cassiosome

English

Etymology

From Cassio(pea) (a genus of jellyfish) +‎ -some, referring to a genus containing some of the jellyfish found to produce them. Coined 2020 by Cheryl L. Ames, et al., in a paper published in Communications Biology (see quotations below).

Noun

cassiosome (plural cassiosomes)

1. A stinging-cell structure, composed of a layer of mainly nematocytes surrounding a core of dinoflagellates, amoebocytes and mesoglea, expelled within mucus by Rhizostomeae jellyfish to sting (and in some cases kill) prey in the surrounding water.
   • 2020 February 13, Ames, Cheryl L., Anna ML Klompen, Krishna Badhiwala, Kade Muffett, Abigail J. Reft, Mehr Kumar, Jennie D. Janssen et al., “Cassiosomes are stinging-cell structures in the mucus of the upside-down jellyfish Cassiopea xamachana”, in Communications Biology, volume 3, number 67, →DOI, →PMID:

     Released within the mucus, we discovered three types of undeployed nematocysts, as well as microscopic, motile, cellular masses composed of nematocytes that we formally call cassiosomes. While cassiosomes bear some resemblance to another cnidarian structure originating in mesenteries of the starlet sea anemone Nematostella called nematosomes, the unique traits of cassiosomes in C. xamachana include their release into the water column within mucus, the ability to trap and kill prey as mobile grenades outside of the medusa, their organization as an outer epithelial layer surrounding a mostly empty core (rather than a solid ball of cells), and the presence of centrally-located endosymbiotic Symbiodinium dinoflagellates.

   • 2020 June 1, Lauren Sara McKee, “The upside-down jellyfish stings you with mucus grenades”, in Massive Science‎^[1]:

     The hagfish produces mucus all over its body when poked. The team investigating the jellyfish grenades found that similar stimuli could provoke Cassiopea to release Cassiosome grenades from some tiny spoon-shaped structures on their arms.

   • 2021 April 13, Ames, Cheryl Lewis, Aki H. Ohdera, Sophie M. Colston, Allen G. Collins, William K. Fitt, André C. Morandini, Jeffrey S. Erickson, and Gary J. Vora, “Fieldable Environmental DNA Sequencing to Assess Jellyfish Biodiversity in Nearshore Waters of the Florida Keys, United States”, in Frontiers in Marine Science, volume 8, →DOI:

     Cassiopea xamachana medusae are known to release large amounts of mucus that contains motile clusters of stinging cells called cassiosomes (Ames et al., 2020). Thought to be an important component of healthy mangrove ecosystems, both spawn and mucus likely contributed to our success in preferentially amplifying Cassiopea eDNA (representing 82% of all matched reads).

   • For more quotations using this term, see Citations:cassiosome.

Usage notes

• Water containing clouds of cassiosomes is referred to as stinging water.

Translations

gelatinous structure of stinging cells released by certain Rhizostomae jellyfish to immobilise or kill prey