Eusphyra

Eusphyra is a genus of box jellyfish (class Cubozoa) noted for its cube-shaped bell and potent venom. It is a monotypic genus, represented by the single described species Eusphyra formosa, commonly referred to as the flower hat jelly. The species is found in tropical Indo-Pacific waters, including coastal regions around northern Australia and parts of Southeast Asia, where it inhabits shallow marine environments near coral reefs and inlets.

Morphology and life cycle are characteristic of cubozoans. Eusphyra medusae have a transparent, cube-like bell with tentacles and sensory structures positioned at the bell’s corners. Like other cubozoans, the life cycle includes a free-swimming medusa stage and a sessile polyp stage, with planula larvae developing from fertilized eggs. The genus is of interest to researchers for its venom complexity and relatively advanced visual system, a feature common to box jellyfish.

Ecology and venom are central to public health concerns. Eusphyra formosa feeds on small marine organisms such as crustaceans and small fish. The venom delivered by nematocysts in the tentacles is typical of box jellyfish and can cause severe pain and systemic symptoms; in some cases stings can be life-threatening, necessitating urgent medical evaluation. There is no universally effective antivenom, and treatment focuses on prompt first aid, removal of tentacles, and supportive medical care as needed. Further research is needed to clarify its distribution, population status, and phylogenetic relationships within Cubozoa.