Venom and cnidome ontogeny of the cubomedusae Chironex fleckeri

This is the first study to explore venom and cnidome variation of individual cubomedusae, Chironex fleckeri, of different ages and from different regional locations in relation to feeding ecology. As medusae matured the proportion of mastigophores (those nematocysts containing the lethal venom component) in the cnidome increased, along with proportion of the vertebrate toxic fraction, in the venom profile. This switch in cnidome and venom occurred at the seven to ten tentacle stage. Whole venom was found to be toxic specifically to vertebrate cardiac cells, as opposed to vertebrate skeletal cells, and dose dependent, along with the vertebrate toxic fraction. The venom and cnidome ontogeny, along with venom toxicity, is correlated with C. fleckeri's known feeding ecology. Large and mature C. fleckeri feed predominantly on vertebrates, and have a greater proportion of mastigophores in their cnidome along with more vertebrate toxic fraction in their venom, compared to when they are young and small feeding on invertebrates.