Painful Sting Research Articles

Has the indestructible insect met its match? Velvet ants as prey to bufonid toads

Velvet ants are a group of parasitoid wasps that are well-known for a suite of defensive traits including bright coloration, a thick exoskeleton, and a painful sting. Previous experiments have demonstrated that while virtually all potential predators avoid velvet ants, toads (family Bufonidae) may be able to prey upon them. We conducted a series of trials to determine whether American (Anaxyrus americanus) and Fowler’s toads (Anaxyrus fowleri) prey upon velvet ants. Toad responses toward velvet ants were variable, ranging between complete avoidance, consumption and regurgitation, and consumption and retention. In total, 12 out of 22 trials resulted in the toads consuming a velvet ant. Of these, velvet ants were either regurgitated unharmed (n = 8) or retained (n = 4). In general, there were no significant differences in responses toward velvet ants between American and Fowler’s toads. Due to a rapid prey acquisition and their unique foraging behavior, toads present the most likely predator to velvet ants. Our results indicate that toads have the capacity to consume and retain female velvet ants. However, female velvet ants demonstrate the ability to endure upwards of 20 min inside the stomach of a toad and survive.

Breastfeeding as an analgesic method during vaccinations.

Infants undergo painful stings such as intradermal and intramuscular stings during vaccination. Clinical trial have showed analgesic methods to reduce the painful in both infants and kids. There are different types of non-pharmacological interventions which have an analgesic effect in infants during vaccinations such as: breastfeeding, cladding the infants, the skin to skin contact, the use of sweetened substance. A review of the primary and secondary literature was carried out in the database Medline(PubMed). The bibliographic research was focused on the critical reading of the studies of the last ten years. Eight articles, including seven randomized clinical trials and one systematic review have been found. All registered studies report a reduction of the average value of the pain measured through both validated rating scales and through the measurement of the average duration of the cry during and after the vaccination in breastfeed infants. However it hasn't been demonstrated a statistically significant improvement in physiological parameters. It is desirable that the literature produce further studies related to the changes of the vital parameters during the breastfeeding which allow a clear comparison between clinical trials.

Defensive Venoms: Is Pain Sufficient for Predator Deterrence?

Pain, though unpleasant, is adaptive in calling an animal’s attention to potential tissue damage. A long list of animals representing diverse taxa possess venom-mediated, pain-inducing bites or stings that work by co-opting the pain-sensing pathways of potential enemies. Typically, such venoms include toxins that cause tissue damage or disrupt neuronal activity, rendering painful stings honest indicators of harm. But could pain alone be sufficient for deterring a hungry predator? Some venomologists have argued “no”; predators, in the absence of injury, would “see through” the bluff of a painful but otherwise benign sting or bite. Because most algogenic venoms are also toxic (although not vice versa), it has been difficult to disentangle the relative contributions of each component to predator deterrence. Southern grasshopper mice (Onychomys torridus) are voracious predators of arthropods, feeding on a diversity of scorpion species whose stings vary in painfulness, including painful Arizona bark scorpions (Centruroides sculpturatus) and essentially painless stripe-tailed scorpions (Paravaejovis spinigerus). Moreover, southern grasshopper mice have evolved resistance to the lethal toxins in bark scorpion venom, rendering a sting from these scorpions painful but harmless. Results from a series of laboratory experiments demonstrate that painful stings matter. Grasshopper mice preferred to prey on stripe-tailed scorpions rather than bark scorpions when both species could sting; the preference disappeared when each species had their stingers blocked. A painful sting therefore appears necessary for a scorpion to deter a hungry grasshopper mouse, but it may not always be sufficient: after first attacking and consuming a painless stripe-tailed scorpion, many grasshopper mice went on to attack, kill, and eat a bark scorpion even when the scorpion was capable of stinging. Defensive venoms that result in tissue damage or neurological dysfunction may, thus, be required to condition greater aversion than venoms causing pain alone.

Effects of sea-level rise onphysiological ecology of populations of a ground-dwelling ant.

