Northeast Atlantic-Mediterranean native Chrysaora hysoscella (Linnaeus, 1767) and the closest GeneBank/BoLD available congener, the West African C. africana (Vanhöffen, 1902). It is suggested that the species is new to science and non-native to the Mediterranean Sea, possibly the sixth introduced scyphozoan species reported in the Levant Sea. [ABSTRACT FROM AUTHOR]

The population explosion of jellyfish Aurelia coerulea occurred in Jiaozhou Bay, China in 2009. The potential predation impact of A. coerulea on zooplankton was investigated. Population clearance potential and residence time (t1/2) for copepods were calculated from laboratory clearance rates and measurements of jellyfish size and abundance from May to August 2009 in Jiaozhou Bay. Clearance rates varied widely with prey organisms, but they were not significantly different among various prey concentrations. Medusae captured rotifers, fish larvae and hydromedusae more efficiently than fish eggs, copepods and chaetognaths. Ephyrae captured rotifers and hydromedusae more efficiently than fish larvae and copepods. Clearance rate linearly increased with the cross sectional area of A. coerulea (size from 0.3 to 7.1 cm). Water temperature also had a marked effect on clearance rate and this was related to the increased beat frequency as water temperature increased. In early May 2009, A. coerulea potentially cleared the volume of water in the Bay less than 0.001 times a day, but this value was estimated to be more than 0.3 times a day in July. The t1/2 for copepods was less than 6 d in June and July. Abundances of copepods, hydromedusae and chaetognaths were extremely low in 2009 compared to 2008 and 2010 (jellyfish non-bloom years). Large predation pressure by the A. coerulea population occurred to control zooplankton communities in Jiaozhou Bay. A. coerulea, when present at a high population level, can be a keystone species in Jiaozhou Bay and control the trophic structure here. [ABSTRACT FROM AUTHOR]

This study presents the first record of a jellyfish of the genus Drymonema from the Istanbul coast of the Sea of Marmara, Turkey, in February 2020. While exceedingly rare in the second half of the 20th Century in the Mediterranean Basin, a specimen of the genus Drymonema (D. dalmatinum) has been recorded in the Gulf of İzmir and Foça (Turkey), but it has never been recorded as far into the Sea of Marmara. A role of citizen science in terms of spotting such rare species is highlighted. [ABSTRACT FROM AUTHOR]

Within the Eastern Bering Sea, the jellyfish Chrysaora melanaster has fluctuated widely over recent decades. We examined the role of C. melanaster as an ecosystem-structuring agent via application of ecosystem models representing inner-, mid-, and outer-shelf regions of comparable areal coverage. Chrysaora melanaster utilize 1% of total mid-shelf consumer production, or 1/4th the energy required by forage fish (capelin Mallotus villosus , Pacific herring Clupea pallasii , age-0 Pacific cod Gadus macrocephalus , age-0 walleye pollock Gadus chalcogrammus). Model simulations show the impacts of C. melanaster are broadly distributed across consumer groups with increasingly negative impacts with higher jellyfish biomass. Age-0 pollock represent the greater part of the forage fish biomass, and observed pollock biomass during low jellyfish years (2004–2007) was significantly greater than during high jellyfish years (2009–2014). However, sensitivity among consumer groups to observed jellyfish variability is small, within 5% of baseline (2004–2015) conditions. Estimates using similar models for the Coastal Gulf of Alaska (CGoA) and Northern California Current (NCC) suggest large differences in the role of scyphozoans among northern Pacific shelf ecosystems. Only 0.1% of total summer consumer production is required to support CGoA Chrysaora , while the coastal NCC population uses 19%. [ABSTRACT FROM AUTHOR]

