![]() Albert is a behavioral neuroscientist, so his interest in moon jellies isn’t really in how they end up on beaches. As it becomes more and more degraded by wave action and decay, all that’s left is the tougher center of the mesoglea disk, which might be as little as 7 cm (2.5 in.). That would represent a fairly intact adult moon jelly. When you find a dead moon jelly on the beach, you may see a blob that is 25-40 cm (10-16 in.) wide, and includes the four horseshoe shaped gonads. These are the moon jelly’s gonads, where it produces eggs or sperm. When you see a live moon jelly, you’ll also notice four prominent horseshoe-shaped objects. Surrounding the mesoglea disk are layers of tissue that contain channels to move tiny particles of food from the edge of the jellyfish bell to the center, where its mouth and stomach are. He says the ones that end up as mesoglea disks on the sand were probably dead before they washed ashore.Ī Little Jellyfish Anatomy: What looks like a simple blob of jelly is actually a fairly complex blob of jelly. Albert asserts that the vast majority of moon jellies don’t become stranded. Still, despite these occasions when the normal behavior doesn’t work, Dr. The ebb tide will serve to help them drift away from the beaches, but the wind initiated currents may be stronger.” ![]() Also, if there is a wind pushing them toward a shore on an ebb tide, they may become stranded. So, a jelly may be less likely to drift out of a shallow area and less likley to avoid stranding. In that case, the ebb stream may no longer be very strong and it may be very thin. For example, in some jellies, swimming toward the surface doesn’t occur until the water has become quite shallow. The behaviours don’t always occur at the optimum time. Their behaviour has to be looked at statistically. Albert says, “Moon jellies have behaviours that help them avoid stranding. When moon jellies reverse their normal behavior in shallow water to position themselves near the surface, they place themselves in that ebb flow and get carried out into deeper water. That seaward flow at the surface is called an ebb flow. When waves break in shallow water and then recede, the overall flow of water is shoreward at the bottom and seaward at the surface. Albert has studied the behavior of moon jellies and has found that while they normally keep themselves a meter or two (about six feet) away from the surface of the water, if they bump into or sense the bottom in shallow water, they swim up and stay near the surface for some period of time. It turns out, however, that moon jellies have behaviors that almost always keep them off the beach.ĭr. So it seems like it might be pretty easy for a moon jelly to end up on the sand, doomed to disintegrate and be picked up by beach goers. By angling in one direction or another, they get some directional control, but for the most part, they can swim up and float down. But although they can swim by pulsing their bell to push themselves through the water, they’re not exactly strong swimmers. How do They Get on the Beach?: A moon jelly doesn’t want to be on the beach, of course.
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