IntroductionSea-level rise is a consequence of climate change that can impact the ecological and physiological changes of coastal, ground-dwelling species. Sea-level rise has a potential to inundate birds, rodents, spiders, and insects that live on the ground in coastal areas. Yet, there is still much to be learned concerning the specifics of these impacts. The red imported fire ant Solenopsis invicta (Buren) excavates soil for its home and is capable of surviving flooding. Because of their ground-dwelling life history and rapid reproduction, fire ants make an ideal model for discovery and prediction of changes that may be due to sea-level rise. There are up to 500,000 individuals in a colony, and these invasive ants naturally have a painful sting. However, observations suggest that colonies of fire ants that dwell in tidally-influenced areas are more aggressive with more frequent stings and more venom injected per sting (behavioral and physiological changes) than those located inland. This may be an adaption to sea-level rise. Therefore, the objective of this study is to elucidate differences in inland and coastal defensiveness via micro-dissection and comparison of head width, head length, stinger length, and venom sac volume. But first because fire ants’ ability to raft on brackish tidal water is unknown, it had to be determined if fire ants could indeed raft in brackish water and examine the behavior differences between those flooded with freshwater vs. saltwater.MethodsTo test the coastal-aggression hypothesis, inland colonies and coastal colonies, which experience relatively greater amounts of flooding, specifically regular tidal and windblown water and oscillations (i.e. El Nińo Southern Oscillation) from the Gulf of Mexico, were collected. To mimic sea-level rise, the colonies were flooded in salinities that correspond to both their collection site and conditions found in a variety of locales and situations (such as storm surge from a tropical storm). Individual ants were immediately taken from each colony for dissection before flooding, 1-hour into flooding, and 24-hours into flooding.Results and discussionFire ants use their venom to defend themselves and to communicate alarm or aggression. Dissections and measurement of heads, venom sacs, and stingers revealed both coastal and inland colonies experience an increase in venom sac volume after 24 hours; in fact coastal colonies increased their venom volume by 75% after 24 h of flooding Whether this venom sac enlargement is due to diffusion of water or venom sac production is unknown. These ground-dwelling ants exhibit physiological and behavioral adaptations to ongoing sea-level rise possibly indicating that they are responding to increased flooding. Fire ants will raft on high-salinity water; and sea-level rise may cause stings by flooded ants to be more severe because of increased venom volume.

Mutagenesis mediated by CRISPR/Cas9 in the red imported fire ant, Solenopsis invicta

CRISPR/Cas9 mediated mutagenesis has revolutionized the testing of gene function in both model and non-model organisms. The red imported fire ant, Solenopsis invicta, is the best-studied ant species because of their painful sting, aggressive nature, and their detrimental effects on invaded ecosystems. We have developed a microinjection protocol for CRISPR/Cas9 mutagenesis of fire ant embryos. As a proof-of-principle we generated individuals mosaic for the knockout of Sinv-spitz or Gp-9. We verified that many injected individuals carry mutations, often to high frequency of the cells within the individual. Observations at the first instar larval stage indicate that mutating Sinv-spitz does not produce a loss of oenocyte phenotype, as would have been expected based on the homologous function of the fruit fly, Drosophila melanogaster, spitz. Our success indicates that CRISPR/Cas9 mutagenesis should be a useful technique for studying gene function in the fire ant at the individual and possibly social levels.

Nest Association between Camponotus fallax (Hymenoptera: Formicidae) and Vespa crabro (Hymenoptera: Vespidae) in Central Iberian Peninsula

Because social wasps often defend their nests by inflicting painful stings or bites, some animals associate with them looking for protection against potential predators. Some neotropical vespids are known to maintain associations with other insect and vertebrate taxa, such as birds and bats, however there are not previous records about associations between ants and hornets in Europe. In this study, we reported the first case of association between the arboreal ant Camponotus fallax and the European hornet Vespa crabro in Europe. The observations were made in Central Spain, where two colonies of C. fallax were found in two different avian nest-boxes inhabited by V. crabro when spotless starlings finished their breeding season. The reasons of this possible association are also discussed.

Evidence for prey specialisation on venomous weeverfish by grey seals

Weeverfish are widely distributed venomous fish that inhabit shallow sandy waters ranging from Norway to Morocco and extending to the Black Sea. Despite the painful sting produced by their venom, we report the first indication of grey seals apparently specialising on this venomous prey. Weeverfish occurred in high numbers within 4% of seal scat samples (n = 149) collected between 2011 and 2013, from Wexford in southeast Ireland. The low frequency but relatively high abundance of weeverfish within the diet samples suggest that some grey seals may have developed a mechanism for specialisation through learned behaviour and/or acquired immunity to weeverfish toxins. The findings highlight potential for investigation into seal foraging behaviour and the mechanisms of venom avoidance.

Scorpion venom yields novel alkaloid

Scorpion venom packs more than a painful sting. It’s also chock full of novel bioactive compounds—most of them polypeptides—that intrigue scientists. For the first time, researchers have identified...