Jellyfish represent an important component of marine food webs characterized by large fluctuations of population density, with the ability to abruptly form outbreaks, followed by rarity periods. In spite of considerable efforts to investigate how jellyfish populations are responding globally to anthropogenic change, available evidence still remains unclear. In the last 50 years, jellyfish are seemingly on the rise in a number of coastal areas, including the Mediterranean Sea, where jellyfish blooms periodically become an issue to marine and maritime human activities. Their impacts on marine organism welfare have been poorly quantified. The jellyfish, Rhizostoma pulmo , is an outbreak-forming scyphomedusa whose large populations spread across the Mediterranean, with increasing periodicity and variable abundance. Studies on cnidarian jellyfish suggested being important vectors of bacterial pathogens. In the present study, by combination of conventional culture-based methods and a high-throughput amplicon sequencing (HTS) approach, we characterized the diversity of the bacterial community associated with this jellyfish during their summer outbreak. Three distinct jellyfish compartments, namely umbrella, oral arms, and the mucus secretion obtained from whole specimens were screened for specifically associated microbiota. A total of 17 phyla, 30 classes, 73 orders, 146 families and 329 genera of microbial organisms were represented in R. pulmo samples with three major clades (i.e. Spiroplasma , Mycoplasma and Wolinella) representing over 90% of the retrieved total sequences. The taxonomic microbial inventory was then combined with metabolic profiling data obtained from the Biolog Eco-Plate system. Significant differences among the jellyfish compartments were detected in terms of bacterial abundance, diversity and metabolic utilization of 31 different carbon sources with the highest value of abundance and metabolic potential in the mucus secretion compared to the umbrella and oral arms. Results are discussed in the framework of the species ecology as well as the potential health hazard for marine organisms and humans. Unlabelled Image • Jellyfish-associated microbiota during a summer outbreak was characterized • Microbiota of three distinct jellyfish compartments was analyzed by culture-based and a high-throughput amplicon sequencing • Jellyfish blooms may represent vectors of potential bacterial pathogens • Jellyfish blooms may be a potential health hazard for marine organisms and humans [ABSTRACT FROM AUTHOR]

Describing species has been a formal, intellectually rich and influential applied and basic area of study for many of the past 260 years. While formally described eukaryotic diversity still falls short of estimated eukaryotic species diversity by many hundreds of thousands of species, some recent accounts have suggested a growing number of taxonomists are within reach of describing all extant species. We present a case study that illustrates, to the contrary, a recent 'taxonomic impediment' in part attributable to derogation of taxonomy as a scientific discipline: contemporary practice has re-interpreted taxonomy largely as an endeavour in enumerating species. We argue that challenges lie in (1) a poor understanding of taxonomy's epistemology; (2) excessive displacement of interest toward ecological or molecular studies; (3) over-interpretation of the contributions of multiple authors describing a species; and (4) perspectives that are strongly influenced by well-known taxa. The historical and recent literature on scyphozoans reveal ghosts of taxonomy's past that persist in the present, but suggest also that a renaissance enabled by integrative taxonomy is possible in the (near) future. [ABSTRACT FROM AUTHOR]

Jellyfish blooms are frequent and widespread in coastal areas worldwide, often associated with significant ecological and socio-economic consequences. Recent studies have also suggested cnidarian jellyfish may act as vectors of bacterial pathogens. The scyphomedusa Rhizostoma pulmo is an outbreak-forming jellyfish widely occurring across the Mediterranean basin. Using combination of culture-based approaches and a high-throughput amplicon sequencing (HTS), and based on available knowledge on a warm-affinity jellyfish-associated microbiome, we compared the microbial community associated with R. pulmo adult jellyfish in the Gulf of Taranto (Ionian Sea) between summer (July 2016) and winter (February 2017) sampling periods. The jellyfish-associated microbiota was investigated in three distinct compartments, namely umbrella, oral arms, and the mucus secretion. Actinobacteria, Bacteroidetes, Chlamydiae, Cyanobacteria, Deinococcus-Thermus, Firmicutes, Fusobacteria, Planctomycetes, Proteobacteria, Rhodothermaeota, Spirochaetes, Tenericutes, and Thaumarchaeota were the phyla isolated from all the three R. pulmo compartments in the sampling times. In particular, the main genera Mycoplasma and Spiroplasma, belonging to the class Mollicutes (phylum Tenericutes), have been identified in all the three jellyfish compartments. The taxonomic microbial data were coupled with metabolic profiles resulting from the utilization of 31 different carbon sources by the BIOLOG Eco-Plate system. Microorganisms associated with mucus are characterized by great diversity. The counts of culturable heterotrophic bacteria and potential metabolic activities are also remarkable. Results are discussed in terms of R. pulmo ecology, the potential health hazard for marine and human life as well as the potential biotechnological applications related to the associated microbiome.

