Despite this benthic lifestyle, warnings have been published alerting sea bathers of the stinging water or toxic mucus phenomena blamed on unidentified potent little grenades in the water column surrounding Cassiopea medusae 20, 21. Cassiopea is an exception to the iconic image of a jellyfish in that it lacks marginal tentacles and, instead of swimming in the water column, lies apex-down on the substrate in mangrove forests, seagrass beds or other coastal waters with its relatively short oral arms facing upward (reviewed in ref. For instance, Cassiopea mucus is known to kill certain species of fish on contact 24. Cassiopea is known to release large amounts of mucus into the water column 17, 18, 19, 20, 21, 22, 23, 24, which has been referred to as toxic mucus due to reports of nematocysts found freely suspended in the vicious substance 17, 20, 25. Additionally, the ubiquity of Cassiopea medusae in healthy mangroves has earned the upside-down jellyfish status as a potential bioindicator species for coastal management and conservation efforts 15, 16.
Some possible explanations for indirect jellyfish stings are contact with tentacle fragments in the water (e.g., jellyfish stings in offshore fishers 11), envenomation by juvenile venomous jellyfish (e.g., Irukandji-like syndrome in United States Military combat divers 12) or Sea Bathers Eruption caused by microscopic jellyfish life forms (e.g., Linuche unguiculata 13).Īnother indirect stinging mechanism is through mucus, such as in medusae of the upside-down mangrove jellyfish Cassiopea xamachana Bigelow 1892 (Class Scyphozoa Order Rhizostomeae), an emerging cnidarian model for its relevance to the study of coevolution as well as symbiosis-driven development (reviewed in ref. In addition to direct stings caused by jellyfish, indirect stings have also been reported. Sea anemones possess unique nematocyte-rich structures (e.g., acrorhagi, acontia) 9, 10 and employ strategies such as tentacle and column contraction and expansion to enhance nematocyst deployment for prey capture and protection, while in medusae (i.e., jellyfish) the first line of defense is their extendable nematocyte-laden tentacles that envenomate prey and predators they encounter in the water column 1, as well as humans participating in marine recreation. As such, cnidarians have evolved a remarkable envenomation mechanism that involves the deployment of subcellular stinging capsules called nematocysts from cnidarian-specific cells called nematocytes, which vary in size, morphology, and bioactive contents 6, 7, 8. Despite their seemingly simple morphology, cnidarians have adapted globally to most saltwater habitats and some freshwater environments 1, 5. These diploblastic animals have two so-called epithelial layers, outer ectoderm and inner endoderm, separated by a gelatinous extracellular matrix called mesoglea 3, 4. Jellyfish, along with corals, anemones, hydroids, and myxozoans, belong to the phylum Cnidaria, the earliest diverging venomous animal lineage 1, 2.
CASSIOPEIA JELLY FISH FREE
xamachana mucus and implicates mucus containing cassiosomes and free intact nematocytes as the cause of stinging water. This inaugural study provides a qualitative assessment of the stinging contents of C. xamachana (Class Scyphozoa Order Rhizostomeae), categorized as either motile (ciliated) or nonmotile types. Furthermore, we report cassiosome structures in four additional jellyfish species in the same taxonomic group as C. Cassiosomes consist of an outer epithelial layer mainly composed of nematocytes surrounding a core filled by endosymbiotic dinoflagellates hosted within amoebocytes and presumptive mesoglea. xamachana mucus and are capable of killing prey. xamachana stinging-cell structures that we term cassiosomes. Using a combination of histology, microscopy, microfluidics, videography, molecular biology, and mass spectrometry-based proteomics, we describe C. Snorkelers in mangrove forest waters inhabited by the upside-down jellyfish Cassiopea xamachana report discomfort due to a sensation known as stinging water, the cause of which is unknown.
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