Scorpion composition and scorpionism in a high-risk area, the southwest of Iran.

BackgroundScorpions are usually defined as predatory arachnids having venomous and painful stings. Scorpionism is considered as one of the health and medical problems in undeveloped tropical and subtropical countries in the world that endangers thousands of people annually.ObjectiveThis study was done for identification of scorpion fauna and scorpionism location in a high-risk area in southwest of Iran.MethodsThis study was carried out in Andimeshk district located in Khuzestan province which has the highest frequency of scorpionism in Iran. In total, 4 urban and 15 rural areas with various climates and topography were selected for monthly scorpion collection in 2016. Additionally, clinical data was obtained from questionnaires over a 5-year period (2012 to 2016) which were completed by physicians and health staff in hospitals and health centers. The data were analyzed by IBM-SPSS Version 20.ResultsA total of 850 scorpion samples with the most frequency in rural areas were collected. Eight species belonging to three families; Buthidae, Scorpionidae and Hemiscorpiidae were identified. A. crassicauda was the dominant species followed by H. lepturus. The largest collection due to scorpion’s activity was recorded in summer. The five-year prevalence of scorpion sting were 9.1/1000 inhabitants. The highest frequency of scorpionism was observed in the male age group of 25–34 years. Most cases had been treated with polyvalent scorpion antivenom within 6–12 hours of the sting.ConclusionBased on the findings, six species of medically important scorpions that were previously reported from Iran were also collected and caught in this study area. The findings of this study can be useful for policymakers at the Andimeshk Healthcare Center to prevent scorpionism and provide appropriate treatment for scorpionism cases.

Lionfish venom elicits pain predominantly through the activation of nonpeptidergic nociceptors.

The lionfish (Pterois volitans) is a venomous invasive species found in the Caribbean and Northwestern Atlantic. It poses a growing health problem because of the increase in frequency of painful stings, for which no treatment or antidote exists, and the long-term disability caused by the pain. Understanding the venom's algogenic properties can help identify better treatment for these envenomations. In this study, we provide the first characterization of the pain and inflammation caused by lionfish venom and examine the mechanisms through which it causes pain using a combination of in vivo and in vitro approaches including behavioral, physiological, calcium imaging, and electrophysiological testing. Intraplantar injections of the venom produce a significant increase in pain behavior, as well as a marked increase in mechanical sensitivity for up to 24 hours after injection. The algogenic substance(s) are heat-labile peptides that cause neurogenic inflammation at the site of injection and induction of Fos and microglia activation in the superficial layers of the dorsal horn. Finally, calcium imaging and electrophysiology experiments show that the venom acts predominantly on nonpeptidergic, TRPV1-negative, nociceptors, a subset of neurons implicated in sensing mechanical pain. These data provide the first characterization of the pain and inflammation caused by lionfish venom, as well as the first insight into its possible cellular mechanism of action.

Mental health effects caused by red imported fire ant attacks (Solenopsis invicta).

Susceptible individuals who have suffered painful stings caused by red imported fire ants, Solenopsis invicta, usually experience physical health effects such as fever, dizziness, generalized urticaria, or other systemic reactions such as anaphylactic shock. Whether S. invicta stings also have negative effects on mental health is not clear. In the present study, the psychological impact of S. invicta stings was evaluated using a questionnaire that included a previously published posttraumatic stress disorder (PTSD) checklist, the Patient Health Questionnaire 9-item (PHQ-9), the Generalized Anxiety Disorder 7-item (GAD-7) scale, the Beck Anxiety Inventory (BAI), and the Pittsburgh Sleep Quality Index, 5th scale (PSQI(5)). A total of 96 valid questionnaires were obtained; 37 participants were placed in the stung group, and 59 participants were placed in the unstung group. Our results showed that symptoms of anxiety, depression and sleep disturbances were not associated with S. invicta stings (for GAD-7 scale, Pearson Chi-Square test, χ2 = 0.152, df = 1, P = 0.697; for the BAI, χ2 = 2.252, df = 1, P = 0.133; for the PHQ-9, χ2 = 0.098, df = 1, P = 0.754; for the PSQI(5), χ2 = 0.536, df = 1, P = 0.453). In total, 2 of 83 individuals stung by S. invicta met the criteria (>50) for PTSD. However, there was no significant difference on PTSD between those stung by S. invicta in the 30-day group and the over 30-day group (χ2 = 0.318, df = 1, P = 0.573). Overall, our data do not show an effect of S. invicta stings on mental health as measured using a range of indicators.