In the Northern Humboldt Upwelling System (NHUS), one of the most productive ecosystems in the world, the large jellyfish Chrysaora plocamia exhibits high inter-annual variability in population size, often resulting in massive blooms. In this study, we examined the geographic patterns C. plocamia in the NHUS and their spatial overlap with ichthyoplankton, zooplankton, and chlorophyll a concentration (Chl a) during two El Niño (EN) years (1982–1983 and 1986–1987), and a neutral year (2014). During EN years, the spatial extent of C. plocamia medusae was larger than in the neutral year. In 1982–1983, medusae were concentrated mainly in the central-southern and southern regions of Peru, where they were associated with zooplankton, sardine larvae, and Chl a. In 1986–1987, medusae occurred in the northern and southern regions and spatially overlapped with sardine larvae and Chl a , and with zooplankton and anchoveta larvae, respectively. In 2014, medusae occurred mainly in the northern region, where they were associated with zooplankton, Chl a , and anchoveta eggs and larvae. Our results indicate strong EN effects on the distribution and abundance of C. plocamia , which can have consequences for zooplankton and ichthyoplankton abundance, as well as fisheries, in the NHUS. [ABSTRACT FROM AUTHOR]

In this study, we reported the species composition and spatial distribution of Scyphomedusae and Cubomedusae from the southwestern Atlantic and Subantarctic region and reviewed the available knowledge of life history traits of these species. We gathered the literature records and presented new information collected from oceanographic and fishery surveys carried out between 1981 and 2017, encompassing an area of approximately 6,7 million km2 (32-60°S, 34-70°W). We confirmed the occurrence of 15 scyphozoans and 1 cubozoan species previously reported in the region. Lychnorhiza lucerna and Chrysaora lactea were the most numerous species, reaching the highest abundances/biomasses during summer/autumn period. Desmonema gaudichaudi, Chrysaora plocamia, and Periphylla periphylla were frequently observed in low abundances, reaching high numbers only occasionally. Phacellophora camtschatica, Aurelia sp., Drymonema gorgo, Atolla chuni, Stygiomedusa gigantea and Pelagia cf. noctiluca were observed always in low numbers. Atolla wyvillei, Stomolophus meleagris, Desmonema comatum and Tamoya haplonema were reported just a few times and mostly individually. Although new species/reports can be found as surveys are undertaken, these results are considered to be the reliable baseline for further ecological studies seeking to understand the ecological role that these jellyfish play in marine ecosystems. [ABSTRACT FROM AUTHOR]

Fatty acids (FAs) are used, often in combination with stable isotopes (SIs), as chemical biomarkers to assess the contribution of different prey to the diet of consumers and define food web structure and dynamics. Extraction of lipids is traditionally carried out using methanol (MeOH) combined with chloroform or dichloromethane, these latter being well-known environmental pollutant and potential carcinogenic agents. Recently, extraction protocols based on methyl tert -butyl ether (MTBE) and MeOH have been proposed as an alternative to halogenated solvents in lipidomic studies. However, no specific investigation has been performed to assess MTBE suitability in marine ecological studies including FA analysis together with SI measurements. We used an analytical workflow for qualitative and quantitative analysis of FAs and SIs in field samples of phytoplankton, zooplankton and the scyphomedusa Pelagia noctiluca , applying MTBE in comparison with chloroform- and dichloromethane-based protocols for total lipid extraction. Our analysis suggested that MTBE is a reliable substitute for lipid extraction in trophic ecology studies in marine planktonic organisms. • Fatty acids (FAs) and stable isotopes (SIs) are biomarkers used to define food web structure. • Conventional lipid extraction protocols mostly rely on harmful halogenated solvents. • A MTBE-based protocol has been applied to three groups of marine planktonic organisms. • FAs and SIs data from MTBE, CHCl 3 and CH 2 Cl 2 extraction protocols have been compared. • MTBE is a reliable and safer alternative for lipid extraction in trophic ecology studies. [ABSTRACT FROM AUTHOR]

