Medusa Stage Research Articles

Incidental consumption of ephyrae of moon jellyfish Aurelia aurita s.l. by three filter-feeding sessile organisms: laboratory experiments

Moon jellyfish Aurelia aurita s.l. has been suggested to have high mortality during the ephyra stage, which potentially affects the population size of the later medusa stage. However, the mechanism behind the high mortality rate has still not been clarified. Ephyrae of A. aurita are liberated from the sessile strobila, which are usually surrounded by filter-feeding sessile organisms. In the present study, we carried out a series of feeding trials at 10 °C, offering A. aurita ephyrae to three potential predatory filter-feeding sessile organisms: the mussel Mytilus galloprovincialis, the ascidian Styela plicata, and the barnacle Amphibalanus eburneus. From the experiments, the mussel was estimated to have the highest ability to consume ephyrae among the sessile organisms. Size-selective filtration experiments showed that the mussel consumed newly liberated ephyrae [3 mm total body diameter (TBD)] at a significantly higher efficiency than larger (5 and 7 mm TBD) ephyrae. Our results demonstrate that filter-feeding sessile organisms, especially the mussel, are potential consumers of the early ephyra stage.

The polyps of Oceania armata identified by DNA barcoding (Cnidaria, Hydrozoa).

The polyps of the widely distributed medusa Oceania armata have never been found in nature and only the primary polyp is known from breeding experiments. The fully developed colony is so far unknown. This report shows that DNA sequence data of the medusa stage of O. armata permits to identify several hydroid colonies from different geographic origins as the most likely polyp stage of this medusa. These hydroids had previously been misidentified as Turritopsis species, a closely related genus which also produces medusae resembling Oceania armata. It is concluded that most Turritopsis hydroids are not reliably identifiable to species level using morphological traits only. However, DNA barcodes, particularly 16S sequences, are an excellent tool to identify the species, although we still lack information on a few nominal species and the identities of some sequence-delimited clades need to be corroborated by the addition of topotype samples.

Box Jellyfish Alatina alata Has a Circumtropical Distribution.

Species of the box jellyfish (Cubozoa) genus Alatina are notorious for their sting along the beaches of several localities of the Atlantic and Pacific. These species include Alatina alata on the Caribbean Island of Bonaire (the Netherlands), A. moseri in Hawaii, and A. mordens in Australia. Most cubozoans inhabit coastal waters, but Alatina is unusual in that specimens have also been collected in the open ocean at great depths. Alatina is notable in that populations form monthly aggregations for spermcast mating in conjunction with the lunar cycle. Nominal species are difficult to differentiate morphologically, and it has been unclear whether they are distinct or a single species with worldwide distribution. Here we report the results of a population genetic study, using nuclear and mitochondrial sequence data from four geographical localities. Our analyses revealed a general lack of geographic structure among Alatina populations, and slight though significant isolation by distance. These data corroborate morphological and behavioral similarities observed in the geographically disparate localities, and indicate the presence of a single, pantropically distributed species, Alatina alata. While repeated, human-mediated introductions of A. alata could explain the patterns we have observed, it seems more likely that genetic metapopulation cohesion is maintained via dispersal through the swimming medusa stage, and perhaps via dispersal of encysted planulae, which are described here for the first time in Alatina.

DNA barcodes unite two problematic taxa: the meiobenthic Boreohydra simplex is a life-cycle stage of Plotocnide borealis (Hydrozoa: Aplanulata).

Genetic barcodes of arctic medusae and meiobenthic cnidarians have uncovered a fortuitous connection between the medusa Plotocnide borealis Wagner, 1885 and the minute, mud-dwelling polyp Boreohydra simplex Westblad, 1937. Little to no sequence differences exist among independently collected samples identified as Boreohydra simplex and Plotocnide borealis, showing that the two different forms represent a single species that is henceforth known by the older name Plotocnide borealis Wagner, 1885. The polyp form has been observed to produce bulges previously hypothesized to be gonophores, and the results here are consistent with that view. Interestingly, the polyp has also been reported to produce egg cells in the epiderm, a surprising phenomenon that we document here for only the second time. Thus, P. borealis produces eggs in two different life stages, polyp and medusa. This is the first documented case of a metagenetic medusozoan species being able to produce gametes in both the medusa and polyp stage. It remains unclear what environmental/ecological conditions modulate the production of eggs and/or medusa buds in the polyp stage. Similarly, sperm production, fertilization and development are unknown, warranting further studies.