Life history and chemical ecology of the Warrior wasp Synoeca septentrionalis (Hymenoptera: Vespidae, Epiponini).

Swarm-founding ‘Warrior wasps’ (Synoeca spp.) are found throughout the tropical regions of South America, are much feared due to their aggressive nest defence and painful sting. There are only five species of Synoeca, all construct distinctive nests that consist of a single sessile comb built onto the surface of a tree or rock face, which is covered by a ribbed envelope. Although locally common, research into this group is just starting. We studied eight colonies of Synoeca septentrionalis, a species recently been described from Brazil. A new colony is established by a swarm of 52 to 140 adults that constructs a colony containing around 200 brood cells. The largest colony collected containing 865 adults and over 1400 cells. The number of queen’s present among the eight colonies varied between 3 and 58 and no clear association between colony development and queen number was detected. Workers and queens were morphologically indistinguishably, but differences in their cuticular hydrocarbons were detected, particularly in their (Z)-9-alkenes. The simple cuticular profile, multiple queens, large size and small number of species makes the ‘Warrior wasps’ an excellent model group for further chemical ecology studies of swarm-founding wasps.

Morphology and ultrastructure of the mandibular gland in the ant Brachyponera sennaarensis (Hymenoptera, Formicidae)

The ‘samsum ant’ Brachyponera sennaarensis is an invasive species in Saudi Arabia, where it forms a serious threat because of its painful sting. As part of a morphological survey of the exocrine system of this species, we studied the mandibular gland of males, queens and workers of this species. The gland of males is similar to the common anatomical appearance the mandibular gland has in ants in general, but is considerably different in queens and workers. In both female castes, the secretory cells are grouped in one single cluster, that is surrounded by a thick sheath of connective tissue. The duct cells, that transport the secretion towards the wrinkled reservoir, appear considerably folded. Both the sheath of connective tissue and the folded ducts are considered as a mechanical reinforcement of the gland, although the reason for such reinforcement remains unclear as we are not aware of any peculiar movements of the mandibles in queens and workers. At the ultrastructural level, the secretory cells in all castes are characterized by a well-developed smooth endoplasmic reticulum, which is indicative for the elaboration of a non-proteinaceous and hence possibly pheromonal secretion. The clear structural differences between males and the two female castes, which so far had not been found in other ant species, show that the mandibular gland in B. sennaarensis most likely has a different caste-dependent function.

Multigene phylogeny of the scyphozoan jellyfish family Pelagiidae reveals that the common U.S. Atlantic sea nettle comprises two distinct species (Chrysaora quinquecirrha and C. chesapeakei).

BackgroundSpecies of the scyphozoan family Pelagiidae (e.g., Pelagia noctiluca, Chrysaora quinquecirrha) are well-known for impacting fisheries, aquaculture, and tourism, especially for the painful sting they can inflict on swimmers. However, historical taxonomic uncertainty at the genus (e.g., new genus Mawia) and species levels hinders progress in studying their biology and evolutionary adaptations that make them nuisance species, as well as ability to understand and/or mitigate their ecological and economic impacts.MethodsWe collected nuclear (28S rDNA) and mitochondrial (cytochrome c oxidase I and 16S rDNA) sequence data from individuals of all four pelagiid genera, including 11 of 13 currently recognized species of Chrysaora. To examine species boundaries in the U.S. Atlantic sea nettle Chrysaora quinquecirrha, specimens were included from its entire range along the U.S. Atlantic and Gulf of Mexico coasts, with representatives also examined morphologically (macromorphology and cnidome).ResultsPhylogenetic analyses show that the genus Chrysaora is paraphyletic with respect to other pelagiid genera. In combined analyses, Mawia, sampled from the coast of Senegal, is most closely related to Sanderia malayensis, and Pelagia forms a close relationship to a clade of Pacific Chrysaora species (Chrysaora achlyos, Chrysaora colorata, Chrysaora fuscescens, and Chrysaora melanaster). Chrysaora quinquecirrha is polyphyletic, with one clade from the U.S. coastal Atlantic and another in U.S. Atlantic estuaries and Gulf of Mexico. These genetic differences are reflected in morphology, e.g., tentacle and lappet number, oral arm length, and nematocyst dimensions. Caribbean sea nettles (Jamaica and Panama) are genetically similar to the U.S. Atlantic estuaries and Gulf of Mexico clade of Chrysaora quinquecirrha.DiscussionOur phylogenetic hypothesis for Pelagiidae contradicts current generic definitions, revealing major disagreements between DNA-based and morphology-based phylogenies. A paraphyletic Chrysaora raises systematic questions at the genus level for Pelagiidae; accepting the validity of the recently erected genus Mawia, as well as past genera, will require the creation of additional pelagiid genera. Historical review of the species-delineating genetic and morphological differences indicates that Chrysaora quinquecirrha Desor 1848 applies to the U.S. Coastal Atlantic Chrysaora species (U.S. Atlantic sea nettle), while the name C. chesapeakei Papenfuss 1936 applies to the U.S. Atlantic estuarine and Gulf of Mexico Chrysaora species (Atlantic bay nettle). We provide a detailed redescription, with designation of a neotype for Chrysaora chesapeakei, and clarify the description of Chrysaora quinquecirrha. Since Caribbean Chrysaora are genetically similar to Chrysaora chesapeakei, we provisionally term them Chrysaora c.f. chesapeakei. The presence of Mawia benovici off the coast of Western Africa provides a potential source region for jellyfish introduced into the Adriatic Sea in 2013.