Jellyfish form associations with a diverse fauna including parasites and commensals, yet, ecological data on these associations, particularly time series, are rare. The present study examined temporal variation in the intensities and prevalences of two symbionts, namely, a sphaeromatid isopod (Cymodoce gaimardii) and a parasitic anemone (Anemonactis clavus) of the scyphozoan jellyfish Catostylus mosaicus over a 2-year period. Jellyfish were captured from Port Phillip Bay, Victoria, Australia, approximately every 6 weeks and inspected for symbionts. The isopod occurred on C. mosaicus on 16 of the 19 sampling occasions; prevalences ranged from 5 to 85%, and were highest in summer and autumn. Intensity ranged from one to five isopods per jellyfish. Juvenile, immature and mature isopods were present. The parasitic anemone A. clavus occurred only between May and September. Prevalences were lower than for the isopod (on 5-20% of jellyfish when present) as was maximum intensity (two anemones per jellyfish). Catostylus mosaicus appears to play an important role in the life history of a suite of symbionts, and the present study is the first to examine temporal changes in the association of the jellyfish with two of these symbionts. [ABSTRACT FROM AUTHOR]

Jellyfish (primarily scyphomedusae) fisheries have a long history in Asia, where jellyfish have been caught and processed as food for centuries. More recently, jellyfish fisheries have expanded to the Western Hemisphere, often driven by demand from Asian buyers and collapses of more traditional local fish stocks. Jellyfish fisheries have been attempted in numerous countries in North, Central, and South America, with varying degrees of success. Here, we chronicle the arrival of jellyfish fisheries in the Americas and summarize relevant information on jellyfish fishing, processing, and management. Processing technology for edible jellyfish has not advanced, and presents major concerns for environmental and human health. The development of alternative processing technologies would help to eliminate these concerns and may open up new opportunities for markets and species. We also examine the biodiversity of jellyfish species that are targeted for fisheries in the Americas. Establishment of new jellyfish fisheries appears possible, but requires a specific combination of factors including high abundances of particular species, processing knowledge dictated by the target market, and either inexpensive labor or industrialized processing facilities. More often than not, these factors are not altogether evaluated prior to attempting a new jellyfish fishery. As such, jellyfish fisheries are currently expanding much more rapidly than research on the subject, thereby putting ecosystems and stakeholders' livelihoods at risk. [ABSTRACT FROM AUTHOR]

The ctenophore Mnemiopsis leidyi A. Agassiz, 1865 is a successful, recent, macroplanktonic invader in European coastal waters, including the Dutch Wadden Sea. It occurs year-round in substantial numbers. The effect of M. leidyi on structure of the gelatinous zooplankton community in the Dutch Wadden Sea was studied by comparing data from before and after its introduction. Gelatinous zooplankton species composition in the western Wadden Sea was largely the same between 1980-1983 and 2009-2012. Only the hydromedusa Eutonina indicans (Romanes, 1876) was absent in recent years while Cosmetira pilosella Forbes, 1848 and Margelopsis haeckelii Hartlaub, 1897 were rare species observed only in 2009-2012. M. leidyi was present since 2006, with high densities every year in summer and autumn. Predation pressure by scyphomedusae, ctenophores, and hydromedusae on fish larvae and zooplankton in 1980-1983 was low because of low densities and a temporal mismatch between gelatinous zooplankton and their prey. Despite the decrease in abundance of scyphomedusae in recent decades, the introduction of M. leidyi and its large annual blooms have increased the overall importance of gelatinous zooplankton as predators in the western Wadden Sea, whereby M. leidyi is responsible for most of the predation pressure on mesozooplankton in the area. Rather than outcompeting local species, M. leidyi appeared to fill in a previously unoccupied niche in the pelagic western Dutch Wadden Sea in late summer and autumn. [ABSTRACT FROM AUTHOR]

The production of natural toxins is an interesting aspect, which characterizes the physiology and the ecology of a number of marine species that use them for defence/offence purposes. Cnidarians are of particular concern from this point of view; their venoms are contained in specialized structures–the nematocysts–which, after mechanical or chemical stimulation, inject the venom in the prey or in the attacker. Cnidarian stinging is a serious health problem for humans in the zones where extremely venomous jellyfish or anemones are common, such as in temperate and tropical oceanic waters and particularly along several Pacific coasts, and severe cases of envenomation, including also lethal cases mainly induced by cubomedusae, were reported. On the contrary, in the Mediterranean region the problem of jellyfish stings is quite modest, even though they can have anyhow an impact on public health and be of importance from the ecological and economic point of view owing to the implications on ecosystems and on some human activities such as tourism, bathing and fishing. This paper reviews the knowledge about the various aspects related to the occurrence and the stinging of the Mediterranean scyphozoan jellyfish as well as the activity of their venoms.

