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Concept: Cnidocyte


The nematocyst is one of the most complex intracellular structures found in nature and is the defining feature of the phylum Cnidaria (sea anemones, corals, jellyfish, and hydroids). This miniature stinging organelle contains and delivers venom into prey and foe yet little is known about its toxic components. In the present study, we identified by tandem mass spectrometry 20 proteins released upon discharge from the nematocyst of the model sea anemone Nematostella vectensis. The availability of genomic and transcriptomic data for this species enabled accurate identification and phylogenetic study of these components. Fourteen of these proteins could not be identified in other animals suggesting that they might be the products of taxonomically restricted genes, a finding which fits well their origin from a taxon-specific organelle. Further, we studied by in situ hybridization the localization of two of the transcripts encoding the putative nematocyst venom proteins: a metallopeptidase related to the Tolloid family and a cysteine-rich protein. Both transcripts were detected in nematocytes, which are the cells containing nematocysts, and the metallopeptidase was found also in pharyngeal gland cells. Our findings reveal for the first time the possible venom components of a sea anemone nematocyst and suggest their evolutionary origins.

Concepts: Gene, Animal, Coral, Cnidaria, Jellyfish, Anthozoa, Sea anemone, Cnidocyte


The nematocyst is a complex intracellular structure unique to Cnidaria. When triggered to discharge, the nematocyst explosively releases a long spiny, tubule that delivers an often highly venomous mixture of components. The box jellyfish, Chironex fleckeri, produces exceptionally potent and rapid-acting venom and its stings to humans cause severe localized and systemic effects that are potentially life-threatening. In an effort to identify toxins that could be responsible for the serious health effects caused by C. fleckeri and related species, we used a proteomic approach to profile the protein components of C. fleckeri venom. Collectively, 61 proteins were identified, including toxins and proteins important for nematocyte development and nematocyst formation (nematogenesis). The most abundant toxins identified were isoforms of a taxonomically restricted family of potent cnidarian proteins. These toxins are associated with cytolytic, nociceptive, inflammatory, dermonecrotic and lethal properties and expansion of this important protein family goes some way to explaining the destructive and potentially fatal effects of C. fleckeri venom. Venom proteins and their post-translational modifications (PTMs) were further characterized using toxin-specific antibodies and phosphoprotein/glycoprotein-specific stains. Results indicated that glycosylation is a common PTM of the toxin family while a lack of cross-reactivity by toxin-specific antibodies infers there is significant divergence in structure and possibly function among family members. This study provides insight into the depth and diversity of protein toxins produced by harmful box jellyfish and represents the first description of a cubozoan jellyfish venom proteome.

Concepts: Protein, Proteomics, Cnidaria, Jellyfish, Toxin, Cnidocyte, Box jellyfish, Chironex fleckeri


Cnidarian envenomations are the leading cause of severe and lethal human sting injuries from marine life. The total amount of venom discharged into sting-site tissues, sometimes referred to as “venom load”, has been previously shown to correlate with tentacle contact length and sequelae severity. Since <1% of cnidae discharge upon initial tentacle contact, effective and safe removal of adherent tentacles is of paramount importance in the management of life-threatening cubozoan stings. We evaluated whether common rinse solutions or scraping increased venom load as measured in a direct functional assay of venom activity (hemolysis). Scraping significantly increased hemolysis by increasing cnidae discharge. For Alatina alata, increases did not occur if the tentacles were first doused with vinegar or if heat was applied. However, in Chironex fleckeri, vinegar dousing and heat treatment were less effective, and the best outcomes occurred with the use of venom-inhibiting technologies (Sting No More(®) products). Seawater rinsing, considered a "no-harm" alternative, significantly increased venom load. The application of ice severely exacerbated A. alata stings, but had a less pronounced effect on C. fleckeri stings, while heat application markedly reduced hemolysis for both species. Our results do not support scraping or seawater rinsing to remove adherent tentacles.

Concepts: Cnidaria, Jellyfish, Cnidocyte, Box jellyfish, Chironex fleckeri, Chirodropidae