Thermal and Osmotic Tolerance of 'Irukandji' Polyps: Cubozoa; Carukia barnesi.

This research explores the thermal and osmotic tolerance of the polyp stage of the Irukandji jellyfish Carukia barnesi, which provides new insights into potential polyp habitat suitability. The research also targets temperature, salinity, feeding frequency, and combinations thereof, as cues for synchronous medusae production. Primary findings revealed 100% survivorship in osmotic treatments between 19 and 46‰, with the highest proliferation at 26‰. As salinity levels of 26‰ do not occur within the waters of the Great Barrier Reef or Coral Sea, we conclude that the polyp stage of C. barnesi is probably found in estuarine environments, where these lower salinity conditions commonly occur, in comparison to the medusa stage, which is oceanic. Population stability was achieved at temperatures between 18 and 31°C, with an optimum temperature of 22.9°C. We surmise that C. barnesi polyps may be restricted to warmer estuarine areas where water temperatures do not drop below 18°C. Asexual reproduction was also positively correlated with feeding frequency. Temperature, salinity, feeding frequency, and combinations thereof did not induce medusae production, suggesting that this species may use a different cue, possibly photoperiod, to initiate medusae production.

Minicollagen cysteine-rich domains encode distinct modes of polymerization to form stable nematocyst capsules.

The stinging capsules of cnidarians, nematocysts, function as harpoon-like organelles with unusual biomechanical properties. The nanosecond discharge of the nematocyst requires a dense protein network of the capsule structure withstanding an internal pressure of up to 150 bar. Main components of the capsule are short collagens, so-called minicollagens, that form extended polymers by disulfide reshuffling of their cysteine-rich domains (CRDs). Although CRDs have identical cysteine patterns, they exhibit different structures and disulfide connectivity at minicollagen N and C-termini. We show that the structurally divergent CRDs have different cross-linking potentials in vitro and in vivo. While the C-CRD can participate in several simultaneous intermolecular disulfides and functions as a cystine knot after minicollagen synthesis, the N-CRD is monovalent. Our combined experimental and computational analyses reveal the cysteines in the C-CRD fold to exhibit a higher structural propensity for disulfide bonding and a faster kinetics of polymerization. During nematocyst maturation, the highly reactive C-CRD is instrumental in efficient cross-linking of minicollagens to form pressure resistant capsules. The higher ratio of C-CRD folding types evidenced in the medusozoan lineage might have fostered the evolution of novel, predatory nematocyst types in cnidarians with a free-swimming medusa stage.

The earliest pelagic jellyfish with rhopalia from Cambrian Chengjiang Lagerstätte

Modern cnidarian medusae generally show a triphasic life cycle with the succession of a larva, a sessile polyp and a pelagic medusa stage. The debate around the metagenesis of sessile polyps into pelagic medusae has lasted for more than 100years. When pelagic forms originated is not clear. Hitherto, the earliest crown-group medusae have been found at Cambrian Stage 5 (traditional Middle Cambrian, 509Ma) in Utah, while diverse stem-group medusozoans were found in the basal Cambrian Fortunian Stage. No reliable medusae have been found from Cambrian Series 2 Stage 3 (ca. 521Ma), although the marine benthic community teemed with many phyla of bilaterians, sponges and ctenophores. Here, we reinterpret Yunnanoascus haikouensisHu et al. (2007), originally described as a ctenophore, as a pelagic, predatory, crown-group medusozoan, based on the presence of rhopalia, possible radial canals and marginal tentacles. The medusae were a predatory member of the pelagic food web at the middle level of the ocean at Cambrian Stage 3.

Towards a phylogenetic classification of Leptothecata (Cnidaria, Hydrozoa).