Freshwater Catfish Envenoming in a Tropical Country

Freshwater catfish are known to cause painful stings in humans. Stings usually cause mild envenomation and, in some instances, can lead to severe secondary bacterial infections. Sri Lanka is a tropical country where catfish stings are not rare. However, presenting signs and symptoms, complications, and management options are scarce in the literature. A retrospective, descriptive, cross-sectional study was conducted by reviewing patient records in the university surgical units and surgical clinic in the teaching hospital in Anuradhapura, Sri Lanka, during 2015. Ten patients presented to the hospital following catfish stings. The common presenting features following stings were severe pain, swelling, and lymphadenopathy followed by cellulitis. Late complication such as tenosynovitis were also observed. Routine procedures are sufficient to reduce further complications. However, people who are at high risk of encountering catfish, and travelers visiting tropical countries, should be aware of the possibility of stings and take necessary precautions.

The Sting of the Wild

The Sting of the Wild Justin O. Schmidty 2016; 280 pages, 13 color plates Johns Hopkins University Press, Baltimore, MD ISBN: 978-1-421-41928-2 $24.95 (hardcover) ![Graphic][1] If you decide to make a list of the stinging insects to most carefully avoid on Earth, The Sting of the Wild is the perfect guide. This book is an entertaining tale of Justin Schmidt's life long research that will incontestably spark the interest of all entomologists. The book provides interesting ecological and behavioral information on a broad array of stinging insects (that is, wasps, hornets, bees, and ants) examined in an evolutionary context. Why do some hymenoptera venoms hurt and some others do not? Why is the bullet ant considered to have the most painful sting among insects? And why is the venom of the Maricopa harvester ant the most toxic for vertebrates? Through the author's own experience, the book discusses the relationship between hymenoptera and vertebrates, particularly humans. Schmidt explains how the evolution of a sting as … [1]: /embed/inline-graphic-1.gif

Jellyfish blooms perception in Mediterranean finfish aquaculture

In recent years, negative impacts of jellyfish blooms (JB) on marine human activities have been increasingly reported. Aquaculture has been affected by jellyfish outbreaks, mostly documented through repeated episodes of farmed salmon mortalities in Northern Europe; however, the valuation of JB consequences on the aquaculture sector still remains poorly quantified. This study aims to provide the first quantitative evaluation effects of JB on finfish aquaculture in the Mediterranean Sea and to investigate the general awareness of JB impacts among Mediterranean aquaculture professional workers. The aquaculture workers' perception about JB was assessed through a structured interview-based survey administered across 21 aquaculture facilities in central and western Mediterranean. The workers' awareness about JB impacts on aquaculture differed among countries. Italian and Spanish fish farmers were better informed about jellyfish proliferations and, together with Tunisian farmers, they all recognized the wide potential consequences of JB on sea bream and sea bass aquaculture. On the contrary, the majority of Maltese respondents considered JB as a non-significant threat to their activity, mostly based on off-shore tuna farming. This study for the first time shows that JB may negatively affect different Mediterranean aquaculture facilities from Tunisia (Sicily Channel) and Spain (Alboran Sea), by increasing farmed fish gill disorders and mortality, clogging net cages, or inflicting painful stings to field operators, with severe economic consequences. Available knowledge calls for the development of coordinated preventive plans, adaptation policies, and mitigation countermeasures across European countries in order to address the JB phenomenon and its impacts on coastal water activities.