The nomenclature of the sea nettle jellyfish from Korea was initially described as Dactylometra quinquecirrha Agassiz, 1862. However its identity has been questioned on the basis of its local distribution and molecular data. Here, we examined morphology and DNA sequences of nuclear rDNA using specimens collected from southern Korean waters in August 2014. Based on morphological characteristics (bell size, umbrella pattern, number of tentacles and lappets) and distribution locality, we reassign the Korean D. quinquecirrha to Chrysaora pacifica (Goette, 1886), and provide a re-description accordingly. The molecular identity of C. pacifica was further confirmed by comparison of nuclear ribosomal DNA sequences. [ABSTRACT FROM AUTHOR]

• Bering Sea jellyfish continue to show fluctuations in biomass. • Jellyfish biomass in the eastern Bering Sea did not increase during warm periods. • Updated models for 1982–2017 estimate trends in Bering Sea jellyfish. • Predictors are lagged biomass, wind stress and mixing, surface temperatures and currents. • Fluctuations in jellyfish biomass may indicate climate-induced ecosystem changes. Globally, there have been few long-term (>30 years), shelf-wide surveys of jellyfish that have allowed for the examination of how populations might respond to changing climatic and oceanographic conditions. One region where investigation of jellyfish responses to climate variability is possible is the eastern Bering Sea, where jellyfish biomass, primarily that of Chrysaora melanaster , has fluctuated dramatically since 1982, when systematic collections of these medusae began. Our previous investigations of a 27-year time series indicated that the timing of the jellyfish biomass increases and declines coincided with transitions between climatic regimes. In the current study, we used updated jellyfish catch and environmental data from 1982 to 2017 and reran our generalized additive model (GAM) analyses to determine if models using solely physical variables and lag of jellyfish biomass could describe accurately the increases and subsequent decreases observed in this jellyfish biomass index. GAMs hindcasting jellyfish biomass for the period 1982–2017 explained a large fraction of the variance, 92.3 % and 86.4 %, for the southeast (SE) and northwest (NW) portions of the survey area, respectively, using jellyfish biomass in the preceding year and physical variables (SE: ice retreat, sea-surface temperature, wind mixing, wind stress and current displacement; NW: sea-surface temperature, ice cover, wind stress and current displacement). We developed more parsimonious models by calculating the variance inflation factor for each term and dropping highly correlated terms from the models. The resulting GAMs continued to explain a significant portion of the variance in jellyfish biomass, i.e., 78.2 % and 73.5 %, in the southeast and northwest survey areas, respectively. Jellyfish biomass in the SE region was correlated with the jellyfish biomass in the preceding year and with wind mixing, wind stress and current displacement. In the NW region, jellyfish biomass was correlated with biomass from the preceding year, and with summer sea-surface temperature and current displacement. Jellyfish biomass in the eastern Bering Sea did not increase during warm periods, as has been speculated to occur elsewhere. Jellyfish, which are both predators and competitors of fish, appear to be responding to changes in physical conditions and are important indicators of ecosystem change in the eastern Bering Sea. The development of models that use physical parameters, as opposed to biological variables that are often not readily available, is key to predicting jellyfish abundance and their impacts on commercially important species. [ABSTRACT FROM AUTHOR]

Massive blooms of Nemopilema nomurai have occurred recently across East Asian waters. They are potentially important as zooplankton predators, as well as being competitors for prey with zooplanktivorous fish. Few studies have estimated the predation effects on zooplankton by N. nomurai in situ. To quantify the natural diets and feeding rates and estimate the predation effects, N. nomurai medusae were collected in the northern East China Sea and southern Yellow Sea, one of the principal nursery grounds of this jellyfish, during May 2019. The gut contents indicated that copepods were an important food source for N. nomurai ; copepods <1000 μm represented the bulk of total prey intake in number (> 99 %). Linear regression analyses showed that the copepods number in the gut contents was significantly influenced by medusa diameter and prey abundance. Calculations using the above data indicated that one medusa (mean diameter: 26.06 ± 9.73 cm) consumed approximately 5248 ± 2768 of copepods daily. However, even the maximum predation pressure was <0.1 % of the total copepods standing stock daily due to the small diameter and low density/biomass of N. nomurai medusae in May 2019. The data presented here suggested that the predation effects of N. nomurai on copepods were low and might not reduce prey availability to fish with diets consisting mainly of copepods during the early occurrence stage of the N. nomurai population. • Copepods were an important food source for Nemopilema nomurai population in the northern East China Sea and southern Yellow Sea. • The copepod number in the gut content was significantly influenced by medusa diameter and prey abundance. • The predation effects of N. nomurai population on copepods were low during the early occurrence stage. [ABSTRACT FROM AUTHOR]