Leptothecata are hydrozoans whose hydranths are covered by perisarc and gonophores and whose medusae bear gonads on their radial canals. They develop complex polypoid colonies and exhibit considerable morphological variation among species with respect to growth, defensive structures and mode of development. For instance, several lineages within this order have lost the medusa stage. Depending on the author, traditional taxonomy in hydrozoans may be either polyp- or medusa-oriented. Therefore, the absence of the latter stage in some lineages may lead to very different classification schemes. Molecular data have proved useful in elucidating this taxonomic challenge. We analyzed a super matrix of new and published rRNA gene sequences (16S, 18S and 28S), employing newly proposed methods to measure branch support and improve phylogenetic signal. Our analysis recovered new clades not recognized by traditional taxonomy and corroborated some recently proposed taxa. We offer a thorough taxonomic revision of the Leptothecata, erecting new orders, suborders, infraorders and families. We also discuss the origination and diversification dynamics of the group from a macroevolutionary perspective.

Mesoglein Expression During Aurelia aurita Life Cycle

Cnidarian is thought to possess two tissue layers: endoderm (gastroderm) and ectoderm, which are separated by the layer of extracellular matrix (ECM) called mesoglea. Aurelia aurita complex life cycle consists of several stages including alternating generations of sexual adult stage medusa and asexual stage polyp (scyphistoma). The main difference between polyp and medusa is the degree of the ECM (mesoglea) development. The new protein “mesoglein” was determined as one of the main components of mesoglea. Mesoglein is the component of the mesoglea “elastic” fibers. Previously we found that according to reverse transcription PCR mesoglein is expressed in the mature medusa exclusively in the mesogleal cells. The aim of the current work was to find out at what stage of development the specific mesoglein expression occurs. Mesogleins’ expression have been checked by PCR with specific primers on the template of transcriptomes’ cDNA from different stages; by mesogleins’ antibody staining on SDSPAGE and on paraffin sections; by histochemistry staining. In A.aurita life cycle mesoglein synthesis begins at scyphystoma polyp stage at RNA and protein level in mesogleal cells (Mc) which separated at this stage as the cell type. Mesoglein stored in granules both in Mc of adult medusa and polyp on its’ way to ECM elastic fibers. Our data perfectly correspond to the recently reported de novo transcriptome assembled from Illumina RNA-Seq data generated from six stages throughout the Aurelia life cycle.

Culturing the freshwater hydromedusa, Craspedacusta sowerbii under controlled laboratory conditions

Craspedacusta sowerbii (phylum Cnidaria, class Hydrozoa, family Olindiiae) is an alien species with a polyp and medusa stage and originates from China. The optimal temperature range for polyp production is 19–25 °C, while medusa production and growth require warmer water (21–30 °C). Reasons for the sporadic occurrence of medusae in nature are still unclear. Culturing medusae has been problematic while culturing polyps in the laboratory is well documented. The successful culturing of C. sowerbii medusae to gonad development is only documented to our knowledge in articles in Japanese with a probable limited readership. We successfully cultured all life cycle stages of Craspedacusta, including medusae. Medusae budded from polyps from Gatun, Panama and were cultured at 23 and 26 °C using local water and Hydra Medium. Medusae bell morphology, tentacle number, gonad development, and the number and size of prey consumed were documented. Smaller medusae were hand-fed, while mature medusae captured prey. Medusae lived for 3–11 weeks and gonad development occurred. A more thorough understanding of temperature, water chemistry, and laboratory feeding protocols during all life cycle stages of C. sowerbii will aid in predicting future distribution patterns of this invasive hydroid in freshwater habitats.

Margelopsis gibbesii (McCrady, 1859) (Cnidaria, Hydrozoa): taxonomic review, and conservation of usage by designation of a lectotype.

The binomen Nemopsis gibbesii McCrady, 1859, originally applied to a species of hydromedusa and its supposed hydroid from South Carolina, USA, has been known for more than a century to encompass two species. The medusa stage is conspecific with that of Nemopsis bachei L. Agassiz, 1849, while the hydroid stage is referable to the genus Margelopsis Hartlaub, 1897. Both that hydroid, and the medusa stage now subjectively linked to it, are commonly assigned to M. gibbesii. With no type having ever been designated for McCrady's species, a lectotype is designated to stabilize nomenclature of the species and serve as the standard for application of the name. In the absence of type specimens, an illustration of the hydroid of N. gibbesii by McCrady is chosen as lectotype, thereby conserving the name Margelopsis gibbesii in its accustomed usage. Hydroids and medusae of the species are re-described from new material, the cnidome of both stages is characterized, and a taxonomic review is given. The hydroid stage is reported for the first time since its original description in the mid-19th century. Medusae of M. gibbesii are also seen infrequently, having been reported only six times earlier.