Do all animals sleep? Sleep has been observed in many vertebrates, and there is a growing body of evidence for sleep-like states in arthropods and nematodes [1-5]. Here we show that sleep is also present in Cnidaria [6-8], an earlier-branching metazoan lineage. Cnidaria and Ctenophora are the first metazoan phyla to evolve tissue-level organization and differentiated cell types, such as neurons and muscle [9-15]. In Cnidaria, neurons are organized into a non-centralized radially symmetric nerve net [11, 13, 15-17] that nevertheless shares fundamental properties with the vertebrate nervous system: action potentials, synaptic transmission, neuropeptides, and neurotransmitters [15-20]. It was reported that cnidarian soft corals [21] and box jellyfish [22, 23] exhibit periods of quiescence, a pre-requisite for sleep-like states, prompting us to ask whether sleep is present in Cnidaria. Within Cnidaria, the upside-down jellyfish Cassiopea spp. displays a quantifiable pulsing behavior, allowing us to perform long-term behavioral tracking. Monitoring of Cassiopea pulsing activity for consecutive days and nights revealed behavioral quiescence at night that is rapidly reversible, as well as a delayed response to stimulation in the quiescent state. When deprived of nighttime quiescence, Cassiopea exhibited decreased activity and reduced responsiveness to a sensory stimulus during the subsequent day, consistent with homeostatic regulation of the quiescent state. Together, these results indicate that Cassiopea has a sleep-like state, supporting the hypothesis that sleep arose early in the metazoan lineage, prior to the emergence of a centralized nervous system.

Concepts: Nervous system, Animal, Neurotransmitter, Cnidaria, Jellyfish, Ctenophora, Sponge, Cnidocyte


Jellyfish (cnidarians) have a worldwide distribution. Despite most being harmless, some species may cause local and also systemic reactions. Treatment of jellyfish envenomation is directed at: alleviating the local effects of venom, preventing further nematocyst discharges and controlling systemic reactions, including shock. In severe cases, the most important step is stabilizing and maintaining vital functions. With some differences between species, there seems to be evidence and consensus on oral/topical analgesics, hot water and ice packs as effective painkillers and on 30 s application of domestic vinegar (4%-6% acetic acid) to prevent further discharge of unfired nematocysts remaining on the skin. Conversely, alcohol, methylated spirits and fresh water should be carefully avoided, since they could massively discharge nematocysts; pressure immobilization bandaging should also be avoided, as laboratory studies show that it stimulates additional venom discharge from nematocysts. Most treatment approaches are presently founded on relatively weak evidence; therefore, further research (especially randomized clinical trials) is strongly recommended. Dissemination of appropriate treatment modalities should be deployed to better inform and educate those at risk. Adequate signage should be placed at beaches to notify tourists of the jellyfish risk. Swimmers in risky areas should wear protective equipment.

Concepts: Clinical trial, Ethanol, Acetic acid, Cnidaria, Jellyfish, Vinegar, Cnidocyte, Box jellyfish


QUESTION Which treatments are effective for treating jellyfish stings from species in North America and Hawaii? REVIEW SCOPE Included studies compared interventions for pain relief, prevention of nematocyst discharge, or extrusion of venom from true jellyfish (Cnidaria), box jellyfish, or Physalia species found in North American and Hawaiian waters. Outcomes were pain or erythema from envenomation, discharge of nematocysts, and extrusion of venom. REVIEW METHODS MEDLINE, EMBASE Excerpta Medica, CINAHL, Cochrane Reviews, Google Scholar, reviews, and reference lists were searched for English-language studies. 19 studies met inclusion criteria; 6 were randomized controlled trials (RCTs) (n = 390), all measuring pain outcomes, and are reported in this abstract. 2 RCTs had inadequate randomization, 2 had inadequate blinding, and 2 had low follow-up. No RCTs measured discharge of nematocysts or extrusion of venom, and none studied stings from Chiropsalmus quadrumanus or Chrysaora quinquecirrha. MAIN RESULTS In general, hot water or application of heat reduced pain from Physalia species and Carybdea alata stings (Table). CONCLUSION Evidence from randomized controlled trials suggests that heat or hot water reduces pain from Physalia species and Carybdea alata jellyfish stings, but few studies were found.Interventions for reducing pain from jellyfish stings (6 randomized controlled trials)SpeciesnComparisonsResultsPhysalia spp.96Hot water immersion vs ice packHot water reduced pain more than ice pack.54Hot shower vs ice packHot showers reduced time to complete relief and had greater overall pain reduction at 15 minutes.20Vinegar vs Stingose* vs methylated spirits vs saltwaterVinegar and Stingose reduced pain; methylated spirits increased pain.Carybdea alata25Hot water immersion vs control (papain or vinegar)Hot water reduced pain.133Hot pack vs cold pack vs placeboHot pack reduced pain more than placebo and cold pack; cold pack did not differ from placebo.62Adolph’s meat tenderizer (papain) vs freshwater vs Sting-Aid† vs seawaterNo difference in resolution of pain.*Stingose = 20% aluminum sulfate in detergent.†Sting-Aid = aerolized mixture of water, detergent, and aluminum sulfate.