Massive occurrences of jellyfish can cause direct impacts on the economy, especially on tourism and commercial fisheries. Translocation of jellyfish species by humans has caused damaging blooms in new habitats. Aurelia aurita s.l. has been introduced in many locations around the world. To test the potential success of Au. aurita s.l. in various habitats, scyphistomae from different climatic locations (Mediterranean, Red and Baltic Seas) were cultured individually for 201 days at three temperatures (14, 21 and 28 °C) with the same salinity, food and light. We tested the null hypotheses that there were no differences in survival or asexual reproduction (budding and strobilation) amongst populations [native (Mediterranean) and exotic (Red and Baltic)]. Survival of the three scyphistoma populations did not differ significantly across temperatures; however, the Red Sea group had lower survival at all temperatures than did the other populations. Most individuals strobilated at 14 °C. Red Sea scyphistomae strobilated more quickly than Baltic and Mediterranean Sea scyphistomae and produced the fewest ephyrae, whereas Baltic Sea scyphistomae produced the most. Our results indicate that Au. aurita from the Baltic or Red Seas introduced into the Northwest Mediterranean Sea would potentially persist and successfully asexually reproduce there. A new invader could even have greater asexual production than the local Au. aurita s.l. Establishment of the invaders could increase genetic variation of subsequent generations and increase their adaptability to environmental changes. Our results suggest that introduction of exotic Au. aurita s.l. populations could increase jellyfish blooms in the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

A species of edible Scyphomedusae jellyfish has been used as food by the local people in Ganghwado, Korea since the 1990s. In order to identify this jellyfish, we collected specimens in Ganghwado during September 2013, and compared these specimens with original descriptions made by Kishinouye (1890). Mitochondrial cytochrome oxidase subunit 1 (CO1) sequences of these specimens were compared with those of Rhopilema esculentum retrieved from GenBank. Our specimens were also compared with jellyfish collected in China, previously confirmed as R. esculentum, based on morphological characters and DNA sequences. Using these two methods, the jellyfish specimens caught in Ganghwado were correctly identified as R. esculentum, a species new to Korean waters. This edible jellyfish has been named 'Gisusik-Yonghaepari' as Korean name. [ABSTRACT FROM AUTHOR]

Using a unique 50-year high-resolution time series of daily kom-fyke catches, long-term patterns of scyphomedusae in the western Dutch Wadden Sea were analysed and related to changes in environmental conditions [eutrophication in the 1980s–1990s and recent climate change (increased water temperature)] in the area. Over the years, species composition and general pattern of appearance has remained the same: the first species that occurred in spring was Aurelia aurita, followed by Cyanea lamarckii/C. capillata. Chrysaora hysoscella and Rhizostoma octopus occurred from June to July onwards. All species appeared earlier in recent decades and first appearance and peak occurrence of A. aurita was in part inversely related to previous winter seawater temperature. Last occurrence of C. hysoscella was related to summer seawater temperature and the species is present longer in recent decades. Phenological relationships might have been decoupled since the seasonality of the phytoplankton bloom did not change. All species showed large inter-annual abundance fluctuations, with prolific years followed by sparse years. Peak catches of the coastal species A. aurita occurred in the late 1970s−early 1990s when eutrophication peaked, however, without a significant relationship with total nitrogen input into the area. Unlike for phenology, the patterns of mean abundance of any species did not show a relationship to climate change in the area. This might imply that population regulating mechanisms do not operate during the planktonic phase but during the sessile demersal polyp stages. [ABSTRACT FROM PUBLISHER]