Sea Jelly Spectacular – Influence on China's Aquariums

Jellyfish are one of the oldest multi-organ animals found today; dating back at least 500 million years and some say even as many as 700 million years. There are even two or three that are considered immortal in that they can revert back to their polyp stage from the medusa stage. How amazing is that? But their increased prominence in our oceans is due to fishing down the food chain so that sea jellies have fewer predators and to the increased nutrients we are adding to our oceans via the rivers where the fertilizers and other chemical run off our land and into the water. Climate change is also affecting our sea jelly populations. Sea jellies are beautiful, graceful, elegant and mesmerizing and because of that, we have the opportunity to connect our visitors emotionally to our oceans and inspire the care and behaviour changes needed to help our oceans become healthy again.Over the past 500-plus million years, these beautifully tetra-radial symmetrical jellies have diversified with over 200 scyphozoans, and possibly up to a couple of thousand hydrozoan species. They can live for only a few hours to six months in the wild, though in our aquariums, they have lived much longer. They have even diversified how they reproduce from asexual budding and fission to sexual reproduction, which makes our job of maintaining sustainable populations within our facilities all the more challenging, and no wonder these amazing jellies have fascinated us for decades.

The life cycle of Catablema vesicarium (A. Agassiz, 1862) (Hydrozoa, Pandeidae)

The hydrozoan classification systems often rely on limited character sets of either polyp or medusa stages, and these classifications stay non-consistent in many cases because of lack of life cycle data. This is usual for hydrozoans with tiny inconspicuous colonies and intermittent medusae production period such as pandeid in the polar latitudes. In this study, the previously unknown life cycle of boreal-Arctic pandeid hydrozoan Catablema vesicarium was elucidated under experimental conditions. Medusae C. vesicarium were found near the Pertsov Biological Station in the White Sea and maintained in a laboratory till spawning. Morphological descriptions of development stages including medusae, eggs, planulae, polyps, and medusae buds are represented. Hydroid C. vesicarium was also collected on the shell with live Astarte elliptica. Identification of this colony was confirmed by comparing the sequences of the mitochondrial CO1, 16S, and nuclear 18S-ITS1-5.8S gene fragments of medusae and polyps. Hydroids C. vesicarium have almost sessile polyps with perisarc cup only at the base, and newborn medusae have rudimentary marginal bulbs which alternate with four marginal tentacles. Identification characters of the cultivated hydrozoan are discussed in comparison with other known pandeids. The data on temperature range of medusae appearing in experiments may be potentially useful for studying seasonality of jellyfish in the sea.

Interspecific Differential Expression Analysis of RNA-Seq Data Yields Insight into Life Cycle Variation in Hydractiniid Hydrozoans.

Hydrozoans are known for their complex life cycles, which can alternate between an asexually reproducing polyp stage and a sexually reproducing medusa stage. Most hydrozoan species, however, lack a free-living medusa stage and instead display a developmentally truncated form, called a medusoid or sporosac, which generally remains attached to the polyp. Although evolutionary transitions in medusa truncation and loss have been investigated phylogenetically, little is known about the genes involved in the development and loss of this life cycle stage. Here, we present a new workflow for evaluating differential expression (DE) between two species using short read Illumina RNA-seq data. Through interspecific DE analyses between two hydractiniid hydrozoans, Hydractinia symbiolongicarpus and Podocoryna carnea, we identified genes potentially involved in the developmental, functional, and morphological differences between the fully developed medusa of P. carnea and reduced sporosac of H. symbiolongicarpus. A total of 10,909 putative orthologs of H. symbiolongicarpus and P. carnea were identified from de novo assemblies of short read Illumina data. DE analysis revealed 938 of these are differentially expressed between P. carnea developing and adult medusa, when compared with H. symbiolongicarpus sporosacs, the majority of which have not been previously characterized in cnidarians. In addition, several genes with no corresponding ortholog in H. symbiolongicarpus were expressed in developing medusa of P. carnea. Results presented here show interspecific DE analyses of RNA-seq data to be a sensitive and reliable method for identifying genes and gene pathways potentially involved in morphological and life cycle differences between species.

