![]() 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. ![]() ![]() 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. While working, lab members experienced “stinging water” when they disturbed the water around the jellyfish (which could indicate a threat), or when prey were dropped in, indicating that cassiosomes can act as both hunting and defense mechanisms.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. These globules, named cassiosomes by the researchers, have cilia around their boundaries, which allows them to move around the water column and sting nearby prey. The upside-down jellyfish can release globules of mucus that contain the stinging cells and their “payloads” (called nematocysts and cnidae, respectively) into the water around them. (In this species, the arms are called “oral surfaces,” since they have many small mouths.) This is where the “stinging water” weirdness comes in. The jellyfish also eat small prey that are killed by specialized venomous cells on their tentacles, which paralyze the prey. This directionality allows both the jellyfish and its symbiotic zooxanthellae to produce carbohydrates via photosynthesis. Rather than floating freely through the water, they instead sit at the bottom of shallow waters, mouth (and stomach) facing toward the sun ( in their adult form). They’re found in the Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico, and have a few unusual characteristics for jellyfish. Cassiosomes can act as both hunting and defense mechanisms.Ī group of scientists recently investigated one of the jellyfish implicated in “stinging water,” the upside-down jellyfish ( Cassiopea xamachana).
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