Moon jellies

At the marina, one afternoon last week, the currents had brought in a swarm of moon jellies. I discovered one in the deep shade between a boat and the dock.

Aurelia labiata. Large male, about 5 inches across.

Out in the open, the jellies are foggy blobs with pale pink horseshoes at the centre. In the dark, even the radial canals that transport liquids through the body are visible.

The pink circles are the gonads; the frilly stuff below (above in this photo, as the jelly turned upside-down for a moment) are the oral arms, that catch the jelly's food and move it up to the mouth in the centre. The stinging tentacles on this jelly are confined to a short fringe around the rim of the bell.

Right side up.

Everything is in multiples of four; four gonads, four oral arms, eight lobes, each divided into two, making 16 scallops along the outer fringe. At the outer corners of each lobe, sensory organs, rhopalia, are just visible in this photo. Each rhopalia contains eyespots, sensitive to light, and statocysts, which alert the jelly when he's off-kilter. (There's a good photo of the rhopalia on E-Fauna, here.)

Moon jelly as seen out of the shade.

GPS: 50.035183, -125.244761