Trends in the diversity, distribution and life history strategy of Arctic Hydrozoa (Cnidaria).

This is the first attempt to compile a comprehensive and updated species list for Hydrozoa in the Arctic, encompassing both hydroid and medusa stages and including Siphonophorae. We address the hypothesis that the presence of a pelagic stage (holo- or meroplanktonic) was not necessary to successfully recolonize the Arctic by Hydrozoa after the Last Glacial Maximum. Presence-absence data of Hydrozoa in the Arctic were prepared on the basis of historical and present-day literature. The Arctic was divided into ecoregions. Species were grouped into distributional categories according to their worldwide occurrences. Each species was classified according to life history strategy. The similarity of species composition among regions was calculated with the Bray-Curtis index. Average and variation in taxonomic distinctness were used to measure diversity at the taxonomic level. A total of 268 species were recorded. Arctic-boreal species were the most common and dominated each studied region. Nineteen percent of species were restricted to the Arctic. There was a predominance of benthic species over holo- and meroplanktonic species. Arctic, Arctic-Boreal and Boreal species were mostly benthic, while widely distributed species more frequently possessed a pelagic stage. Our results support hypothesis that the presence of a pelagic stage (holo- or meroplanktonic) was not necessary to successfully recolonize the Arctic. The predominance of benthic Hydrozoa suggests that the Arctic could have been colonised after the Last Glacial Maximum by hydroids rafting on floating substrata or recolonising from glacial refugia.

Transcriptome profiling of the dynamic life cycle of the scypohozoan jellyfish Aurelia aurita.

BackgroundThe moon jellyfish Aurelia aurita is a widespread scyphozoan species that forms large seasonal blooms. Here we provide the first comprehensive view of the entire complex life of the Aurelia Red Sea strain by employing transcriptomic profiling of each stage from planula to mature medusa.ResultsA de novo transcriptome was assembled from Illumina RNA-Seq data generated from six stages throughout the Aurelia life cycle. Transcript expression profiling yielded clusters of annotated transcripts with functions related to each specific life-cycle stage. Free-swimming planulae were found highly enriched for functions related to cilia and microtubules, and the drastic morphogenetic process undergone by the planula while establishing the future body of the polyp may be mediated by specifically expressed Wnt ligands. Specific transcripts related to sensory functions were found in the strobila and the ephyra, whereas extracellular matrix functions were enriched in the medusa due to high expression of transcripts such as collagen, fibrillin and laminin, presumably involved in mesoglea development. The CL390-like gene, suggested to act as a strobilation hormone, was also highly expressed in the advanced strobila of the Red Sea species, and in the medusa stage we identified betaine-homocysteine methyltransferase, an enzyme that may play an important part in maintaining equilibrium of the medusa’s bell. Finally, we identified the transcription factors participating in the Aurelia life-cycle and found that 70% of these 487 identified transcription factors were expressed in a developmental-stage-specific manner.ConclusionsThis study provides the first scyphozoan transcriptome covering the entire developmental trajectory of the life cycle of Aurelia. It highlights the importance of numerous stage-specific transcription factors in driving morphological and functional changes throughout this complex metamorphosis, and is expected to be a valuable resource to the community.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1320-z) contains supplementary material, which is available to authorized users.

The non-Siphonophoran Hydrozoa (Cnidaria) of Salento, Italy with notes on their life-cycles: an illustrated guide.

The majority of Hydrozoa is represented by not readily noticeable, small species. In recent decades, however, taxonomic knowledge of the group has increased worldwide, with a significant number of investigations focused on the Mediterranean Sea. Over more than two decades, 115 species of hydrozoans were recorded from coastal waters along nearly 300 km of the Salento Peninsula (Apulia, Italy). For each species, records from different collections were merged into single sheets of a general database. For each species, the following information is reported: description, cnidome, biology, occurrence in Salento, worldwide distribution, and bibliography. Descriptions refer to the benthic hydroid stage and, when present, also to the planktonic medusa stage. The 115 species of Hydrozoa, recorded along the Salento coastline, represent 25% of the Mediterranean Hydrozoa fauna (totaling 461 species), and nearly 3% of 3,702 world's known species covered in a recent monograph. Four species are non-indigenous, three of them with invasive behavior (Clytia hummelincki, Clytia linearis, and Eudendrium carneum), and one species now very common (Eudendrium merulum) in Salento. The complete life cycle of Clytia paulensis (Vanhöffen, 1910) is described for the first time.