Ts8 scorpion toxin inhibits the Kv4.2 channel and produces nociception in vivo

The venom from the scorpion Tityus serrulatus (Ts) has been extensively studied mainly because of its rich cocktail of neurotoxins. Neurotoxins are the major and the most known components based on their modulation of voltage-gated ion channels. Until now, electrophysiological studies demonstrated that the Ts venom comprises toxins that affect Nav and Kv channels. However, although many studies have been conducted in this field, many peptides from Ts venom await further studies, including Ts8 toxin. Here we report the isolation and electrophysiological study of Ts8. The toxin Ts19 Frag-II was used as negative control. Ts8 demonstrates, among 20 tested channels, to be a selective modulator of Kv4.2 channels. Based on studies investigating the involvement of Kv4.2 on controlling nociception, we further investigated the modulation of pain by Ts8. Using intraplantar injections, Ts8 induced overt nociception (licking and lifting behaviors) and decreased the mechanical nociceptive threshold (hyperalgesia). Furthermore, the hyperalgesia was prolonged when intrathecal injections were performed. Independent of the severity, most of the victims stung by Ts scorpions report an intense and persistent pain as the major manifestation. The new role of Ts8 on nociception could explain, at least partially, this phenomenon. Additionally, our study also stresses the involvement of toxins specific to Nav channels and inflammatory mediators on the Ts painful sting. This work provides useful insights for a better understanding of the prolonged and intense pain associated with Ts envenoming for the development of specific therapies.

Investigation into the hemolytic activity of tentacle venom from jellyfish Cyanea nozakii Kishinouye

Cyanea nozakii Kishinouy e (C. nozakii), a giant cnidarian of the class Scyphomedusae, order Semaeostomeae and family Cyaneidae, is widely distributed in the East China Sea, the Yellow Sea and the Bohai Sea, and is abundant from late summer to early autumn. Venom produced by C. nozakii during mass agglomerations can contaminate seawater resulting in death of the halobios and seriously damage commercial fisheries. Swimmers and fishermen commonly suff er painful stings from this jellyfish, resulting in local edema, tingling, breathing difficulties, depressed blood pressure and even death. Such effects arise from the complex mixture of biologically active molecules that make up jellyfish venom. In the present study, the hemolytic activity of venom from tentacles of C. nozakii and factors aff ecting its activity were assayed. The HU50 ( defined as the amount of protein required to lyse 50 % of erythrocytes) of the venom against dove and chicken erythrocytes was 34 and 59 μg/mL, respectively. Carboxylmethyl chitosan and glycerol could increase hemolytic activity at concentrations greater than 0.06% and 0.2 mol/L, respectively.

Length Is Associated with Pain: Jellyfish with Painful Sting Have Longer Nematocyst Tubules than Harmless Jellyfish.

A large number of humans are stung by jellyfish all over the world. The stings cause acute pain followed by persistent pain and local inflammation. Harmful jellyfish species typically cause strong pain, whereas harmless jellyfish cause subtle or no pain. Jellyfish sting humans by injecting a tubule, contained in the nematocyst, the stinging organ of jellyfish. The tubule penetrates into the skin leading to venom injection. The detailed morphology of the nematocyst tubule and molecular structure of the venom in the nematocyst has been reported; however, the mechanism responsible for the difference in pain that is caused by harmful and harmless jellyfish sting has not yet been explored or explained. Therefore, we hypothesized that differences in the length of the nematocyst tubule leads to different degrees of epithelial damage. The initial acute pain might be generated by penetration of the tubule, which stimulates pain receptor neurons, whilst persistent pain might be caused by injection of venom into the epithelium. To test this hypothesis we compared the lengths of discharged nematocyst tubules from harmful and harmless jellyfish species and evaluated their ability to penetrate human skin. The results showed that the harmful jellyfish species, Chrysaora pacifica, Carybdea brevipedalia, and Chironex yamaguchii, causing moderate to severe pain, have nematocyst tubules longer than 200 μm, compared with a jellyfish species that cause little or no pain, Aurelia aurita. The majority of the tubules of harmful jellyfishes, C. yamaguchii and C. brevipedalia, were sufficiently long to penetrate the human epidermis and physically stimulate the free nerve endings of Aδ pain receptor fibers around plexuses to cause acute pain and inject the venom into the human skin epithelium to cause persistent pain and inflammation.