The box jellies are sufficiently distinct to be placed in their own class, Cubozoa.   Befitting the name of the group, the bell of these primarily tropical jellies is indeed somewhat cuboidal with 4 flattened sides.  Box jellies tend to be transparent and can be quite difficult to see in the water, even with large individuals.  The bell margin lacks any scallops and has a velum-like rim similar to that in hydromedusae.  Another characteristic, the possession of gastric filaments, is more like that in scyphozoans.  A tentacle (or tentacle group) originates from each of the 4 corners.  One of the more remarkable aspects of box jellies is their possession of a complex eye within each of the 4 rhopalia that enables them to track moving objects and quickly respond to changes in light intensity.  Box jelly polyps can reproduce asexually by budding to form new polyps.  They do not strobilate, however, and instead each develops directly into a small medusa.  Among the box jellies is the notorious sea wasp of Australia (Chironex fleckeri), which can have a fatal sting.  

    Our West Coast waters are not well endowed with box jellies.  The one species that does enter California waters is Carybdea marsupialis (pictured here).  Although primarily a warm-water species, it visits nearshore habitats off Santa Barbara and other southern California areas from August through November.  This species may have a bell of up to 4 cm high, with numerous nematocyst containing nodules on the outer part.  The bell also usually is marked by light tan specks.  Four distinctive spade-like structures (the  pedalia) are aligned with the 4 tentacles and the septa that separate the gastric pouches.  Each tentacle is capable of extending more than 10 times the height of the bell.  Carybdea tends to swim most of the time while seeking crustaceans and small fishes.  When visiting southern California waters, this box jelly favors shallow sandy habitats inshore of the kelp beds.  Fortunately for bathers in the area, this species lacks a potent stinging punch.  In addition to southern California, Carybdea marsupialis ranges farther south into Mexico, and also is known from the Atlantic Ocean and Mediterranean Sea.  

All photographs © David Wrobel and may not be used or copied without permission!