Deep-sea epibiotic hydroids from the abyssal plain adjacent to the Kuril–Kamchatka Trench with description of Garveia belyaevi sp. nov. (Hydrozoa, Bougainvilliidae)

Examination of material collected by the German–Russian KuramBio Deep-Sea Expedition to the abyssal plain adjacent to the Kuril–Kamchatka Trench revealed about 17 hydroid species, including two species presumably new to science. Before the KuramBio Expedition only fragments of the unidentified hydroids and Cryptolaria sp. were collected in the Kuril–Kamchatka Trench from depths exceeding 3000m. Descriptions of three species of epibiotic hydroids (including one new species, Garveia belyaevi sp. nov.) are presented herein. A colony of G. belyaevi sp. nov. (the third deep-sea and deepest species of the wide distributed genus Garveia) was attached to the spines of unidentified irregular sea urchins from depths 5217 to 5229m. Нalitholus (?) sp. (Hydrozoa, Anthoathecata) colonized the skin of spoon worms (Echiura) but could not be identified to species level because the mature medusa stage was absent in the material. An unidentified juvenile polyp (Pandeidae) was found on the bryozoan Tricitella minini attached to spines of irregular sea urchins Echinosigra amphora. Colonial sedentary organisms inhabiting abyssal plains with soft bottoms may colonize invertebrates which are seldom used as substrates for epibiota in shallow waters. Epibiosis among abyssal colonial invertebrates, though extremely poorly studied, appears to be rather frequent.

The hydroid and early medusa stage ofOlindias formosus(Cnidaria, Hydrozoa, Limnomedusae)

Olindiasspp. medusae are found worldwide in sublittoral tropical and sub-tropical coastal regions; their occurrence near shore can result in human envenomation events. While behaviour of medusae and human contact with medusae has been documented for the genus, the hydroid (polyp) phase of theOlindiaslife cycle has eluded investigators for over a century. Given the recent debate among public media and scientific communities that jellyfish blooms are increasing worldwide, there is a growing urgency to understand how and why jellyfish populations bloom. In order to understand jellyfish population dynamics, the asexual benthic phase must be studied to determine when, where, and how juvenile medusae are produced. In this study, husbandry management strategies, including the creation of artificial habitat forOlindias formosusmedusae in aquaria were developed to encourage spawning and larval settlement. The resultant hydroid colony ofOlindias formosuswas discovered in November of 2012, utilizing the natural fluorescence of the medusa as a detection method. A description of the hydroid and early medusa stage is presented. These techniques provide a basis for locatingin situthe benthic hydroid phases within this genus and other fluorescent medusae, the discovery of which may lead to a better understanding of the causative factors for jellyfish blooms.

An endogenous green fluorescent protein–photoprotein pair in Clytia hemisphaerica eggs shows co-targeting to mitochondria and efficient bioluminescence energy transfer

Green fluorescent proteins (GFPs) and calcium-activated photoproteins of the aequorin/clytin family, now widely used as research tools, were originally isolated from the hydrozoan jellyfish Aequora victoria. It is known that bioluminescence resonance energy transfer (BRET) is possible between these proteins to generate flashes of green light, but the native function and significance of this phenomenon is unclear. Using the hydrozoan Clytia hemisphaerica, we characterized differential expression of three clytin and four GFP genes in distinct tissues at larva, medusa and polyp stages, corresponding to the major in vivo sites of bioluminescence (medusa tentacles and eggs) and fluorescence (these sites plus medusa manubrium, gonad and larval ectoderms). Potential physiological functions at these sites include UV protection of stem cells for fluorescence alone, and prey attraction and camouflaging counter-illumination for bioluminescence. Remarkably, the clytin2 and GFP2 proteins, co-expressed in eggs, show particularly efficient BRET and co-localize to mitochondria, owing to parallel acquisition by the two genes of mitochondrial targeting sequences during hydrozoan evolution. Overall, our results indicate that endogenous GFPs and photoproteins can play diverse roles even within one species and provide a striking and novel example of protein coevolution, which could have facilitated efficient or brighter BRET flashes through mitochondrial compartmentalization.