Concepts: Randomized controlled trial, Aluminium, North America, Cnidaria, Jellyfish, Cnidocyte, Box jellyfish, Carybdea alata


Directional swimming in the box jellyfish Tripedalia cystophora (cubozoa, cnidaria) is controlled by the shape of the velarium, which is a thin muscular sheet that forms the opening of the bell. It was unclear how different patterns of visual stimulation control directional swimming and that is the focus of this study. Jellyfish were tethered inside a small experimental tank, where the four vertical walls formed light panels. All four panels were lit at the start of an experiment. The shape of the opening in the velarium was recorded in response to switching off different combinations of panels. We found that under the experimental conditions the opening in the velarium assumed three distinct shapes during a swim contraction. The opening was (1) centred or it was off-centred and pocketed out either towards (2) a rhopalium or (3) a pedalium. The shape of the opening in the velarium followed the direction of the stimulus as long as the stimulus contained directional information. When the stimulus contained no directional information, the percentage of centred pulses increased and the shape of the off-centred pulses had a random orientation. Removing one rhopalium did not change the directional response of the animals, however, the number of centred pulses increased. When three rhopalia were removed, the percentage of centred pulses increased even further and the animals lost their ability to respond to directional information.

Concepts: Animal, Cnidaria, Jellyfish, Ctenophora, Cnidocyte, Box jellyfish, Chironex fleckeri, Medusa


Nematocytes, the stinging cells of cnidarians, are the most evolutionarily ancient venom apparatus. These nano-syringe like weaponry systems reach pressures of ~150 atmospheres before discharging and punching through the outer layer of the prey or predator at accelerations of more than 5,000,000g, making them one of the fastest bio-mechanical events known. To gain better understanding of the function of the complex, phylum-specific nematocyst organelle, and its venom payload, we compared the soluble nematocyst’s proteome from the sea anemone Anemonia viridis, the jellyfish Aurelia aurita and the hydrozoan Hydra magnipapillata, each belonging to one of the three basal cnidarian lineages which diverged over 600 million years ago. Although the basic morphological and functional characteristics of the nematocysts of the three organisms are similar, out of hundreds of proteins identified in each organism, only six are shared. These include structural proteins, a chaperone which may help maintain venon activity over extended periods, and dikkopf, an enigmatic wnt ligand which may also serve as a toxin. Nevertheless, many protein domains are shared between the three organisms' nematocyst content suggesting common proteome functionalities. The venoms of Hydra and Aurelia appear to be functionally similar and composed mainly of cytotoxins and enzymes, whereas the venom of the Anemonia is markedly unique and based on peptide neurotoxins. Cnidarian venoms show evidence for functional recruitment, yet evidence for diversification through positive selection, common to other venoms, is lacking. The final injected nematocyst payload comprises a mixture of dynamically-evolving proteins involved in the development, maturation, maintenance and discharge of the nematocysts, which is unique to each organism and potentially to each nematocyst type.

Concepts: Coral, Cnidaria, Jellyfish, Scyphozoa, Polyp, Hydrozoa, Sea anemone, Cnidocyte


Cnidarian venom research has lagged behind other toxinological fields due to technical difficulties in recovery of the complex venom from the microscopic nematocysts. Here we report a newly developed rapid, repeatable and cost effective technique of venom preparation, using ethanol to induce nematocyst discharge and to recover venom contents in one step. Our model species was the Australian box jellyfish (Chironex fleckeri), which has a notable impact on public health. By utilizing scanning electron microscopy and light microscopy, we examined nematocyst external morphology before and after ethanol treatment and verified nematocyst discharge. Further, to investigate nematocyst content or “venom” recovery, we utilized both top-down and bottom-up transcriptomics-proteomics approaches and compared the proteome profile of this new ethanol recovery based method to a previously reported high activity and recovery protocol, based upon density purified intact cnidae and pressure induced disruption. In addition to recovering previously characterized box jellyfish toxins, including CfTX-A/B and CfTX-1, we recovered putative metalloproteases and novel expression of a small serine protease inhibitor. This study not only reveals a much more complex toxin profile of Australian box jellyfish venom but also suggests that ethanol extraction method could augment future cnidarian venom proteomics research efforts.

Concepts: Protein, Serine protease, Protease, Cnidaria, Jellyfish, Cnidocyte, Box jellyfish, Chironex fleckeri


Of the 6,000 reef fish species, only 128 feed on corals [1,2]. Despite being widely available on tropical reefs, corals appear to represent a particularly challenging trophic resource, with mucus- and nematocyst-laden tissues spread over a sharp coral skeleton. Here we report that coral-feeding tubelip wrasses use highly modified lips to suck material from the coral surface. These lips have a specialized mushroom-like lamellar epithelium that secretes mucus. This mucus may facilitate suction and reduce damage by nematocysts in a manner akin to anemonefishes. The remarkable lip specializations observed in tubelip wrasses highlight the potential role of soft tissues in shaping the trophic ability of fishes.

Concepts: Species, Animal, Coral, Coral reef, Scleractinia, Tissues, Cnidaria, Cnidocyte